

Potentially Habitable Planet Discovered - ygd
http://arbesman.net/blog/2010/09/29/potentially-habitable-planet-discovered/

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spicyj
Discussion: <http://news.ycombinator.com/item?id=1741330>

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hartror
And indepth analysis and reality checks by Phil Plait
[http://blogs.discovermagazine.com/badastronomy/2010/09/29/po...](http://blogs.discovermagazine.com/badastronomy/2010/09/29/possible-
earthlike-planet-found-in-the-goldilocks-zone-of-a-nearby-star/)

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Devilboy
And on the other end of the journalistic quality spectrum, News.com.au has
this article

[http://www.news.com.au/technology/perpetual-twilight-of-
red-...](http://www.news.com.au/technology/perpetual-twilight-of-red-dwarf-
planet-gliese-581g-may-host-band-of-life/story-e6frfro0-1225932102533)

The link from the main page reads: _Odds of life on new planet '100 per cent'_

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hartror
Odds of tabloid misquoting a scientist to sell more copy "100 per cent.

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hugh3
It seems to be an accurate quote from Vogt:

 _During a press briefing, Prof Steven Vogt told The Daily Telegraph,
“Personally, given the ubiquity and propensity of life to flourish wherever it
can, I would say, my own personal feeling is that the chances of life on this
planet are 100 percent.”_

which sounds rather excessive to me.

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robryan
It's still a bit of a stretch to describe this as habitable in our sense of
habitable here on earth. I prefer the phase most earthlike planet. Which in
this case is still a fair way off being very similar, as usually there is
always the conflict between the scientists that advise caution because of the
unknowns in there findings compared to the media which at times skim the first
few pages and sensationalize it all.

Will be very interesting to see the results from Kepler in a few years in
relation to finding a planet in a similar period at a similar distance to our
position in the solar system.

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iuguy
Bear in mind that this planet is supposed to be in the habitable zone. There
are three known planets within the solar system's habitable zone - Venus,
Earth and Mars. Only one of them has any confirmed life.

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olefoo
And coincidentally the only planet in our solar system's habitable zone that
supports life is the one with a largish moon.

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8ren
Our Moon is also in the Goldilocks zone, and rocky. But it lacks an
atmosphere.

Is this because the Moon is small, and some threshold of gravity is required?
Or somehow related to the Moon's cold and inert interior, thus no gaseous
volcanoes? Or just a happenstance of composition?

The Moon is a concrete anchor for imagining exosolar worlds.

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troels
I talk out of my ass, by if I recall the numerous pseudo-scientific tv-show
I've seen correct, the moon is pretty much similar to the Earth, but due to
its smaller size, it has cooled down much faster. Additionally, it's not heavy
enough to sustain an atmosphere, which can bind water to the planet.

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dbrannan
Feel free to correct my math

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

Voyager 2 (man's fastest space craft) is traveling 35,000 miles per hour / 60
= 583 miles per second.

187,000 miles per second equals the speed of light.

Light can travel 57,395,520,000,000 miles in one year (roughly 5.7 trillion
miles).

So, in 21 years that would equal 57,395,520,000,000 miles x 21 years, or
roughly 120 trillion miles.

Thus, if Voyager 2 was our space craft we'd have 583 miles per second x 60
seconds x 60 minutes x 24 hours x 365 days x 21 years to get 386,095,248,000
billion miles towards our new planet.

There is a huge gap between 386 billion and 120 trillion miles, like 311
times.

That means it would take us roughly 310 x 21 years = 6528 years to get there
using current technology.

I just don't see us going there as being very practical.

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retube
At 35,000mph would take 402,000 years. Inter-stellar travel is not for the
feint-hearted. It's probably possible to accelerate a space-craft to around
10x this speed using current motor technology. Even so, that's still 40,000
years - and 21 light years is like a nano-meter away on a galactic or
cosmological scale.

Really, if you want to cross inter-stellar space in any kind of reasonable
time - O(human lifetime) - you need to go faster. Possible solutions are:
solar sail or new kinds of ion thruster. Both of these impart a very small
force (and hence acceleration) for an exceedingly long time, resulting in very
high velocities. Your target speed is about 10% of c. In the case of the solar
sail it receives momentum from sun for ~ 50% of distance (assuming similar-
sized star to our sun), and then is braked by the momentum from the target
star for the rest of the journey.

