Transcript:
Intro
hmm
um
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carol can you hear us we can't hear you
it seems you're muted carol
operator sorry about that it usually is
it usually is okay good to see you good to see you so i'm running a little
late i'm gonna have to reinstall a zoom on my original computer i had to reinstall everything else i lost much
more programs so i said the joys [Laughter]
yeah did you get everything back no i've got several programs i've got to reinstall manually but oh wow it got
corrupted the microsoft portion of it did oh my gosh i that's it's awful when your computer crashes or something like
that happens and i know i probably had uh probably half of my programs i don't use very often
but in case i ever needed to app sort of right yeah definitely you kind of get used to
what's on your computers and you know you want to depend on it so that's exactly right
hi john i don't think i've met you before hey no i i can't say that you're
familiar either so hi nice to meet you nice to be here yeah you bet you
you look like you've got sunshine there carol well yeah a little bit uh that's good
is it cloudy you're in your direction yeah usually when i get your wet weather like the next day so i'm glad to see
sunshine it's definitely cloudy here i think it's sunday's when we're supposed to get rain on easter sunday
so maybe you'll dodge the bullet yeah i think i'll get away i've noticed the snow a few times on easter sunday so
it can be all over the place you can keep that to yourself i've had enough this year
truth some place in the north seemed like it was montana in the last couple of days they got seven feet of snow
oh my gosh i just came back from alaska they had 93 inches this season in snow wow
yeah i've never seen snow so deep it was really deep
it sounds like you had some wonderful observing when you were up there oh man it was unbelievably beautiful yeah
yeah that's what's inspired me to start on a aurora series
finally another sunspot on the sun today yay yeah they were making progress
yeah it's hard to believe how active the sun's been yeah it's been beautiful
yes it has been it took a little bit of a break and now it's back again that's what we like to see
our little
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Welcome
[Music] well hello everyone this is scott roberts from explore scientific and the
explorer alliance and we welcome you to the 16th astronomical live program
hosted by terry mann uh terry um why don't we get started uh
and um it's a pleasure to have you on as always thank you scott and thank you for
broadcasting this we appreciate it thank you thank you
so what i would like to do is just go ahead and start with david levy and ask him if he would open us up here and get
us going well thank you very much terry it's a real honor and pleasure to be
here i love going to the um astronomical league online events and i would have loved to
come to albuquerque this summer but it turns out that i won't be able to come but i am here today
and i love these online meetings our quotation for today is going to come from sort of with an
emphasis on sort of from shakespeare's play julius caesar and you know how he wrote at the very
end when when brutus gets killed and mark anthony is standing over
brutus's body and gives us this is the noblest roman of them all speech
beautiful beautiful speech but i like to think that after he's done writing that speech finishes the play
and he goes and sets up his telescope
down fairly low he probably takes a night flight to tucson and sets up an explore scientific
telescope and he looks at omega centauri
if any of you have seen omega centauri this is a cluster to beat all clusters
it is i think the most beautiful star cluster in the sky one of the most beautiful
things in the sky and i would like to think that after shakespeare looked at it with
his telescope he would have written these lines this is the noblest star cluster of them
all the star clusters save only he did what they did in envy of this great
cluster he only in a general honest thought and common good to all made one
of them his life was gentle and the elements so mixed in him that nature might stand
up and say to all the world this is a star cluster
thank you very much and back to you thank you david that's good i like that
all right um tonight we're going to do something just a little bit different uh i'm going
to do a presentation so i am going to work on sharing my screen
and i'll explain to you why i thought it might be important at this time to do
this um some of you know i just returned from alaska
Alaska
i was there for a little while and this has been one of the most beautiful
trips i think i've ever made to alaska as you know
Back from Alaska
these are three of my images from i just came back about 10 days ago these are three of my images from when i
was back there so why i am doing this is i am very very
impressed the colors oh my gosh you know i have been there before seen a lot of greens mostly greens some reds you know
some really gorgeous reds but i was amazed at the amount of color that i saw on this trip
every night was colorful it didn't matter what time it was whether it was sunrise sunset in between
the skies were beautiful and i am guessing this has to do with the activity on the sun
with solar max being on the way and they are predicting we'll hit solar max about
2024-2025 so what i want to do is start a series
Aurora
um of aurora because i think i've been amazed at when i've flown or been in
places and people asked about you know where'd you just get back from or have you been traveling or what did you see
how many people have aurora on their bucket list so i felt like it was important we've
got three probably really good years here that we are probably going to see
some of the best auroras we have seen in a while and so for people on the bucket list
that maybe don't know a whole lot or maybe have some questions um i thought i would start up a series
about this and take you all the way through from planning clear to getting images and wherever else we go at that
point so what i'm going to do here is just touch a little bit on what i will do and
then we'll talk a little bit more about how it's going to be presented at the end
but a lot of people want to know where can i see the aurora well
i have seen uh the picture here in the middle i did see up in the up of minnesota they
have many drums many many lakes up there i don't know
which one this was for sure but this was up off the gun flint trail
in minnesota uh way up towards the u.p and the up of michigan oh my gosh and
marquette up in that area that is another great place in the lower 48 to see it
i've seen it in a lot of the well in a few of the northern states and wisconsin's another
good one and every once in a while when we have a very large cme i have seen it
in my backyard my front yard and that is what this picture is to the right
that is actually in my front yard shooting out of my front yard and you can see the reds the colors it's amazing
so depending on how large of a cme a coronal mass ejection from the sun we
have it could be possible to see aurora i've heard of it as far south as florida i
have not seen it down there but i've seen pictures so there is a time and a place if
conditions are right probably anywhere in the u.s you might have a chance of seeing the aurora
Canada
but what about outside of the lower 48. now i wouldn't mind going to norway but
from what i've read cloud cover is can be a serious uh problem there and these
other places iceland canada we've seen beautiful pictures from canada uh alan dyer's pictures are just
outstanding that he has shot from canada i have some friends that have been to iceland that theirs were just beautiful
but i chose alaska i tend to go to alaska um
Why Alaska
and part of the reason i chose to go to alaska is just like conditions like this
now this is actually live i need to kill the sound you're gonna hear me walking all over the place
this is live real time and yeah this is up by the big dipper this
is what you saw naked eye this is not what i've ever seen in ohio
you know uh when you get way way up north this is a type of thing that you
will see and that is why one of the reasons why i choose to go to alaska the others are
alaska's easy to get to um i mean no airfare is cheap don't get me wrong but major air
lines do fly there and i always whenever i'm planning a trip to doing kind of imaging or
anything i always want to know what else have they got that i can do if i get
clouded out and believe me on one of my trips to alaska i was just about totally skunked
i had clouds almost my whole trip one time so you need to look and see if
there's other things that you can do and you know what would be there that you could do
but a fairbanks is really ideal because you are under the auroral oval
and that is the ring-shaped zone over the far north where the activity is
actually pretty well concentrated and that's why you see it so active and this time i was in alaska for quite
a few days and i only had two cloudy nights and what was amazing was weather
forecast predicted clouds almost every night and it did it had a few clouds but then it
cleared off and the nights were totally amazing and as i said there's plenty of things
to do in that area um i didn't spend there i don't spend very much time in anchorage but maybe as the cmes get
stronger i'll be more comfortable because for me i'm there to image the aurora and i want to be as far north as
i can get to do this because if it's a small cme are kind of
weak it's not really going to go clear down to anchorage so i spend most of my time
around the fairbanks general area i travel around a bit through there
When to see the Aurora
and so they want to know when's the best time to see it well usually when i go very honestly on
their new moon in march usually this time i stayed the latest in april i
ever have and as you see there um april usually i
stayed till the fourth one time and i think i stayed until the sixth this time and
you're losing daylight you're losing i mean you're losing darkness and you're losing it pretty fast as you can see
here in the course of april in fairbanks you rapidly have more daylight the length of the day
in april from the start of the month increases by 3 hours and 19 minutes so
an average of every day you gain almost seven minutes of daylight every day in april
so i don't really stay late in april it is something to see in the beginning of
april this was taken at sunset and you can see it's sunset uh you have the
purples and you have some of the blue sunrise and sunset is just a beautiful
time to shoot the aurora if it is out and you know it is gorgeous but i just don't
stay late in april i try to spend most of my time in march and maybe the very beginning of april for that reason
um and again in the lower 48 when you can see this anytime the conditions are
right i mean i've seen it in ohio i haven't seen it here since 2003 maybe
uh but if it's dark and conditions are right you can see it anytime
that it is dark and believe me it's nice to watch the aurora when it's warm i have i have been able to do that a few
times in alaska i i'm dressed up you know you are totally dressed up in march i think
our lowest temperature that i saw we this time was uh somewhere i'm thinking where i was at it was
