

A Habitable Exoplanet - for real this time - hugh3
http://www.wired.com/wiredscience/2010/09/real-habitable-exoplanet/

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phreeza
Link to the actual paper: <http://arxiv.org/abs/1009.5733>

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anigbrowl
20 lightyears is a long way, but not that long. What we're 'seeing' via our
instruments was taking place around 1990.

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patio11
So if we had pointed Voyager at it back in the 1970s, we would only have
19.997 lightyears left to travel!

Space is big. We are slow. Everything cool about scifi is fiction. None of
this will change in our lifetimes.

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grackle
I would argue that this falls into the "cool" part of what, until now, has
been entirely scifi - and that I'm absolutely ridiculously excited about
seeing more and more of these discoveries in the years to come.

No, there's no hope of ever visiting this place in our respective lifetimes
(sans cryogenics), but I'd put money on the prediction that we will certainly
see real imagery of exoplanets within 50 years. And that's cool. Really cool.
So cool that we'll look back and laugh at the original question of "are all
exoplanets bigger than Jupiter and closer to their suns than Mercury?"

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hugh3
Borderline habitable, anyway. Rocky planet, two Earth masses, looks promising,
but so close to its (small, dim) star that it's probably tidally locked,
meaning the same side will always point towards its sun. This means that the
vast majority of its surface will either be too hot or too cold for life.

But a certain ring will have constant perfect weather!

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aaronbrethorst
FTA:

"That means the planet has...a band of eternal sunrise or sunset where water —
and perhaps life — could subsist comfortably."

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ugh
That would be awesome as premise for a science fiction short story or novel!

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tocomment
Would gravity there be three Gs? I don't think we could handle that. The
atmosphere might be too thick for us too. May it has a nice moon?

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kqr2
According to
[http://news.yahoo.com/s/afp/20100929/sc_afp/usastronomyplane...](http://news.yahoo.com/s/afp/20100929/sc_afp/usastronomyplanet_20100929210707)
, surface gravity might only be slightly higher than earth's.

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tocomment
How is that possible?

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cryptoz
Density of a planet's interior is not uniform, and gravity tapers
exponentially with distance. So, a planet with a dense core and a less-dense
middle area could easily have less gravitational force than you might expect
since the surface is so far away from the dense core.

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hugh3
Surprisingly not so.

If you have a body with a spherically symmetric mass distribution, from the
outside it always has exactly the same gravitational field as a point mass at
the centre.

Proof: [http://hyperphysics.phy-
astr.gsu.edu/hbase/mechanics/sphshel...](http://hyperphysics.phy-
astr.gsu.edu/hbase/mechanics/sphshell.html)

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cryptoz
Wait, but didn't I specifically say I was referring to a body _without_ a
spherically symmetric mass distribution? Maybe I'm incorrect in my
understanding of symmetric, but I was definitely referring to a non-symmetric
case in my text.

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hugh3
Spherically symmetric means that it looks the same no matter which way you
rotate it. You talked about a dense core, less dense middle-region planet,
which is spherically symmetric.

If the planet had an ultra-dense region off to one side then it wouldn't be
spherically symmetric and it would have gravity slightly stronger on one side
than on the other... it's hard to imagine such a planet existing though.

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cryptoz
Ah, gotcha. Thanks!

