Night Sky of Alpha Centauri: Sol as a Bright Star

[swampwiz]

I finally got around to watching the movie "Avatar", which takes place in the Alpha Centauri system. I was thinking that a great little scene between the 2 main characters (i.e., the paraplegic Earthling and the Centauri woman) would have been looking up at the night sky and seeing Sol as a bright star. Of course, to do this properly, the astronomical maps would need to be done from the POV of Alpha Centauri, and it seems that this could be a fairly easy computation to come up with. And with the exception of the close stars, Sol's region should be very similar to the celestial-sphere antipode of Alpha Centauri.

EDIT: OK, the Wikipedia article for Alpha Centauri has such a view, with Sirius almost a double star with Betelgeuse. :)

https://en.wikipedia.org/wiki/Alpha_Centauri#/media/File:Sky-from-alpha-centauri.jpg

 

[fresh_42]

I assume you mean the solar system by sol. There are some artificial impressions of how the sun looks on other planets
https://www.iflscience.com/sun-looks-like-every-planet-solar-system-36853
a real photo of Earth seen from Mars
https://climate.nasa.gov/climate_resources/89/earth-from-mars/
or a real photo of the Sun from Mars
https://solarsystem.nasa.gov/news/925/what-does-a-sunrise-sunset-look-like-on-mars/

The sun seen from any other star is probably just a tiny point in the sky. Maybe I misunderstood you with all that Avatar stuff.

 

[DaveC426913]

 

[swampwiz]

I assume you mean the solar system by sol. There are some artificial impressions of how the sun looks on other planets
https://www.iflscience.com/sun-looks-like-every-planet-solar-system-36853
a real photo of Earth seen from Mars
https://climate.nasa.gov/climate_resources/89/earth-from-mars/
or a real photo of the Sun from Mars
https://solarsystem.nasa.gov/news/925/what-does-a-sunrise-sunset-look-like-on-mars/

The sun seen from any other star is probably just a tiny point in the sky. Maybe I misunderstood you with all that Avatar stuff.

Yes, of course Sol is our Sun, and would be a point of light just like Alpha Centauri is to us (OK, Sol would be slightly less bright). I was more interested in what the star region around would look like.

 

[phyzguy]

I think the OP's question is what would a star map look like from Alpha Centauri. Most of the distant stars would look about the same, but the positions of the nearby ones would change. In what constellation would the sun fall? I've never seen such a map, but it would be very interesting. We have the knowledge to build a map like that, but I don't know if anyone has ever done it.

 

[Vanadium 50]

I've never seen such a map

Plenty on the Interwebs.

The sun would be in Cassiopeia (and the brightest star in that constellation).

 

[snorkack]

Extending the W. Between Cassiopeia and Perseus actually.
What is "night" for you?
How strong is light scattering in Pandora´s atmosphere compared to that of Earth?
Are you talking of PoV of Alpha Centauri A, or of B?

 

[phyzguy]

The difference in the appearance of the night sky between A and B would be negligible.

 

[snorkack]

The difference in the appearance of the night sky between A and B would be negligible.

In terms of the constellations, yes (which is not the case with Proxima!)
The sky of both A and B will feature the local zodiac... the same for both.
Unlike the Earth zodiac (the distance to Sun varies only by 3%, so the luminosity and angular speed of Sun only by 6%), the Alpha Centauri zodiac features luminosity and angular speed varying over tenfold. And the epoch of a position on the zodiac is opposite for A and B.
See a drawing of Alpha Centauri orbit:
https://en.wikipedia.org/wiki/Alpha_Centauri#/media/File:Orbit_Alpha_Centauri_AB_arcsec.png
Unfortunately, what this drawing does not have is constellations. I have seen images of Alpha Centauri sky of fixed stars but those in their turn miss out the orbit.
Now, the epoch of Avatar is 2155. Note that 2155, like 2075 and 1995, is epoch of apoapsis - for both stars but opposite constellations.
Alpha Centauri orbital inclination is 79 degrees... which means that the zodiac must pass within 11 degrees of Sun.
The orientation of orbit is quoted like B is further from Sun than A is, at apoapse? That is, at apoapse A should see B at more than 90 degrees from Sun, while B should see Sun less than 90 degrees from A, but not at the close approach?

