August 24, 2016


We advised skepticism earlier, but  it has now been confirmed that Proxima Centauri, the closest known star to our solar system, does indeed have a rocky "Earthlike" planet.

It get's better...

  Although Proxima is considered a moderately active star, its rotation period is about 83 days (ref. 3) and its quiescent activity levels and X-ray luminosity4 are comparable to those of the Sun. Here we report observations that reveal the presence of a small planet with a minimum mass of about 1.3 Earth masses orbiting Proxima with a period of approximately 11.2 days at a semi-major-axis distance of around 0.05 astronomical units. Its equilibrium temperature is within the range where water could be liquid on its surface5.

One of The Brickmuppet's Crack Team of Science Babes has thoughts on the matter....


There is more here and here

This is still, an insanely long way out. An Orion drive (which involves propelling a ship by exploding atom bombs behind it) could get a crewed expedition there in about 100 years. More advanced nuclear pulse propulsion systems (that, unlike Orion would require considerable advancements to get working) could make a one way trip in around 45 years, as could the proposed laser sail designs. 

Ok, that's a littler silly given that one needs to be darned sure of a destination if one embarks on a one way trip.

Obviously an unmanned probe could get there faster little as 15 years for one design using near term technology and a very small probe. Well, that design now has a concrete goal. 

And IF there was something very interesting found there...well, assuming a 20 year lead time to build the ship (which would involve the equivalent of constructing 4-10 Nimitz class aircraft carriers in terms of mass) then we could still put a, flag, some footprints and a small town there in the lifetime of the people that set the project in motion.

This is, on the one hand, unspeakably extravagant and optimistic given the challenges our civilization faces regarding its health and even survival in the near term. However, given those difficulties and others peculiar to having all of our eggs in this pale blue basket, such an extravagant project is not quite as insane as it sounds at first blush, given that a successful implementation would mean that our civilization would be multi-stellar at that point and our species's survival far more likely. 

In any event, this is an awesome development in astronomy, for other reasons. The fact that the very closest star to our sun just happens to have one of these planets makes the odds of such things far more likely...especially since red dwarf's such as Proxima Centauri are the most common type of star in the galaxy. 

The implications for that are nontrivial indeed. 

UPDATE: This image, by ESO Calcada is, of course, pure speculation regarding the planet's appearance, but it gives a very good idea of the scale of space. Note that Proxima Centauri is generally considered to be a part of the Alpha Centauri System, Alpha Centauri A and B are both about the same size and brightness of our sun (A liitle larger and a little smaller respectively). Keeping in mind that they are in the same solar system as Proxima, note their distance from their little red companion in this picture.

Posted by: The Brickmuppet at 03:08 PM | Comments (3) | Add Comment
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It is by no means certain that Proxima is part of the Alpha Centauri system, by which I mean in orbit around the two main stars. It's possible Proxima is making a one-time hyperbolic pass.

Which wouldn't matter for our purposes; either way it will be thousands of years before it has moved very far away from where it is now. And if it is in orbit the orbital period is probably measured in tens of thousands of years.

Posted by: Steven Den Beste at Wed Aug 24 18:08:26 2016 (+rSRq)


The big question I would have about any planet which is that close to its star (even if the star is a midget like Proxima) is whether the planet is tide-locked. If so, with the same face always toward the star, then you can forget about life.

And you can forget about terraforming.

An artificial colony might still be possible, built at one of the dawn/dusk lines, but it would have to be entirely enclosed.

A different possibility is that it's like Mercury and caught in a 3:2 resonance. Which means each planetary day is 1.5 planetary years long. In that case each day would be 8 Earth days long and each night likewise. I think you can still forget about life; the daily temperature swings would be brutal.

And the only places you might be able to build artificial colonies would be the poles.

Sorry; I'm no fun.

Posted by: Steven Den Beste at Thu Aug 25 20:02:38 2016 (+rSRq)

3 Unless it has a substantial moon (unlikely at that distance from the star) it is almost certainly locked tidally. That doesn't preclude life if its in the habitable zone, especially if there is an ocean that allows heat circulation. 
There is also the possibility that the atmosphere might provide convectional temperature stabilization and preventing the atmosphere and oceans from freezing out. Interestingly, a study on this recently found that 2/3rds of simulations had this result and due to something to do with coriolis effects,  this happy result was quite likely if the day/year was less than 12 Earth days. Proxima Centauri b has a 11 day long year.

As you mention, it could be in resonance Mercury in which case it has long days and nights. Given that this planet's year is about 11 earth days long, 3:2 resonance would mean nights lasting 14-15 earth days which isn't a deal breaker. Dense, biologically rich forests in Alaska have that much darkness or more. 
A bigger concern, would be magnetic fields, though even regarding that, Ganymede, which is an icy moon, far less dense than Earth, and tidally locked to something far less massive has a powerful magnetic field. A much more massive terrestrial planet with a big iron core would have a far more powerful one which might protect it from having the atmosphere stripped off. 
Finally, a tidally locked world still has a slight wobble (libration), allowing for a "day/night" cycle around the twilight band.

Posted by: The Brickmuppet at Thu Aug 25 23:18:42 2016 (1zM3A)

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