
Earth-sized exoplanet ‘habitable zone’ - pseudolus
https://www.nature.com/articles/d41586-020-00014-7
======
jcims
> _Astronomers have discovered a world only a little bit bigger than Earth,
> whirling around a bright star about 31 parsecs from our planet._

Parsec is one of those units that is difficult to remember if you just look at
the conversion (1 parsec = 3.26 light years). If you remember how it's
defined, however, it somehow becomes easier (for me anyway). One parsec is the
distance at which one astronomical unit (AU, mean distance between earth and
sun) spans one arcsecond in the sky. One arcsecond, in turn, is 1/3600th of a
degree, and is approximately the width of a human hair from 20 meters away.

On a side note, if you think that's small, many stars in the night sky have
apparent diameters measured in thousandths of an arcsecond.

~~~
dmurray
I just remember that a parsec is the same as a light year. By astronomical
standards of precision, that's about right.

~~~
fastbeef
I remember it as 1/12th of a Kessel Run, easy peasy

~~~
basilgohar
The Kessel Run as performed by the Millennium Falcon; not just any ship can do
that!

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ppeetteerr
I've been pondering this for a while: once we have artificial gravity in space
(from rotation, for instance), would we ever want to shackle ourselves to the
gravity of a foreign planet? It would be so much easier just to create the
ideal environment in a large, rotating cylinder instead of having adjust a
planet's environment to our needs.

Take this new discovery for instance. Imagine that this planet is 400m years
younger than earth. Would it have the necessary composition in its atmosphere
to make it breathable? Does it share our gravity? Does it deflect enough
stellar radiation?

I doubt we'll find earth 2, but we can recreate a comfortable environment in
our own solar system. We just have to let go of the notion that we will
colonize another planet for more than just curiosity-sake

To give some idea of what I mean by rotating cylinder, check out the O'Neill
Cylinder
[https://en.wikipedia.org/wiki/O'Neill_cylinder](https://en.wikipedia.org/wiki/O'Neill_cylinder)

~~~
ur-whale
I think the reason earth-like exoplanets generate so much interest is not
because of the terraforming / colonization potential but rather because they
are more likely places where we might find alien life.

~~~
blaser-waffle
We have to wonder if they're thinking the same about us.

"That 3rd planet looks easy to colonize. I wonder if there are any upright,
talking primates there?"

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CWuestefeld
According to this [1] it's probably tidally locked, which means that despite
being in the goldilocks zone, the environment is likely problematic for life.

[1] [https://www.sciencealert.com/nasa-found-a-tatooine-like-
plan...](https://www.sciencealert.com/nasa-found-a-tatooine-like-planet-and-
an-earth-sized-word-in-the-habitable-zone)

~~~
pushpop
People keep saying that for extreme climates on Earth and are then constantly
surprised by the variety and abundance of life - admittedly sometimes just
microbiology - found in those locations. So I wouldn’t write off a planet just
for tidal lock.

~~~
nwallin
The problem is that the atmosphere and weather is global. Meaning that snow
that falls on the cold side will never melt or evaporate. Therefore there's
probably no liquid water.

Liquid oxygen is dense enough for icebergs to float over to the warm side, but
there won't be any oxygen before life can start photosynthesizing, and it
would boil off long before ice could float close enough to the hot side to
melt or evaporate. Liquid nitrogen is less dense than ice, so that doesn't
help. Most other plausible liquids (methane, ammonia) are also less dense than
ice.

It's difficult to say life would be impossible on a tidally locked planet, but
it's certainly very unlikely. Remember that it took Earth something like two
billion years to develope life, and this place is downright cozy.

~~~
pushpop
Last year there was a discovery where some single cell organisms were
extracting electrons directly from solid rock. So I don’t think ice is a
barrier.

I do agree that it’s unlikely that life would exist on that planet. But I
think the chances of life being slim are more down to the difficulty in the
bootstrapping stage rather than the environment being too inhospitable to host
life. By that I mean DNA forming (for example) might be 90% of the problem and
survival might be 10%. Figures obviously made up but I hope you understand my
(crudely expressed) point.

There’s also the point that extraterrestrial life might not mimic the typical
examples we see on Earth. In fact in plausible for silicon and/or arsenic to
be building blocks for DNA and that’s only narrowly widening our expectations
of life.

~~~
nwallin
> But I think the chances of life being slim are more down to the difficulty
> in the bootstrapping stage rather than the environment being too
> inhospitable to host life.

I'm 100% in agreement on this.

My argument is that with no oceans, abiogenesis is basically impossible.
There's not really a useful starting point if everything is rock and ice.

I have no doubt that in 200 years a prepared group of humans could be dropped
there and thrive. (transportation issues not withstanding) But life couldn't
start there from nothing.

I don't think silicon based life is plausible. It can't form double silicon
silicon bonds. Overall its chemistry is utterly boring compared to carbon's,
and carbon is far more common than silicon is. Again, same argument. If
silicon based life were intelligently created, sure, it would probably thrive.
But there's no way it would spontaneously create itself. And honestly, it
would probably evolve to being carbon fairly quickly.

~~~
pushpop
I’ve read plenty of material which would disagree with your skeptisim there eg
(top link in DDG)

[https://www.astrobio.net/news-exclusive/possibility-
silicon-...](https://www.astrobio.net/news-exclusive/possibility-silicon-
based-life-grows/amp/)

Regarding life, I don’t just think human life could thrive in such
environments, I think even single cell organisms could...if implanted there
that is. As I said earlier, we have life on Earth in seemingly less hospitable
environments like naked rock faces, sulphur-rich volcanic lakes, etc. We even
have microbial life on Earth that uses arsenic as one of the chemical elements
for DNA. So while 99.99% of life here does fall into a narrow spectrum, even
on Earth we are constantly surprised by the ability for life to thrive and
adapt in environments it classically shouldn’t. Therefore I think we should be
open minded to the possibility of surprises outside our own ecosystems. Albeit
bootstrapping aside.

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monkeycantype
Not sure on the social norms here, I commented on the post of this news that
didn’t rise to the front :

‘completes one orbit every 10 Earth days' Excellent news for fans of the
French Revolutionary Calendar. 'The French Revolutionary Calendar, created at
the same time as the metric system, was an attempt to create a metric calendar
and time system.' [https://www.cooksinfo.com/french-revolutionary-
calendar](https://www.cooksinfo.com/french-revolutionary-calendar)
[https://en.wikipedia.org/wiki/French_Republican_calendar](https://en.wikipedia.org/wiki/French_Republican_calendar)
[https://twitter.com/sansculotides](https://twitter.com/sansculotides)

