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Next stop Gliese 581g

by waht
Tags: 581g, gliese, stop
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Orion1
#37
Oct2-10, 12:47 AM
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A planet with mass of 3.1 to 4.3 times that of the Earth and no atmosphere?

Now that is some good science fiction!
DaveC426913
#38
Oct2-10, 10:00 AM
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Quote Quote by Orion1 View Post

A planet with mass of 3.1 to 4.3 times that of the Earth and no atmosphere?

Now that is some good science fiction!
As mentioned, it's also larger in diameter, so surface gravity is closer to 2x Earth.

Who claimed it has no atmo?
Orion1
#39
Oct2-10, 10:09 AM
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DaveC426913
#40
Oct2-10, 10:12 AM
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Quote Quote by Orion1 View Post
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OK, then I guess I don't get what your original "sceince fiction" point was, beyond: yes, if it has no atmo it won't be all that interesting.
Orion1
#41
Oct2-10, 11:01 AM
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D H
#42
Oct2-10, 12:20 PM
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Quote Quote by Orion1 View Post
However, much of the material is the result of supernova residue, so I would expect that such a star system would have planets even more matter rich than Sol's system.
What makes you think that? Your own data contradicts this:
In fact, when I compare the metallicity of the two, this is in fact the case:
Sol metallicity: Z = 0.0177
Gliese 581 metallicity: [M/H] = −0.33 0.12
That negative metallicity means that Gliese 581 has about a half as much metal by concentration than does the Sun.

For example, I would expect Gliese 581 g to have an atmosphere with at least twice the amount of gaseous matter and at least twice as dense
What makes you think that? This is pure speculation. The correlation between body size and atmosphere mass in our solar system is rather low. Venus is only slightly smaller than the Earth but its atmospheric mass is 93 times that of the Earth. Mars' mass is 1/10 that of the Earth but its atmospheric mass is 1/200 that of the Earth. Titan is even smaller than Mars but its atmospheric mass is 20% more than that of the Earth.

and a magnetic field to be at least equivalent to or greater than that of Earth, including the rate at which its core would have cooled despite its age.
What makes you think that? If anything, I would expect just the opposite. Metallicity of the central star is half that of the Sun, and the planet's rotation rate is 1/37 that of the Earth's rotation rate.

Until we learn more about this system, the only thing we can legitimately say about this planet's atmosphere and magnetic field is we don't know.
DaveC426913
#43
Oct2-10, 03:56 PM
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Quote Quote by Orion1;2911 howe 959
it most certainly had an ocean as well in its geologic history, probably at least twice the volume as Earth's ocean.
I can see you suggesting why it might not be implausible that it has an ocean - but how can you possibly guess about its volume while keeping a straight face?

Quote Quote by Orion1;2911 howe 959
The Uranian system has a unique configuration among the planets because its axis of rotation is tilted sideways nearly into the plane of its revolution about the Sun, resembling a planet that is tidally locked, yet it has a complex, layered cloud structure, with water thought to make up the lowest clouds, and methane thought to make up the uppermost layer of clouds, therefore I would expect that hot solar driven winds to sweep from the hot side of the planet to the cooler side, and the cooler sided winds to sweep to the hot side of a tidally locked planet as opposed to just everything that is capable of freezing out to simply freeze completely out and condense on only one side.

If single sided freezing were the absolute case than the water vapor that composes the lower cloud bands on Uranus would have been swept to the cooler side, to simply freeze out into crystals and condense onto the surface of the cold side and remain trapped there, yet this is not the case.
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Not sure why you're using a gas giant as a comparison to a rocky body. There is not enough surface for gas to condense on. It has to have a complex cloud structure because it's almost entirely atmo.
Brett13
#44
Oct2-10, 10:49 PM
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Am I the only one that HAS heard of this planet before it was talked about on the 29th? I forget what show but it was naked science or how the universe works or something like that. One of them (I forget which) has talked about a rocky planet bigger than the earth and closer to its star thats in the goldilocks zone around the star gliese 581.. Maybe its just another one in the goldilocks zone?
DaveC426913
#45
Oct2-10, 11:03 PM
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Quote Quote by Brett13 View Post
Am I the only one that HAS heard of this planet before it was talked about on the 29th? I forget what show but it was naked science or how the universe works or something like that. One of them (I forget which) has talked about a rocky planet bigger than the earth and closer to its star thats in the goldilocks zone around the star gliese 581.. Maybe its just another one in the goldilocks zone?
Yes, 581c was the big hopeful several years ago.

