Possible 'Goldilock's' Planet Discovered

[El Mahdi]

Could_'Goldilock's'_Planet_be_just_right_for_life!

Awesome!!!

 

[Thornir Alekeg]

It is interesting. It leads me to questions for some of the physics and astronomy folks here.

They say the planet orbits a dwarf star that will live longer than our sun. Would that star have once been hotter and is now a dwarf star at the latter end of its life cycle? If so, then wouldn't any chance of water or atmosphere be much lower?

What about other radiation? Being that much closer to the star, would there be higher radiation or is it all proportional to size and visible light intensity?

The article states that the planet does not rotate much, so one side is almost always, the other dark. How do rotation and orbit correlate? I'm just thinking about our moon, with a rotation and orbit that are both about 28 days, so we always observe the same face from Earth. With a 37 day orbit, if the planet did not rotate at all then wouldn't it have a light/dark cycle of 37 days? Perhaps the definition of rotation is based only upon orientation to the sun, so the moon rotates on a 28 day cycle in relation to the sun, but not at all in relation to Earth?

 

[Umbran]

They say the planet orbits a dwarf star that will live longer than our sun. Would that star have once been hotter and is now a dwarf star at the latter end of its life cycle? If so, then wouldn't any chance of water or atmosphere be much lower?

Gliese 581 is an "M Type" star, more colloquially called a "red dwarf". This is not a star at the end of its life, but just a star that started out small to begin with (this one is about 0.3 solar masses). The bigger a star is, the hotter it is in the middle, due to the increased pressure. the hotter it is, the faster it burns through nuclear fuel. So, big stars don't last long, small stars last longer.

What about other radiation? Being that much closer to the star, would there be higher radiation or is it all proportional to size and visible light intensity?

How much "radiation" you get on the surface of the planet depends on many things, perhaps most importantly on the nature of any magnetic field the planet has, and the planet's atmosphere.

Yes, the planet is closer to the star, but it's a cool, placid star.

The article states that the planet does not rotate much, so one side is almost always, the other dark. How do rotation and orbit correlate? I'm just thinking about our moon, with a rotation and orbit that are both about 28 days, so we always observe the same face from Earth.

Yes. It's called "tidal locking", and the situation for this planet is just like for our Moon - one face always toward the object it is orbiting.

It may be best to think of this not relative to the Sun or Earth, but relative to the distant stars (which don't move appreciably over this kind of timescale). Set up a telescope on the Moon, and have it point directly overhead. As the lunar day goes on, the view the telescope gets sweeps across those distant stars. 28 days later*, you're pointing back at the same chunk of distant sky you started pointing at.



*I'm leaving out some details, but this works for first approximation

 

[RangerWickett]

With a 37 day orbit, if the planet did not rotate at all then wouldn't it have a light/dark cycle of 37 days? Perhaps the definition of rotation is based only upon orientation to the sun, so the moon rotates on a 28 day cycle in relation to the sun, but not at all in relation to Earth?

As Umbran said, plus to clarify, there isn't a light-dark cycle. The same spot on the planet would constantly have the same illumination.

 

[Merkuri]

Aren't Venus and Mars in the "Goldilocks" zone of our own sun?

Being in that range doesn't automatically equal life, it's just more likely than other planets outside that range. They're talking about this on the news like we found ET, talking about how the civilization could live within the "twilight" zone on the planet between the day and night sides.

That does get my mind churning to think about what life might be like on a planet that doesn't rotate, though... I might file that away for a future campaign setting.

 

[jonesy]

Aren't Venus and Mars in the "Goldilocks" zone of our own sun?

Mars is partially on the outer edge half the time, mostly outside half the time.

Venus is clearly out of the 'habitable zone'.

 

[Joker]

Let's hope there was life there and it's all extinct now so we can get their oil.

 

[jonesy]

Let's hope there was life there and it's all extinct now so we can get their oil.

I'd rather hope there was life who'd come up with perfect fusion and were willing to trade for it.

 

[Umbran]

Aren't Venus and Mars in the "Goldilocks" zone of our own sun?

That depends on who is doing the calculating.

Being inside the Habitable Zone does not guarantee that you'll have liquid water, and being outside the HZ doesn't mean you cannot have liquid water. The HZ only marks an area where it is highly likely there'll be liquid water on the surface.

It is also important to note that since stars are not static, the Habitable Zone does not stay put forever. As the star ages, its properties change, and the location of the HZ will change.

That does get my mind churning to think about what life might be like on a planet that doesn't rotate, though... I might file that away for a future campaign setting.

Two notes, for sake of completeness:

1) Technically, a tidally locked planet does rotate. It rotates so that it's day and year are the same length, so the sun always remains in the same position relative to the surface.

2) Technically, they don't know that Gliese 581g is tidally locked. It is likely that something the size of a rocky planet of that mass, that far from a star of that size, will be tidally locked, but it isn't guaranteed.

 

[jonesy]

That depends on who is doing the calculating.

Being inside the Habitable Zone does not guarantee that you'll have liquid water, and being outside the HZ doesn't mean you cannot have liquid water. The HZ only marks an area where it is highly likely there'll be liquid water on the surface.

It is also important to note that since stars are not static, the Habitable Zone does not stay put forever. As the star ages, its properties change, and the location of the HZ will change.

Totally agree. Europa is a good example of other possible options.