around 22 below but most of the time it ranged somewhere
around 10 below to 15 below maybe in the evenings and there were times it was just hovering around zero really just
depends now as i said you can see the aurora anywhere
Equipment
okay i am on lake superior chasing aurora and this is the kind of stuff can happen
this is what can happen uh lake superior came to life and uh pretty much totally
nothing there to see but again i'm up in the u.p of minnesota and this
is lake superior and even though it was nasty out it still had a beauty of its own with raging nature
uh it was something to see and just to stand out in the snow and watch that so
always consider wherever you go weather is going to play a factor and have a back-up plan of something to do
if you don't enjoy the weather too much and what else we will cover we'll get
into equipment that you'll want to have fast lenses fast glass maybe you've got
a newer camera that can handle the higher isos that you don't need quite as
fast of a lens but it's always nice to have but by no means do you need to have a
brand new expensive camera an expensive lens to do that and you can see a lot of phone pictures
of the aurora that you can at least take home you know a piece of the aurora or a part of the aurora so depending on your
equipment honestly you will be able to get something but the first thing too you have to
consider and i have to work on this whenever i fly getting that equipment
wherever you're going to go i do not check my lenses or my cameras or my
laptop so i am always carrying a very heavy carry-on
that is something that you always need to consider about everything that you are taking with you how you're going to do it if
you fly that becomes an issue and clothing uh in alaska you definitely in the
winter time you definitely need to make sure you have the correct clothing or you will be very cold and honestly over
the years i bought almost every piece of clothing as far as outdoor while i was in alaska
they they just the timing you go up there in march and it seems like your prices are a little bit cheaper um but
it they have clothes that are made for their weather so it makes it nice uh weather is always going to be a
consideration it is to me whenever i'm going anywhere if i can make a last-minute guess and
it's a lot better but most of the time i'm checking historical data and that doesn't always tell you everything but
it gives you a good idea and think about how long you need to see i know they say in alaska if you stay
three or four days you have a very good chance of seeing aurora and i do believe that as long as it's clear you will you
won't see you might not see the active stuff that i just showed you the one video
but you will see green aurora within i would guess three to four days
if it is clear and again figure out what else you can do um there
are other things there there's a lot you know a lot of them are your
tourist trap type deals but it's still you know if i'm someplace i don't mind looking around at some place new
if i'm someplace different so um we'll cover a lot of that and this this
was a nightmare when i went to the total eclipse in aruba in 98 you can see all the equipment we're carrying and uh we
carried a ton of equipment and we flew but it's something just you have to
think about getting it moved around and lifting it getting it sometimes through customs
we've i've never had a problem with customs flying equipment but i've always done everything to make it as easy as
possible but some you know you can overload the problem is i think with a lot of us imagers or at least maybe me
um i think i need to have lenses to cover and anything that i might see if i don't have the lens to cover
what it is i want to shoot i'm really not real happy so i take i'll i take what i need with me and try to
figure out how to adjust that weight limit and again uh some of what we're going to
Travel in Alaska
cover is understanding the aurora the weather choosing a location and a lot of times
that location might be here in the u.s it might be outside of the u.s could be alaska or canada or you know
think about the location you're going to and why what you're going to deal with equipment and what you will need
we're going to cover imaging the aurora and time lapse and video
for aurora and clothing and preparing for possible emergencies that is something traveling in alaska there's
times you're out running around all night long and it can be 22 below and you have to think about things like this
whether your phone will work in the area you are at if you need another way to contact
people there are a lot of possibilities and when you're traveling in an area where weather is a
real can be a real problem you really have to think about things like this that maybe you wouldn't i mean
the first couple years there i didn't um like i said the more snow i've seen in
alaska and the more bad roads when i've been there i've really thought a lot about that and
we'll cover whatever else comes up with that so uh right now i just
New Series
uh haven't got every detail worked out so we will be announcing this series as
soon as we decide the best way to present it because i want to do it in a way that just makes it simple and easy
for people to interact it will be announced on the lead web
web leads facebook page i'm going to twist scott scott's arm and put me on the
global star party side they'll take a lot of twisting well we'll definitely announce it there
or on al live but i'm not quite sure the best way to present it and so i want
some input on that so we will definitely let you know so that is going to be the end of mine
Closing Comments
and carol as i'm shutting down i am going to go to you
thank you terry you've wanted her appetite to go to alaska and look at aurora and spend some time and take it
seriously been on my bucket list for a while i've seen one or two but i i need some more
yeah everybody everybody that i've talked to i've heard that comment more times in the last ever since i've been
home and traveling home uh you know and that's another reason i thought this is a time to do it because so many people
have questions and really would like to do this and it you know depending on where you go it can be an expensive trip
so you need to have all the knowledge that you can so you know but i i think that's why
it's important so david i guess you wanted to say something too yes i do i wanted to congratulate you terry on this
wonderful presentation if this is the quality of presentations we can expect from the astronomical
league god bless you this is wonderful my first northern lights
i'll never forget it was before i knew how to take a picture it was on the 4th of july 1966
at the adirondack science camp the same site where we do our annual retreat now and it was magnificent it started at
sunset and the sun was going down and it had gone down and the twilight was in the west but instead of revealing a
beautiful sky the twilight appeared to just shift over to the north
and that was a bright glow that turned into a radar and finally it ended the
night with an all-sky aurora with coronal effects and wonderful i'll never
forget it and it was one of the most thrilling nights i've ever had in my life
terry thank you so much for your talk well thank you for your comments david because i think that's the way so many
people feel especially when you see a really active display it just it just
knocks your socks off it really does it's amazing so thank you i appreciate that
okay all right carol as far as the lake we've got a little bit of information as most of you know
we didn't have an active in-person outcome for two years but now we're
in the middle of registration and things are going very well one thing for all of you master
observers who are listening out there from the league one thing uh those have piled up a little bit the
number of people who have gained those awards but who haven't received the black ship
so we're going to uh publicize this as much as possible to get as many people
to alcon to get your award in person the plaque as possible we would like to have
your information however by the end of this month or the early may the latest
so we can make sure we have the blacks ready and so on anything you want to know involving
alcon 2022 can be found at alcon 2022.astroleg
whether you have not made your room reservations yet at the embassy suites and by the way that is a very nice hotel
each room is a two it's a two room suite so it's very nice very reasonable rates and so make sure
you go to that link it will give you the registration information as well as
uh the link to actually go ahead and reserve your room
so uh there's a lot going on there and uh if you uh
like i say if you've uh been thinking about well i've got my my observing awards together just go
ahead and do it get registered and we'll see you in albuquerque uh we're going to have a lot of guest
speakers there as always that are all cons and one of the things that some of you may not have seen is one of the
larger ray facilities there in uh just out of albuquerque about an hour's drive out and that's going to be
held at the end of alcon on the sunday and it will allow you plenty of time to thoroughly enjoy the experience so i
would encourage you to stay over a day or two we've got some special rates room rates
not only during the convention but a couple days before as well as a couple days after so i'd encourage you to do
that again this year we've got a lot of entrance from the youth award winners as
well as the adult winners so it uh it's going to be a a great experience so
hope to see you all there and i think that's it for right now terry back to you okay
thank you carol yeah i'm looking forward to that uh it's they have do they still
have the is it harrison smith that they're going to do yes i neglected to mention that the
astronaut there's going to be a special event uh with him and that's separate
from the rest of the convention at dinner with him and it's on the registration forum you could pre-register for that a very reasonable
price and he is very articulate and he is always willing
to share uh his experiences in outer space wouldn't it be great to to have
that phenomena i have that experience but he's more than willing he's uh he's
really very accessible to the public and the membership that's i'm looking forward to that so okay
carol uh appreciate it so now we're going back to me again um
as you know we asked questions for uh at the astronomical league live
and so what i'm going to do is get this ready again
Questions
this time as you can see this will probably be the last time we do 2022 calendars
there'll be three calendars given away and if we're shipping internationally please remember we have had problems uh
with it it has slowed down shipment so if these this will be the door price
for tonight and please answer the questions in the next 30 minutes uh
this one's not like the gsp uh we're gonna i will be announcing the winners after
john gets done speaking and someone from the astronomical league will contact the
winners short sometime in the next week or so
so here are the questions for tonight how wide is the cosmic bubble that
surrounds earth i'm gonna do it again how wide
is the cosmic bubble that surrounds earth
next question how many seconds has a hubble space telescope been operating since january
