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Star-hopping a way home for a superman; astronomers needed

  1. May 21, 2013 #1

    chasrob

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    I'm writing a novel which has as a protagonist a super-powered being, like in the comics (only he is the sole such critter in the universe). Like Superman he has the ability for flight through space, but he cannot take any matter, baryons, with him. I'm hoping some astronomy experts could help me out in my narrative.

    He has recently acquired those powers, and discovers he can go FTL... at just about any multiple of c that he requires. OK, he starts by launching himself out into interplanetary space and finds out that it's relatively easy to find your way about, all the planets being so bright and in one plane, the ecliptic.

    Going interstellar and intergalactic is not so easy, he surmises, since he can't take any maps, or holographic projections, or whatever with him. So he consults with some professional astronomers about nearby space and our galaxy. Me being an amateur astronomer for--let's call it decades--I decided on a star-hopping scheme for the MC to follow to get back to Earth. Ie, go to a star, look for another, hopefully red and 1st or second magnitude, and hop back to Sol.

    A while back I discovered this neato web page, Distant Worlds Star Mapper, where you can choose any star in the database and it will pull up a map of the sky from the pov of that star (or even a point in space).

    OK, so this guy, being, entity, whatever, wants to journey far enough out to gaze on the whole Milky Way. He doesn't have super-vision, just above-average vision in our visible range. Since at that distance he cannot see Earth, much less the Sun, he wants to plan his way back with help from the scientists. With help from the Star Mapper, here's what I have:

    He works on his plan, memorizes, and engages FTL; travels to a point 100,000 light years out, above the galactic plane, gazing down. He's floating there, sees what he came for, the magnificent spiral in view. Now he wants to get back, timely if possible. That's where my plan comes in.

    Red supergiants--very luminous, can be located at great distances, with the added plus that they stand out because of their color. 6 Geminorum is an M1Ia red supergiant with a galactic latitude of 188 deg., which means it's anti-center of earth. AIUI, it's on the edge of the MW disc with the added advantage that it's in an open cluster other red supergiants. Is it the only cluster of reds on the edge of the disc? Dunno, but clusters of red sg's are rare I think. So I'll say it's the only one. ;)

    The thing is, from 100k ly out, he's looking that amount of years into the past, and supergiants can change drastically in that time. So he cruises closer. 6 Gem located, he draws a mental line to the galactic core; two/thirds of the way out is the Orion Spur, on the core-ward edge of the Perseus Arm. I would think it would stand out, and he zips above it.

    The Gould Belt with its bright stars should be obvious, with red cM Betelgeuse in a cluster with white sg's like Rigel.

    From Betelgeuse, no bright red stars that would help, but white Bellatrix is mag 1.1 and the Orion Nebula is nearby so it's next.

    Bellatrix... Alhena, gamma Gem, is kinda dim at 2.7, but Antares appears close-by and is 1st mag. It forms a near perfect triangle with Spica and Alhena, so the target Alhena would be the next jump.

    Alhena... Arcturus, red but at 2.5, is between bright red Antares and white Castor. Could be memorized and located.

    From the skies of Arcturus... first magnitude Sirius forms a triangle with bright Rigel and Capella, with a orangish Aldebaran inside the triangle shining as bright as Arcturus.

    Sirius... Sol is a bright 1st mag between Vega and Altair, a leg of the Summer Triangle, which appears the same from Sirius.

    The protag would memorize each step before he leaves, which should be easy since he's a wannabe actor. Seem like a good method of finding his way back?

    Apologize for the length. Thanks for any help.
     
  2. jcsd
  3. May 21, 2013 #2

    Bandersnatch

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    In my opinion, he'd get hopelessly lost, but see for yourself.

    Try running this freeware planetarium software:
    http://en.wikipedia.org/wiki/Digital_Universe_Atlas

    It is one of the best ones, data-wise, yet it only contains good data for stars in a ~3000 ly radius(cf.: almost all the stars you see in the night sky are within 1,5 kly radius).

