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cbclark4

Joined: 20 Aug 2006
Location: Masan

Posted: Mon Jun 11, 2007 5:28 pm Post subject:

Hollywoodaction wrote:

And how are we supposed to travel at the speed of light for 20 years, OP? Aboard the Millennium Falcon? Yeah, that's right. I wouldn't pack my bags just yet if I were you.

Just a bit out of touch.

Did you read the thread or did you just jump in head first.

Watch out for rocks.

cbc

cbclark4

Joined: 20 Aug 2006
Location: Masan

Posted: Mon Jun 11, 2007 5:31 pm Post subject:

Yes very nice thread. Iis there anyway to ban the detractors, Freefromthought, mimicme2, and the jackass jr., from this thread. Two thousand evocreo topics and they have to stain this one. cbc Last edited by cbclark4 on Tue Jun 12, 2007 4:24 pm; edited 1 time in total

mithridates

Joined: 03 Mar 2003
Location: President's office, Korean Space Agency

Posted: Mon Jun 11, 2007 6:46 pm Post subject:

cbclark4 wrote:

Yes very nice thread is there anyway to ban the detractors, Freefromthought, mimicme2, and the ajckass jr., from this thread.

Two thousand evocreo topics and they have to stain this one.

cbc

I like to think of them as fighting gerbils inside a type of apparatus that keeps the thread afloat the more they struggle with each other, and in the meantime we can keep posting on-topic replies.

freethought

Joined: 13 Mar 2005

Posted: Mon Jun 11, 2007 6:58 pm Post subject:

cbclark4 wrote:

Yes very nice thread is there anyway to ban the detractors, Freefromthought, mimicme2, and the ajckass jr., from this thread.

Two thousand evocreo topics and they have to stain this one.

cbc

So by that you mean you don't want people to post unwarranted personal attacks against others in this thread... (SEE THE QUOTED PASSAGE ABOVE)

Oh, I should also point out that WAY back on page one, I spoke up to keep this thread on topic against the very thing you claim you lament yet are doing yourself.

Brilliant post, bud.

mithridates

Joined: 03 Mar 2003
Location: President's office, Korean Space Agency

Posted: Mon Jun 11, 2007 7:12 pm Post subject:

Looks like freethought's right. Now in order to stay on topic I'll add a bit from the Wikipedia article that is quite interesting. We still don't know much about this planet at all and it could possibly also be another Venus if the atmosphere is thick enough. Impossible to tell at this point and the telescope didn't detect a transit in front of the star so we'll have to use other methods.

Quote:

Climate and habitability

[edit] Temperature

Using the measured stellar luminosity of Gliese 581 of 0.013 times that of our Sun, it is possible to calculate Gliese 581 c equilibrium surface temperature, which does not take into account a possible atmosphere. According to Udry's team the equilibrium temperature for Gliese 581 c is −3� C / 26.6� F, assuming an albedo (how much light is reflected by the planet's surface) such as Venus (0.64) and 40�C / 104� F for an Earth-like albedo (0.35).[7][2] The actual temperature on the surface also depends on the planet's atmosphere, which remains unknown. Xavier Delfosse of the research team expects that the actual surface temperatures will be hotter; for instance, the corresponding calculation for Earth yields an "effective surface temperature" of 256 K (−17 �C), yet Earth's true surface is 32 K warmer (an average of 288 K (15 �C)) due to the greenhouse effect. Gliese 581c receives more heat from the star than Venus does.

[edit] Liquid water

Gliese 581 c is within the habitable zone where water�a necessary ingredient for life as we know it�could exist.[3][14] However, no direct evidence has been found. Techniques like the one used to measure HD 209458 b could be applied to determine the existence of water vapor in an extrasolar planet's atmosphere, but only in the rare case of a planet with an orbit including transit directly between its star and our planet, which Gliese 581c is not known to do.

[edit] Tidal forces

Because of its small separation from Gliese 581, the planet is quite likely to be tidally locked, with one hemisphere always day (facing the star) and the other always night (facing away).[15]. Even then, the planet would undergo violent tidal flexing, because the orbital eccentricity is between 0,09 and 0,23. The planet might also be in a different tidal lock, like Mercury, with eccentricity of just 0,20, which is tidally locked 3:2, so that every point is in sunlight once over 2 orbital periods. The permanently lit hemisphere would be extremely hot and the dark hemisphere extremely cold, while the narrow terminator or "twilight zone" between them might have a moderate climate more suitable for life. In any case, even in case of 1:1 tidal lock, the planet would undergo libration and the terminator would be alternatively lit and darkened during libration.[16]

Theoretical models predict that volatile compounds such as water and carbon dioxide, if present, might evaporate in the scorching heat of the sunward side, migrate to the cooler night side, and condense to form ice caps. Over time, the entire atmosphere might freeze into ice caps on the night side of the planet. Alternatively, an atmosphere large enough to be stable would circulate the heat more evenly, allowing for a wider habitable area on the surface.[17] For example, although Venus has a small axial inclination, very little sunlight reaches the surface at the poles. A slow rotation rate approximately 117 times slower than Earth's produces prolonged days and nights. Despite the uneven distribution of sunlight cast on Venus at any given time, polar areas and the night side of Venus are kept almost as hot as day by globally circulating winds. However, it remains unknown if water and/or carbon dioxide are even present on the surface of Gliese 581 c.

[edit] Greenhouse effects

It has been hypothesized that, due to its strong gravity and proximity to the hotter edge of the habitable zone, Gliese 581 c could be prone to a runaway greenhouse effect, and would not be habitable, thus mimicking what happened to Venus in our solar system.[18]

mindmetoo

Joined: 02 Feb 2004

Posted: Mon Jun 11, 2007 9:15 pm Post subject:

cbclark4 wrote:

Yes very nice thread is there anyway to ban the detractors, Freefromthought, mimicme2, and the ajckass jr., from this thread.

