A second-generation planet candidate, potentially composed of material from a dead star, has been discovered orbiting a white dwarf for the first time, according to astronomers.
In a recent paper published in Nature Astronomy, a team of astronomers led by researchers at the University of Warwick reports the first-ever observation of a phoenix-like second-generation planet orbiting the remains of its own star.
The discovery came as a surprise, as earlier hypotheses expected such second-generation planets to form around pulsars rather than white dwarfs. Although the phenomenon appears to be rare, the discovery raises the possibility that more such second-generation planets could be found, since white dwarfs are more common than pulsars.
White Dwarfs
“Second-generation planets are worlds that form out of the material a star casts off as it dies,” said first author Jamie Williams, a PhD student in the Department of Physics, University of Warwick. “They’re incredibly rare, and finding one around a white dwarf was completely unexpected. It’s a bit like finding a planet that has risen from the ashes of the very star it once orbited.”
Typically, white dwarfs behave in the opposite way, accreting material from surrounding planetary bodies rather than contributing material to their formation. Using spectral data from material accreting onto a white dwarf, astronomers can identify its composition. Such material tends to be rich in silicon and iron, elements that form rocks, but around this unusual star, HS 0209+0832, the team found a strange signal indicating extremely high levels of zinc, copper, and niobium.
Recognizing a Second-Generation Planet
The team was surprised, since niobium had never been discovered in the orbit of a white dwarf. More intriguingly, all of these elements were associated with processes occurring late in stellar evolution.
“This pattern of elements is a telltale sign of the ‘s-process,’ a nuclear reaction that builds heavy elements inside dying stars during their bloated red giant phase,” said co-author Dr Nicholas Stone, Department of Astronomy, University of Wisconsin-Madison. “It’s a chemical signature no ordinary, ‘first-generation’ planet should carry, which told us that this new planet was something different.”
To explain the unusual data, the researchers hypothesized that material produced during the original star’s evolution and death settled into a planet-forming disk around the white dwarf. This led to the formation of a second-generation planet enriched in unusually heavy elements, material from which is now apparently accreting onto the white dwarf and producing the unusual spectral signature.
“Forming the protoplanetary disc in this situation is not easy and helps explain why these planets are so rare,” Williams explained. “A single, isolated star dies and sheds mass in a roughly symmetrical way. To form a disc of material necessary to birth a planet, HS 0209+0832 likely required a companion star that pulled the ejected material back into orbit, rather than letting it escape.”
Confirming a Second-Generation Planet
Further evidence came from NASA’s TESS satellite, which identified a faint, regularly repeating brightness signal. The signal repeated every 4.4 days, consistent with what researchers would expect from a tidally locked gas giant. In such a tight orbit, the white dwarf’s radiation would be expected to heat the planet intensely, causing its atmosphere to inflate and escape before being accreted by the white dwarf. That material could explain the strong spectral signatures of those elements detected around the star.
“What’s remarkable about the planet around HS 0209+0832 is that this isn’t a planet from somewhere else, or a survivor from the system’s birth, it looks like it was built from the very material its own star cast off as it died. In a sense, this system has given birth to a new world using the foundations of the old one,” concluded co-author Professor Boris Gänsicke, Department of Physics, University of Warwick.
“Finding this one example raises the question of how many more might be out there and might our own Solar System host a second-generation planet formed from the ashes of our Sun,” he added.
With time, additional investigations may help determine how unusual such systems are, and what kinds of worlds are capable of forming during the final stages of stellar evolution.
The paper, “1 Discovery of a Second-Generation Planet Candidate Accreting onto a White Dwarf,” appeared in Nature Astronomy on October 5, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.