Astronomers have detected mysterious X-ray signals coming from a nearby white dwarf star for more than 40 years. We may now know where they’re coming from – the death throes of a planet being torn to shreds and raining down on the star.
The Helix Nebula is an eye-catching sight in the sky – and not just because it looks like a giant eye. Located about 655 light-years from Earth, it’s the site of a slow-motion explosion, from a star that went supernova more than 10,000 years ago. In the center lies the remnant of that old star – a white dwarf.
Since 1980, observatories studying this nebula have detected high-energy X-rays coming from the white dwarf at its core. Since these objects don’t normally emit X-rays, the signals have stumped astronomers for decades.
But now we might finally have an answer. According to a new analysis of data from several observatories, we may be picking up the screams of a planetary apocalypse, as a Jupiter-sized world ventured too close to the white dwarf and was ripped apart by the intense gravity.
“The mysterious signal we’ve been seeing could be caused by the debris from the shattered planet falling onto the white dwarf’s surface, and being heated to glow in X-rays,” said Martin Guerrero, co-author of the study. “If confirmed, this would be the first case of a planet seen to be destroyed by the central star in a planetary nebula.”
The team analyzed data from four different X-ray observatories over the decades – Chandra, XMM-Newton, Einstein and ROSAT. These showed that between 1992 and 2002 the X-ray signal stayed steady, with more or less the same level of brightness. But on closer inspection, there seemed to be a very subtle short-term variation – a flicker that occurred every three hours. That’s evidence, the team suggests, of the shredded remains of a planet very close to the white dwarf.
It’s an intriguing story, especially considering that this planet has already survived one apocalyptic scenario – when the star exploded as a supernova 10 millennia ago. But further observations of this and other white dwarf stars would be needed to clarify the conundrum.
The research was published in the journal Monthly Notices of the Royal Astronomical Society.
