Gliese 581 and the habitable zone (APOD 26 Apr 2007)

[ta152h0]

http://antwrp.gsfc.nasa.gov/apod/ap070426.html

is it possible to annotate Gliese 581 ?

[makc]

It is right in the middle of the pic. This image is centered at Gliese 581, you might use it for reference.

p.s.: for everybody's record, there's related thread in Cafe.

[BMAONE23]

The funny thing is, the descriptive text for the APOD says "The FAINT, unremarkable star centered in this skyview..." but is it actually the brightest star in the center of the image?

[ta152h0]

that is exactly what confused me. I was going to share the photo with some people and found I couldn't really answer the basic question here.

[NoelC]

One thing about the Digitized Sky Survey... Stars that look bright in DSS images are really very faint.

Bright stars - e.g., those you could see with your naked eye - in the DSS look like Alnitak (Orion's leftmost belt star) near the top of this image:



-Noel

[iamlucky13]

Fascinating. Gliese 581 is only 20 light-years away, but has an apparent magnitude of only 10.56. Far too dim to see with the naked eye. In comparison, Polaris is 430 light-years away with a magnitude of 1.97.

[didjshaman]

Although the temp is right for water now, this is after the solar lifecycle has largely expended itself. At the sun's peak and then later thru its giant phase, don't you think any surface water would have boiled off and been swept off planet by powerful solar winds? Or perhaps with so much iron content, a sufficient magnetosphere exists to have sheltered the planet...? I would think that a planet so close to a sun would have nothing but blasted surface minerals.

[BMAONE23]

It might also be the core remnant of a hot jupiter that has long since lost its gaseous outer layers.

[iamlucky13]

In general, red dwarfs don't have a giant phase because they don't have enough mass to initiate helium fusion. They also burn relatively cooly and most have main sequence times longer than the current age of the universe, so it's not likely this planet has experienced anything quite that cataclysmic. Red dwarfs also have a weaker stellar wind.

However, Gliese 581 is a variable star, and the frequent fluctuations in output may affect the survivability of life on the surface of the planet.

Also, because of it's cooler temperature, it isn't nearly as bright in the visible range compared to our sun, but mostly in the infrared. Even from it's close orbit daylight would be relatively dim. The bonus is reduced amount of UV radiation, which of course is dangerous to us.

It's possible the weak stellar wind may be something of a liability, as it appears our system's solar wind plays a role in slowing down high energy cosmic rays from elsewhere in the galaxy.

[BMAONE23]

Iamlucky13,
I guess I glossed over the "Red Dwarf" fact but you are right, being a red dwarf star the planet is likely NOT a core remnant of a gas giant. Further, the "Red Dwarf" link indicates in all likelihood, the planet, given its orbital period and therefore close orbital proximity to the star, is likely Tidally Locked to its star. Much like the Earth Moon system and would therefore create a habitat that might not be conducive to the formation and longevity of higher life forms.

[aichip]

Given the size and mass for this planet, we can see that it would have about 2.2 times our surface gravity. This would mean that it can still hold a thick atmosphere in all likelihood, even if it were an old world.

It also probably has a large core and would have volcanic activity that would replace gas lost to space, so this would provide some shielding to radiation and even if it were tidally locked (which is very likely, considering) then it would still have atmospheric heat transport to help even out the temperatures.

It might be a world where a perpetual band of sunset surrounds the planet while one face is hot and the other very cold. Glaciation on the back would then be the order of things, and most of the life, if any, would probably be most at home in the ring of twilight.

Imagine a place where the sun was a swollen, dim red ball about ten times the diameter of the full moon, where it was always evening, and winds circulated away from the day side in large storms. This would be a world where everything was dragged down under the pull of gravity, and spectacular, stormy skies would be normal, if there is indeed any significant water.

The other possibility for its diurnal cycle is that it is in resonance, giving a day that is actually a couple of weeks long, and daylight would march around the world, thawing the ice and bringing things to life in a brief period like the rains in the Kalahari, or spring in Alaska.

Of course, this is pure speculation, but it brings some spice to the science of astronomy to see where such worlds might actually exist.

