Giant planet orbits small star

The origins of the huge planet are not yet clear.
By Andrew McDonald | May 01, 2015
According to a statement from the Australian National University, researchers have discovered a massive gas giant exoplanet orbiting a relatively small star known as HATS-6. HATS-6 is located about 500 light-years away and is an M-dwarf.

M-dwarf stars are the one of the most abundant classes of star in the Milky Way; however, due to their dimness and small size, they are not readily observed and analyzed. HATS-6 is comparatively cool and very dim, giving off only one twentieth as much light as our Sun.

Surprisingly, observations obtained by the university's Siding Spring Observatory showed a periodic diminishment in the star's brightness, indicating the presence of an orbiting planet passing across the face of the star.

Subsequent observations by the more powerful Magellan Telescope in Chile and amateur astronomer T G Tan in Perth, Australia confirmed the presence of the planet. The gas giant planet is similar in mass to Saturn but has a radius similar to that of Jupiter. The planet orbits extremely close to its host star, at a distance only one-tenth of the distance between the Sun and Mercury. One orbit takes only 3.3 days.

The planet's atmosphere and origins remain mysterious. HATS-6 is so faint that it cannot heat up its planet to any great degree. As for how the planet came to orbit such a small star, the researchers hypothesize that it must have formed farther away and migrated inwards early in its history, though this process itself is not yet understood.

The new findings have been published in the Astronomical Journal.

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