# Positions of stars as seen from Mars-different than from Earth?

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1. Aug 11, 2012

### KenJackson

Positions of stars as seen from Mars--different than from Earth?

I'm reading a novel that says , "On Mars the stars seemed a bit out of place, not in their correct position."

Could that be true?

I suspect that if you disregard anything within our solar system, the stars would be so far away that the distance between Earth and Mars would be insignificant. So the stars as seen from Mars would look exactly the same as from Earth. Only the positions of the planets would be different.

Am I right or is the novelist?

2. Aug 11, 2012

### phinds

Re: Positions of stars as seen from Mars--different than from Earth?

You are correct. There is probably a measurable difference but so tiny that it would NOT be seen directly by the human perception system.

3. Aug 11, 2012

### Staff: Mentor

Re: Positions of stars as seen from Mars--different than from Earth?

Yes, they would differ by a measurable amount. However even the closest star, Proxima Centauri, only has a parallax measurement of 0.768 arcseconds. The maximum parallax you would see from Mars would be about 1 arcsecond, well below what would be required to notice it visually without measuring instruments. For comparison, the full moon has a diameter of about 0.5 degrees. There are 60 arc minutes in 1 degree, and 60 arc seconds in 1 arc minute. So we are talking about a shift in position of 1/1,800th of the full moon. And Proxima Centauri isn't even visible to the naked eye. It's slightly further away companions are however.

4. Aug 11, 2012

### KenJackson

Re: Positions of stars as seen from Mars--different than from Earth?

Thanks, guys.

Though I did just think of one other thing. Mars and Earth probably do not spin on parallel axes. So Polaris wouldn't always point north. And if you're used to specific constelations rising and setting a particular way, that part would probably be different.

Maybe that's what the novelist meant.

5. Aug 11, 2012

### Staff: Mentor

Re: Positions of stars as seen from Mars--different than from Earth?

Perhaps. I expect it is more likely that the author just didn't know what they were talking about.

6. Aug 12, 2012

### phinds

Re: Positions of stars as seen from Mars--different than from Earth?

Yep, that would be my guess too.

7. Aug 12, 2012

### Jimmy

Re: Positions of stars as seen from Mars--different than from Earth?

That's possible, but in this context the stars are more than a "bit" out of place. What novel is this from?

The north celestial pole of Mars is in Cygnus. See:

8. Aug 13, 2012

### KenJackson

Re: Positions of stars as seen from Mars--different than from Earth?

There's a link for the novel in the original post. The indie author confesses it's his first. I had assumed that since some of it took place on Mars that it was a scifi novel. But it's not. It's just a novel which partially takes place on Mars. That's disappointing since I prefer hard scifi--where the author uses science doesn't violate the known laws of science. Even worse, it contained misconceptions about God and religion. But even with all that, it had a non-obvious plot which held my interest.

But I think you guys are right. The author probably instinctively knew the stars would not be exactly the same from Earth and Mars so he added an ambiguous line as cover.

Cygnus, huh. I was going to ask, but didn't get around to it.

9. Aug 13, 2012

### Jimmy

Re: Positions of stars as seen from Mars--different than from Earth?

Ah, I missed the link. Thank you. I really need to style those so that they stand out better.

10. Aug 14, 2012

### twofish-quant

Re: Positions of stars as seen from Mars--different than from Earth?

Also, one piece of software that I would recommend for this is "celestia". You can travel to different places and see what the stars look like.

One thing to do is to go to Alpha Centauri. The constellations look quite different, but they are still mostly recognizable.

11. Aug 14, 2012

### Jimmy

Re: Positions of stars as seen from Mars--different than from Earth?

^ I love Celestia. It looks quite interesting if you leave the constellation outlines on and exit the solar system at a fair clip.