[makc]

It might be a world where a perpetual band of sunset surrounds the planet while one face is hot and the other very cold. Glaciation on the back would then be the order of things, and most of the life, if any, would probably be most at home in the ring of twilight.

Imagine a planet that is still rotating a bit longer than it takes to go around the star. Then poor creatures would probably have to constantly run away from heat into the cold darkness



But what about plant-like stuff? Their plants can't have any roots, or else they will be burned in no time, so these green fellows are also running around like in above pic, eating dirt and soil, or what? Oh wait, they would have to carry soil around with them, or else they would have nothing to eat after one circle.

[Doum]

If that planet have a big moon in orbit around it then it will still be rotating and "might" have plenty of life like earth. If the earth didnt have a moon it would also have stop its rotation with time (Like venus i suppose) but it didnt because of the moon. Read that sumwhere. I just dont remeber where.

[NoelC]

Given that there may be conditions to support life as we know it (or similar), there are two possibilities:

1. Earth developed life first, and so the new planet is no more than a potential destination to us. It will be a pain to have to deal with heavy gravity, but it should be extremely interesting to explore.

2. Life developed long ago on the newly discovered planet, and the intelligent beings have since moved away from using electromagnetic radiation. So there they sit, surfing their fiber optic internet and listening to net radio, and are blissfully ignoring our SETI attempts to communicate with them. Or not. Probably likely they'd still have radio receivers.

Were any of the attempts by SETI to communicate with this planet more than 40 years ago? If not perhaps there's a reply message on the way back as we speak.

-Noel

[BMAONE23]

Does this system sit anywhere near the location of the "WOW" signal?

[makc]

It will be a pain to have to deal with heavy gravity...

Why don't we just attach some nuclear rocket super engines to planetary equator to spin it up a bit and therefore lower the gravity?

[rigelan]

umm. . . Lower the effective gravity. . .

[C0ppert0p]

Metals are also something else red dwarfs don't have much of. I can't see a planet with a metallic core forming under those conditions.
Little or no metallic core yields an extremely weak magnetosphere or none at all. No magnetosphere suggests no protection against solar radiation and since this one is a variable star ....

In general, red dwarfs don't have a giant phase because they don't have enough mass to initiate helium fusion. They also burn relatively cooly and most have main sequence times longer than the current age of the universe, so it's not likely this planet has experienced anything quite that cataclysmic. Red dwarfs also have a weaker stellar wind.

However, Gliese 581 is a variable star, and the frequent fluctuations in output may affect the survivability of life on the surface of the planet.

Also, because of it's cooler temperature, it isn't nearly as bright in the visible range compared to our sun, but mostly in the infrared. Even from it's close orbit daylight would be relatively dim. The bonus is reduced amount of UV radiation, which of course is dangerous to us.

It's possible the weak stellar wind may be something of a liability, as it appears our system's solar wind plays a role in slowing down high energy cosmic rays from elsewhere in the galaxy.

[pdna1298]

If this planet is so close to its parent star, then wouldn't radiation from the star cancel out any possibility of life? Wouldn't any protective atmosphere be blown away at such a close proximity?

[iamlucky13]

Possibly, but since Gliese 581 is a red dwarf, it has a much lower output of harmful effects like UV radiation and cosmic rays than larger stars like our sun. However, red dwarfs are also typically variable in their output, which may cause further challenges.

That said, it's still theoretically possible that life might have found some way to adapt to harsh conditions, such as being extra resilient to radiation or living entirely underground.

[neil]

If a planet is tide locked to it's star, the center of the hot side is perhaps 122 degrees f = 50 degrees c. The center of the cold dark side perhaps minus 5 degrees c = 23 degrees f. This will produce a great glacier = ice cap near the center of the dark side. If too little water remains for the hot side, solar space mirrors may be necessary to warm the darkside. Neil

[neil]

There will be a wide twilight and sunset band with temperatures comfortable for humans, but perhaps not enough light for photosynthesis. I believe some micro organisms thrive at 122 degees f and some large creatures live at much higher temperatures and very high pressure near ocean bottom vents. Neil

[neufer]

http://antwrp.gsfc.nasa.gov/apod/ap070426.html

http://www.colbertnation.com/the-colber ... asse-tyson