Sun's closest solo star may have company

Posted November 17, 2018

This image shows an artists's impression of the surface of Barnard's star b, a cold Super-Earth discovered orbiting Barnard's star 6 light-years away. A few telescopes with coronagraphs-devices for masking a star's light-have directly imaged a few large planets in wide orbits, but something like Barnard's star b will require the greater resolution of giant telescopes coming in the next decade, such as Europe's 39-meter Extremely Large Telescope.

Since the planet's initial detection, an worldwide effort called the Red Dots collaboration - led by Guillem Anglada-Escude at Queen Mary University of London and formerly based at the University of Hertfordshire - has been monitoring Barnard's star with high precision instruments to investigate the signal.

At almost six light-years away Barnard's star is the next closest star to the Sun after the Alpha Centauri triple system. So cool, in fact, that it's right at the location where some volatile chemicals, like water, would start to freeze out and form clumps of ice-scientists call that distance the snow line.

"HARPS played a vital part in this project", said Guillem Anglada Escudé of Queen Mary University of London and the co-lead scientist on the team, said in the statement.

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The rocky planet, at least 3.2 times the size of Earth, is orbiting Barnard's Star, one of the closest and most well studied red dwarf stars in the Galaxy and the sun's nearest neighbouring single star.

It is outside the habitable zone at a distance exceeding the so-called "snow border", where liquid water can not exist and has no chance at life. For this reason, life on its surface is unlikely to exist - the typical temperature on the surface do not exceed minus 170 degrees Celsius. However, if the planet has a substantial atmosphere the temperature could be higher and conditions potentially more hospitable.

The largest changes in a star's radial velocity will come when the plane of the planet's orbit is aligned with Earth.

All of the planets in our (earth's) solar system orbit the sun. This makes Barnard's Star b a prime candidate for us to use powerful spectroscopic techniques to, one day, peer into its atmosphere (if it has one) and understand what it's really made of.

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"However, we must remain cautious and collect more data to nail the case in the future, because natural variations of the stellar brightness resulting from starspots can produce similar effects to the ones detected". Until 1992, when the first exoplanets were found, and then in 1995 when the first one was found around a star like the Sun, we didn't know if other stars had planets at all. As they migrate closer to their host stars, gathering more material, they become planets.

"At a distance of only six light years, Barnard's Star b could conceivably be visited by people from Earth".

Astronomers described their discovery of Barnard's star in a paper published Wednesday in the journal Nature. "A planet in the "habitable" or surface liquid water zone of Barnard's star would have a period between 10 and 40 days, much shorter than the detected planet at 233 days".

"Technological developments over the last 20 years have shown that planets are common, and we are now pretty sure - based on statistics - that the majority of stars have planets".

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The dimness of Barnard's Star also explains the difficulty and the slight uncertainty surrounding the detection. It is so close that the next generation of telescopes may be able to image it directly, the researchers said. In the 1960s, the Dutch astronomer Peter van de Kamp, working in the U.S., published his evidence for a planetary companion, based on perturbations in the motion of the star.