Astronomers Detect Giant Exoplanet GJ504b Around Sun Like Star

With the help of the infrared data from the Subaru Telescope, which is mounted at Mauna Kea in Hawaii, astronomers have imaged a giant Jovian exoplanet around a star similar to the Sun, and named it GJ 504b. This is the lowest mass planet detected as a part of the Strategic Explorations of Exoplanets and Disks with Subaru (SEEDS) survey.

The exoplanet GJ504b is four times bigger than Jupiter and has a temperature of 460 degrees Fahrenheit. The star around which GJ504b revolves is slightly hotter than the Sun and can be faintly seen through the naked eye in the constellation Virgo. It lies at a distance of 57 light years away from the Earth and astronomers estimate that the system is only 160 million years old, compared to our own 5 billion year old solar system and planet.

"If we could travel to this giant planet, we would see a world still glowing from the heat of its formation with a color 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, Md. "Our near-infrared camera reveals that its color is much more blue than other imaged planets, which may indicate that its atmosphere has fewer clouds."

This new discovery challenges the theoretical explanation about the origins of giant planets as well as their atmospheric properties because this lowest mass exoplanet GJ 504b orbits its star at nine times the distance Jupiter revolves around the sun.

According to the core-acceleration model, planets like Jupiter are formed from the debris disk rich in gas and dust that surround a newly formed star.  A basic core is formed when asteroids and comets collide and on attaining sufficient mass, the core's gravitational pull attracts gas and dust from the disk to form the planet. This model stands true for planets like Neptune, which revolve 20 times Earth's average distance from the Sun. But for those that are at the farthest distance from their stars, this model is challenging.  GJ 504b lies at a proposed distance of 43.5 AU ( Astronomical units) from its star.

Team member Markus Janson, a Hubble postdoctoral fellow at Princeton University in New Jersey explains, "This is among the hardest planets to explain in a traditional planet-formation framework. Its discovery implies that we need to seriously consider alternative formation theories, or perhaps to reassess some of the basic assumptions in the core-accretion theory."

The finding will be published in The Astrophysical Journal.