A planet may have formed from the ashes of a dead star, and the clue sat unnoticed in NASA’s Hubble Space Telescope archive for more than 25 years.
Astronomers at the University of Warwick in England and the University of Wisconsin–Madison say a white dwarf called HS 0209+0832 appears to have a giant planet orbiting it that formed after the star died. If confirmed, it would be the first known “second-generation” planet of its kind. The study was published in Nature Astronomy, and NASA highlighted it this week.
A Cold Case Reopened
Hubble observed the white dwarf in 1999. The data showed roughly 100 chemical fingerprints that nobody could identify at the time.
Jamie Williams, a doctoral candidate at Warwick and the study’s lead author, reran the old data against an updated chemical database. Many of the mystery features matched niobium, a heavy metal that had not been reported in any other white dwarf studied so far.
“I was truly gobsmacked,” co-author Boris Gänsicke of Warwick said of the finding.
Niobium matters because ordinary fusion inside stars doesn’t make it. According to co-author Nicholas Stone, a theorist at UW–Madison, elements like it are forged only in the extreme conditions of a dying star, which makes niobium a marker of the star’s final stages.
Where the Planet Comes In
Archival data from NASA’s retired FUSE ultraviolet observatory also showed strong niobium signals. Then four months of monitoring by NASA’s TESS satellite picked up repeating changes in the star’s brightness, hinting at a planet about 3.7 million miles (6 million kilometers) from the white dwarf. That is far closer than Mercury is to the sun.
The team’s explanation goes like this: as the star died, it threw off material enriched with heavy elements. Some of that material clumped into a new gas giant, roughly the size of Jupiter. Today, the white dwarf’s heat is stripping that planet’s atmosphere, possibly forming a comet-like tail and a disk that rains down onto the star. That falling material would explain the niobium Hubble saw.
“What Hubble is showing us in this white dwarf system is something we haven’t seen before,” Williams said.
The Catch
- It’s a candidate, not a confirmed planet. The paper’s own title uses the word “candidate,” and NASA calls it “suspected.”
- The case rests on reinterpreting archival data and on a model of how the planet loses its atmosphere. The TESS brightness signal is suggestive, not proof.
- How such planets form, and how common they are, is still unknown. Williams plans several more years of Hubble observations to find out.
Williams thinks that if the planet is real, it will likely survive. As the white dwarf cools, he said, it could sit in a stable habitable zone for millions of years.
More on Contoh
- NASA’s Roman Space Telescope Passes a Key Steadiness Test and Takes Its First Coronagraph Look
- Astronomers Find the Fastest Star Yet Circling Our Galaxy’s Black Hole