Error in Today's APOD writup (02 May 2007)

[eteq]

he red dwarf star Gliese 581 rises through clouds above a calm ocean of its planet Gliese 581c.

Whoops! It's almost certainly tidally locked... there would never be a sunrise (except maybe at the very beginning of the planet's life).

[BMAONE23]

well It is just a picture and some poetic liscense was taken. Being tidally locked, the sun would be perpetually rising but never setting from this particular vantage point. This would likely be the only longitude where liquid water could exist. The noon longitude would bake and probably boil and liquid water while the midnight longitude would be in permanent ice age. The temperate longitudes would be a windy and stormy environment due to the world wide temperature changes.

[cosmo_uk]

I don't like the purple, but hey!

[Dr. Skeptic]

he red dwarf star Gliese 581 rises through clouds above a calm ocean of its planet Gliese 581c.

Whoops! It's almost certainly tidally locked... there would never be a sunrise (except maybe at the very beginning of the planet's life).

As in our solar system, the planet could be tidally locked to an object(s) other than its Sun.

[orin stepanek]

I think it is May 2 APOD! Anyway here is link. http://antwrp.gsfc.nasa.gov/apod/ap070502.html
Orin

[Doum]

If that planet have a big enough moon (Mars size may be), then it wont be tidally lock. Like the earth is not tidally locked because of its moon. I read somewhere that because of the moon, the earth is still having a revolution. Otherwise it would have loose more of its revolution if not all (Being then tidally locked). Can that be confirm by an astronomer? I want to know if its true.

[craterchains]

Tell that to Venus, , it has no moons and is not tidally locked.

I think this artist is more woo wooo than artist.

[cosmo_uk]

after looking at her homepage I'd have to agree with you crater

http://www.artofkaren.blogspot.com/

I like the one of torvill and dean ice dancing on a frozen planet!!!

[BMAONE23]

On the subject of Venus, doesn't it rotate very slowly and backward to its orbit with respect to the direction of Earth's orbit? I've also heard that the same side of Venus always faces Earth.

[NoelC]

It's a nice bit of art. A bit abstract, perhaps, but I don't think it's trying to come across as perfectly photo realistic.

Can someone here please explain why the planet should be likely tidally locked? That's being said a lot, as though it's almost a given. Just curious. Is it because it's fairly close to its star?

Oh, and isn't Gliese 623 supposed to be a binary star system, with an even cooler/smaller star orbiting at 200 million miles?

-Noel

[iamlucky13]

Right. It's very close to the star, so over time it should slow into tidal lock. However, it may not have had enough time to do so (unlikely) or may be disturbed by the other two large planets in the system. Also, it's quite possible that it may be in a resonant lock like Mercury, which due to the eccentricity of it's orbit has a 3:2 lock...3 days every 2 years. In this case it would have a sunrise every couple of weeks. One source said Gliese 581c has an eccentricty of nearly 0, another said a very pronounced 0.3. I'm not sure which to trust or neither.

By the way NoelC, that link is for Gliese 623, not 581. Here's 581:
http://en.wikipedia.org/wiki/Gliese_581.

Would earth be tidally locked without it's moon? I think it's far enough away to keep spinning for a while. Not to mention the moon is a more dominant slowing force than the sun.

[NoelC]

Oops, thanks for catching that number mixup on my part. Guess I'm getting old... All Glieses are not created equal!

-Noel

[makc]

I think it is May 2 APOD

edited the topic

[Dr. Skeptic]

On the subject of Venus, doesn't it rotate very slowly and backward to its orbit with respect to the direction of Earth's orbit? I've also heard that the same side of Venus always faces Earth.

Earth and Venus are locked into a 3:2 tidal resonance.