Published: Thu, November 15, 2018
Research | By Raquel Erickson

Frozen super-Earth exoplanet found in second closest star system

Frozen super-Earth exoplanet found in second closest star system

Astronomers have now discovered an exoplanet more than three times the mass of Earth, orbiting a star that's only six light-years away.

The exoplanet was found after stitching together 20 years of data, including 771 individual measurements, from seven instruments.

Barnard's Star has always been "the great white whale" of exoplanet hunting, said Carnegie astronomer Paul Butler, a co-author on the Nature paper.

An artist's impression of Barnard's star b. The researchers believe that it is an icy desert with no liquid water, a hostile environment where the average surface temperature is around minus-274 degrees Fahrenheit. That's because Barnard's Star provides the frigid planet with only 2 per cent of the energy that the sun provides Earth. That might suggest a warm, temperate world - but Barnard's Star is a dim object, far less luminous than the Sun.

Here's another cool fact: it's also an old star that predates our own solar system. "He recognized that this star had the largest known proper motion a century ago". That dip, which occurs every 233 days, might be the telltale sign that a planet is in orbit around it.


The study says that the newly discovered planet exists near the star's "snow line", where objects receive so little sunlight that most water present would condense into ice. This region in a planetary system is where the building blocks of planets are thought to form, collecting material to become cores. This method is sensitive to the mass of the exoplanet and measures changes in the host star's velocity.

Even if the other potential planets turn out to be busts, the one that does appear to be there would be close enough to us, and far enough from Barnard's star, that we could image it directly using hardware that should come online within the next decade. It's the second closest exoplanet to Earth after Proxima Centauri b, whose discovery was announced in 2016. "It is only by combining data and working collaboratively that this very challenging detection was possible". This is how we find exoplanets actually: As they orbit their host stars, their gravity causes their stars to wobble, pulling them toward and away from the telescope on Earth, creating a frequency shift that corresponds to the exoplanet's mass orbital period. 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.

"There´s not so many stars in our immediate neighbourhood".

What was going on? van de Kamp's observations were made using a large refracting telescope, and astronomers eventually realised that the telescope's main objective lens had been cleaned and modified several times during the decades of his study. His claims of how planets could fit in orbit around the star were refuted, and he died five months before the first verifiable discovery of an exoplanet was made in May 1995, Butler said. His data invoked the presence of two planets tugging the star around as it moved through space. "Van de Kamp is a true pioneer in extrasolar planets". Thus, closer studies of Proxima b, Barnard's Star b and other super-Earths should help scientists come closer to figuring out whether the conditions for life are rare or common in the universe. "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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