Scientists Find Evidence of a Second-Generation Planet Around a White Dwarf
Hubble data may reveal a second-generation planet around white dwarf HS 0209+0832, a first if confirmed.
The Hubble data from HS 0209+0832 contained 100 chemical features that could not be identified at the time. According to Engadget, the Warwick-led team says those chemical features indicate that the white dwarf hosts a second-generation planet. A white dwarf is what remains of a star like the sun after its red giant phase, when it runs out of hydrogen, expands into a massive fireball that is expected to consume nearby planets, and then sheds its outer layers. What is left is a dense core.
The planets in our solar system, including Earth, are first-generation planets, meaning they formed from materials present at the sun's birth. Second-generation planets form from materials a dying star casts off. They are very rare and are mostly suspected to exist around pulsars, which are highly magnetic and rapidly spinning remnants of dead neutron stars. White dwarfs are more common than pulsars. Jamie Williams, the lead author of the study, said finding a second-generation planet around one "was completely unexpected," according to Engadget.
Williams found the evidence by looking at Hubble's decades-old observations and comparing them to an updated chemical database. The unidentified chemical features matched an element called niobium, which "can only be synthesized in the exotic conditions that briefly emerge inside dying stars," the report said. Niobium levels in the system were 1,000 times higher than the sun's, and that amount points to the formation of a planet from the dying star's materials.
The scientists said the white dwarf is still extremely hot and is still blasting the planet with enough heat to strip out its outer layers. But they believe the planet will stay and that it will remain in the white dwarf's habitable zone for millions of years. The European Research Council, which funded the study, said HS 0209+0832 would be the first white dwarf found to host a second-generation planet if the team's findings are confirmed, Engadget reported.