    Fly away from the solar system to the limit of the data range(where there's little stars), and see if you can find your way back by hopping bright stars from there. I don't think you'll be able to do it, but maybe it's just me.

    Adding to the simple problem of telling one star from the other amongst myriads of alike-looking points of light, are the following obstacles:

    1.Stars have peculiar velocities. They move a bit relative to each other. The program simulates this, for those stars with known velocities.
    As he flies around the galaxy, the stars will appear to be rearranging their positions, making orientation even more daunting.

    2.Distance measurements have large error bars for far away stars. For example we can't tell if Betelgese is 400 or 800 ly away. Good luck memorising the position of stars that might not even be where you think they are.

    3.Before he even starts worrying about the above, the protagonist needs to recognise the galactic neighbourhood he needs to get back to. But we don't really know how the Galaxy looks like exactly. The information about arms etc. comes from various indirect measurements, but it's hardly enough to draw an accurate "artist's impression" of the structure.
    It might look right, but it might be way off, and the latter seems more probable.
    What he could do instead, is triangulate his way back by memorising the positions of the local cluster galaxies.


    Go ahead and try playing with the planetarium. It's a very powerful tool, but I should warn you: the user interface is not the best, so you better read the manual carefully.
     
  4. May 21, 2013 #3

    Office_Shredder

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    He starts accelerating towards the stars, everything blue shifts into oblivion (I have no idea what happens when he gets past c) and he's flying blind
     
  5. May 21, 2013 #4

    mfb

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    I think with some preparation, it would not be impossible.

    The Andromeda galaxy and the galactic disk are easy to see if the eyes are adapted to darkness, they allow to determine the own orientation in space everywhere close to our galaxy.

    4 of the 5 main stars of the southern cross are more than 200 light years away, and visible within at least 500 light years. If you can find those, you can estimate your own position. Basic angle measurements are possible with a human (or Superman's) body, or anything you can find on planets.


    Within ~10000 years (the distance needed to see the galactic disk), those movements are within ~1 light year. And you cannot resolve this position shift from 10000 light years anyway. I assume that Superman travels superluminal, but not backwards in time relative to the galaxy or the cosmic microwave background. If time travel gets involved, things get complicated.

    You could explore this first. Parallax measurements are easy if you can just travel the Alpha Centauri and check the apparent position of the star there.
     
  6. May 21, 2013 #5

    chasrob

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    If he tried flying around until he spotted earth, yeah, he'd get lost fast. That's why he's planning carefully first. Probably get lost anyway.

    The Digital Universe Atlas a great link; I'm downloading the manual now. A quick glance on their page--I don't think their database is any larger than the Star mappers', just stars with reliable trig parallaxes from Hipparcos, the Yale Catalogue, Gliese's... the thing is, you go to Betelgeuse and a bright star in its sky may actually be a nearby dwarf like the sun. Bright in its sky, but too dim to be included in any catalogue used by the DUA or star mapper. It could mess up his memorized version of B's sky and his search for the next star in the trek, Bellatrix, the other foot of Orion (Rigel being one).

    Orientation would be a big problem, you're right. However, I have him able to maintain his orientation when he goes FTL and after he stops. So he would start by flying several earth radii above the equator, his head up toward the north, then engage FTL. When he stops, hopefully at his target star, his orientation would match the map he memorized from the internet. Unless he makes the effort to turn or spin in place, his orientation remains the same. :smile:

    That's true for stars beyond a hundred parsecs or so. Other methods rather than parallax can determine star's distances to within 20%, I heard. For the purposes of my story, the latest estimates will have to do.

    I think orienting yourself when you're laying off the Milky Way would be the easy part. Say he starts by going to a point near the earth and locates galactic north, in Draco I believe. He zips out to 100k ly's and his view should roughly match
    this view, eg. You're right, it's theoretical, but like the distances, I'll have to go with what I have.

