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Making Maps and Watching Weather On Planets Like Ours

posted by Tim Carmody   Nov 16, 2018

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A team of astronomers believe theyve found an exoplanet orbiting Barnards Star, in the solar system closest to ours. The evidence is uncertain, but if its there, its about three times the size of Earth, and orbits much closer to the much dimmer star. This puts it near the snow line, where terrestrial planets like ours are found. This also means its close enough to us and the right distance from our star where we can take a really good look at it. From the paper in Nature:

The candidate planet around Barnards star is a cold super-Earth, with a minimum mass of 3.2 times that of Earth, orbiting near its snow line (the minimum distance from the star at which volatile compounds could condense). The combination of all radial-velocity datasets spanning 20 years of measurements additionally reveals a long-term modulation that could arise from a stellar magnetic-activity cycle or from a more distant planetary object. Because of its proximity to the Sun, the candidate planet has a maximum angular separation of 220 milliarcseconds from Barnards star, making it an excellent target for direct imaging and astrometric observations in the future.

On Twitter, Charlie Loyd wrote this thread, and I cant stop thinking about it:

Assuming its confirmed, this means both the closest star systems have planets. (Okay, the three closest if you count the one were in. Very good.) Thats delightful. But also: as the abstract points out, this new one is an excellent candidate for direct imaging. Check my math, but reasonably conservatively, I think it should be about 0.3 nrad (1.7e-8) across from here.

Theoretically, to resolve that in visible wavelengths, you need a ludicrously large telescope. But! If you think hard enough about the wavefronts of the light that they see, you can use a set of spread-out smaller telescopes to work as one big one. This is an interferometric array, and last I checked the best one was CHARA, in the hills over Los Angeles (https://t.co/Rr3zPT1gpR). It can resolve down to about 1 nrad (5.5e-8). Its seen sunspots on other stars.

So we dont have anything that can see features on the face of the new planet say, continents and weather systems, if any. Even a 0.3 nrad telescope couldnt do that. But were closer than you might think.

If we fund it CHARA was founded with @NSF money odds are fair that well map alien worlds and watch alien weather in our lifetimes. Okay, have a nice day.

What a fantastic project that would be. And if were ever going to send a probe to or make a first-person visit a world outside our solar system, it would be an essential one. Why do space science, if not for things like this?