Fine Structure

Found: One Habitable Exoplanet

Huge news today! Scientists looking at the star Gliese 581 have found one of the planets to be squarely in the system's habitable zone - the space in which a planet could potentially support liquid water on the surface - and that means that there's a potential for life, or a place where humans could survive on the surface.

We knew that a habitable zone planet would come along soon enough and this one is especially close, "only" about 20 light-years away. The entire system (five planets so far) is contained within an orbit that's only slightly larger than the orbit of Venus. Why is everything so damn habitable then? Well, as a red dwarf, Gliese 581 isn't terribly bright (sorry Gliese). Whereas we'd be quite toasty that close to our sun, the planet we're talking about - the fourth one out, also known as g - is in just the right place to be a comfortable temperature for this system.

The kicker is that because of the compact system size, it's likely that the rotation of g is locked to its parent star. It travels around the star once every 36 days, the whole time with one side facing the star and the other perpetually pointed towards the great unknown.

So let's answer some burning questions. How long would it take us to get there? At light speed, 20 light-years would take us - wait for it - 20 years. Of course, we can't travel anywhere close to the speed of light but we did speak briefly about Icarus the other day which could potentially travel at 12% of light speed. Let's go with that.

If we're traveling only at 12% the speed of light, we're really aiming to get there in ~166 years from the perspective of Earth. However, because of time dilation (i.e. very fast things feel time moving more slowly), you and your shipmates on the Icarus will age slightly slower than than the rest of us on Earth. Though, in the grand scheme of things 0.12c isn't that fast and the Icarus will only feel 165 years go by.

Now, if we wanted to get there relatively fast from the star travelers' perspective - I'd say 26 years on an interstellar freighter is just about the most I could deal with - we'd have to travel at roughly 60% the speed of light, which of course would feel a little longer on Earth at just about 33 years. Getting our technology to push us at 0.60c might still be a bit outside of our range though, and who knows when we'll actually have the technology to go that fast.

Tomorrow: g may be in the habitable zone but half of the planet is baked in the Sun all day and the other half is shrouded in night. Where would we live?

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