1st 2022 that's a tough one
how many seconds has the hubble space telescope been operating since january
1st 2022 and the last question what astronomer
coined the name aurora borealis please send your answers to secretary
at astrolege.org as soon as possible
and we're not going to give the answers i'll stop right there
yeah that's why i have to put that in there i have done this before so what we're gonna do now
we're running really quick on time but scott let's just take maybe a five minute break let john get set up and
we'll just take a five-minute break and we'll come right back with john winskovich
sounds good okay
do this and i'll adjust the time
Silent Visualization
yeah as long as it's around five that's good just 10 minutes around five maybe not
hey if we need to do ten we can do ten we don't need to do ten here we go oh
you're good okay thank you scott
i
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you
do
um
well that was a silent visualization of jay west at the l2
point and i'm going to turn this back over to you terry
but uh thanks for tuning in to the 16th astronomical league live program you
guys thank you scott now i have a question that this visualization it was pink of
me is that does that actually happen could it be a reflection of sunlight or maybe
john would know the answer to that or it might just be how visually nice it
looked well john does uh data visualization so maybe he has a good answer
no unfortunately i can't say that i have a good answer for that one um it might be a bit of artistic license it might be
uh some some other effect that they've modeled yeah okay i just wondered because it
turned such a pretty shade of pink underneath and i thought maybe it's sunlight or something so all right we
will get started uh our keynote speaker tonight is john winskovic john is a
visual analytics researcher at pacific northwest national lab and a professor
in computer science in the computer science department at virginia tech
his current research focuses on human al co-learning and teaming
trust in machine assistance human in the loop data science
analytical provenance and the application of visualization to both the
sciences and cyber security he teaches courses in on information visualization
data analytics computer graphics and human computer interaction which i think
all sounds amazing your job must be really amazing so
john i would like you to just go ahead and take it away
Introduction
sounds great thanks uh so much for the introduction thanks for for having me as a speaker here on uh ale live
well thank you let me give the the usual commentary while i
share my screen and get all my windows organized uh so hopefully everybody is is able to
see the presentation and we're ready to get started okay great so uh before i really get started
i want to definitely make sure to thank john goss who who connected me to to be able to give this talk uh for a second
time uh so the history of this talk is that uh i was originally asked to present on the the james webb space
telescope and the lagrange points uh during a meeting in february for our
roanoke valley astronomical society meeting um and now you all get to see i
guess an extended version you get the uh the director's cut uh where we get to talk a little bit more about james webb
and we get to talk a little bit more the the lagrange point uh but i want to get started with this
Hubble Space Telescope
presentation uh by talking about something that's not in the title of the presentation and
that's the hubble space telescope so uh hubble well it's it's iconic we we
all know hubble we all know the the hubble space telescope i i would make an argument from a scientific perspective
that you know it's it's probably the most important thing that nasa's ever done even beyond that whole landing humans on the moon thing
um the the hubble space telescope and it's been doing science for decades uh
it launched when i was two and a half years old and i've had my phd for more than two and a half years and the whole
educational span uh in between the the hubble telescope has been doing great great science uh and just to pull up a
couple of images uh to really give the hubble it's due uh right we've we've got
the pillars of creation in the eagle nebula in in messier 16. uh and we've
got some of the the impacts of the shoemaker levy 9 comet on jupiter that were taken by hubble
uh the the hubble extreme field looking way way off into the past looking way off into a tiny little sliver of space
and seeing all of these galaxies that are just so distant and so tiny
um and even being able to view uh exoplanets being able to directly image
planets outside of our solar system uh the the hubble space telescope i mean it's it's
i i can't even say enough praise about how much work it's done
but it's also 32 years old at this point and that's just 32 years in orbit it's
it's time for us to start planning its successor uh and even though james webb
isn't you know purely a successor to hubble that's the way it's been billed and so i'm gonna go with the the nasa
lingo of james webb being the hubble successor so one of the the nice things about
hubble is that it's not too far away uh in fact here's a nice visualization of
the the hubble space telescope orbit uh it's close to earth it's a little bit higher up than the the international
space station uh and it's a little bit smaller than the international space station so it's a good deal dimmer in
the sky but you know whenever the the sun angle is right and whenever it's in the sky close to sunrise or sunset you
can go outside and you can see the hubble space telescope kind of just drift across the sky
and another benefit of hubble being so close is that we have the ability to
go off and fix it uh if you'll recall from uh the the early 90s when hubble
was first launched it was a little bit of a disaster because of some issues with the the main primary mirror
and so the the very first servicing mission servicing mission one that you see here uh had to install some
corrective optics on the hubble space telescope so that instead of having
images that were a little bit messy and blurry like this one that's uh melnick 34 star
which has this kind of distortion as a result of this this aberration in the primary mirror you know we were able to
to correct for this and we were able to get our our amazing images that we're so used to seeing
coming back from hubble okay so hubble it's nearby
james webb is not and one of the reasons why the james webb space telescope is
not going to be positioned anywhere close to earth is the fact that earth is
warm um maybe not quite this warm this is uh an image that i see on a lot of blog
posts whenever they're commenting on climate change uh but earth is a warm
place earth takes in uh light from the the sun solar radiation it warms up
and it generates infrared emissions it reflects heat back off of its surface
that is a bit of a problem for the james webb space telescope because the james webb space telescope
is designed to be an infrared observatory it's designed to look at these longer wavelengths of light
and well if we're going to have an infrared telescope we need to make sure that our infrared telescope stays nice
and cool uh stays away from the earth and doesn't get all of this bright heat reflecting away from the earth and
messing up all of its images and so whenever they were designing the the james webb space telescope and
figuring out what the mission parameters were going to be they decided to put it somewhere else
and the place that they decided to put it is well it's called l2 and that's the main topic behind this presentation the
james webb space telescope and what exactly is l2 and the the overall lagrange point
family so here is a nice infographic that nasa
released as far as the james webb space telescope launch and deployment goes so it launched from earth on christmas of
last year uh it took off and it started assembling itself it started unfolding
the the mirrors locked into place the sun shield locked into place uh and eventually after all of these individual
steps after about 30 days had gone by uh it made it out to this point here in
space called l2 which that's great uh but it doesn't really communicate all that well about
where l2 is uh if i can give you a little bit of context this gray oval
that you can see all the way back here that is the orbit of the moon so l2 uh
we can see just right from the very beginning here is well beyond the orbit of the moon we're going way way out into
space there are definitely reasons why we'd want to take it that far out away from earth but it also seems like that's
going to be something that complicates our mission right we we first off don't have the ability to do quick and easy
servicing it's going to be really distant and so we don't really have the human space flight capability to be
able to go out there at the moment and we've never had the ability to get that far away from earth
in addition to that well if we're getting this far away from earth aren't we going to eventually lose the
telescope isn't it eventually going to drift away from the earth even further what's so special about this l2 point
that we decided that we want to put it there let me give you just another quick
example about just how far away this l2 is here's a nice nasa image where
everything is not to scale as you're going to see from a lot of this presentation there's a good bit here
that's not going to be to scale but you can see that up here we've got a hubble hubble is in orbit around the earth and
they've got this number 570 kilometers uh for us in in america you know think
of it as 400 ish miles uh we've got 384 000 kilometers to the moon we've got 1.5
million kilometers to l2 just how big of a distance is that
so let's take the size of the earth the entire big planet uh and let's reduce
that down to be about the size of a quarter which is a little bit less than
an inch across at this scale hubble is this far away from the edge of our
quarter 0.0427 inches which is not an easy number to try to
parse so let's switch back to metric for that one it's a millimeter uh the hubble space telescope is a millimeter away
from the edge of this earth coin uh as it orbits around the planet
okay so then we've got the moon the moon is 384 400 kilometers away it's going to be a
little bit more distant at this scale the moon is 2.4 feet away
that's uh a pretty sizable distance that's a big step from from low earth orbit whenever we're a millimeter away
from our quarter to being two feet away from our quarter uh but then we've got this 1.5 million
kilometers for l2 and that is going to be further and further away still on
this scale whenever earth is the size of a quarter we're putting this 10 billion
observatory about nine and a half feet away nine and a third feet away it's a good long
distance away uh and this this second image uh also generated by nasa which
better labels the orbit of the moon uh really kind of puts that out there right we've it's huge distance from the earth
to the sun we've got this huge distance from earth to l2 and this for some
reason is where we're going to put this 10 billion dollar telescope
so that brings us to the the other major point of this presentation and that's talking through
well what is a lagrange point what are we actually talking about whenever we're talking about these these look range