 

[swampwiz]

I think the OP's question is what would a star map look like from Alpha Centauri. Most of the distant stars would look about the same, but the positions of the nearby ones would change. In what constellation would the sun fall? I've never seen such a map, but it would be very interesting. We have the knowledge to build a map like that, but I don't know if anyone has ever done it.

I would imagine that to the Alpha Centauri observer, Sol would appear in a constellation that would be similar to the one that is at the antipode of Centaurus. And yes, the near stars (e.g., Sirius) could be in a very different from far stars (e.g., those of Orion). Interestingly, Sirius is practically on top of Betelgeuse, rather than being well south of it.

 

[snorkack]

I would imagine that to the Alpha Centauri observer, Sol would appear in a constellation that would be similar to the one that is at the antipode of Centaurus.

That´s been discussed. Cassiopeia. Between Cassiopeia and Perseus (extending the W)

And yes, the near stars (e.g., Sirius) could be in a very different from far stars (e.g., those of Orion). Interestingly, Sirius is practically on top of Betelgeuse, rather than being well south of it.

And even there, the constellations directly along your parallax baseline - Centaurus/Circinus and Cassiopeia/Perseus - have limited changes, compared to the constellations far from the baseline.
You do have some changes, besides the trivial ones (Sun and α Centauri). In Cassiopeia from Sun, the brightest stars are:

1. α. 2,24 - 2nd point of W. 228 ly
2. β. 2,28 - 1st, end of W. 54 ly
3. γ. 2,47, but var, as bright as +1,6. 3rd, middle of W. 613 ly
4. δ. 2,68. 4th. 99 ly
5. ε. 3,35. 5th - the end of W (towards Sun). 442 ly
6. η. 3,46. In the middle of 2nd section of W - between α and γ. 19 ly

Note the proximity of η. Moving away from Cassiopeia would do little to the shape of W, apart from shrinking it, but η would fade compared to the others.

 

[Vanadium 50]

I would imagine that to the Alpha Centauri observer, Sol would appear in a constellation that would be similar to the one that is at the antipode of Centaurus

Discussed and named multiple times in this thread.

Um...are you reading the answers to your questions?

 

[snorkack]

That´s been discussed. Cassiopeia. Between Cassiopeia and Perseus (extending the W)

And even there, the constellations directly along your parallax baseline - Centaurus/Circinus and Cassiopeia/Perseus - have limited changes, compared to the constellations far from the baseline.

Note the proximity of η. Moving away from Cassiopeia would do little to the shape of W, apart from shrinking it, but η would fade compared to the others.

Sorry. Did not realize but it is not the case.
The relative position of η between α and γ would stay unchanged if we moved directly towards or away from η.
But this is not the case. The position of Sun is off the end of W, some distance from η.
Which means η would move appreciably relative to α and γ.

 

[collinsmark]

According to my calculations, The Sun (Sol) would be right at the edge of the Heart Nebula (IC 1805) when viewed from the Alpha Centauri system.

A big difference is the Heart Nebula and Soul Nebula would look smaller, angular wise. These nebulae are about 6500-7500 light-years from Earth, but about 10,800-11,800 light-years from the Alpha Centauri system. As such, they would appear correspondingly smaller. [Edit: nevermind. The nebulosity would appear roughly like it does here on Earth.]

The position of the Sun relative to the background stars, as seen from the Alpha Centauri system, would be right around where Marker 1 is in the above image. (The image above is as seen from Earth; there might be minor parallax differences not reflected in above image as when viewed from the Alpha Centauri system.)

[Edited to correct a minor distance error in calculations (4 ly vs 4000 ly)]

 

[phyzguy]

These nebulae are about 6500-7500 light-years from Earth, but about 10,800-11,800 light-years from the Alpha Centauri system.

How can that be? The sun and Alpha Centauri are only 4 light years apart. It's like saying that Los Angeles is 3000 miles from New York, but 6000 miles from Brooklyn.

 

[collinsmark]

How can that be? The sun and Alpha Centauri are only 4 light years apart. It's like saying that Los Angeles is 3000 miles from New York, but 6000 miles from Brooklyn.

Oh, you're right. I was off by a factor of 1000 again. oops.

I'll edit my post with corrections.