Astronomers Found A 'Snowy' Super-Earth Less Than 6 Light-Years Away — And It May Be The First Planet We'll Photograph Beyond The Solar System

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Astronomers have suspected for decades that a nearby red dwarf star, called Barnard’s star, might be hiding an Earth-size planet.

On Wednesday, researchers revealed that they have discovered the first such exoplanet with about 99.2% certainty.

A team of dozens of scientists published that work in the journal Nature, and said there are even hints that a second world may lurk nearby.

 

An illustration of the exoplanet candidate Barnard’s star b, also known as GJ 699 b.

Barnard’s star is just 5.87 light-years away from Earth, making it the closest one-star system to us. Only Proxima Centauri, a three-star system, is closer.

What’s more, the newly discovered world is close enough to Earth – yet far enough from its blindingly bright star – to be photographed by an upcoming generation of giant telescopes.

“This is probably the first Earth-sized planet we will directly image by future missions,” Abel Méndez, an astrobiologist at the University of Puerto Rico at Arecibo who wasn’t involved in the study, told Business Insider.

The new world is currently known as Barnard’s star b or, in other circles, GJ 699 b. The team that found it used more than 20 years of telescope observations, and that data suggests the planet is at least 3.2 times more massive than Earth and has a 233-day-long year.

The world appears to orbit in the “snow line” of Barnard’s star – a region just on the edge of the habitable zone, where liquid water can exist on the surface of a planet.

For that reason, scientists consider the possible planet to be a “cold super-Earth,” and some are wondering if alien life might exist there.

 Exoplanet extrasolar planet cold super earth barnards star b gj 699 b illustration ESO M Kornmesser

ESO/M. Kornmesser

Barnard’s star is not like the sun. It’s what astronomers call an M-dwarf, which means it’s smaller, cooler (and redder), less massive, and billions of years older than our own star.

“M dwarfs are prime targets for planetary searches because they favor the detection of small [planets],” Rodrigo F. Díaz, an astrophysicist at University of Buenos Aires who wasn’t part of the research team, wrote in a Nature “News and Views” piece.

This is because M-dwarf stars are small enough to “wobble” when rocky planets orbit them. Such wobbling is caused by the gravity of the planet and the star mutually tugging at one another (a planet’s orbit is rarely perfectly circular), and some telescopes can detect this behavior.

Barnard’s star b took so long to find because red dwarf stars often have sunspots, which can throw off the sensitive measurements. Pooling together more than two decades of telescope observations, however, helped the research team find the signal of a presumable planet in the noise of Barnard’s star’s light.

 Exoplanet extrasolar planet cold super earth barnards star b gj 699 b orbits sun distance illustration IEEC Science Wave Guillem Ramisa

An illustration showing the sun in relation to Barnard’s star and the Alpha Centauri triple-star system.

The newly discovered planet is about as far from its star as Mercury is from the sun. That’s fairly close. However, next to a smaller and lower-temperature star, this puts Barnard’s star b at the edge of its habitable zone in the snow line region.

Practically, this means the surface temperature of Barnard’s star b is likely -150 degrees Celsius. This is cold enough to freeze carbon dioxide solid into dry ice, let alone water into ice.

But bone-chilling temperatures doesn’t mean the exoplanet is a dead world that’s bereft of liquid water.

 Europa jupiter ice moon half hemisphere 2x1 nasa jpl galileo pia19048

Half of Jupiter’s icy moon Europa as seen via images taken by NASA’s Galileo spacecraft in the late 1990s.

Although Barnard’s star b is -150 deg C, the surface of Europa – an icy moon that orbits Jupiter – is 10 degrees colder. Meanwhile, Ganymede – a smaller icy moon around Saturn – is about 20 degrees colder than that.

Yet both tiny worlds hide expansive oceans of salt water beneath their crusts, and there’s growing evidence that organic molecules are mixed into that liquid, too.

This temperature estimate also assumes there’s no atmosphere hugging the world. But there very well could be.

“Since the planet is more massive than Earth, it may retain a hydrogen atmosphere,” Sara Seager, the deputy science director for NASA’s TESS mission and an astrophysicist at MIT who wasn’t involved in the study, told Business Insider. “Hydrogen is a potent greenhouse gas and could conceivably keep the surface temperature warm enough for life, if the atmosphere pressure is high enough.”

It’s not a far-fetched idea. Seager added that all planets – even Earth – are born with a hydrogen atmosphere. This is because hydrogen is the dominant material in nebulas, the clouds of gas and dust out of which stars (and their planets) form.

“Assuming it has the estimated minimum mass, then it is probably a rocky or frozen ocean world with a thick atmosphere, maybe like Titan in the solar system,” Méndez said.

On the other hand, 3.2 Earth masses is a minimum estimate for the new world. “It’s mass could be larger and therefore a mini-Neptune,” Méndez added.

 Thirty meter telescope laser guide illustration tmt corporation

A laser on TMT will help the observatory take space-quality images.

Astronomers have already taken photos of very large exoplanets. These worlds are akin to giant Jupiters or failed stars, though, which means they’re all extremely hot, gassy, and uninhabitable.

Future ground observatories like the European Extremely Large Telescope in Chile, or perhaps even the Thirty Meter Telescope in Hawaii, may be able to capture a small image of Barnard’s star b.

If the exoplanet does indeed exist, it may look like a tiny dot or blob. However, the data trapped in such a picture could tell scientists whether the planet is small and rocky like Earth, big and gassy like Neptune, or somewhere inbetween.

What’s more, some of the light that passes through or bounces off the world’s atmosphere might even be sampled for indirect signs of life. Such gases might include methane, oxygen, carbon dioxide, and perhaps 14,000 other so-called biosignatures.

Even if Barnard’s star b turns out to be a bust for biosignatures, future observations may discover the Earth-size world isn’t alone.

“I don’t discard the possibility of smaller Earth-sized planets in the habitable zone of Barnard’s Star, now we know that Barnard has planets and there is plenty of space between the star and this new planet for a few small ones,” Méndez said.

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