Neptune-Like Giant Hidden Planet Discovered Orbiting a Dwarf Star

Astronomers discovered a Neptune-like giant planet orbiting a dead star. The planet is four times bigger than the white dwarf star. It has been found 1500 light-years away from Earth in the constellation Cancer. The Earth-sized star, WDJ0914+1914 was identified in a survey of ten thousand white dwarfs observed by the Sloan Digital Sky Survey. The planet orbits the star about once every ten days, leaving a comet-like tail of gas comprising hydrogen, oxygen, and sulphur in its wake.


The astronomers from the University of Warwick's Department of Physics and the Millennium Nucleus for Planet Formation (NPF) at the University of Valparaíso discovered the fact, published in the journal Nature on 4th December 2019. After this discovery, there is a possibility that there could be many more planets around stars yet to discover.


Dr. Boris Gansicke, the lead author of the study from the University of Warwick in a press release, said, "At first, we thought that this was a binary star with an accretion disc formed from mass flowing between the two stars. However, our observations show that it is a single white dwarf with a disc around it roughly ten times the size of our sun, made solely of hydrogen, oxygen, and sulphur. Such a system has never been seen before, and it was immediately clear to me that this was a unique star."


Dr. Matthias Schreiber, the co-author of the study, explained, "It took a few weeks of very hard thinking to figure out that the only way to make such a disc is the evaporation of a giant planet."


They could get a close view of the star and the planet with the Very Large Telescope (VLT) of the European Southern Observatory (ESO) in Chile and found that the shape of the three elements indicated the presence of a ring of gas around WDJ0914+1914. The experts concluded, saying that it has similarities with our own solar system’s ice giants, Uranus and Neptune.


“This is the first time we can measure the amounts of gases like oxygen and sulfur in the disk, which provides clues to the composition of exoplanet atmospheres,” said co-author Dr. Odette Toloza, from the University of Warwick.


Dr. Matthias showed through a set of calculations that the 28,000 degrees Celsius hot white star is slowly evaporating the planet by bombarding it with high energy photons. The team showed after calculating that approximately 3000 tons of material are stripped away into the disc every second.


Dr. Gaensicke said, "This star has a planet that we can't see directly, but because the star is so hot it is evaporating the planet, and we detect the atmosphere it is losing. There could be many cooler white dwarfs that have planets but lacking the high-energy photons necessary to drive evaporation, so we wouldn't be able to find them with the same method. However, some of those planets might detectable using the transit method once the Large Synoptic Survey Telescope goes on the sky."


"This discovery is major progress because, over the past two decades, we had growing evidence that planetary systems survive into the white dwarf stage. We've seen a lot of asteroids, comets, and other small planetary objects hitting white dwarfs and explaining these events require larger, planet-mass bodies further out. Having evidence for an actual planet that itself was scattered in is an important step."


Earlier, in November, the astronomers found a planet orbiting a red giant using TESS. This is for the second time they have found a planet in an unexpected place. After the two discovery, experts are suspecting there are many more. Authors say, if there are 10 billion white dwarfs in the Milky Way, there will be 1 million of them with planets.


Earlier, in November, the astronomers found a planet orbiting red giant using TESS. For the second time, they have discovered a planet in an unexpected place. After the two discoveries, experts are suspecting there are many more. Authors say, if there are 10 billion white dwarfs in the Milky Way, there will be 1 million of them with planets.