    It's going to be rough for him, being basically stripped of all aids (including his clothes). :smile: It's going to be experiment, experiment experiment; since he never sleeps he can do that 24/7
     
  7. May 21, 2013 #6

    chasrob

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    As I've written it, that's basically what happens. :smile: He engages FTL, his vision is blasted by fierce white light. Nothing but white.

    He disengages, normal vision returns instantly. It's point and shoot, he sees a star, planet or whatever, turns on the juice, counts to himself, stops, and hopes he's somewhere near his destination.:tongue: Needless to say, he has to experiment a helluva lot, starting "small" with the planets and solar system, get a feel for how hard to "push" it.
     
  8. May 21, 2013 #7

    chasrob

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    Interesting, try to approach earth from another direction? If he's skimming across the galactic disc, how can he locate them? They're distinctive from earth, but from 5000 lys above? They wouldn't form any cross from that perspective, would they? Three of the four are blu-white giants, fairly common even in the Gould Belt, indistinguishable from many other stars... O thru G classes. That's why I picked a red supergiant, they're rare, distinctive, and can be seen from thousands of ly's away.


    I don't deal with the time travel aspects of FTL; I have enough issues to worry about:devil:. As I mentioned in the above post, he's flying blind, and dares not travel very far without trying to determine, for one thing, his approximate velocity.

    One chapter I have has a section on early trials with this flight capability. He sets up a fortified building on the far side of the moon. Fortified because, long story short, going interstellar involves some very destructive side effects.:devil:

    Inside the structure he has an electronic timer, built for vacuum, with a big button on top:smile:. He gets a map of Sirius' sky and the location of Sol, memorizes it, makes a trial flight to Sirius (going easy on the pedal) and back to get the journey down. Now he's ready.

    He presses the button, the timer starts, and off he zooms to Sirius. He arrives there, finds Sol and returns to Luna. Hits the button to stop the timer. Since the distance to the nearby Dog Star is well known, high school math will give him his velocity at that rate of "push". He stops and starts a lot on the way there, tries different "pushes", etc. Now he can point at further targets like Betelgeuse and try to stop in the vicinity.:tongue:
     
  9. May 22, 2013 #8

    mfb

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    Well, those stars are useful close to the sun only. It allows to find sun from any star within ~500 light years. Remember the orientation of those 4 stars for that target, find them, travel in steps of a few LYs, and you can find sun based on that.

    Hmm.... maybe we could just use Andromeda as reference and the stars as backup only. Travel 100 ly in the opposite direction, remember how some nice constellations look like. Repeat that a few times. Afterwards, increase the step size. To go back, just head towards Andromeda again.
     
  10. May 22, 2013 #9

    chasrob

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    Maybe instead of the Southern Cross, use the constellation Orion. Its stars are all bright supergiants and giants, far enough away that their orientation doesn't change. For treks even a few hundred lys from the sun. Use it for orientation too? The hunter right side up?

    I didn't think of using galaxies. Maybe use M33 too, for triangulation? Come to think of it, wouldn't M31 look the same from just about any point in the MW? It's so far away, though yeah if it didn't matter what destination you went to and you went exploring opposite (towards Crater?), you could at least find your way back. Starting and stopping, stuttering jumps, and hoping you don't overshoot! Since he's flying blind like Shredder said.

    I think I'd have him spending a few hundred man-hours in the solar neighborhood within 10 parsecs, getting a hang on estimating his velocity, before he wanders out very far into the spiral arm:wink:

    Even if he gets that down, it's like Bandersnatch said--he's going to get lost, and real easy.
     
  11. May 22, 2013 #10

    chasrob

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    I just used the Star Mapper and ticked the map to show the view from alpha Crucis towards the sun, and, as amateurs know, the "W" of Cassiopeia is flipped upside-down into an "M" from that star. Within it lies the sun, 'tho dim at mag 9.8. Funny thing is, none of the stars of the asterism is the same as from our sky. My protag could use them to point him to earth but those "M" stars are really too faint at 4th magnitude.
     
