Exoplanet Guide

Scienceline’s Guide to the Exoplanets: The Icehouse Down the Road

Barnard’s Star b: Another nearby planet with a hidden world

June 29, 2020
A fake planet with "Scienceline's Guide to Exoplanets" labeled across its equator. Other planets zoom past behind it.
Your favorite planets, and you didn't even know they existed. [Credit: Curtis Segarra | CC BY-NC-ND 2.0]

The Icehouse Down the Road
Barnard’s Star b
Discovered by: Ignasi Rabas, et al
Discovered: 2018
Distance from Earth: ~6 light-years
Mass: >3.2 Earth masses
Surface climate: Ice, probably
Habitability for humans: Do you like swimming?

Barnard’s Star, as I’ve mentioned before on this blog, is one of the nearest stars to the Earth: only six light-years away. Even though it’s a red dwarf, small and dim enough that it isn’t even visible to the naked eye, it’s close enough that astronomers have repeatedly looked at it for traces of other worlds. It certainly helps that Barnard’s Star shines bright in the infrared — and it’s small, so the pull of large planets upon it would be slightly easier to see.

That’s made it a very tempting target for exoplanet hunters. In fact, as early as the 1960s — decades before anyone actually found exoplanets — an astronomer by the name of Peter van de Kamp suggested that movements in the star’s position suggested it was orbited by gas giants. Van de Kamp’s claims found wide acceptance in the pre-exoplanet days of 1960s and 1970s, but fell out of favor in decades since as astronomers looking at the star failed to find what Van de Kamp had.

The search continued, as through the 2000s, astronomers ruled out the possibility of supermassive gas giants around Barnard’s Star. Finally, in 2018, as detection methods and technology advanced by leaps and bounds, astronomers found something.

(Technically, the planet hasn’t quite been confirmed, but it’s far more likely it exists than not. I could also be wrong.)

The size and mass of Barnard’s Star b, as this planet that’s definitely not a star is so aptly called, are still unknown. Astronomers only know it’s at least 3.2 Earth masses — and, if it’s not too much larger than that, the planet is likely terrestrial, a Super-Earth.

Of course, even that glimmer of suspicion begs the natural question: could Earth-like life exist on Barnard’s Star b? Could humans even one day be able to stand upon its surface?

On the surface, the signs aren’t quite so encouraging. The planet is located out past Barnard’s Star’s snow line: the distance from the star where it’s too cold for liquid water to exist on its surface. Astronomers believe the planet’s surface to be in the neighborhood of -170 degrees Celsius, or -275 degrees Fahrenheit: about the temperature of Saturn’s surface.

In any event, if the planet is solid, that makes its surface far too cold for anything resembling Earthlike.

But the planet could have internal heating. Like Jupiter’s moon Europa or likely even Pluto, the planet might have a buried ocean — one that would be warm enough to be recognizable as Earth-like temperatures.

What next? For one, Barnard’s Star b’s close distance means that it remains a tantalizing search for astronomers trying to find more detail. What might be found upon its surface, for instance? Could the planet have an atmosphere?

It’s also close enough that astronomers might be able to catch the planet transiting its host star — something that might lead to some truly stunning images.

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