points of which l2 is is one of the the five so before we get too far into this uh
let me just do a quick note on terminology so i'm gonna try to be pretty consistent
with using lagrange point or lagrange point i can i can pronounce it either way inconsistently uh but sometimes
you'll hear lagrangian point uh sometimes you'll hear l point sometimes you'll hear libration points
these are all equivalent terms these are all referring to the same thing uh in
our universe these are all uh l points these are all our lagrange points so
with that terminology node out of the way what is a lagrange point what is l2
What is L2
let's start off with this image that again i pulled down from wikipedia uh
these are our lagrange points and we label them as l1 all the way up through
l5 and you can see that they're just kind of almost oddly distributed around this
image we've got earth sitting here with the moon in orbit uh and we've already seen that l2 is somewhere out in this
direction away from the sun side of the earth well beyond the moon's orbit you know somewhere out here but we've also
got l1 and it's also on the outside of moon's orbit uh and it's on the the side
closest to the sun which is interesting so we're saying that we've got this point here l1 uh which is
well interesting but why is it interesting why is l1 l2 l3 all the way
over here l4 l5 kind of off on the sides why are these so important
so it turns out that these are places in the universe
where spacecraft can be safely positioned because of a balance in the
forces acting on these spacecraft and so let's take this image and let's
make it just a little bit more complicated so if you're used to looking at
topographic maps you can imagine this is a topographic map if you're not so used to topographic
maps well you can kind of think of this as trying to show the the gravity wells
of the sun and the earth if you want to think about it in 3d terms here's a very blurry screenshot
that i took of an animation from nasa where you can see these gravity wells
dipping down for the sun and for the earth into these these cones that drop down below the the spheres
but going back to our 2d view uh l1 well it looks like it's kind of almost on
this little saddle point right we've got the the gravity well of the sun dropping off to the left we've got the gravity
well of the earth dropping off to the right and elbot is kind of balanced at a really nice position where those forces
end up being nicely balanced that one is probably the one that intuitively makes
the most sense it's in between these two different major gravitational sources and it's at this nice balance point but
it turns out that if you start looking at all of the interactions for how these gravity wells bend and curve space we've
got some other points that work out to balance these forces really nicely and l2 is one of those points it's also sort
of on a saddle it's at a point where the gravity well of the earth is coming up away from the
earth or if you want to think about it from the top downward dropping down to the the left
and as we're getting further and further away from the sun the sun's overall gravitational field is getting a little
bit weaker and so it's slowly dropping off toward the right and so this is another one of those
nicely balancing points uh inside of this uh earth sun system
we've got l3 over here and l3 well it doesn't quite look like it's on
so narrow of a saddle point but you can see that there's a curve coming up around the side and you can see there's
a curve coming down around here it is still on the saddle point it's just a much much broader saddle overall uh in
this gravitational space uh and then we've got l4 and we've got l5 and these are again not really at saddle points i
guess really they're not at saddle points at all you can almost think of them as being at the top of some really smooth hills
and so l 4 and l 5 are a little bit more regional they're not really mathematical
points although there is a mathematically optimal location uh but it is more of a
you know a range of places where we could try to to put spacecraft in a nice gravitationally balanced way
uh so again we've got all of these different renderings that are trying to communicate where these different lagrange points are uh here's just one
more that i wanted to add in because maybe it's a little bit easier to stare at it's not as quite a bright and
colorful image but you can still see some contours that are drawn here and you can see that l1
is kind of at this nice intersection l2 is at the intersection l3 is at this intersection uh and then l4 and l5 will
kind of over here at the tops of these hills okay so those are our lagrange points
talk over uh well not quite so much because there's a lot more to really talk about with with respect to lagrange
points uh and the first thing to talk about is maybe a little bit of the history so how did we figure out that
these things exist uh and it turns out that this is not a space age discovery
these are points that were identified uh as being at least mathematical
curiosities all the way back in the 18th century uh and so here is a copy of a
Rectilinear motion of 3 bodies
mathematical paper uh you can tell that it's an 18th century paper because they were writing papers in latin at this
point uh and this is the the first time where it was published that there are
some of these nice balance points that exist out in space uh just taking a quick pass trying to
translate the title uh it comes out to about the rectilinear motion of three bodies attracting one another
and so we can break that down a little bit uh so three bodies we're talking about three different things we've got
two big massive gravity wells we've got the sun and the earth and then we've got this third body and
this third body is what we'd like to place at that nice balanced gravitational point
uh and then there's the whole thing about attracting one another well that's the gravity piece we've got the the
spacecraft pooling very very slightly on the sun pulling very very slightly on earth
but then the other way around the sun is tugging on this spacecraft the earth is tugging on the spacecraft uh and then
there's the the motion piece because we also have everything in orbit around the sun
and so we need to think about well we've got a a messy coordinate system that's going to be constantly changing
because of this orbital motion of the earth and how that's going to have an impact on these uh look range points
speaking of lagrange if you look a little bit further down at the author of this paper uh the author of this paper
is not a guy named lagrange which was something that i didn't know about uh
when i started to prepare this talk i was you know under the assumption that hey all of these points are named after
lagrange so you must have been the guy who discovered them uh but it turns out that the first three l1 l2 and l3 were
discovered by everyone's favorite uh 18th century mathematician leonard
euler and so my you know kind of conspiracy theory mind is
thinking along the lines of euler already has 6 000 different things named after him he's one of the the greatest
mathematicians of all time and so even though he found these first three lagrange points uh you know they they
just kind of threw the whole thing over to lagrange whenever he found numbers four and five
maybe that's what happened maybe it's not what happened uh but that's that's at least my head cannon for why uh these
discoveries from euler ended up being named after lagrange uh so it turns out that these two folks did know each other
and they were in pretty regular communication uh and so let me just give you a little bit of an extended bit of
the the history lesson here so oiler was uh born in 1707 he was a
swiss mathematician uh but back in the the 1700s there were a few different
really prestigious places uh where mathematicians would go and work
and one of them is the imperial russian academy of sciences in st petersburg in
russia and i just want to take another quick uh tangent to note that all of these different places are named academy
of sciences and i really wish that universities still recalled something like academy of
sciences uh because it just feels uh a bit more prestigious but but anyway that's that's
a digression so euler goes off uh to russia he goes to st petersburg uh he
works at the the russian academy of sciences for a few years uh and then well there's a little bit of political
instability that starts to happen in russia you know peter they're great uh passes uh there's there's some issues
with succession there's some issues with the economy uh and eventually he decides to make a move to berlin to the royal
prussian academy of sciences uh where he spends the next 25 years
so there's a couple of different dates that i found for when euler actually
proved the existence of l1 l2 and l3 uh i've read that it's you know somewhere
around 1750 i've read 1765 what we do know for sure is that he published the
work uh in 1767 which is one year after he returned to russia
after his his stint in berlin so that's going to take us over to joseph louis lagrange
he was born a little bit later he was born in 1736 uh he is italian uh despite the the
evidently french name uh and that's in part because of his later time at french academy of sciences uh but as an italian
he was working in torino the terrain academy of sciences uh and he was making
a really big name for himself and so i i also want to make sure that i go back to to correct my head canon a little bit
and note that uh it's not like this was a pity award to name these things after him he was a pretty good mathematician
in his own right uh especially knowing uh as i did a little bit more reading
that euler actually tried to get lagrange to come to berlin as early as
1756 when he was only 20. uh he was he was getting these emails from euler
saying hey you really need to come to berlin and work with us because this is a great place to work and well lagrange
didn't until euler was ready to leave maybe euler was you know a little bit too intimidating to work with as a
co-worker so anyway in 1766 euler returns to russia lagrange takes over
his position at the royal account uh prussian academy of sciences in berlin uh and so there's this little bit of an
overlap where it seems that the euler already had this idea was already working on these nice balancing points
that exist in gravitational dynamics and so he publishes the first three and then a few years later in 1772 uh le
garage comes along and he publishes the the existence of these two other points that euler himself wasn't even aware of
uh and so eventually while lagrange makes his way to france at a very inopportune time in history to make his
way to france uh and well that's the end of this little bit of a history lesson uh aside from going through one more
slide to show you uh a picture of lagrange uh and all of his varying names uh both the the french stylized version
and the italian stylized version and also one of his papers on the problem of three bodies free body
problem okay so that's going to take us back to
these lagrange points so all of the the examples that i've been talking about so far have been talking about the sun and
the earth but i also want to make sure that it's really clear that these points exist for
