The newly discovered planet called 51 Eridani B is about twice the mass of Jupiter, and orbits a star about 97 light-years from Earth.
The discovery, reported in the journal Science, will provide new insights into how planets and planetary systems are made.
“Only a handful of planets have been imaged like this so far, and they were each at least five times the mass of Jupiter, so it’s incredibly hard to do,” said the study’s lead author Professor Bruce Macintosh of Stanford University in California.
“Planets like Jupiter in our solar system are a billion times fainter than the sun, so planets are usually lost in the bright light from their star.”
Macintosh and an international team of 90 scientists made the discovery using the Gemini South Observatory’s new planet imager, one of a new generation of instruments designed specifically for discovering and analyzing faint planets orbiting bright stars.
It is also adept at finding very young planets, which are luminous and visible at infrared wavelengths.
Young planets
When planets form, material coalescing into the planet release energy which heats the planet up. Over the next hundred million years or so, the planet will gradually cool, radiating away most of that energy as infrared light,
“Finding very young planets is important because one of the biggest puzzles in modern astronomy is understanding how planets form,” said Macintosh.
“Twenty years ago we had a nice model that could form [planets in] our solar system, which was the only one we knew about.
“But in the intervening 20 years we’ve discovered that other solar systems look completely different to ours.”
There’s now a wide range of possible scenarios which could form planets, either quickly or slowly, using either solid or gaseous material.
“This is the first planet we’ve seen which has the kind of chemistry and atmospheric composition that Jupiter has in our solar system,” said Macintosh.
“Its atmosphere is full of methane and its surface is not completely enshrouded in big thick clouds, so we’ve really reached the point where we’re seeing a young 20-million-year-old equivalent of Jupiter which probably formed in a similar way.”
Prior to this discovery, methane signatures have been weak or absent in directly imaged exoplanets.
“Many of the exoplanets astronomers have imaged before have atmospheres that look like very cool stars,” said Macintosh.
However, 51 Eridani B has a far cooler atmosphere with a temperature of just 430 degrees Celsius.
“So this one looks like a planet,” said Macintosh.
51 Eridani B orbits its host-star at a distance of about 13 astronomical units, an astronomical unit is the average distance between the Earth and the Sun.
Read more at Discovery News
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