Astronomers find 'phoenix planet' reborn from its dead star's ashes

Astronomers have found the first evidence of a “phoenix planet” — a world reborn from the ashes of its own dead star — according to a study published on 5 October in Nature Astronomy (University of Warwick, Science News).

The team, led by Jamie Williams at the University of Warwick, detected unusual chemistry in the atmosphere of the white dwarf HS 0209+0832: high concentrations of zinc, copper and niobium — the first time niobium has ever been found in a white dwarf. The pattern is the signature of the s-process, a nuclear reaction that builds heavy elements inside dying stars, indicating the polluting material came from the star’s own death rather than an ordinary planet (phys.org).

The most likely explanation, the researchers say, is that the white dwarf is feeding off a newly formed, second-generation giant planet that condensed from a disc of the star’s expelled material. Data from NASA’s TESS satellite detected a 4.4-day brightness signal consistent with a Jupiter-sized, tidally locked gas giant whose outer atmosphere is boiling away and raining down onto the star.

The existence of second-generation planets was predicted theoretically more than 15 years ago, but this is the first evidence ever seen, said planetary scientist Zifan Lin of Washington University in St. Louis, who was not involved in the work. Forming the disc likely required a companion star to pull the ejected material back into orbit rather than letting it escape, the team said.