every pair of solar system bodies that are in orbit around each other and so there are these five balancing
points for the earth and the sun there are these five balancing points for the earth and the moon there are these five
balancing points for the sun and jupiter for the sun and neptune for saturn and titan uh any pair of massive bodies in
orbit around each other have these nice balanced points
and so let's talk about the math and well i'm not going to go too much detail into the math
there are some great explainer videos on youtube that talk you through how to solve these uh there's one that i'm
going to show a screenshot of in a couple more slides that is very intimidating looking but there are some
others that talk you through it in a little bit more detail but those videos are you know on the order of 50 minutes long and you know
talking about math for 50 minutes is a great way to get me thrown off this show so uh let's talk just about a little bit
about some of the math so there are two different sets of forces that we're trying to balance here
there are the gravitational forces and there are well also the the momentum the
the actual uh velocity changing as this thing is moving its way around the sun
which in part is is still you know uh governed by by the gravitational
forces uh and so let's just think about this for a couple of seconds so we've got our sun all the way up here at the
top uh and we've got our eight planets eight planets uh going down our column
uh and each one of these planets gets a little bit further away from the sun as it's a little bit further away from the
sun the sun's gravitational influence gets a little bit weaker as a result of that required velocity necessary to stay
in orbit around the sun drops and drops and drops as you move further out into the solar system
and that's what gives each of our planets uh in part a different orbital period
we've got mercury that's racing its way around the sun every 88 days uh we've got the earth that takes exactly one
year what a coincidence to make its way around the sun uh all the way out to neptune which takes 160 465 years
uh and so we're saying that there's this l1 spot right here that is a little bit closer to the sun than the earth is uh
and there's this little spot here l2 on the other side of the earth a little bit further from the sun than the earth is
uh and so if the only thing that we needed to worry about with this distance then we would make the assumption that
well our orbital velocity at l1 is going to be a little bit faster than what we have for earth uh and our orbital
velocity for l2 is going to be a little bit further a little bit lower than what we have for earth and so the the orbital
period for something at l1 uh you know just thinking about it in terms of orbits should be a little bit less than
a year and for l2 could be a little bit more than a year but then we also have to think about the
gravitational aspect uh and here maybe a good intuitive way of sort of thinking
about it is just thinking about the gravity of the earth so we've got something here in in orbit around the
sun at l1 and it's trying to make its way along its orbit a little bit faster
than earth's orbit it's trying to make its way you know around the sun uh in 360 days instead of 365 days
as it keeps trying to move its way forward earth's gravity is pulling it back earth's gravity is tugging it back
into this l1 point and the same thing kind of goes for l2 so in l2 you know maybe it's something
like 370 days would be the optimal orbital period for something at this location and so it's slowly trying to
drift way backwards taking a little bit less time to orbit or a little bit more time to orbit on than the earth does uh
orbiting the sun a little bit slower than the earth does but as it keeps drifting back the earth's gravity is
going to keep pulling it forward and trying to maintain it in this location
that's something that we actually see in a variety of different places in the solar system and one of them is in the
rings of saturn so the rings of saturn have these shepherd moons uh and i guess the the rings of all of the gas giant
planets occasionally have some of these shepherd moons uh but this is uh saturn's effering and it's
gravitationally bound by these two moons prometheus and pandora and you can see
some of these gravitational influences in the individual ring particles uh as they're being contained inside of this
really narrow orbit uh and so pandora is working to slow these things down prometheus is working to speed these
things up and they just kind of get gravitationally trapped in this nice little narrow band
so it's not a unique thing to our lagrange points this is this is orbital dynamics this is something that happens
whenever we're trying to balance orbits with gravity okay so we need to start thinking about
this in terms of forces then at this point what we've got here uh not to scale is
the sun over here on the left and we've got the earth over here on the right and in the middle hopefully it's coming
through well enough we've got this tiny little spacecraft uh and maybe it'll be a little bit more visible when i start
adding in some of the labels and so let's start thinking about some of the terms that we need for these gravitational formulations so newton's
gravitational laws require some mass and some distance and mass is pretty easy because mass is
just something that's inherent to each of these bodies and so let's say the sun well it's big
and important it can be number one so it gets mass m1 uh and the earth gets the mass m2 and our tiny little spacecraft
which has to be a lot smaller than the earth and the sun gets a mass of m3
and then we need to start thinking about some distances uh and i guess i probably should make clear that this is l1 that
we're looking through in this example again because l1 is maybe the more intuitive of of the five and so here's
our spacecraft at l1 in between the earth and the sun so distances uh well we know that we're
going to have the the distance from sun to the earth that's something that's pretty well known at this point and so
we've got the capital r uh that can represent distance from the earth to the sun and then we know that there's going
to be some distance between the center of the earth and where we want to put spacecraft to get nice gravitational and
orbital balance and this is what we're solving for we're trying to figure out what this distance is how far do we need
to park the spacecraft away from earth so that it stays there so that all of these points are are balanced and all of
these forces are balanced uh and so here's our our force
of the earth interacting with the spacecraft we've got newton's gravitational constant uh we've got the
the two masses and we've got the distance between the two uh and we've also got words of the sun interacting
with the spacecraft and so again gravitational constant m1 m3 and now the distance between the
sun and the spacecraft is the distance between the earth and the spacecraft minus the distance between or the
distance between the sun and the earth minus the distance between the sun and or the earth and the spacecraft too many
things to talk through uh so here's what our math looks like the equations are a little bit easier to talk through than
than saying sun and earth and satellite 20 times evidently but then also remember that there's this orbital
component and so there's there's this uh uh angular momentum that the the
spacecraft is going to have as it keeps trying to work its way around the sun and trying to pull its way forward
ahead of the earth so we're trying to balance out all of these forces we're trying to solve this
lowercase r and so then a bunch of fancy math happens i like this comic the uh
then a miracle occurs uh in the middle of this proof i'll put up a screenshot
of the math in a couple of seconds uh but what the solution eventually works out to is this
so our value for this lowercase r our value for this distance between the earth and the spacecraft that is optimal
for this gravitational balance is map uh is tuned into distance between
the sun and the earth so the the distance between the two gravitational bodies is important uh and then we've
got a cube root uh with a relationship of the mass of the earth m2 and 3 times
the mass of the sun m1 what this works out to is the the distance that you saw before for l2 uh
it's about one and a half million kilometers it's about 900 and some thousand miles that's how far we have to
get away from the earth in the direction of the sun to get this nice balance uh
and if you're familiar with some of the the other equations of physics this turns out to be the same equation that
we use for the sphere where the hill sphere is the region of
space where the earth's gravity or the the gravity of any planet has more influence over things in that
area than the the sun's gravitational field does which makes sense because we're looking for the balance point
between the gravitational field of the sun and the gravitational field of the earth it's natural that that balance
point would be right at the edge of the earth's overwhelming hillsphere influence
so this is a solution for l1 and if we want to get really really terminology specific about it uh this is one of the
five equilibrium solutions to the differential equations of motion for the circular restricted three-body problem
that's a mouthful um here's what that mouthful looks like in overall math form uh and again as i mentioned there are
several videos on youtube that talk you through all of this math in a lot of detail this one's using some slightly
different notation than i was just using so they've got this capital l which represents the same thing as the
lowercase r that we were trying to solve for uh they've got this lowercase r sub es which is representing the capital r
the the distance between the earth and the sun uh but what it eventually works on its way down to is the same thing
that we just saw in that equation that i had put up uh that whole big messy thing about the circular restricted three body
problem there's our solution so that's l1 and remember that we've got
four other lagrange points that we need to think through so where are these other lagrange points going to be well
we're gonna have some gravitational balance on the other side of the earth as well uh and so we just flip around
some of the signs you know now the the distance between the sun and the spacecraft is going to be the distance
between the sun and the earth and then the earth to the spacecraft uh and so we
have some r plus r's instead of r minus rs but what it eventually works out to
is the same exact formula which again makes sense because well we called it a
hill sphere this sphere of gravitational influence spheres are nice and round right they should be about the same size
uh going from the center out toward l1 as they are from the center out toward l2
and so the math eventually coincidentally works out that the distance to l2 is basically the same as
the distance to l1 all right l3 so l3 if you'll recall is
the one all the way over on the other side of the sun and as i was preparing this talk you know for the longest time
i was thinking it is the exact opposite point from the earth it is you know on the earth's orbit uh just on the
