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

[chasrob]

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.

 

[Bandersnatch]

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.

 

[Office_Shredder]

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

 

[mfb]

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.

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.

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.

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.

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.

 

[chasrob]

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

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).

As he flies around the galaxy, the stars will appear to be rearranging their positions, making orientation even more daunting.

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.

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.

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.

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.

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). It's going to be experiment, experiment experiment; since he never sleeps he can do that 24/7

 

[chasrob]

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

As I've written it, that's basically what happens. 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.

 

[chasrob]

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.

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.

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.

I don't deal with the time travel aspects of FTL; I have enough issues to worry about. 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.

Inside the structure he has an electronic timer, built for vacuum, with a big button on top. 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:

 

[mfb]

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.

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.

 

[chasrob]

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.

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

Even if he gets that down, it's like Bandersnatch said--he's going to get lost, and real easy.

 

[chasrob]

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.

 

[snorkack]

Hmm... maybe we could just use Andromeda as reference and the stars as backup only.

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.

 

[mfb]

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.

 

[chasrob]

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.

 

[mfb]

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?

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.

 

[snorkack]

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?

 

[chasrob]

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.

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

 

[chasrob]

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?

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!

 

[Vanadium 50]

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.

 

[chasrob]

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.

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.

 

[snorkack]

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?

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.

 

[chasrob]

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.

Great photo, thanks. Andromeda is there, pretty distinctive, a small slash on the left below the MW. Andromeda and the clouds are both south of the gal. plane, IOW, but on opposite sides of the sky from the viewpoint of the MC when he's in the sun's sector, I'm thinking.

How he could use them to try and zero in close enough to make out the sun, or like Vanadium 50 posits, Betelgeuse, or Arcturus, is what I don't quite understand. He has no precision instruments for such measurements that are needed, esp. when the objects are on the opposite sides of the sky.:tongue:

For instance, if he memorized the dark rifts of the center and its star clouds from the earth, then went trekking and found they didn't match, it would only tell him he wasn't in the Earth's neighborhood. Not how to get the vista to match, correct?

 

[snorkack]

For instance, if he memorized the dark rifts of the center and its star clouds from the earth, then went trekking and found they didn't match, it would only tell him he wasn't in the Earth's neighborhood. Not how to get the vista to match, correct?

One obvious pointer is, for example, the angle between the direction to Clouds and the direction to Milky Way centre. Since the Clouds are known to be far away, if he travels ahead towards the Clouds then the centre is left further behind to his side - if he travels away from Clouds, the centre will be further forward.

The next pointer would be 47 Tucanae. You can see it just to the left of Small Cloud.
While Milky Way centre is 25 000 lightyears away, relatively diffuse object and needs measurement of a large angle, for Sun 47 Tucanae is fortunately very near Small Cloud. Identify 47 Tucanae. Then just remember that it is a foreground object relative to Clouds. If 47 Tucanae is closer to Milky Way compared to Small Cloud, he is too far and should travel a bit towards Magellanic Clouds and vice versa. Likewise, from Sun 47 Tucanae needs to be slightly towards the Milky Way centre from Small Cloud. If it is too far, he is too far from Milky Way centre; if it is too near or actually in front of Small Cloud or on the wrong side of Small Cloud (away from Milky Way centre, towards Big Cloud) then he is too near Milky Way centre and should travel away from it.

The angular distance between (somewhere in) Small Cloud and 47 Tucanae is just 2 degrees, so this should be easy to measure. If he can get the picture of Small Cloud and 47 Tucanae right within precision of, say, half a degree then, because the distance to Sun from 47 Tucanae is about 14 000 lightyears, he will be within 125 lightyears of Sun... and may try to identify nearer pointers.
47 Tucanae with Clouds should look like this:
http://upload.wikimedia.org/wikipedia/commons/f/f3/Magellanic_Clouds_%E2%80%95_Irregular_Dwarf_Galaxies_.jpg

 

[Vanadium 50]

But the galactic center... how would you recognize it naked eye from anywhere in the disc?

