Super-Earth Jelly discovered at six light-years

Astronomers have discovered a frozen exoplanet representing more than three times the mass of the Earth, orbiting a star six light years from the planet. The exoplanet revolves around Barnard's star, the solitary star closest to our sun.

This makes it the second known exoplanet closest to us. Previously, an exoplanet was in orbit around the three-star system Proxima Centauri.

The exoplanet was found after assembling 20 years of data, comprising 771 individual measurements, from seven instruments. The analysis that led to the discovery is detailed in a study published Wednesday in the journal Nature.

For years, astronomers thought that they would find a planet around the nearby star, but that escaped them.

"The star of the host is the big kick of this discovery," wrote in an email Paul Butler, co-author of the study and astronomer at the Carnegie Institution for Science. "Barnard's star is the" great white whale "of planetary hunting."

The planet, called Barnard's star b, is probably dimly lit by its star and slightly cooler than Saturn. Researchers believe that it is an icy desert without liquid water, from a hostile environment where the average temperature at the surface is about 274 degrees Fahrenheit.

The red dwarf star itself emits only about 0.4% of the brightness of our sun; the planet receives about 2% of the intensity that the Earth receives from its sun. This is because Barnard's star belongs to the class of dwarf M stars, cooler and less massive than our sun. It is also an old star that precedes our own solar system.

And to look through a telescope, the star seems to move the fastest among the other stars in the night sky. It's because it moves quickly in relation to the sun, and it's the closest star to the sky, Butler said.

"The star was named in honor of the great American astronomer Edward Emerson Barnard, pioneer of stellar photography and astrometry," Butler said. "He recognized that this star had the greatest known motion known a century ago."

The planet is at about the same orbital distance from its star as Mercury from our sun, making a complete turn around the star every 233 days. This places it in the "snow line" of the star, where it is cold enough for the water to freeze in solid ice. In this region of a planetary system, it is thought that the constituent blocks of the planets are formed and collect materials to form nuclei. As they migrate closer to their hosts, gathering more matter, they become planets.

This is the first time that a planet as small and far from its star is detected using the radial velocity technique, to which Butler has contributed to pioneering work. This method is sensitive to the mass of the exoplanet and measures the speed changes of the host star. The instruments can be used to detect tiny flickering in the orbit of the star caused by the gravity of the planet.

"I think this discovery shows the power of the [radial velocity] A technique to detect longer periods, small planets much more difficult or impossible to detect with missions like Kepler and TESS, which focus on the search for exoplanets in transition in shorter orbital periods, "Johanna Teske , co-author of the Hubble Study and Scholar at the Carnegie Institution for Science, writes in an email. "This study is a wonderful example of collaboration and coordination across multiple teams and multiple datasets, which may not always be successful in exoplanet research. It is only by combining data and working together that this very complex detection has been possible. "

These methods are not always available for astronomers looking for exoplanets. For most of the last hundred years, the only way was the astrometric technique, in which astronomers are looking for the host star's oscillation relative to stars in the background, Butler explained. It worked only for the nearest stars and was made by taking photographs of the star and measuring its positions relative to each other.

"This made Barnard's star the most important star in the sky because it's the closest star in the sky," Butler said.

In the 1930s, American astronomer Peter van de Kamp began a quest to study Barnard's star that will last most of his 93 years. His claims about how planets could orbit the star were refuted, and he died five months before the first verifiable discovery of an exoplanet in May 1995, Butler said.

"He worked hard to improve the only technique at that time of finding planets and spent decades collecting data," Butler said. "Van de Kamp is a true pioneer of extrasolar planets."

Given its proximity to our solar system and its long orbit, future missions and telescopes will be able to provide new information about Barnard's star b.

"Future space telescopes such as WFIRST may be able to observe the light reflected off Barnard's star off the planet and provide information on the composition of the surface and / or atmosphere of the planet," he said. said Teske.