opposite side of the sun turns out that's not quite so true uh and there are a variety of depictions that are a
little bit inaccurate at showing where l3 is let's look at a couple of them
uh here's the first one i put up uh and here's l3 you can see the point is
definitely drawn right on the earth's orbit uh you know if you want to get you know pixel perfect maybe it's a little
bit further out than earth's orbit the center of the point is a little bit to the left of the orbit but you know the
point is drawn on earth's orbit and so it's trying to communicate that it's basically there
uh here's the nice uh topographic map of of the gravitational fields uh and here
our point definitely is on the outside of the earth's blue orbital ring it's just a little bit outside but they show
it definitely on the outside uh here's the the nice 3d rendering and here our
point is again definitely on the outside it's on the outside of this nice green ring that's trying to signify the the
earth's orbit but here was the the easy on the eyes version and this time l3 is well inside
this ring that represents the the earth's orbit or in this case just generally the orbit of the second mass
m2 and so which of these is correct is it right on the earth's orbit well i
already kind of hinted that that's not the case or is it a little bit outside is it a little bit inside is it a lot outside is
it a lot inside turns out that it's just a little bit inside and if you go through and you work out
all the math you get this very slightly different looking equation it still relies on all the same terms we're still
solving for a lowercase r in this case our lowercase r is the distance inside
of the earth's orbit so we've got this longer r which represents two times the
the distance between the earth and the sun because earth sun and then all the way over to earth on the other side but
then we have to come back a little bit because well both things are pulling the spacecraft to the left uh the earth is
pulling the spacecraft to the left the sun is pulling the spacecraft to the left uh and what it eventually works its
way down to is this again relationship between the distance between the earth and the sun uh and the masses of the
earth and the sun with some other constant thrown in turns out that this works out to about 163 miles so l3 is
163 miles inside of earth's orbit on the other side of the sun
so those were euler's contributions to this presentation now let's actually get to uh the lagrange contribution to this
presentation uh l4 and l5 well these are both it turns out equilateral triangles
uh and so we've got this distance r between the earth and the sun that's going to be the same distance r between
the sun and our spacecraft and because it's an equilateral triangle that's also going to be the distance lowercase r uh
between the earth and the spacecraft so we've got these two different points that are 60 degrees ahead of the earth
and 60 degrees behind the earth uh where we've got this this bigger broader
gravitationally stable region but these regions come with some caveats
uh and one of those caveats is about the the mass relationship between our three bodies but it turns out that if the the
mass of the earth was more than the mass of the sun divided by 25 which is
definitely not the case uh then we would end up with uh no l4 and l5 that are
valid the the mass relationship doesn't work out and these become gravitationally unstable point uh the
same thing goes for this relationship between the mass of the earth and the mass of our spacecraft uh if we ended up
launching a spacecraft that has a mass that is about three times the mass of the moon uh we can't put it at l4
because that's going to be a gravitationally unstable point at that point uh and this actually does come into play
in our solar system uh because the mass relationship between pluto and its moon
charon is less than that 25 to one and so our plutocheron system well it's got its l1
and it's got its l2 and it's got its l3 but because the mass of pluto is only eight times greater than the mass of
cheron well we fail this constraint and so we don't have l4 and l5 points that
are gravitationally stable in this system
all right uh hopefully you're all still awake you made it through the the math you made it through the forces let's get back to
talking about l2 and let's get back to talking about the james webb space telescope so we've got this model set up now we've
got sun sitting here nicely in the middle of the solar system we've got the earth not to scale a little bit further
off to the right we've got the james webb telescope sitting all the way out here at l2 again not to scale we're good
we just need to put the space telescope there and it's going to stay there turns out that it's a little bit more
complicated than that so let's go back to that big mouthful that i mentioned before the equilibrium solution to the
differential equations of motion for the circular restricted three-body problem there's two big problems with that
there's the the circular part and there's the three-body problem part so let's start with the circular part
the circular part automatically fails right from the very beginning because the earth's orbit is not a circle the
earth's orbit is elliptical and because the earth's orbit is elliptical there are some points in the
orbit when the earth is closer to the sun there are some times when the earth is further away from the sun that means
that inside of our nice balanced forces that capital r is going to change and
because the lowercase r that distance to l2 is dependent on capital r that means
that our location of l2 is going to change and so every single second the
earth is moving its way around the sun it's changing its distance to the sun slightly and so the location of l2 that
mathematically balanced point for l2 is gonna change essentially every single
second uh the second problem that we need to start thinking about is the three body
problem so if the entire universe was only made up of the sun and the earth and the james webb space telescope then
well at least we would pass that problem but there are complications and the first complication is that big annoying
right thing in the sky that we all hate unless we're doing the lunar observing programs uh it's about an 81st of the
mass of the earth and so you know 1.2 the mass of the earth but that's still a pretty big number and so it still has a
pretty big gravitational influence and sometimes it's on the same side of the earth as l2 and so anything that exists
at l2 is going to be pulled a little bit more toward the moon in this case but then sometimes well the moon is over
on the other side of the earth it's still pulling in the same direction but it's not pooling as strongly because it
is further away and sometimes the moon is over here which means that it's still pulling a
little bit to the left but it's also pulling a little bit forward in orbit and so we've got this extra messy thing
with the moon changing the gravitational balance we no longer have a three-body
problem we have a four-body problem and that breaks all of the solutions that we talked about with respect to these
lagrange points uh and it's not just the moon you know we've got other big things in the solar system as well we've got
this big planet called jupiter which has a huge amount of gravitational influence even though it gets no closer than about
400 million miles away and it can sometimes be pulling on the james webb space telescope or anything else that we
want to put at l2 in the other direction uh unless of course it's at a point in its orbit where jupiter is over here in
which case it's going to be pulling on the james webb space telescope or anything else at l2 in the other
direction and you know we've got other big planets as well that aren't going to have as much gravitational influence but still
can screw things up inside of our orbital dynamics and we've got this other planet venus
which is about the same size as the earth uh it's gonna be still pretty distant you know it doesn't get much
closer than 25 26 million miles uh but at the same time sometimes it's pooling
from a distance of 26 million miles and sometimes it's pulling from a distance of 160 million miles uh and so all of
these are going to be changing this nice gravitational balance you know solar system wide
and so two conclusions that we can draw from this immediately is well again the exact position of l2 is going to be
constantly changing because this distance between the earth and the sun is going to be constantly changing
and even if we put the james webb space telescope right at l2 that's not even the point of solar system scale
gravitational stability uh and so we're going to have a problem if we just put it at l2 and expect that it's going to
stay at l2 but let's say that we did let's say that we put it exactly at l2 how long is it
gonna stay there let's go back to our nice little plot of all of these different lagrange points
which we've now broken uh these points are obviously still going to be useful because why else would we put a 10
billion dollar space telescope at l2 uh well it turns out that l1 and l2 if
you put something there and you just left it alone it's gonna stay at that point for you know on the order of 23
days that's the the number that i seem to read the most often and so 23 days it's going to start drifting to the
point where you know you have to start firing some thrusters to be able to correct for it that's not great
and so we're going to have some problems if we just stick it right at l2 we're going to have to come up with some other solutions
if you're curious about some of these others uh the number that i saw most often for l3 is about 150 years
something's going to be stable there for l3 up for about 150 years and then it's going to start drifting a little bit too
far l4 and l5 well those are a little bit harder to define and so i'm just going
to give the the very very scientifically rigorous a while uh and this is because well again these
aren't well they they still are points but the the gravitational forces end up making them regions
and a good example of this is to look at the trojan asteroids that are co-orbital with the planet jupiter
here's a nice little nasa animation all of these green points are the location of these different
trojan asteroids before jupiter in its orbit and beyond jupiter in its orbit
uh you can see if you watch this animation carefully with respect to where i'm putting this dot uh jupiter is
moving closer and further from the sun because its orbit is also elliptical this is kind of trying to keep this line
between the sun and jupiter even in place uh and you can see that all of these things are still nicely captured
inside of l4 still nicely captured inside of l5 but they're moving around
uh and because these things are so small uh in in relation to the mass of the sun
in relation to the mass of jupiter they can stay there for a reasonably long
period of time but if we end up breaking that mass relationship if we try to put something
more massive at l4 or l5 we can have some problems
and those problems occasionally at least as far as scientific theories go end up with the creation of that annoying
bright moon up in the sky uh so one of the the most highly regarded theories behind the the formation of the moon is