Why do you need to be in the disk? Fly out of plane - look around, get your bearings, and fly back into the plane?

 

[chasrob]

One obvious pointer is, for example, the angle between the direction to Clouds and the direction to Milky Way centre. Since the Clouds are known to be far away, if he travels ahead towards the Clouds then the centre is left further behind to his side - if he travels away from Clouds, the centre will be further forward.

The next pointer would be 47 Tucanae. You can see it just to the left of Small Cloud.
While Milky Way centre is 25 000 lightyears away, relatively diffuse object and needs measurement of a large angle, for Sun 47 Tucanae is fortunately very near Small Cloud. Identify 47 Tucanae. Then just remember that it is a foreground object relative to Clouds. If 47 Tucanae is closer to Milky Way compared to Small Cloud, he is too far and should travel a bit towards Magellanic Clouds and vice versa. Likewise, from Sun 47 Tucanae needs to be slightly towards the Milky Way centre from Small Cloud. If it is too far, he is too far from Milky Way centre; if it is too near or actually in front of Small Cloud or on the wrong side of Small Cloud (away from Milky Way centre, towards Big Cloud) then he is too near Milky Way centre and should travel away from it.

The angular distance between (somewhere in) Small Cloud and 47 Tucanae is just 2 degrees, so this should be easy to measure. If he can get the picture of Small Cloud and 47 Tucanae right within precision of, say, half a degree then, because the distance to Sun from 47 Tucanae is about 14 000 lightyears, he will be within 125 lightyears of Sun... and may try to identify nearer pointers.
47 Tucanae with Clouds should look like this:
http://upload.wikimedia.org/wikipedia/commons/f/f3/Magellanic_Clouds_%E2%80%95_Irregular_Dwarf_Galaxies_.jpg

Yep, I think that's the way to do it, with that photo of SMC and 47 Tuc. Super! Although the small cloud is somewhat extended. Maybe too, get some hand-width measurement between the two before he goes. I'm thinking you could match all the angles of that photo but still be thousands of lys away from the sun's position.

 

[Vanadium 50]

Also, once he finds Sol, how does he find Earth? Stars don't twinkle in space. I think this is where a knowledge of astronomy is more important.

 

[chasrob]

Fly directly at the sun until its about the size it is in our sky. Be sure to shift into first gear--pedal to the metal at 100,000 mi per sec, for the last few million miles. Look for the brightest few points of light. The bluish one would be earth.

 

[Vanadium 50]

Not so simple. What if the Earth is behind the sun? Or between you and the sun? Spotting a planet in space is not so easy, since stars don't twinkle, and I doubt that from 100 million miles the Earth is particularly blue.

I think what you really need to do is to find the ecliptic (why I said you needed some astronomy knowledge), get to the right orbital radius, and follow it around the sun until you spot the Earth.

 

[chasrob]

I read that the Earth shown blue from Voyager, billions out.

Unlikely you ending up there, but if the Earth is hidden, you're on the ecliptic. All the brightest half dozen "stars" are planets. Move toward one and get them all in sight.

 

[Bandersnatch]

I will keep advising on trying your ideas out in planetarium softwares. For example, running Celestia, you can see that at 1 AU the Earth is hardly distinguishable from background stars, but circling the Sun for a while will inevitably expose planets as the "wandering stars". That is, they will visibly change their positions w/r to the background stars as your protagonist moves around the Sun.
Recognising the Northern Star(Polaris) and the Southern Cross constellation will help him identify the plane in which he should look for planets, but he should be able to do without.

 

[mfb]

Too see colors with a human eye, the object needs some minimal brightness - this is easy for images of Voyager, as the cameras there are not human eyes and your computer monitor has sufficient brightness.

As seen from the sun, Earth is one of the brightest objects in space and the (visible) moon is nearby. That should be easy to spot.