Two thousand evocreo topics and they have to stain this one.

cbc

And what are you doing now?

The Bobster

Joined: 15 Jan 2003

Posted: Mon Jun 11, 2007 9:31 pm Post subject:

I guess my hopes about Gliese 581 might sound a little selfish ... can I teach English there? I'm pretty good at that, you know.

beachbumNC

Joined: 30 May 2007
Location: Gumi

Posted: Tue Jun 12, 2007 8:03 am Post subject:

Hollywoodaction wrote:

And how are we supposed to travel at the speed of light for 20 years, OP? Aboard the Millennium Falcon? Yeah, that's right. I wouldn't pack my bags just yet if I were you.

You must be stupid. Everybody knows the USS Enterprise is way faster than the Milennium Falcon. It's bigger and nicer on the inside, too, and a lot of hot babes work there.

mithridates

Joined: 03 Mar 2003
Location: President's office, Korean Space Agency

Posted: Tue Jun 19, 2007 4:27 am Post subject:

New calculations suggest that maybe the other planet (the one 7.7 times more massive than the Earth) is the one that could be habitable:

http://www.space.com/scienceastronomy/070618_mm_gliese_581d.html

Quote:

Hopes Dashed for Life on Distant Planet
By Ker Than
Staff Writer
posted: 18 June 2007
06:38 am ET

Scientists earlier this year announced they had found a small, rocky planet located just far enough from its star to sustain liquid water on its surface, and thus possibly support life.

Turns out the scientists might have picked the right star for hosting a habitable world, but got the planet wrong. The world known as Gliese 581c is probably too hot to support liquid water or life, new computer models suggest, but conditions on its neighbor, Gliese 581d, might be just right.

The findings are detailed in the May 25 issue of the journal Astronomy & Astrophysics.

So much promise

Gliese 581c, discovered in April by a team led by Stephane Udry of the Geneva Observatory in Switzerland, is about 50 percent bigger than Earth and about five times more massive. It is located about 20.5 light-years away, and circles a dim red dwarf star called Gliese 581.

Of the more than 200 extrasolar planets, or "exoplanets," discovered since 1995, Gliese 581c was the first found that resides within the habitable zone of its star, if only barely. The habitable, or "Goldilocks" zone is the region around a star where the temperature is neither too hot nor too cold, so water can exist on a planet's surface in its liquid state. Water is a key ingredient for life as we know it.

But new simulations of the climate on Gliese 581c created by Werner von Bloh of the Institute for Climate Impact Research in Germany and his team suggest the planet is no Earthly paradise, but rather a faraway Venus, where carbon dioxide and methane in the atmosphere create a runaway greenhouse effect that warms the planet well above 212 degrees Fahrenheit (100 Celsius), boiling away liquid water and with it any promise of life.

Another contender

But the same greenhouse effect that squashes prospects for life on Gliese 581c raises the same hope for another planet in the system, a world of eight Earth-masses called Gliese 581d, which was also discovered by Udry's team.

"This planet is actually outside the habitable zone," said Manfred Cuntz, an astronomer at the University of Texas at Arlington and a member of von Bloh's team. "It appears at first sight too cold. However, based on the greenhouse effect, physical processes can occur which are heating up the planet to a temperature that allows for fluid water."

And where this is fluid water, there is the chance of life as well. The researchers speculate that "at least some primitive forms of life" might exist on Gliese 581d. There is no evidence to support that speculation, however.

Jury still out

David Charbonneau, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA) who was not involved in the study, said the results from von Bloh's team are "probably a sound calculation but we don't actually know if it's correct."

Gliese 581d demonstrates the importance of taking a planet's atmospheric conditions into account when considering its potential for habitability. The concept of a habitable zone "is a very useful thing because it does inform us a great deal, and it explains a lot in the solar system. But it's not the whole story," Charbonneau said.

Jaymie Matthews, an astronomer at the University of British Columbia in Canada, doesn't treat the new findings as conclusive, but finds them "interesting as an illustration of how we can use remote exoplanetary environments as possible test beds for climate models."

The models made by von Bloh's team could be tested if scientists can measure thermal emissions and the reflectivity, or "albedo," of the planets, Matthews said.

Scientists "have done this already for HD 209458b, a hot Jupiter, but we will need to do this for possibly 'Earthy' planets to truly assess their habitability," he added.

A stable star

Matthews own research, recently presented at the annual meeting of the Canadian Astronomical Society, suggests one reason Gliese 581 is such a promising star for finding habitable planets is that it is similar to our own sun in that it is remarkably stable.

Matthews and his team used a Canadian space telescope called MOST to monitor Gliese 581 for six weeks. During that time, they observed very few instances of the powerful solar flares common among red dwarf stars.

"If the star showed significant variations in brightness during the weeks we monitored it, that would at least complicate the thermal equilibrium of the planets around it," Matthews explained.

The stability of the light also suggests Gliese 581 is old and that is has been around for at least a few billion years.

"Young stars, like young people, can have bad cases of acne (large starspots and activity) and spin around," Matthews said in an email interview. "Older stars like the sun have relatively clear complexions and rotate rather sedately."

Gliese 581's advanced age is good news for scientists hoping to find signs of life in the system.

"We know it took about three and a half billion years for life on Earth to reach the level of complexity that we call human," Matthews said, "so it's more encouraging for the prospects of complex life on any planet around Gliese 581 if it's been around for at least as long."

Treefarmer

Joined: 29 May 2007

Posted: Tue Jun 19, 2007 5:43 am Post subject:

i'm going, that's all there is to it

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