In a discovery that could transform our understanding of space, an international team of astronomers reported on Wednesday that an intact exoplanet orbits close to a white dwarf, something previously thought impossible.
“We report the observation of a candidate for the title of giant planet transiting the white dwarf WD 1856 + 534 every 1.4 days,” the authors write in an article published for scientific journal Nature.
Part of the reason the discovery is so strange is that it defies so much of what is known about the formation of planets.
What are white dwarfs?
Stars like our sun “burn” hydrogen fuel, turning it into helium in nuclear fusion reactions that heat the planets.
However, when the stars run out of hydrogen, “some unusual processes will take place,” he explains. for Salon, Andrew Vanderburg, assistant professor of astronomy at the University of Wisconsin-Madison.
“First, the star will swell and become very, very big. This is a bit like his death. Once it runs out of hydrogen, it begins to burn helium and eventually turn it into carbon and oxygen.
But this is an inefficient process and does not take very long. So, quite quickly after the star runs out of hydrogen, it loses much of its mass, so that the outer layers of the star are blown into space and what is left is the hot core of the star, which no longer produces energy.
This hot core, Vanderburg explained, is what we call a white dwarf – and one of the defining characteristics of a white dwarf is that, due to its strong gravitational force, it tends to pull celestial bodies towards it and decompose them in the process.
However, the possible planet discovered by scientists using the Transiting Exoplanet Survey Satellite and the Spitzer Space Telescope has remained intact.
“The most likely explanation is that there were other planets or other objects in the system,” Vanderburg explained.
“We know that there are two other stars that orbit this white dwarf very far. Maybe it could have exerted some influence on this planet that we initially saw, when it orbited far away, because it had to orbit far away, otherwise it would have been swallowed.
Or maybe it could have changed its orbit so that it was very, very elliptical, and when it got close to the star, it barely touched the surface. “
He added: “The other alternative explanation is that the planet was actually swallowed by the star, but it was heavy enough to be saved in essence.”
What’s new in astronomy: how much do we really know?
Vanderburg also said that, like the recent discovery of phosphine gas in the atmosphere of the planet Venus, the new discovery about this planet could suggest new types of planets on which we could look for signs of life.
“I think the biggest implication for this is that there is a possibility that life may be in places I hadn’t really considered before,” Vanderburg said.
As Vanderburg pointed out, planets are believed to be able to sustain life only if they exist in a “habitable zone” – that is, close enough to a given star to benefit from its heat, but not so close that heating eliminates the conditions necessary to sustain life.
“In a system of white dwarfs there is also a habitable area, but because the white dwarf is very small and cools and is very, very weak, it must be crowded much closer to the star in order for it to be potentially habitable.” , said Vanderburg.
Thus, as the discoveries of astronomers expand, we will be able to be closer to a more comprehensive knowledge of what life and processes in space mean. And who knows? Maybe we will be able to know other methods that shape life outside our planet.