Lowest-mass exoplanet around a Sun-like star found

Astronomers have spotted the lowest-mass planet ever detected around a Sun-like star in the constellation Virgo.

Using infrared data from the Subaru Telescope in Hawaii, an international team of astronomers imaged the giant planet around the bright star GJ 504.

Several times the mass of Jupiter and similar in size, the new world, dubbed GJ 504b, is the lowest-mass planet ever detected around a star like the sun using direct imaging techniques, researchers said.

“If we could travel to this giant planet, we would see a world still glowing from the heat of its formation with a colour reminiscent of a dark cherry blossom, a dull magenta,” said Michael McElwain, a member of the discovery team at NASA’s Goddard Space Flight Center in Greenbelt.

“Our near-infrared camera reveals that its colour is much more blue than other imaged planets, which may indicate that its atmosphere has fewer clouds,” McElwain said.

GJ 504b orbits its star at nearly nine times the distance Jupiter orbits the sun, which poses a challenge to theoretical ideas of how giant planets form.

GJ 504b lies at a projected distance of 43.5 AU from its star, the actual distance depends on how the system tips to our line of sight, which is not precisely known.

“This is among the hardest planets to explain in a traditional planet-formation framework,” said Markus Janson, a Hubble postdoctoral fellow at Princeton University.

The researchers found that GJ 504b is about four times more massive than Jupiter and has an effective temperature of about 237 degrees Celsius.

It orbits the G0-type star GJ 504, which is slightly hotter than the Sun and is faintly visible to the unaided eye in the constellation Virgo.

The star lies 57 light-years away and the team estimates the systems is about 160 million years, based on methods that link the star’s colour and rotation period to it age.

The study was published in The Astrophysical Journal.