Problem with solar sail is it needs to be GIGANTIC, and composed of materials
stronger and lighter than those available today. Additionally force from
sunlight is proportional to 1/r^2 so your acceleration decreases with
distance.

So, nuclear powered ion thruster is probably the answer. But, obviously, this
kind of project is expensive. And either way, you need living quarters for an
entire society to live and reproduce.

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avar
Why do you limit a reasonable amount of time to a human lifetime? If we're
going to colonize interstellar space with anything like our current technology
we're probably going to have to ditch that requirement.

There's no reason you can't have a multi-generational ship that takes a
thousand years to arrive. You don't have to send thousands of people either,
it's enough to send a hundred or so, have them populate on the way, and maybe
send some frozen sperm & eggs with them to increase genetic diversity.

Another possibility that'll probably become viable within 50-200 years is to
not send any humans at all, but to only send a fast & small ship with human
sperm & eggs that can start hatching humans once it gets there. Raising the
infants could be done with robots and other infrastructure manufactured once
we get there.

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Rhapso
Read 'Orphans of the Sky' by Robert Heinlein to get an idea of the many
problems with this approach. Human society is not culturally stable enough to
utilize a generation-ship method of space exploration.

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sprout
Most human societies aren't stable enough for that. But visit most presently
isolated communities, and you'll find that they're quite stable.

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antipaganda
If you can visit them, they're not isolated.

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zeteo
This all seems dependent on the planet being tidally locked. How do they know
that? Does a certain distance from the sun absolutely guarantee it?

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hugh3
Check out the equation towards the bottom of

<http://en.wikipedia.org/wiki/Tidal_locking>

which gives a timescale for how long it takes for a body to become tidally
locked to the body it orbits. I haven't plugged in the numbers for this
planet, but I'm gonna assume it winds up being much shorter than the age of
the star.

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zeteo
Well, the link you're giving says (at the bottom)

"Gliese 581 g may be tidally locked to its parent star Gliese 581"

So it's not known for certain.

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scotty79
Let's suppose there is a lot of water. Can you imagine weather at terminator
with incredible winds blowing from hot side to cold side and back closer to
surface and evaporating oceans on hot side that constantly rain down on the
cold side of the planet?

First order of business for any life that might arise there is to NOT catch
the wind and NOT get in the flow.

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hugh3
On the upside, there's a tremendous amount of available energy for lifeforms
to harvest.

Here on Earth, life gets its energy from soaking up solar energy, or from
eating things that have been soaking up solar energy, or from eating things
which have eaten things which.... you get the idea. The sole exception is at
deep-sea geothermal vents, where you can pick up energy from the thermal
gradient. On Gliese 581g, there's huge amounts of energy to be picked up just
from the constant flow of energy from hot side to cold side, so I'd expect
lifeforms to somehow be tapping into that.

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scotty79
Piezoelectric tendrils gathering energy from ever flowing water. I like that.

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Garbage
This might be nth time I am hearing a news "Potentially Habitable Planet
Discovered". Nothing happens after that.

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anateus
Really? This is the first time I'm hearing that. I've seen "planet discovered"
a bunch of times, with a crescendo of excitement. I was always disappointed
that they were almost exclusively super-giants and the "so what" line always
said something like "and if this super-giant has moons, they could be
habitable!"

This is the first time I've seen a story about an actual earth-like (with
fairly loose parameters) planet that is roughly in the life-zone! Usually
headlines that say "earth-like planet discovered!" involve either a frozen
rock orbiting way outside of its sun, or a burning pebble right next to it.

However important this particular planet is, I think it's a first as far as
fairly plausible life candidates go. Here's to more!

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skbohra123
Given the options, I would still prefer earth.

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ck2
Now we have somewhere to go when that asteroid hits in 2098

[http://blogs.discovermagazine.com/badastronomy/2010/09/28/th...](http://blogs.discovermagazine.com/badastronomy/2010/09/28/the-
newest-tiny-threat-to-earth-2010-st3/)

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rblion
"we’ve almost totally depleted this planet, we can just go to this one that is
21 light-years away."

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rblion
thanks.

~~~
rblion
all things must pass. ever heard of biocapacity?

