First planet found orbiting a white dwarf

The process of formation of a white dwarf destroys nearby planets, yet a team of astronomers has located, for the first time, what could be a large planet orbiting a star of this type, according to a study published today, Wednesday, Nature.

The research, which is signed, among others, by Spanish scientists from the Canary Islands Astrophysical Institute (IAC), used data from NASA’s TESS satellite, the now-retired Spitzer space telescope and the Gran Telescopio de Canarias (GTC). It is worth mentioning that in recent days, several secrets of the Universe have been revealed, from the existence of phosphine on Venus to the beginning of a new solar cycle.

The object that astronomers consider to be a planet has been called WD 1856 b, it is very large – roughly like Jupiter – and orbits the star every 34 hours, about 60 times faster than Mercury around the Sun.

The star, however, is a cool and quiet white dwarf, much smaller than the planet, is about 18 thousand kilometers in diameter, can be up to ten billion years old, and is a distant member of a triple star system in the constellation Draco.

How is a white dwarf formed?

The process of creating a white dwarf destroys nearby planets, and anything that then gets too close is usually ripped apart by the star’s immense gravity.

For this reason, lead author Andrew Vanderburg of the University of Wisconsin-Madison, USA, noted that they still have “many questions about how WD 1856 b got to its current location without experiencing one of those destinations.”

The team believes that “somehow” the object, which was detected by TESS “came very close to its white dwarf and managed to stay in one piece.”

When a star similar to the Sun runs out of fuel, it swells up to hundreds or thousands of times its original size, forming a cooler red giant star, the IAC explains in a statement.

Subsequently, it expels its outer layers of gas, losing up to 80 percent of its mass, and the remaining hot core turns into a white dwarf.

The IAC researcher and co-author of the article Felipe Murgas explained that any nearby object is engulfed and incinerated during this process, which in this system would have included WD 1856 b in its current orbit. Therefore, the team considers, according to Murgas, that it is possible that the planet originated at least 50 times further from its current location.

The power of white dwarfs

Astrophysicists know that long after the birth of white dwarfs, small distant objects such as asteroids and comets can scatter towards these stars, which are usually turned into debris by the white dwarf’s gravity.

The team suggests several scenarios that could have pushed WD 1856 b onto an elliptical path around the star, a trajectory that would have become more circular over time as gravity stretched the object, creating huge tides that dissipated its orbital energy. .

Finding a possible world orbiting close to a white dwarf has led researchers to consider the implications for studying the atmospheres of small rocky worlds in similar situations, since the tiny size of the white dwarf makes it easier to characterize the planet’s atmosphere.

There is currently no evidence to suggest that there are other worlds in the system, but it is possible that additional planets exist and have not yet been detected.

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