  12. May 23, 2013 #11
    Right idea, wrong galaxy. Andromeda nebula is a small and nondescript nebula of magnitude +3,4. There are other such nebulae, such as Praesepe, magnitude +3,7.

    We in Milky Way are lucky to have much better pointers!

    The Magellanic Clouds.

    Big Magellanic Cloud is magnitude +0,9, spans 11x9 degrees, at 33 degrees from Milky Way disc. Small Cloud is magnitude +2,7, spans 5x3 degrees, at 44 degrees from Milky Way.

    At 160-200 thousand lightyears, these brightnesses, sizes and latitudes stay within narrow ranges over the 80 000 or so lightyear width of Milky Way. Arriving at unknown location within the Milky Way disc, with full 4π sr field of view, scan the bands of 30-50 degrees from Milky Way on both sides of Milky Way to spot the Clouds.

    Whan you do, and also have completed the rest of the scan, you have found out a lot:
    you know that you are in Milky Way because, for example, the satellites of Andromeda Nebula would be different is size, brightness and position relative to each other
    you have identified the poles of Milky Way
    and you have one direction pointer.

    Because of the size and brightness of the Clouds, it is hard for anything to mix them up. Say, Presepe - at 600 lightyears it is a nebula because the brightest star is +6,58 and therefore invisible. At 400 lightyears, Presepe would be +2,7 like Small Magellanic Cloud, but it would betray identifying details... the brightest stars would be +5,58 so noticeable, the size at about 2,5 degrees across would be noticeably smaller and thus more concentrated than Small Cloud, it would probably not be elongated the same way... and it would not have the same relationship with Big Cloud.

    Generally, the only nebulae found far from Milky Way disc are globular clusters. The other foreground nebulae - diffuse nebulae, supernova remnants, planetary nebulae and open clusters - are all in the disc. And open clusters can only be unresolved nebulae in Milky Way. If you are close enough that they are far from Milky Way, you are close enough to resolve them into stars.

    Thus, the foreground nebulae which can end up in the same bands as Magellanic Clouds can be globular clusters outside disc or gas nebulae in the disc. And Magellanic Clouds would be still there, in their right position, brightness, shape and size. The worst combination might be if a foreground nebula actually covers much of the Clouds... it would not obscure them, but can outshine the parts of Clouds directly behind.
     
  13. May 23, 2013 #12

    mfb

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    The Magellanic clouds are interesting to find the own orientation in space, but their large apparent size is bad for a precise navigation. You need features as narrow as possible to get your path right.
     
  14. May 23, 2013 #13

    chasrob

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    Ok, you've located what galaxy you're in, and maybe your orientation. How do you go about finding a particular G2 dwarf that will only stand out, naked eye, if you're within 5 parsecs?

    With no instruments, what do you use, finger widths, like do-it-yourself amateurs with an 8" Coulter?

    If he's a few AUs out from a candidate yellow star, how could he tell whether he's one AU from a G2 dwarf or hundreds from a G2 supergiant?

    I was going to say that what galaxy would be the easy part, but apparently M31 is also claimed to be a barred galaxy. Although I can't see any evidence of it from photos.
     
    Last edited: May 23, 2013
  15. May 23, 2013 #14

    mfb

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    Travel 1 AU orthogonal to the star, see if it changes its position in the sky.

    "What galaxy" is easy, as the superhero does not plan to leave the vicinity of the milky way.
     
  16. May 23, 2013 #15
    Looking from the disc, Milky Way bar was hard to spot. The Magellanic Clouds are better identification of Milky Way - Andromeda Nebula´s satellites would look different.

    If you look at the sky images, the centre of Milky Way is obvious when you know that the centre itself is hid by the Great Rift. So, once you have found the Magellanic Clouds and the Milky Way centre, you can verify which sector of Milky Way you are in.

