A new analysis of Hubble observations from 1999 suggests a planet may have formed from material thrown off by a dying star. The possible second-generation planet orbits the white dwarf HS 0209+0832. If confirmed, it could change our understanding of how planets form.
HS 0209+0832 is the remnant of a star that exhausted its nuclear fuel and shed its outer layers. Several chemical features in Hubble’s original observations remained unexplained. Jamie Williams, an astronomer at the University of Warwick, and his team revisited the data with a more up-to-date database.
TESS observations also support the hypothesis
The team identified much more niobium than expected around the white dwarf. Like other elements heavier than iron, niobium can be produced by extreme processes at the ends of stars’ lives. The researchers suggest its presence could indicate that some material expelled by the star later gathered together to form a new planet.
Observations from NASA’s TESS space telescope also support the hypothesis. TESS watched the white dwarf for four months and detected recurring brightness changes. Those variations suggest a gas giant roughly the size of Jupiter could orbit just six million kilometers from the stellar remnant, far closer than Mercury is to the Sun.
The possible planet would face harsh conditions. The relatively young white dwarf is still extremely hot, and its radiation could rapidly strip material from the gas giant’s outer atmosphere. The escaping gas might form a comet-like tail, potentially explaining the chemical traces Hubble detected.
The researchers nevertheless suggest that the planet could survive over the long term. As the white dwarf gradually cools, conditions around the orbiting world could also change. For now, it’s still uncertain how common planets formed after their stars’ deaths are, or exactly which processes create them. The study was published in Nature Astronomy.
Sources: Nature Astronomy, Science Daily
