Astronomers Identify First Suspected Second-Generation Planet Orbiting a White Dwarf

A planet born from stellar remains

The unusual system centres on the white dwarf HS 0209+0832, the dense, collapsed core left behind after a star exhausts its nuclear fuel.

Unlike ordinary planets, which form from the disc of material surrounding a young star, the suspected planet appears to have formed much later. Researchers believe it condensed from material expelled when the original star died.

Such bodies are termed second-generation planets because they are thought to form from material produced during a star’s death rather than from the original planetary system.

Astronomers detected unusually high levels of heavy elements, including zinc, copper and niobium. Niobium was found at concentrations more than 1,000 times higher than those observed in the Sun.

These unusual elements are associated with the slow neutron-capture process, or s-process, which occurs inside ageing stars during their red giant phase.

A planet formed during the star’s youth would not be expected to contain this distinctive chemical fingerprint. The researchers therefore propose that the material being absorbed by the white dwarf originated from a planet formed from the star’s own expelled matter.

A companion star may have facilitated this process. Rather than allowing the material shed by HS 0209+0832 to escape into space, the companion could have helped draw some of it back into orbit, creating a disc from which a new planet could form.

Observations from NASA’s TESS satellite provide further evidence. Astronomers detected a faint, repeating change in brightness occurring approximately every 4.4 days.

The signal is consistent with a Jupiter-sized gas giant orbiting extremely close to the white dwarf. At this distance, the planet would be subjected to intense radiation, heating its atmosphere and gradually evaporating it.

Some of this escaping material could then accrete onto the white dwarf, accounting for the unusual elements detected in its atmosphere.

Could there be more ‘reborn’ worlds?

If confirmed, the discovery would constitute the first evidence of a second-generation planet around a white dwarf and could open a new avenue for planetary research.

Astronomers can now search other white dwarfs for similar chemical fingerprints, potentially revealing additional planets formed from stellar remains.