 

[chasrob]

You're right, I've been observing the sky with my 8" Dobsonian on-and-off for 30 years and I can't tell the difference in color of an 0,B,A,F, or G class star. The only color I can discern in star-points is a faint orange tinge with M class or K's like Aldebaran. Which is why I chose stars like Betelgeuse and 6 Gem for the MC's star hopping.

Hmm. Has anyone calculated the H magnitude of earth?

 

[snorkack]

Also, once he finds Sol, how does he find Earth? Stars don't twinkle in space. I think this is where a knowledge of astronomy is more important.

That should be easy!

The starry sky is exactly the same for hundreds of AU from Sun. So all light dots that do not belong are planets (or nearby asteroids or comets).

Stay out of the ecliptic, and Sun cannot obscure any planets, nor can planets be in conjunction. Within the few AU of Sun, the light spots of negative magnitude are Jupiter, Venus, Earth, Mercury and Mars if nearby.

And Earth is the only one with a bright, conspicuous satellite.

I'm thinking you could match all the angles of that photo but still be thousands of lys away from the sun's position.

Half a degree is the width of Moon disc - with quite some detail for normal naked eye vision. It also is 9 mm at distance of 1 m.

If the Superman can measure the distance between 47 Tucanae and Small Cloud with half degree precision, then since the distance to 47 Tucanae is 14 000 ly away, you can only be 125 ly away from the line through Sun.

You can be a bit further along this line, but this would mean being off the Milky Way plane. The asymmetry of Milky Way and its rifts would give away this... so matching the intersection of the plane and the line gives the solar neighbourhood with error of maybe 200 ly.

The next pointers? I suggest Orion and Taurean Pleiades. Any others?

 

[chasrob]

[...]
Half a degree is the width of Moon disc - with quite some detail for normal naked eye vision. It also is 9 mm at distance of 1 m.

If the Superman can measure the distance between 47 Tucanae and Small Cloud with half degree precision, then since the distance to 47 Tucanae is 14 000 ly away, you can only be 125 ly away from the line through Sun.

You can be a bit further along this line, but this would mean being off the Milky Way plane. The asymmetry of Milky Way and its rifts would give away this... so matching the intersection of the plane and the line gives the solar neighbourhood with error of maybe 200 ly.

Right, he could get that angle down by that method. Wouldn't it help if also he estimated the http://upload.wikimedia.org/wikipedia/commons/f/f3/Magellanic_Clouds_%E2%80%95_Irregular_Dwarf_Galaxies_.jpg of 47 Tucanae and a line extended through the large and small clouds? Say, "47 Tucanae must be at a 10 o'clock position when the clouds are oriented horizontally"?

 

[snorkack]

Yes. He should estimate the angle, because this gives him his location along second direction.

I wasn´t sure what the baseline should be to measure the angle of Small Cloud-47 Tucanae from. My idea had been a line parallel to Milky Way. The line between Big Cloud and Small Cloud is another option, and a third obvious possibility is to use the elongation axis of Small Cloud.

Or maybe use all third, to check his naked eye impression for errors. After all, both Clouds are somewhat extended smudges.

 

[chasrob]

So, nobody's too impressed with my OP scenario using stars? Y'all have some great ideas, but the protag is... well, before he manifested he was a starving actor. Limited, IOW, with regard to most things involving geometry and trig. Plus according to the "laws" of the story he emerged from FTL naked, with no tools--sextants or whatever--to help him, except the Mark I eyeball.

BTW, some errors I made--

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).
[...]
6 Geminorum is an M1Ia red supergiant with a galactic latitude of 188 deg., which means it's anti-center of earth.

I meant longitude of course. The Milky Way has a lot of arms, partial arms, and spurs, but it would be simple, I would think, to extend a straight line from that supergiant cluster to the center of the galaxy, then look for a certain spur 2/3 of the way out from the center.

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.

Double checking, Bellatrix is ~190 ly from Betelgeuse and ~250 from Earth while the nebula is 1500 from the earth, so it should be behind Betelguese if you're there looking at Bellatrix, correct?

If so, what does the protagonist do from there?