It's what inspired me to write my Gliese primer.
Vanadium 50
#46
Oct4-10, 01:33 PM
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Before we get too excited, red dwarfs have some problems. One is that many of them - perhaps half - are UV Ceti variables, also called flare stars. They have sporadic flares which are much more dangerous than solar flares - both because they are more energetic (especially in X-rays) and because their planets are closer.

Unfortunately, Gl 581 falls into this category. (When looking it up, it's also NSV 7023. NSV stands for New Suspected Variable)
kamenjar
#47
Oct5-10, 11:47 AM
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Quote Quote by DaveC426913 View Post
...
It's what inspired me to write my Gliese primer.
though, I am wondering how would we be able to even in theory do acceleration of 1g for 10 years. in fact that would need to increase over time as the ship's clock decelerates or it's mass increases (I think the effect is the same just explained differently).

I mean, 6 years trip sounds pretty optimistic. I wonder if there's any propulsion tech that is close to getting this achieved.
DaveC426913
#48
Oct5-10, 11:55 AM
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Quote Quote by kamenjar View Post
though, I am wondering how would we be able to even in theory do acceleration of 1g for 10 years.
Well, no.

Current proposals for interstellar travel inlcude the Bussard ramjet and Project Orion (which is in principle constructable with existing technology). But they do not reach those kinds of acceleration.
Quote Quote by kamenjar View Post
in fact that would need to increase over time as the ship's clock decelerates or it's mass increases (I think the effect is the same just explained differently).
This is not how relativistic travel works.

Its mass increases to an outside observer, and its time dilates to an outside observer, this simply means that the ship will be observed to approach c closer and closer but never reach it.

However, the occupants will not experience any increase in mass, nor any slowing of their clock. And most importantly, they will experience the trip taking only 6 years.
kamenjar
#49
Oct6-10, 03:08 PM
P: 101
Quote Quote by DaveC426913 View Post
...
I think I realized what you are saying about mass. That prompted me to post on the Relativity forum. Maybe you can help...
Gaius Baltar
#50
Oct7-10, 02:26 AM
P: 49
Just look how misleading this is:

An astronomer picked up a mysterious pulse of light coming from the direction of the newly discovered Earth-like planet almost two years ago, it has emerged.

Read more: http://www.dailymail.co.uk/sciencete...#ixzz11eggOi2T
http://www.jb.man.ac.uk/~drl/publications/clf+00.pdf

http://en.wikipedia.org/wiki/47_Tucanae

Just goes to show, research goes a long way...
DaveC426913
#51
Oct7-10, 08:19 AM
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Quote Quote by Gaius Baltar View Post
What a terrible article.

Apparently, hey have already decided its composition is "...rocky with liquid water and atmosphere..."

And I like this comment: "It takes just 37 days to orbit its sun which means its seasons last for just a few days."

The one-face Gliese planets do not have seasons.

Nevermind the fact that they give no details about the mysterious light.
Gaius Baltar
#52
Oct7-10, 08:23 AM
P: 49
Completely Agree Dave.

It just goes to show, the Media and other sources of news outlets will stop at nothing to promote lies & fear mongering. Shame 60% of people who read, believe...

**Sigh....**
stevebd1
#53
Oct11-10, 06:51 AM
P: 611
Quote Quote by kamenjar View Post
I mean, 6 years trip sounds pretty optimistic. I wonder if there's any propulsion tech that is close to getting this achieved.
While it's not hard science, I thought this was a great website for ideas and suggestions regarding long distance space travel-

http://www.projectrho.com/rocket/rocket3aj.html
GlieseWorm
#54
Jan24-11, 03:30 PM
P: 7
Quote Quote by waht View Post
Amazing discovery. Carl Sagan would be thrilled to read this article. Gliese 581g is only 20 light-years away. It would make a nice weekend getaway spot.

http://www.space.com/scienceastronom...le-100929.html
what planet do you live on where 40yrs equates to a weekend? Christ , this is a physics site not Miils n Boom.


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