// NASA BREAKING NEWS — SPAZIO & SCIENZA
Suspected Second-generation Planet Solves NASA Hubble Cold Case
Diligent sleuthing by astronomers has broken open a cold case in the data archive of NASA’s Hubble Space Telescope. In a study published Monday in Nature Astronomy, researchers report uncovering a surprising chemical clue that indicates the white dwarf star HS 0209+0832 may host a second-generation planet.
A white dwarf is the remnant core of a low-mass star that has burned through all its nuclear fuel and lost its outer envelope of gas and dust to space. A second-generation planet is a world that forms around the stellar remnant from its cast-off material.
“Rather than the white dwarf stage being a kind of epilogue to the story of a star and its planets, this research points to the systems we are familiar with only being the first chapter of a potentially much longer tale, with some new characters showing up. That’s a really exciting prospect to pursue,” said Jamie Williams, astronomer and lead author, a doctoral candidate at the University of Warwick in the United Kingdom.
Earth and the other planets in our solar system are first-generation planets, which form from material left over from a star’s birth.
“What Hubble is showing us in this white dwarf system is something we haven’t seen before: a high abundance of the element niobium, the signature of which I was unfamiliar with when I first found it in the archival data,” Williams said.
When Hubble first observed the star in 1999, the data contained roughly 100 chemical features that could not be identified. Williams went back to those records armed with an updated chemical database and found that niobium matched many of the mystery features.
Williams explained that, while niobium is found in our solar system and has multiple uses on Earth, including in jewelry and medical imaging devices, the amount Hubble found in the HS 0209+0832 system points to a planet forming not from a star’s birth, but from the material ejected as it dies.
"Niobium and other elements heavier than iron are astronomically special because, unlike many common elements, they are not formed in the cores of stars by thermonuclear fusion,” said Nicholas Stone, a theoretical astrophysicist at the University of Wisconsin – Madison and member of the research team. “Instead, these heavy elements can only be synthesized in the exotic conditions that briefly emerge inside dying stars. The presence of niobium is a signpost of these ‘death’ throes, and the expulsion of the dying star's innards into space.”
Once the star ejected this chemically enriched material, the team theorizes that some of it coalesced into a gas giant planet. The remainder of the ejecta dispersed long ago, but the planet remains.
“When Jamie asked me about niobium in relation to this study I was truly gobsmacked, as that element had not been reported in any other white dwarf analyzed to date. Once we realized it was there, everything fell into place,” said astronomer and study co-author Boris Gaensicke, also at the University of Warwick.