Astronomers have found a frozen exoplanet more than three times the mass of the Earth, orbiting a star just six light-years away. Exoplanet revolves around the Barnard star, the closest lonely star of our Sun.
This makes it the second best known exoplanet for us. Earlier, an extrasolar planet was found in orbit in the three-star system Proxima Centauri.
The exoplanet was found after 20 years of data were combined, including 771 individual measurements, from seven instruments. The analysis that led to the discovery was described in detail in a study published on Wednesday in the journal Nature.
Over the years, astronomers thought they would find a planet around a nearby star, but they miss it.
"The greatest" kick "of this discovery is the host star," wrote Paul Butler, co-author and astronomer at the Carnegie Institution for Science. "Barnard's Star is a" big white whale "hunting for the planets."
The planet, known as Barnard's star, is probably poorly lit by a star and a bit colder than Saturn. Scientists believe that it is an ice desert with no liquid water, a hostile environment in which the average surface temperature is around minus 274 degrees Fahrenheit.
The red star of the dwarf emits only about 0.4% of our solar radiation, so the planet receives about 2% of the intensity that Earth receives from its Sun. This is because Barnard's star belongs to the class of M dwarfs, colder and less massive than our Sun. It is also an old star that is ahead of our own solar system.
And looking at her through the telescope, the star seems to move the fastest among other stars in the night sky. This is because it moves quickly in relation to the sun and is the closest star in the sky, Butler said.
"The star was named after the great American astronomer Edward Emerson Barnard, who was a pioneer in stellar photography and astrometry," Butler said. "He knew that this star had the largest known movement for a century."
The planet is located about the same orbital distance from the star, which is Mercury from our Sun, which causes the full displacement of the star every 233 days. It places it in the "snow line" of the star, where it is cold enough for the water to freeze in constant ice. This region in the planetary system is where it is believed that blocks of planets are being built, collecting material to become the core. As they migrate closer to their mother stars, accumulating more material, they become planets.
For the first time, this small planet, distant from the star, was detected using the radial velocity technique that Butler helped pioneers. This method is sensitive to the mass of an exoplanet and measures changes in the velocity of the parent star. Instruments can be used to detect small vibrations in the orbit of a star that are caused by gravity on the planet.
"I think this discovery shows power [radial velocity] detection of longer periods, small planets that are much more difficult or impossible to detect with missions such as Kepler and TESS, which focus on finding transit exoplanets in shorter orbital periods "Johanna Teske, co-author and Hubble Fellow at the Carnegie Institution for Science, wrote in an e-mail. "This study is a great example of collaboration and coordination in many teams and many data sets, which is not always successful in exoplanet research. Only by combining data and collaborative work is it very difficult to detect. "
These methods have not always been available to astronomers seeking exoplanets. For most of the past hundred years, the only way was the astrometric technique in which astronomers look for a host star that wobbled around the background stars, Butler said. It worked only for the nearest stars and was achieved by photographing the star and measuring its position in relation to each other.
"It made the Barnard star the most important star in the sky, because he is the closest single star in the sky," said Butler.
In the 1930s, the Dutch-American astronomer Peter van de Kamp began looking for Barnard, who lasted nearly 93 years. His claims of how planets could fit into the orbit around the star were rejected, 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 the time, which had a prayer to find planets, and he spent decades collecting data," said Butler. "Van de Kamp is a true pioneer in the field of extrasolar planets."
Considering the closeness of our Solar System and its long orbit, future missions and telescopes will be able to provide new information about Star Barnard's star.
"Future space telescopes, such as WFIRST, may be able to observe the light reflected from the Barnard star outside the planet, and thus tell us something about the composition of the surface and / or the atmosphere of the planet," said Teske.