Fade To Indigo


So many billions of shades of color. Not to mention the infrared, ultraviolet, radio, and gamma rays.

Is someone on Proxima Centauri B looking up a their sky with the same sense of wonder and awe at the beauty of it?

Not to be a buzzkill, but probably not. There’s an excellent Twitter thread by Dr. Kathryn J Mack (@AstroKatie) which you can read here even if you don’t have a Twitter account. The short version is that because there are so many hundreds and thousands of variables that we have no data on, the odds are massively stacked against Proxima B actually being inhabited or actually “habitable” by anything resembling us.

Proxima Centauri is a dim, red star. Proxima B is orbiting in its “habitable zone,” which is defined as the region around the star where it would be warm enough to have water on the surface not freeze solid, and cool enough so that it doesn’t boil away. For obvious reasons, this is also commonly referred to as “The Goldilocks Zone.”

Being in the “habitable zone” doesn’t make a planet actually be “habitable.” To hold life similar to ours, it would still need an atmosphere, water that is busy being neither frozen nor boiled, and probably a magnetic field to protect the planet from solar flares. We can’t tell if Proxima B has any of those things.

But the odds are against it. Because Proxima Centauri is such a dim, cool, red star, its habitable zone is much closer in than the Sun’s is. This has a couple of likely scenarios, mostly bad for life as we know it.

First, the planet is likely to be in tidal lock with one side always facing the sun and one side always in darkness. (This is very similar to the way Earth’s moon is tidally locked, with one face always turned toward the Earth.) With a sun and a planet, you’ll get one hemisphere boiling and the other freezing. You might have a strip along that terminator that would be tolerable, but that combination of heat on one side and cold on the other would drive hellacious straight-line winds, quite possibly hundreds of miles an hour.

Assuming you have an atmosphere. The atmosphere on Mars, for example, is thin and getting thinner by the millennium due to the planet’s lack of a magnetic field. The magnetic field blocks all or most of the worst effects of the solar winds. Left unabated, the solar wind over time will carry away the atmosphere and leave a planet looking like the moon or Mercury.

Can we tell if Proxima B has an atmosphere or a magnetic field? Not at the moment – but we’re close. The James Webb Space Telescope (which I saw being assembled here last year) could directly image the atmosphere, and radio telescopes or other instruments in the next decade could determine if there’s a magnetic field. Also, if there is an atmosphere and a magnetic field there should be aurora, which the JWST could look for.

Should we say it’s too hard and give up? Of course not, don’t be ridiculous.

Should we have newspaper and website headlines screaming about “Earth’s twin” being “right next door” and “habitable?” Of course not, don’t be ridiculous.

How about if we stay cool, breathe a bit, get excited about the prospect, work to get some actual data – and in the meantime rest assured that even if there isn’t someone on Proxima B looking at their sunset (probably through a 200 mph wind!), it’s an unbelievable huge universe and even with the long odds that life faces, there are almost certainly some things some where (and probably billions of some things on billions of some where planets) staring in awe at their sunsets.

They just might not be 4.25 light years away.

Or they might!

Let’s find out.

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