    Next... Near Sun, the globular cluster 47 Tucanae is conveniently near Small Magellanic Cloud. Can you use it to reach solar neighbourhood within a few hundred lightyears?
     
  17. May 23, 2013 #16

    chasrob

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    The way I have to protag written, he has two gears--

    1. "pedal" press for zero to 100,000 miles/second: comes in handy for interplanetary travel; however, only the only rate he's computed (at first) is the top end, 100k mi/s. Anything in between, he has just guesses at his velocity, using planets, their surface features, the distance to the moon, etc. He could go at pedal-to-the-metal in this gear for... 930 seconds?

    2.FTL: arbitrarily, expontentially high multiples of c; good for interstellar, intergalactic, intra- and inter- multiuniversal travel. Works as I outlined above.

    Ergo:Say he stops at a target star. The only way he can gauge his rate of travel is use 1st gear and push it to the max.

    Doing that on the million or so stars visible to his naked eye every time he stops, could take a bit of time:smile:
     
  18. May 23, 2013 #17

    chasrob

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    Do you mean try and home in on the earth from 47 Tuc? It's 17,000 ly's out. The sun is... 19th mag. with millions of similar points of light in the foreground and back ground. Remember, his vision is human norm and he has nothing--no maps, telescopes, binocs...

    EDT: Yeah, he knows earth's general direction, but... he can't even see Sol. The way I figure:he has 20/15 vision. A lot of people have eyes this good, eg many baseball players are around 20/12!

    In vacuum of space, I read somewhere that you could see roughly 5 mags deeper. I also read once where during WWII, amateurs in the desert southwest of US could pick out 8th magnitude stars because of the blackout.

    So reasoning he could see 8+5 ... 12 or 13th mag. From 47 Tuc Sol is almmost 19th. Invisible. He has to move closer and hope he's in the right direction!
     
    Last edited: May 23, 2013
  19. May 23, 2013 #18

    Vanadium 50

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    This doesn't seem too hard - it'll take memorization, but it won't be impossible.

    As suggested, first get M31, M33, the LMC and the SMC all in about the right orientations relative to the galactic center and be in the galactic plane. This is probably within 1000 ly of Earth.

    Next, find Alnitak, which will be the brightest or second-brightest O-class star in the sky, and it will be near several other bright blue stars: the Orion OB1 association. Go there. Betelgeuse will be a 1st magnitude red star. Fly there, and keep going a similar duration. Now turn 90 degrees and go about half that far again, until the constellation of Orion looks about right.

    Now you're within about 100 ly of Earth. The brightest orange star in the sky is Arcturus. Go there. Find Sirius. Near Sirius are two bright yellow stars. Try the closer one first.
     
  20. May 23, 2013 #19

    chasrob

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    You're on to something here, M31 and the galactic center. Looking at Ottewell's Astronomical Companion, M31 and the galactic center are nearly opposite in the sky from earth. Arranging yourself with one on one side and the other on the other would place you in the right half of the MW at least. But the galactic center... how would you recognize it naked eye from anywhere in the disc? The globular cluster M22 is close to the center, use it and M31? M31 is so far away its brightness would not change much I would think, but the GC would maybe?

    From there memorize a star hopping scheme.
     
  21. May 24, 2013 #20
    How would you identify a specific cluster, near the centre where various globular clusters concentrate?

    But enjoy Milky Way panorama, from Earth:
    http://4.bp.blogspot.com/_R_fTYHVWAzI/Sw2sakiORVI/AAAAAAAAA2M/Qp4odFv2twA/s1600/milky_way.jpg

    1600 pixels, so it should not have details too small for naked eye. It is distorted like any globe would be, because is spans whole sky.

    It is centered on Milky Way centre... but the brightness and the dark rift should indicate where the centre is.

    I´m not quite sure where Andromeda is - but the Magellanic clouds are unmistakable. In projection, I think they are about right angle from the centre... so if they are not, you are in a wrong sector of Milky Way, and you can figure out which.
     
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