that well there was this other planet thea and this other planet thea well it might
have stayed gravitationally balanced along with the earth's orbit at l4 or l5
for a while uh but a while is a pretty short amount of time with respect to the the overall time scales of the solar
system and so eventually it got to the point where it was a little bit less stable in its orbit and it was probably
you know a little bit closer to the mass of the earth than something tiny and so it probably failed that one to 25
relationship eventually they slammed together and well after everything settled down we had a new moon and we
had a slightly larger earth as well uh again
uh probably failing this relationship okay so james webb space telescope we
got to come back around to that the james webb space telescope as you saw in some of the animations earlier it
looks a little bit like this uh it's got this big sun shield on here at the bottom and the goal of the sunshield is
to shield the instrument from the sun and this is because well as an infrared
observatory it needs to keep its instruments cold and it needs to keep all of these other heat influences away
from interfering with its imaging and so here's something that i got from the the james bug space telescope website a
couple of months ago uh showing the temperatures on the sunshield side uh being fairly comfortably warm maybe a
little bit warm unless you like living in death valley uh but over here on the cold side we're close to
negative 375 negative 380 degrees fahrenheit um holding in celsius cold and kelvin as
well uh and this is going to be really important with respect trying to put this telescope somewhere close to l2 and
here's why uh again let's say that we put this telescope over here at l2 uh
and our telescope has a hot side facing the sun and it has a cold side facing away from the sun
uh but jupiter ends up being over here and so jupiter is going to start tugging on our james webb space telescope craft
and it's going to start pulling it away and away and away from l2 and again once it gets so far away from l2 that it just
kind of generally leaves the region we're going to lose the telescope unless we turn the telescope around and
start firing its thrusters to get it back over to l2 that puts the imaging
side of the telescope on the hot side of the telescope uh and as my little emoticon shows that
makes astronomers bad so we don't want to do that and so the solution actually turns out to be
the james webb space telescope is positioned a little bit closer to the earth than l2 and the idea here is
basically well if here is our sun here is our earth and here is our l2 point if we put the space telescope on the earth
side of l2 and over time the earth's gravity is going to win this battle it's going to start falling down the gravity
well in the direction of earth we can fire the thrusters and we can start pushing it back towards l2 a
little bit and as long as we don't fire that thruster for too long we can start pushing it back toward l2 and we can
wait for gravity to start drifting it back a little bit and that works out really nicely for us because then we can keep the cold side
of the telescope away from the sun and we can keep doing science
uh there's another reason why we probably don't want to put a telescope exactly at l2 uh and that's the fact
that a lot of our spacecraft are still solar-powered and if we put it right on
the other side of the earth from the sun uh well it's not going to get quite as
much solar power it turns out that l2 is a little bit outside of the earth's umbra so this is still going to be a
penumbral eclipse but it's going to be enough to really cut down on the amount of power that we can get to the space
telescope so we don't want to put something exactly at l2 because well then it's not going to get any sunlight
or it's not going to get much sunlight so the final solution ends up being a
really nice pair of orbits uh that are called halo orbits and lina joule orbits
assuming that i'm pronouncing that second one correctly and what basically ends up happening is we can design
orbits that orbit around l2 even though there's nothing at l2 even
though l2 is just this gravitational location in space where there's no mass
we can design something where the forces balance out just nicely enough so that
james webb and any other mission that we put at l2 can stay there for the long
term uh by just generally orbiting around this location and if you want another view of what
those look like because they were a little bit abstract in the visualization sense you know imagine an orbit that
looks kind of like this where it's drifting to the left it's drifting to the right it's drifting forward it's
drifting backward a little bit uh there's a really great youtube video with a visualization produced by nasa
that shows this orbit in 3d uh but i was never able to actually get it embedded successfully in powerpoint
so that's really the bulk of the presentation as far as james webb goes but i want to talk a little bit about
some of the other uses of the lagrange points before i really step away and take a couple of questions the first
thing to talk about is the fact that well l1 and l2 are really popular as far as space missions go which makes sense
because we can put spacecraft away from the earth in a reasonably gravitationally stable place
and let them stay there for long periods of time uh and so here's just a summary
of the space missions that are currently at l1 and currently at l2
we've got soho which is off observing the sun we've got discover which occasionally takes really nice full
earth images uh in in photos we've got gaia that's doing a lot of uh photometrics uh and trying to determine
distances to stars sitting out at l2 we've got james webb sitting out at l2 but this is just active missions
we can also think about some past missions uh and so there are a variety of missions that either for part of
their mission or for the entire mission were sitting out at l1 or l2
uh and then we've got planned missions which are not quite as easy to find images of because they're planned
missions uh and so i had to use a little bit of a futuristic spacecraft design to show these missions we've got lots and
lots of things that are planned for l1 and l2 missions coming up in the future
uh what else might we find at these lagrange points well the first thing that we can start thinking of is
asteroids because these l4 and l5 points are really really convenient with
respect to keeping things and trapping things that are of low mass with respect to the other two masses uh jupiter far
and away is the the planet that has the most of these captured asteroids at their lagrange points um but we have a
couple that we found for other planets as well we found an asteroid at the the sun venus l4 we found a couple of
asteroids at the earth sun l4 uh we found a bunch of them all the way out at neptune uh earth trojans it turns out
despite the fact that they're nice and close to us because they're at our l4 and l5 points while they're they're
tough to find both because of the small size and because of the proximity to the sun we can only see them you know a
little bit before sunrise a little bit after sunset and then they start to drop down into the atmosphere and we start to
have problems locating them the big surprise that i came up with here uh is that we don't know of any
saturn trojan asteroids uh and so i went off and i tried to do a little bit of research and i found this paper called
where are the saturn trojan and it turns out that when they did some of their mathematical modeling what they
found is that the earth saturn or the sorry the sun saturn l4 and l5 points
turn out to be really gravitationally influenced by jupiter because saturn's orbit is so large and l4 and l5 are so
far away from saturn and because jupiter is so massive well jupiter starts
tugging things out of those l4 and l5 semi-stable positions so too bad for saturn but it turns out
that saturn also has some other interesting lagrange relationships uh so here is saturn and two of its
moons that you can go out and see with a reasonably sized telescope tethys and diony
and it turns out that both of these moons have co-orbital moons at their l4
and l5 points uh and so we've got telesto which is orbiting a little bit ahead of tethys you know 60 degrees
ahead of tethys and we've got calypso that's 60 degrees behind tethys and they're co-orbital uh the same thing for
helene and polyduceus uh with with the other moon with diony um and so the the
fact that uh saturn doesn't have any trojan asteroids well let's not be too sad about it because these are the only
instances that i'm aware of in the solar system that we've discovered co-orbital moons orbiting planets uh and to have
two pairs of them is is really incredible uh what about the earth and the moon
system we said that any two massive pairs of of bodies that are in orbit around each other
have these lagrange points and it turns out that there are things that are kind of similar to the zodiacal light called
cordolevski clouds that exist at the the earth moon l4 and l5 positions basically
think of it as a bunch of trapped dust that exists 60 degrees ahead of the moon's orbit uh and 60 degrees behind
the moon's orbit they get a little bit tricky to see because well they can be blended in with some of the zodiacal
light and well the moon is going to be pretty bright anytime you can see them above or below the horizon uh and so
this is something that was only recently confirmed as a discovery only a couple years ago even though it was
mathematically suspected since i think sometime around the the 60s uh other potential uses for these
lagrange points coming up in the future aside from some of those other space missions that we've talked about
uh so arthur c clarke the sci-fi author uh one of the things that he had proposed in some of his other works was
this idea of putting spacecraft at geostationary orbit but it turns out that he also came up with its idea of
putting some futuristic spacecraft at l2 or at least orbiting around l2 of the
earth moon system where the logic is we've got something orbiting around earth moon l2 uh that means that we can
send signals off to this satellite sitting all the way out there and then that satellite can reflect those signals
can bounce the signals to potential space missions on the far side of the moon
well it actually has become a reality because china landed a lander on the far side of the moon and they have a relay
satellite which is orbiting around or was orbiting around l2 and maintaining communication between this lander which
is otherwise not able at all to contact earth and the earth command centers
interesting couple more so the b612 foundation uh the idea behind this
foundation is that they really want to try to find potential earth impactor asteroids that are coming from the
direction of the sun well that's pretty difficult because the sun is big and bright and so if
something is coming from that direction toward earth we're going to have a hard time seeing it so what they've proposed
is to put a sentinel satellite at the sun venus l3 point so that it can
look away from the sun it can look outward toward the the distant reaches of the solar system and look for
something that could be potentially on a collision course with earth of course if this is going to be on the
