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another "potentially habitable" exoplanet: HD 8551

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graywyvern
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25 Aug 2011, 7:09 pm

From the radial velocity data, "if the planet exhibits more than 50% cloud coverage...its surface could remain cool enough to allow for liquid water if present."

My take on it:

http://springtail.blogspot.com/2011_08_ ... 4871074862


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25 Aug 2011, 7:15 pm

Cannot find source data on HD-8551. Please provide link.


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25 Aug 2011, 11:04 pm

As of May 16, the only candidate for the status of "habitable exoplanet" seems to be Gliese 581d. (581g appears to not exist, having been merely an artifact of instrument noise; the other possibility, riding the inner edge of Gliese 581's "Goldilocks zone", has been shown to receive too much heat from its star, such that if it had liquid oceans, they would have long since evaporated into an eternal cloud cover, giving the planet a runaway greenhouse effect not unlike that which afflicts Venus. 581d, however, may have a thick-enough atmosphere, provided that it consists largely of carbon dioxide (a supposition we are as yet unable to check, at a distance of 20 lightyears). 581d is tidally locked to its sun, so its habitable zone would seem weird and depressing to us (eternal purple twilight, with a constant wind blowing from the noon pole to the midnight pole), and its surface gravity would be about twice that of Earth, but it could be technically habitable for complex life-forms...

I can't find any references to HD 5881, however, and am beginning to doubt such a designation exists.


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26 Aug 2011, 1:56 am

DeaconBlues wrote:
As of May 16, the only candidate for the status of "habitable exoplanet" seems to be Gliese 581d. (581g appears to not exist, having been merely an artifact of instrument noise; the other possibility, riding the inner edge of Gliese 581's "Goldilocks zone", has been shown to receive too much heat from its star, such that if it had liquid oceans, they would have long since evaporated into an eternal cloud cover, giving the planet a runaway greenhouse effect not unlike that which afflicts Venus. 581d, however, may have a thick-enough atmosphere, provided that it consists largely of carbon dioxide (a supposition we are as yet unable to check, at a distance of 20 lightyears). 581d is tidally locked to its sun, so its habitable zone would seem weird and depressing to us (eternal purple twilight, with a constant wind blowing from the noon pole to the midnight pole), and its surface gravity would be about twice that of Earth, but it could be technically habitable for complex life-forms...

I can't find any references to HD 5881, however, and am beginning to doubt such a designation exists.


Not so. NASA's Kepler spacecraft has identified an additional 54 exoplanets that are in the habitable zones of their parent stars. Even though these 54 exoplanets do not orbit stars similar to our sun, since detecting earth-like planets orbiting sun-like stars will take a few more years, these planets are also potentially habitable. People in the research group involved with Kepler have estimated that the Milky Way Galaxy as a whole could be home to 500 million potentially habitable planets based on Kepler's data.

To be honest though, I can't find any reference to HD 5881 either.



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26 Aug 2011, 2:42 am

I can find 5881 in the kepler logs here

http://archive.stsci.edu/kepler/host_stars.html

But I think the OP was referring to HD85512b

http://arxiv.org/abs/1108.3561

http://www.google.co.uk/search?pws=0&gl=uk&q=HD85512b



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26 Aug 2011, 10:27 am

Most likely Gliese 581-D. It is 20 light years distance.

We cannot get from here to there and back.

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26 Aug 2011, 10:49 am

If HD85512b is indeed 3.5 times the mass of Earth, a person who weighs 200 pounds on Earth would weigh 700 pounds there, and likely die of a heart attack from trying to stand up.

So much for being "Habitable".


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26 Aug 2011, 12:02 pm

ruveyn wrote:
Most likely Gliese 581-D. It is 20 light years distance.

We cannot get from here to there and back.

ruveyn

Correction: We cannot get from here to there and back today, using current technologies. There are proposals for constant-boost craft that could make the trip in 30 years or so from our perspective (probably more like 20 or 25 years from onboard perspective); however, given the described probable conditions for Gliese 581d, I don't see why anyone would build such a craft. Maybe a one-way robot probe reporting back by maser, but not a manned craft, as the planet isn't worth colonizing (it would be easier to preserve an offworld sample of humanity by colonizing Mars or the asteroids).

I'm really hoping the Kepler deep-space telescope gets built; the proposal would be for multiple telescopes orbiting out around the orbit of Jupiter (to get as far away as is practical from distortions induced by solar gravity), with data coordinated by a central computer, giving an artificial aperture several kilometers across. It would be capable of resolving images of planets the size of Earth at a distance of quite a number of lightyears. Then we might have a chance to discover a really useful exoplanet...


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26 Aug 2011, 3:39 pm

DeaconBlues wrote:
ruveyn wrote:
Most likely Gliese 581-D. It is 20 light years distance.

We cannot get from here to there and back.

ruveyn

Correction: We cannot get from here to there and back today, using current technologies. There are proposals for constant-boost craft that could make the trip in 30 years or so from our perspective (probably more like 20 or 25 years from onboard perspective); however, given the described probable conditions for Gliese 581d, I don't see why anyone would build such a craft. Maybe a one-way robot probe reporting back by maser, but not a manned craft, as the planet isn't worth colonizing (it would be easier to preserve an offworld sample of humanity by colonizing Mars or the asteroids).

