Astronomers find batch of "super-Earths"

[Taktiq]

I don't know if anyone else saw this but, I just came across this article and found it quite amazing:

 

"Mon Jun 16, 7:53 AM ET

 

European researchers said on Monday they discovered a batch of three "super-Earths" orbiting a nearby star, and two other solar systems with small planets as well....

 

The planets are bigger than Earth -- one is 4.2 times the mass, one is 6.7 times and the third is 9.4 times.

 

They orbit their star at extremely rapid speeds -- one whizzing around in just four days, compared with Earth's 365 days, one taking 10 days and the slowest taking 20 days." (Quote from article)

[Martin]

Thanks for spotting that news item. It's interesting. It is not the first discovery of a system with several planets in that mass range, though. What these discoveries do is fill out the picture and allow astronomers to estimate the odds that a star will have planets with masses like the earth or some small multiple of earth mass.

 

What they are building up is a a picture of the statistical distribution of earth-like planets.

 

These planets reported Monday are not especially earth-like in the sense that they are probably too hot for liquid water to exist on surface and thus for familiar kinds of surface life.

 

But they help to fill out the statistics. Exoplanets where liquid water might exist have been found. I may be able to get a link. In all about 300 exoplanets have been found----but most are too hot or too cold to offer a familiar habitable environment. Or too massive, like Jupiter.

 

The fact that seems now to be emerging is that MANY stars may have planets with earth-like masses. Perhaps 30 percent. There is an international conference on this topic going on now at Nantes---16-18 June. Earlier not so many of these planets were detected because the instruments were not sensitive enough----it was easier to detect Jupiter-mass planets, giant planets. So we got a biased sample. Now there are more sensitive instruments and we begin to get a better sample, showing that planets in the earth-mass range are more common.

 

So maybe there are a lot of planets with the right mass for our kind of life.

Still, even then, only a small percentage of these would have the right temperature for liquid water on the surface. It will take a lot more work to reliably estimate the statistics on that.

 

I will try to find a link or two about this.

 

========================

Yeah

http://www.sciencedaily.com/releases/2007/12/071213101403.htm

the star I was thinking of is about 20 lightyears away and called Gliese 581

 

the two planets are called C and D, and D is the farther out and colder of the two.

That planet would be called

Gliese 581D

you might try googling "Gliese" and see what you get, or

"Gliese habitable"

Both planets are in the right mass-range----a few times more massive than the earth.

They would be rocky planets able to hold a decent atmosphere with a respectable atmospheric pressure and greenhouse effect. Liquid water is definitely a possibility at least on one of the two.

Edited June 17, 2008 by Martin

[Reaper]

Wasn't Gliese C later shown to be more likely a Venus-like planet, rather than Earth like?

[Martin]

Wasn't Gliese C later shown to be more likely a Venus-like planet, rather than Earth like?

 

I think that there is a high liklihood of that. I mentioned Gliese 581D because I think it is a better prospect for liquid water.

 

Planet D has an elliptical orbit around the outer edge of the habitable zone, so part of the time it would be in the habitable zone and part of the time it would be below freezing-----if the model they are using is right.

 

All these estimates are based on models. How much atmosphere. What the pressure and density. How much atmospheric greenhouse keeps the planet warm.

 

When we get better instruments to observe these planets we will begin to know more, and there won't be so much guesswork in the modeling.

[h4tt3n]

Earlier not so many of these planets were detected because the instruments were not sensitive enough----it was easier to detect Jupiter-mass planets, giant planets. So we got a biased sample. Now there are more sensitive instruments and we begin to get a better sample, showing that planets in the earth-mass range are more common.

 

I'd say the sample is still very biased, due to the lack of instrumental sensitivity you mention. The planets found are either very heavy or - as these - very close to the central star, or both.

[Klaynos]

Venus is very earthlike...

[Edtharan]

It seems that we might be able to start filling in some of the numbers for the Drake Equation. There is still a lot of uncertainty, but this should help narrow down the limits.