2011 preview: Expect Earth's Twin Planet

New Scientist ^ | 12/21/2010 | New Scientist

[Dallas59]

In 2010, one new exoplanet appeared every four days or so; by the end of the year, the total topped 500. But in September, a truly exceptional find punctuated this steady drumbeat of discovery: the first alien planet that could host life on its surface.

Gliese 581 g, spotted by a team led by Steven Vogt of the University of California, Santa Cruz, inhabits a "Goldilocks" zone around its host star, a band just warm enough to boast liquid water. At 3.1 to 4.3 times the mass of Earth, it is also small enough that it should be made mostly of rock. Although a second team of astronomers failed to find signs of Gliese 581 g in their data, if its existence is confirmed, it will be the most habitable exoplanet yet found.

[moovova]

2011 preview: Expect Earth's Twin Planet

OMG! Does that mean there are two Obamas?

[Jolla]

Steven Vogt of the University of California, Santa Cruz, inhabits a “Goldilocks” zone

I bet he does

[Dallas59]

And...four...MICHELLE’S!

[davisfh]

If Gliese has a composition similar to earth and is 3.1 to 4.3 times the mass of Earth, the gravity would be pretty enormous. If so, it would be very difficult for humans to exist there. There might be some human-like creatures there who would be much like Superman to us. I also assume that the term “mass” used here means just that.

[Dallas59]

They may be very small and lightweight...

[mikrofon]

Wouldn't one expect to find the Goldilocks Zone in the constellation Ursa Minor?

[BenLurkin]

http://www.johnspeedie.com/healy/wacky.wav

[Dallas59]

No Green Slave Women...

[mamelukesabre]

this from wiki: "It is estimated that the average global equilibrium temperature (the temperature in the absence of atmospheric effects) of Gliese 581 g ranges from 209 to 228 K (−64 to −45 °C, or −84 to −49 °F) for Bond albedos (reflectivities) from 0.5 to 0.3 (with the latter being more characteristic of the inner Solar System). Adding an Earth-like greenhouse effect yields an average surface temperature in the range of 236 to 261 K (−37 to −12 °C, or −35 to 10 °F).[1][20] So it's like antarctica with MAYBE some small warm spots warm enough for liquid water here and there.

[mamelukesabre]

Most earthlike planets known to date:

70 virginis b

giliese 581 d

giliese 581 g

[BenKenobi]

Depends on the rock density. Surface gravity is a function of the radius of the planet.

[Dallas59]

No Green Slave Girls?

[txhurl]

It’s the Oort gals shakin we have to worry about.

[3niner]

Mass/gravity relationships are not quite that simple. If a planet, 4 times the mass of Earth, were the same density as Earth, it would also be larger. This means that someone standing on the surface would be further from the center of mass, partially compensating for the increase in mass.

It has been many, many years since I've done these kinds of calculations, but I believe the difference in surface gravity would be a factor of the cube root of 4 (about 1.6). This would be heavy gravity for a human, but would allow for walking about.

Of course, the other planet might be denser, the temperature might be much higher or lower (even if it is in the "Goldilocks Zone"), and the atmosphere could be very different. The biggest difficulty, however, would be in getting there to take a stroll on it.

[6SJ7]

... but I believe the difference in surface gravity would be a factor of the cube root of 4 (about 1.6).

A factor of 1.6 in weight!? That's going to ruin my diet!

[PAR35]

That looks more like a rat than a bear.

[Chode]

Nibiru???

[Chode]

Nibiru???

[Seven plus One]

There might be some human-like creatures there who would be much like Superman to us. I also assume that the term “mass” used here means just that.

It probably means just the opposite.