New Distant Planet Undergoing Nuclear Fusion Directly Imaged for the First Time

Artist’s concept of the Gaia spacecraft. Credit: ESA.

The Global Astrometric Interferometer for Astrophysics (Gaia) mission launched by ESA in 2013 is tasked with creating the largest three-dimensional map of the Milky Way galaxy to date by surveying approximately 1% of the galaxyโ€™s estimated 100 billion stars. While the mission’s primary purpose is to classify stars, with approximately 1 billion star observations released in 2015 and approximately 2 billion observations released in 2018, a secondary ability of the mission is to detect planets. With the catalog approaching 10 billion stars, the Gaia mission may have just detected its first official exoplanet.

An international team of researchers led by Sasha Hinkley of the University of Exeter have detected a previously unknown class of exoplanets by observing subtle motions of star HD206893, located some 750 trillion miles from Earth and about 30% larger than our Sun. Pinpointed by Gaia and using observations from the Very Large Telescope, the team could directly measure the spectrum of light emitted from the atmosphere of exoplanet HD206893c. The apparent brightening of HD206893c (more light emitted than expected) strongly suggests the burning of deuterium (heavy hydrogen) by nuclear fusion in the planetโ€™s core. While stars undergo fusion, planets do not. However, HD206893c is nearly 13 times more massive than Jupiter, which is on the boundary between planets and brown dwarfs (defined as between 13 to 80 Jupiter masses). Understanding how the exoplanet HD206893c and its companion 26 Jupiter mass brown dwarf (HD206893b) evolved can help future missions and studies to discriminate between true brown dwarfs and exoplanets. The results are significant from another vantage point: it shows that current missions can directly characterize the atmospheres of exoplanets at 2-4 AU (the distance between our Sun and Earth), which is the distance where many exoplanets are thought to orbit. READ MORE