Super-Earth discovered orbiting Suns nearest star

James Marshall
November 15, 2018

Barnard's star is the second-closest star system, and the nearest single star to us. One thing we have learned through the exoplanet era is that, where one planet lurks, more are sure to follow. Previously, an exoplanet was found orbiting in the three-star Proxima Centauri system.

This new discovery came from an investigation that saw astronomers from around the world combining more than 20 years of data on the star from seven different instruments. Spotting planets at a huge distance is still important, and every new planet researchers are able to detect adds to our knowledge of the universe and nature itself, but majority are so distant that we'll likely never actually visit them.

The radial velocity method was developed in the 1990s and has been steadily improving ever since, Ribas said.

"The biggest "kick" about this discovery is the host star", Paul Butler, study co-author and astronomer at the Carnegie Institution for Science, wrote in an email. At this distance, the planet only receives about two percent of the energy that the Sun gives to Earth, putting its surface temperature at a frigid -340 degrees Fahrenheit (-170 degrees Celsius).

Finding out more about Barnard's star b will likely require telescopes able to detect light from the planet itself. It would be as close to its parent star as Mercury is to our own sun - but because Barnard's Star is a dim red dwarf, surface conditions would be far too chilly for life as we know it.

And to look at it through a telescope, the star appears to be moving the fastest among the other stars in the night sky. "He recognized that this star had the largest known proper motion a century ago".

The dimness of Barnard's Star also explains the difficulty and the slight uncertainty surrounding the detection.

There is hope the planet could have a thick atmosphere trapping some heat, but astronomers say it's located beyond the "snow line" where any water on the surface is probably frozen. This region in a planetary system is where the building blocks of planets are thought to form, collecting material to become cores. But the methods we've used to detect a lot of them are biased toward finding large planets that orbit close to their host stars.

The radial velocity method used in exoplanet hunting requires precise observations of a star's spectrum. Instruments can be used to detect tiny wobbles in the star's orbit that are caused by the planet's gravity. These alien worlds occupy the mass range between the small rocky planets (like Earth, Mars and Venus) and the larger gaseous planets (like Neptune). "This study sets a wonderful example of collaboration and coordination across multiple teams and multiple data sets, something that doesn't always happen successfully in exoplanet research". Most exoplanets, including the thousands identified by NASA's recently retired Kepler space telescope, were found using the "transit" technique: looking for a periodic dip in starlight as a planet passes in front. It worked only for the nearest stars and was achieved by taking photographs of the star and measuring its positions in relation to one another. So one way or another, Barnard's star will likely make numerous appearances in the headlines over the next few years.

"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".

Rodrigo Diaz, an astronomer at the University of Buenos Aires who was not involved in the new work, said that, while the findings are promising, he'd still like to see more evidence of the new planet's existence.

But despite their best efforts, astronomers elsewhere could find no evidence of van de Kamp's worlds.

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. "However, we'll continue to observe this fast-moving star to exclude possible, but improbable, natural variations of the stellar brightness which could masquerade as a planet".

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