Earth-sized exoplanet ‘habitable zone’ • Hacker News Board

Re: Earth-sized exoplanet ‘habitable zone’

#21

Post by fastbeef » Wed, Jan 08, 2020, 7:58 PM UTC

dmurray wrote: post #15

jcims wrote: post #4

> 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 di…

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

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

Re: Earth-sized exoplanet ‘habitable zone’

#22

Post by madrox » Wed, Jan 08, 2020, 7:59 PM UTC

ppeetteerr wrote: post #16

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 y…

Should it ever become practical to do so, the reasons for doing so will look very similar to the reasons Europeans colonized America. The thing about densely populated environments is it requires lots of governance, and populations have a habit of increasing exponentially, which would be difficult for artificial environments to keep up with indefinitely. When you're on the frontier, you have a lot more freedom.

Re: Earth-sized exoplanet ‘habitable zone’

#23

Post by [deleted] » Wed, Jan 08, 2020, 8:00 PM UTC

dmurray wrote: post #15

jcims wrote: post #4

> 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 di…

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

[deleted]

Re: Earth-sized exoplanet ‘habitable zone’

#24

Post by nxpnsv » Wed, Jan 08, 2020, 8:00 PM UTC

jcims wrote: post #4

> 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 di…

Or that 1 apc (attoparsec) is ~3cm...

Re: Earth-sized exoplanet ‘habitable zone’

#25

Post by fullstop » Wed, Jan 08, 2020, 8:01 PM UTC

ppeetteerr wrote: post #16

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 y…

You can step outside without being in a vacuum.

Have you read the Expanse books? They kind of touch on this subject.

Re: Earth-sized exoplanet ‘habitable zone’

#26

Post by sukilot » Wed, Jan 08, 2020, 8:04 PM UTC

dcminter wrote: post #17

saagarjha wrote: post #7

Earlier quoted context omitted.

I’m not sure if the definition helped.

The point of a parsec is that if you're stuck on earth a very long way from the stars and you're trying to work out where they are relative to each other, you can take advantage of the fact that the earth itself moves around the sun. So if you take a photo of a star in summer and then take another photo of it in winter, your vantage point has conveniently moved 2AU because during that time you've moved to the other s…

That's a great way to compute the distance to a star from yourself stuck on Earth for half a year.

It's not a great way to understand the magnitude of that distance when planning a trip.

Re: Earth-sized exoplanet ‘habitable zone’

#27

Post by sukilot » Wed, Jan 08, 2020, 8:04 PM UTC

kempbellt wrote: post #8

jcims wrote: post #4

> 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 di…

That was a lot of fascinating information in one comment. Also fun to note that you mentioned "mean distance" and not just "distance" from the Sun because the Earth's orbit isn't perfectly circular. Thanks for the explanation.

Many people say distance when they mean distance.

Re: Earth-sized exoplanet ‘habitable zone’

#28

Post by gwbas1c » Wed, Jan 08, 2020, 8:05 PM UTC

giarc wrote: post #19

pushpop wrote: post #6

Earlier quoted context omitted.

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.

Probably best to say "unlikely to contain multicellular life" or maybe even complex life. As we know from here on Earth, microorganisms exist in almost every extreme location on Earth.

Given how fast the human race evolved (compared to how old the earth and life is,) I wouldn't make any assumptions about multicellular life.

Re: Earth-sized exoplanet ‘habitable zone’

#29

Post by XaspR8d » Wed, Jan 08, 2020, 8:07 PM UTC

nxpnsv wrote: post #24

jcims wrote: post #4

> 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 di…

Or that 1 apc (attoparsec) is ~3cm...

Pretty close to 1.2in, hence why I just prefer to remember a parsec as quite close to 0.1 eft (exafoot).

Re: Earth-sized exoplanet ‘habitable zone’

#30

Post by dcminter » Wed, Jan 08, 2020, 8:09 PM UTC

sukilot wrote: post #26

dcminter wrote: post #17

Earlier quoted context omitted.

The point of a parsec is that if you're stuck on earth a very long way from the stars and you're trying to work out where they are relative to each other, you can take advantage of the fact that the earth itself moves around the sun. So if you take a photo of a star in summer and then take another photo of it in winter, your vantage point has conveniently moved 2AU because during that time you've moved to the other s…

That's a great way to compute the distance to a star from yourself stuck on Earth for half a year. It's not a great way to understand the magnitude of that distance when planning a trip.

But if you're planning a trip, why would you plan it in Parsecs rather than Light Years (or some other more convenient unit) when you're not stuck on earth?