I'm really hoping the Kepler deep-space telescope gets built; the proposal would be for multiple telescopes orbiting out around the orbit of Jupiter (to get as far away as is practical from distortions induced by solar gravity), with data coordinated by a central computer, giving an artificial aperture several kilometers across. It would be capable of resolving images of planets the size of Earth at a distance of quite a number of lightyears. Then we might have a chance to discover a really useful exoplanet...


To get a time dilation of 2 (which is just about what you are proposing) we would have to get of approximately .88 of light speed. There not even a hint of a glimmer of that kind of propulsion in sight. The fastest vehicle ever launched from Earth has reached about 60,000 miles per hour.

We have not got anything that will propel a vehicle to almost .9 light speed. That includes propelling vehicles by blowing up H-bombs in the tail.

ruveyn



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26 Aug 2011, 6:05 pm

I agree with Ruveyn, this constant boost technology sounds like star-trek science.

The closet thing would be an ion thruster or a hall effect thruster and there is no way either of those techs will scale up even in theory to being able to accelerate itself let alone a craft to that speed and slow down again in the time-scale you are giving.



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26 Aug 2011, 6:12 pm

Why even bother with determining the means of interstellar travel when there is really no place to go?

I mean, of all the exoplanets so far discovered, are there any that have liquid water, a nitrogen-oxygen atmosphere, a compatible biology, a mean surface temperature of about 22°C, and surface gravity within just a few percentage points of Earth's?


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26 Aug 2011, 6:32 pm

Fnord wrote:
Why even bother with determining the means of interstellar travel when there is really no place to go?

I mean, of all the exoplanets so far discovered, are there any that have liquid water, a nitrogen-oxygen atmosphere, a compatible biology, a mean surface temperature of about 22°C, and surface gravity within just a few percentage points of Earth's?


Don't assume life needs conditions similar to earths to prevail, even complex life. There should be plenty of interesting places to go lol.

At present we can only detect large exoplanets with some degree of accuracy. Obviously liquid water at ground level would be unlikely on a large planet. Some exoplanets have been found that reflect light back at wavelengths that suggest the surface is covered with water. This should be seen as pure speculation though.



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26 Aug 2011, 6:39 pm

Tom_Kakes wrote:
Fnord wrote:
Why even bother with determining the means of interstellar travel when there is really no place to go? I mean, of all the exoplanets so far discovered, are there any that have liquid water, a nitrogen-oxygen atmosphere, a compatible biology, a mean surface temperature of about 22°C, and surface gravity within just a few percentage points of Earth's?

Don't assume life needs conditions similar to earths to prevail, even complex life.

I'm not. I'm suggesting that if an exoplanet does not have the qualities that I've mentioned, then it may not be worth sending humans there.
Tom_Kakes wrote:
There should be plenty of interesting places to go

Interesting, certainly. But hospitable to humans without terraforming and/or protective enviro-suits? Where is such a world? Have any (besides Earth) ever been discovered?
Tom_Kakes wrote:
At present we can only detect large exoplanets with any type of accuracy. Obviously liquid water at ground level would be unlikely on a large planet. Some exoplanets have been found that reflect light back at wavelengths that suggest the surface is covered with water. This should be seen as pure speculation though.

Agreed. I'm just enough of a romantic to believe that other Earth-like worlds might exist, but I'm also enough of a realist to understand that such a world, if it exists, would be so far away as to make colonization extremely impractical, if not impossible.


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26 Aug 2011, 6:49 pm

Fnord wrote:
Tom_Kakes wrote:
Fnord wrote:
Why even bother with determining the means of interstellar travel when there is really no place to go? I mean, of all the exoplanets so far discovered, are there any that have liquid water, a nitrogen-oxygen atmosphere, a compatible biology, a mean surface temperature of about 22°C, and surface gravity within just a few percentage points of Earth's?

Don't assume life needs conditions similar to earths to prevail, even complex life.

I'm not. I'm suggesting that if an exoplanet does not have the qualities that I've mentioned, then it may not be worth sending humans there.
Tom_Kakes wrote:
There should be plenty of interesting places to go

Interesting, certainly. But hospitable to humans without terraforming and/or protective enviro-suits? Where is such a world? Have any (besides Earth) ever been discovered?
Tom_Kakes wrote:
At present we can only detect large exoplanets with any type of accuracy. Obviously liquid water at ground level would be unlikely on a large planet. Some exoplanets have been found that reflect light back at wavelengths that suggest the surface is covered with water. This should be seen as pure speculation though.

Agreed. I'm just enough of a romantic to believe that other Earth-like worlds might exist, but I'm also enough of a realist to understand that such a world, if it exists, would be so far away as to make colonization extremely impractical, if not impossible.


It's a sad time to be born in really. Hopefully, in the future technology will overcome the need for a ready made ecosystem either that or AI will rule...



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26 Aug 2011, 7:05 pm

What I was pointing out though in all probability there are many worlds about the size of earth, in the same position as earth to the sun, in relation to their sun. They are just too small for the current technology we have to detect. I doubt many of these planets would support life like ours though. Even our moon is much needed to stabilize the climate enough for complex life to have developed.