Astronomers have discovered a Jupiter-sized planet orbiting the smoldering remains of a dead star, the first time an intact exoplanet has been discovered while traveling around a white dwarf, according to a study released Wednesday.
The researchers said the fate of this giant planet, called WD 1586b, offers a potential view of our own solar system as the Sun eventually ages into a white dwarf in about five billion years.
When it has burnt its reserves of hydrogen, a star like the Sun enters its agony, first swelling tremendously into a glowing red giant that burns and engulfs neighboring planets.
Then it collapses, reducing it to its burnt core.
This is the White Dwarf, an extremely dense stellar ember that glows faintly with the remaining thermal energy and slowly fades over billions of years.
Previous research has suggested that some white dwarfs may hold remnants further away from their planetary systems.
But so far, no intact planet has been detected orbiting one of the dead stars.
“The discovery was kind of a surprise,” said Andrew Vanderburg, an assistant professor at the University of Wisconsin-Madison, who led the research published in Nature.
“A previous example of a similar system, where an object passed a white dwarf, showed only a field of debris from a decaying asteroid.”
The planet is about ten times the size of its constricted mother star, known as WD 1856 + 534.
It was detected scanning the white dwarf every 1.4 days using NASA’s Transiting Exoplanet Survey Satellite (TESS).
Siyi Xu, an assistant astronomer at the US National Science Foundation’s Gemini Observatory, said that due to the lack of discernible debris from the planet around the star, the researchers concluded that it was intact.
“We have had indirect evidence of planets around white dwarfs and it’s amazing to finally find a planet like this,” Xu said, in a statement from NSF’s NOIRLab.
The discovery suggests the planets may end up in or near the white dwarf’s habitable zone, and potentially be hospitable even after their star dies, the statement said.
– “Tempting” –
What remains a mystery, however, is how the planet came close to the white dwarf.
The red giant phase is believed to make the survival of nearby planets unlikely – when the same process occurs for our Sun, Venus and Mercury are expected to be engulfed and possibly Earth as well.
“Our finding suggests that WD 1856b must have initially turned away from the star, and then somehow moved inward after the star became a white dwarf,” Vanderburg said.
“Now that we know that the planets can survive the trip without being shattered by the gravity of the white dwarf, we can search for other, smaller planets.”
After simulating various scenarios, the authors suggest that WD 1586b may have been thrown into close orbit due to interactions with other planets.
In an independent commentary on the discovery, Steven Parsons of the University of Sheffield said the discovery “offers the tempting prospect of detecting additional planets in this system in the future”.
According to current estimates, about a third of all Sun-like stars host planetary systems, while the Milky Way contains around ten billion of these stars, he said.
The WD 1856 + 534 white dwarf is only 82 light years from Earth, so Parsons said the gravitational effects of other planets on the white dwarf would potentially be detectable by space observation missions.
“This system therefore opens up a whole new field of exoplanetary research”, he added.
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