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Hubble Reveals Second-Generation Planet in Cold Case
Confirmed
In Short: Astronomers using Hubble data from 1999 have found evidence of a second-generation planet around a white dwarf.
In a study published Monday in Nature Astronomy, researchers led by Jamie Williams, a doctoral candidate at the University of Warwick, report uncovering a chemical clue indicating the white dwarf star HS 0209+0832 may host a second-generation planet.
When Hubble first observed the star in 1999, the data contained roughly 100 chemical features that could not be identified. Williams noted the presence of niobium, an element not typically formed in stars.
Williams explained that the amount of niobium 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.
The research team confirmed the Hubble observations with data from NASA's retired FUSE mission, which also showed strong signatures of niobium.
NASA’s TESS observed the white dwarf for four months, detecting periodic brightness variations that indicate a planet orbits at a distance of about 3.7 million miles, much closer than Mercury orbits the Sun.
The white dwarf star is still very hot, likely stripping the planet's outer material. Despite this, Williams believes the planet is likely to survive for millions of years.
The presence of niobium is a signpost of the dying star's 'death' throes, and the expulsion of its innards into space.
Williams emphasized that the discovery highlights the potential for planets to form long after a star's initial planetary system has dissipated.
The Hubble Space Telescope, operating for over three decades, continues to make groundbreaking discoveries that shape our understanding of the universe.
The artist’s concept imagines the evolution of a Sun-like star into a white dwarf surrounded by a disk of its expelled outer layers, from which a second-generation planet forms.
What's confirmed
- 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.
- “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.
- “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 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.
- “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.
- The research team confirmed the Hubble observations with data from NASA's retired FUSE (Far Ultraviolet Spectroscopic Explorer) mission, which also showed strong signatures of niobium in the HS 0209+0832 system.
- NASA’s TESS (Transiting Exoplanet Survey Satellite) also observed the white dwarf for four months, allowing it to detect periodic brightness variations that indicate that a planet orbits at a distance of about 3.7 million miles (6 million kilometers), much closer than Mercury orbits the Sun.
- Because the white dwarf star is relatively new, it is still very hot and likely blasting this planet with energy that is stripping its outer material.
- Despite this mass loss, Williams said that the planet is likely not a temporary blip on the cosmic radar.
- “If the second-generation planet is there, I think it is likely to survive. Eventually the white dwarf will cool and then maintain a consistent temperature, with the planet in its stable habitable zone for millions of years,” Williams said.
What's still developing
- “I think this research is an important example of the fact that scientific discovery is not a straight path,” Gaensicke said.
- The remainder of the ejecta dispersed long ago, but the planet remains.
- Dips indicate where niobium, nickel, and calcium are absorbing light, so less light in that part of the spectrum reached Hubble.