A Milky Way-surveying spacecraft found a planet 12 times more massive than Jupiter, along with a brown dwarf, each distantly orbiting stars smaller than the sun.
Scientists have dubbed the exoplanet, a world well outside our solar system, Gaia-4b. The brown dwarf, not quite a planet or a star, is Gaia-5b. Respectively, they are 244 and 134 light-years away.
The European Space Agency's Gaia spacecraft, which has recently retired because it's running out of fuel, is responsible for the discoveries. Both enormous celestial objects were made official after confirmation from other instruments. Though Gaia concluded science observations on Jan. 15, these results are an intriguing tease to a vast data release from the mission anticipated next year.
"This discovery is an exciting tip-of-the-iceberg for the exoplanet discoveries we can expect from Gaia in the future," said Matthew Standing, an ESA research fellow, in a statement.
The number of confirmed exoplanets has tipped 5,800, according to NASA, with thousands of additional candidates under review. The growing tally is a tiny sampling of planets in space. With hundreds of billions of galaxies, the universe probably teems with many trillions of stars.
Gaia-4b is considered a super-Jupiter planet, a relatively cold gas giant, orbiting its star over 570 Earth-days. That star is estimated to be 64 percent the mass of the sun. That makes Gaia-4b one of the most hulking planets known to circle a small star.
The brown dwarf, sometimes referred to as a failed star because it lacks the scale to generate its own nuclear power, orbits its even smaller star — about 34 percent the sun's mass — in a slightly shorter Earth-year. Though it may not have been able to hack it as a star, this thing is no shrinking violet. It's about 21 times more massive than Jupiter. For the sake of comparison, Jupiter's mass is equal to about 318 Earths.
The findings were published in The Astrophysical Journal.
The exoplanet is Gaia's first independent success using the "wobble" technique, aka astrometry, according to the space agency. Since the mission launched in 2013, the spacecraft has used a pair of optical telescopes to scan the sky. Because of its precision in tracking the motion of stars, scientists believe its data will potentially lead to thousands of new discoveries.
The gravitational tugs of orbiting planets can cause host stars to wobble in an almost corkscrew-like pattern, and planet hunters are adept at interpreting these jitters in the data. But confirmation from other telescopes is key for these candidates because there are other possible reasons for the motion, such as the influence of another nearby star. The WIYN 3.5-meter Telescope at the Kitt Peak National Observatory in Tucson, Arizona, provided crucial follow-up observations.
"Massive planets around low-mass stars are known to be relatively rare," said Guðmundur Stefánsson, lead author of the paper, in a statement, "but when they occur, they cause a larger wobble, and therefore a stronger astrometric signature that is easier to detect."
