Page 1 of 1

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

Posted: Thu Apr 26, 2007 4:42 am
by ta152h0
http://antwrp.gsfc.nasa.gov/apod/ap070426.html

is it possible to annotate Gliese 581 ?

Posted: Thu Apr 26, 2007 7:58 am
by 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.

Posted: Thu Apr 26, 2007 1:06 pm
by 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?

Posted: Thu Apr 26, 2007 4:45 pm
by 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.

Posted: Thu Apr 26, 2007 5:31 pm
by 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:

Image

-Noel

Posted: Thu Apr 26, 2007 10:41 pm
by 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.

I wonder if water would still be there

Posted: Fri Apr 27, 2007 5:47 pm
by 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.

Posted: Fri Apr 27, 2007 7:18 pm
by BMAONE23
It might also be the core remnant of a hot jupiter that has long since lost its gaseous outer layers.

Posted: Fri Apr 27, 2007 10:09 pm
by 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.

Posted: Sat Apr 28, 2007 1:43 am
by 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.

Think about the conditions there

Posted: Sat Apr 28, 2007 3:45 am
by 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.

Re: Think about the conditions there

Posted: Sat Apr 28, 2007 6:27 am
by makc
aichip wrote: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

Image

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.

Posted: Sat Apr 28, 2007 2:46 pm
by 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.

Posted: Sat Apr 28, 2007 4:03 pm
by 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

Posted: Sat Apr 28, 2007 6:25 pm
by BMAONE23
Does this system sit anywhere near the location of the "WOW" signal?

Posted: Sun Apr 29, 2007 10:14 am
by makc
NoelC wrote: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?

Posted: Sun Apr 29, 2007 4:29 pm
by rigelan
umm. . . Lower the effective gravity. . .

Posted: Wed May 02, 2007 6:25 pm
by 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 ....
iamlucky13 wrote: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.

Gliese 581c

Posted: Thu May 03, 2007 2:23 pm
by 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?

Posted: Thu May 03, 2007 6:30 pm
by 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.

Posted: Fri Jun 01, 2007 5:11 pm
by 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

Posted: Fri Jun 01, 2007 5:20 pm
by 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

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

Posted: Fri Jun 05, 2009 8:28 pm
by neufer