Scientists find planet unlike anything ever seen before

 Astronomers believe they have found a planet unlike any previously seen – and it is made up of the pieces of a dying sun.

They believe that it is the first time that we have ever seen a “second-generation” planet of this kind: a world made up of pieces of the dead star that it now orbits.

"Second-generation planets are worlds that form out of the material a star casts off as it dies,” said Jamie Williams, a PhD student at the University of Warwick, who led the research.

“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."

Astronomers have spotted possible “reborn” worlds of this kind around the intense stars known as pulsars before. But it is the first time that one has been seen around a white dwarf – and, since those dead stars are much more common in the universe, it suggests there might be more of those reborn worlds around than we have previously thought.

White dwarfs are the collapsed cores that are left behind when a star runs out of fuel. They pull in material from panels that are nearby, and leave behind a chemical signature that astronomers can use to understand the planets that are in orbit around them.

In the new research, scientists looked at a white dwarf named HS 0209+0832. As they did, they found an unusual chemical signature, including vast amounts of a material called niobium that is created as a star dies, but has not been found in a white dwarf before.

Astronomers believe that the signal is happening because the white dwarf is feeding off a newly formed giant planet that is nearby. And that giant planet was itself made out of pieces left behind as the star died and became a white dwarf, they said.

That finding gained further credence after researchers used data from Nasa’s TESS telescope. That showed a faint signal coming from the planet that repeats every 4.4 days, which would bee explained by a Jupiter-sized planet that was orbiting closely around the white dwarf.

Given it is so close to the star, material from the planet’s outer atmosphere is likely boiling away because of the radiation from its dead sun, the researchers suggest. As that escaped material hits the white dwarf’s surface, it produces the unusual chemical signature.

If it is confirmed, the planet would not only be the first ever planet of this kind ever seen. It would also allow for a new way to find more of them, by looking for the same chemical signature in the light of other dead stars.

It might also represent another opportunity in the search for habitable worlds and the alien life that might live on them. A better understanding of how planets of this kind form will help us understand whether planets around white dwarfs are habitable – and planets around white dwarfs are relatively easy to spot.

The work is reported in a new paper, ‘1 Discovery of a second-generation planet candidate accreting onto a white dwarf’, published in the journal Nature Astronomy.

In the same issue, a separate study looked at other kinds of dwarf stars. Researchers found a binary system in which a brown dwarf and red dwarf orbit around each other – and observations and modelling suggests that material is flowing from the brown dwarf onto the red dwarf, a process that has also never been seen before.

That work is reported in a separate paper, ‘Stable mass transfer from a substellar object onto an M dwarf’, published in the same journal.