opposite side of the sun from venus it's also going to be on the opposite side of the sun from earth
and so we're going to need another one of those relay satellites maybe off at l4 or off at l5
which can bounce signals back and and handle the the necessary communication
uh a satellite at the earth sun l3 can really do some good things for helping
us monitor solar storms on the other side of the sun uh and this is especially true with solar maximum
coming up as we saw in the the earlier presentation so if there's going to be an active region on the other side of
the sun it would be pretty great if we had the ability to have a satellite on the other side of
the sun which is something that the the stereo spacecraft were doing uh for a while but they weren't actually
positioned at l3 they were just in orbits that were drifting the the spacecraft toward the other side of the
sun over time again this is going to be something that requires us to have another communication satellite to be
able to talk to earth from the the other side of the sun but there's another benefit to potentially
putting a satellite at the the earth sun l3 and that is enabling communication with
mars uh whenever mars is on the other side of the sun from earth so right now uh we lose contact with our
rovers we lose contact with our orbiters around mars uh for about a week or two every year during solar conjunction well
if we had a spacecraft that was on the other side of the sun all the time whenever mars drifts over there we can
still communicate uh through several bounces now this time with all of our emissions to
mars uh another interesting idea and now we're starting to get really far out there really starting to dream big so
the whole idea of terraforming mars gets a little bit difficult because mars is too small to really retain a good
atmosphere and it also doesn't have a magnetic field uh that would also help to keep that atmosphere in with with the
solar wind constantly blasting mars so what's a really out there solution let's
take a giant magnet and let's put a giant magnet at sun mars l1 and this
giant magnet can create a big enough magnetic field to start to to prevent the the new uh terraformed atmosphere of
mars from from being pushed away uh and so that would uh enable a little bit better with with future space missions
with future terraforming space future uh colonization uh there's also this l5 society and the
l5 society was founded to promote some of these space column colony uh ideas
that gerard o'neill created uh and so l5 well it's it's named after l5 it's it's
a proposed location along with l4 uh for putting something like a huge rotating
space habitat uh this is what's called a stanford taurus uh and so the idea would be you've got this big rotating ring
and people can live on the inside of the ring the ring spins to to give us a nice gravity simulation uh and because it's
nice and and balanced at the earth moon l4 and l5 points well we can put things
there and let them stay there for for long periods of time without needing any extra corrections without needing any
extra gravitational influence the very last thing that i'll mention is this whole idea of the interplanetary
transport network and the idea here is that we can make use of these lagrange points to
efficiently move through the solar system with very very little energy used imagine putting a spacecraft at the the
sun earth l2 and then just giving it a little kick and this little kick needs to be timed perfectly but if you time it
perfectly this spacecraft can then just start drifting through space and eventually get trapped at say the the
sun mars l2 or the sun mars l1 and then it can start uh going through
any other course corrections that it needs to and well you end up with a very cheap
propulsion method but also a very long propulsion method uh to get a probe out
to some other point in the solar system uh and some of these ideas have been tested the the genesis solar wind sample
return mission actually used some of these ideas uh trying to uh come up with
an efficient way of transitioning that spacecraft to where it needs to be uh for its mission
so i've definitely talked longer than i promised but well we've got to take advantage a little bit of
the fact that the the early program went a little bit short and so i guess at this point i'm happy to take any
questions that anybody has okay
yeah i have a i have a comment to make john if we are going to understand
the james webb space telescope it is imperative that we understand
at the beginning the lagrangian points and their history and their use and john
gave us a full description and discussion of this which is really
fundamental to our understanding of what we hope to get out of the webb telescope
i first heard of the lagrangian points when i began working with jean shoemaker and carolyn shoemaker
they were about to begin a study of the lagrangian l4 and l5 asteroids
uh in those near those points of jupiter but in the summer early summer of 1990
while gene and carolyn were in australia i just i photographed and discovered an
asteroid it turned out to be the first one at the lagrangian five point
of mars orbit we decided to name that one eureka
which has since been transformed into the name of my telescope that scotty has provided me with and that's
one of the reasons why it's such a very special telescope named for an extremely special asteroid and today we thank you
for a very extremely special presentation thank you john thank you i i really appreciate that
comment um yeah thanks um
other comments was uh uh jeff wise uh watching on youtube he says that was uh that was outstanding
joe schmuckatelli says john you crushed it thank you so much um
norm hughes says that was an amazing presentation on the complexity of lagrange points
thanks i i definitely appreciate all those comments i'm uh i'm i'm still uh you know trying to adapt to the ability
to accept so much praise um but i i do appreciate them all thank you
well you walked them through it and and uh so that was that was fantastic
yeah i definitely learned a lot more than i actually knew which was not much thank you that was an excellent
presentation yeah and and i learned a lot putting it together as well it was it was a
pleasure to be able to present it for a second time well we're glad you did thank you so
much does anybody else uh here have any questions uh presentation i knew enough to be
dangerous about the whole discussion and that really brought in more understandable type
usage thank you all right well thank you and john again
thank you that was that was that i learned a lot it's kind of overwhelming because i never really thought about it
yeah there's a lot to comprehend here you get you start to get some ideas so new possibilities of space travel um
and communication you know so it's very cool it is it's amazing when you really stop and think about it it's really amazing i
actually thought that if something set at l1 or l2 it would stay in that orbit i did not really think about the drift
and the gra the pole you know so that's amazing yeah when when i was first putting this
presentation together for the the roanoke group um you know i was i was thinking at the beginning how am i going
to talk for more than 15 minutes about lagrange points and uh well you just heard me ramble for an hour like i do to
my classes so there's a lot there that i i probably could have included that i didn't
yeah well thank you thank you so much we really do appreciate that
so all right i am going to go over my share my screen and go over the answers
to the questions and thank you everyone for the answers
there we go all right how wide is the cosmic bubble that surrounds earth it is one thousand
light years wide michael overracker got that
how many seconds has the hubble space telescope been operating since january 1st 2022
1 billion seconds that's amazing and josh kobach
will be receiving a calendar what astronomer coined the name aurora
borealis well that was galileo galilei in 1619 and barbara brown got that one
so she will be receiving a calendar so thank you again everybody for your answers we really appreciate it
and someone from the astronomical league will be in touch with you before long
so tonight i'd like to thank scott roberts our broadcasting genius i keep that up
there and david levy we always appreciate all of the readings from
david they are amazing thank you david and carol org astronomical league
president thank you for being here and showing us and telling us what's coming up in the league
and john winskovic thank you that was an amazing presentation that really gets you
thinking all right and join us again for friday
may 13th at 7 pm eastern daylight time we will have dr
jessica novello she will be speaking on the cryovolcanism in the solar system the
coolest geological process so we will have dr
jessica novello with us so please join us on friday may 13th
7 pm and yeah it will be exciting we have had
some excellent speakers tonight included really we've learned so many different things
about everything you know i think that's what i really like about being on zoo
is you can reach out so much further and everybody specializes in so many different areas
and we get the benefit of being able to invite them along so thank you john again i appreciate it
and thank you carol david and scott you guys are amazing thank you for putting up with
this every month thank you there was a question uh towards the end
um uh people were wondering wondering if they could get a copy of your
presentation john um but uh you know
where could where can people find out more information from you yeah i'm i'm definitely happy to share
the slides um from from my experience sharing them earlier when when some of the roanoke
folks asked they're they're a bit too big to attach to an email um but i'm definitely happy to put up something
like a google drive link uh and so you can you can definitely reach out to me uh the easiest way is maybe just going
with my full name john wenscovich gmail.com uh or you can definitely contact me through through the rest of
the folks who are here on the call uh and and i'm happy to share them i guess the other possible constraint uh
well constraint probably isn't the best word but uh you saw the presentation the presentations were very image based and
then you got my voiceover um if you're just going to stare at the slide you lose that voice over but hopefully you
retain enough to to get the the general idea well the other way is you can re-watch
this program on the astronomical league's facebook page where it's permanently recorded so
uh that would be um an easy solution as well so
because without the voiceover um well you explain so much so yeah
definitely okay
anybody got anything else i think that's it
all right well thank you again to everybody on the program and thank you to everybody that's watching we really
appreciate it and we will be back on may 13th please join us then
thank you
yeah do something with that count because everybody would like to say goodbye [Laughter]
the new look there yes all all right thank you everyone thank you
thanks everybody on monday uh with more programming so thanks for watching and take care and
thank you to the astronomical league take care thank you scott thank you bye-bye bye-bye
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