Published: Thu, November 15, 2018
Sci-tech | By Patricia Wade

'Super-earth' discovered orbiting red dwarf known as 'Barnard's Star'

'Super-earth' discovered orbiting red dwarf known as 'Barnard's Star'

At almost six light-years away Barnard's star is the next closest star to the Sun after the Alpha Centauri triple system.

Given its proximity to our solar system and its long orbit, future missions and telescopes will be able to provide new insights about Barnard's star b. But the methods we've used to detect majority are biased toward finding large planets that orbit close to their host stars.

The planet candidate, called Barnard's star b (or GJ 699 b), is a super-Earth with a minimum of 3.2 Earth masses. Mini-Neptunes and super-Earths are the most common kind of planet found orbiting other stars.

"Barnard's star is an infamous object among astronomers and exoplanet scientists, as it was one of the first stars where planets were initially claimed but later proven to be incorrect". That is true in the Solar system (Jupiter), and also seems true for Barnard's Star - if the planet really exists.

In the coming decade, the next generation of astronomical observatory will revolutionise our ability to peer into the space close to the nearest stars, looking for the dim glow of their planets, reflecting the light of their host stars.

From this orbital information, the team calculates the planet must weigh at least 3.2 times as much as Earth.

While there are different snow lines for each chemical (carbon dioxide doesn't freeze out where water will), the presence of any solids should dramatically change the dynamics of the disks that give rise to planets. One thing astronomers are confident about, though, is that this new planet is not habitable. Worse, the method used to find the exoplanet means taking spectra of the star, spreading its light out into thousands of individual colors.

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Barnard's Star is theorized to be about twice as old as our Sun, but only one-sixth the size and two per cent as luminous.

Although it is about as close to its own star as Mercury is to our sun, scientists say it is probably as cold as Saturn.

The only known exoplanet closer to Earth was discovered in 2016 orbiting one of a cluster of stars in the Alpha Centauri system, just over four light-years away. Lacking atmosphere, its temperature is likely to be about minus 170 degrees Celsius, which makes it unlikely that the planet can sustain liquid water on the surface.

To find Barnard´s Star b, Ribas and the team studied more than 20 years´ worth of observations from seven separate instruments. This is where planets are detected using gravity-both the star's influence on the planet and the planet's influence on the star. That dip, which occurs every 233 days, might be the telltale sign that a planet is in orbit around it. Despite that, the planet is incredibly cold, with a temperature no lower than -170°C, though maybe a touch less frigid... so Earth-like it ain't.

Graphic representation of the relative distances to the nearest stars from the sun.

Even the most powerful telescopes in use today would not be able to image Barnard's Star b directly.

He added: "Difficult detections such as this one warrant confirmation by independent methods and research groups. a signal for the planet might be detectable in astrometric data - precision measurements of stellar positions - from the Gaia space observatory that are expected to be released in the 2020s". The European Space Agency's Gaia mission could eventually shed light on this question, since the spacecraft is created to precisely track the movements of stars. However, if astronomers record observations of this starlight over many years, they may notice slight periodic frequency shifts.

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