Dead ‘cannibal’ star spotted with metallic scar after consuming part of planet

2024-02-27 10:14:00

(CNN) — Astronomers have spotted an unusual sign that a dead star fed on a fragment of a planet orbiting it. This is a metallic scar on the surface of the star. The revelation sheds light on the dynamic nature of planetary systems even in the final stages of a star’s life cycle, and might presage the eventual fate of our own solar system, scientists say.

Planets form from swirls of gas and dust called a protoplanetary disk that surround a newly formed star. But as the star ages and dies, the stellar object can consume the very planets and asteroids it helped create.

Astronomers observed a dead star, known as a white dwarf, located regarding 63 light-years from Earth using the European Southern Observatory’s Very Large Telescope in Chile. The observation revealed a metallic feature on the star’s surface that the researchers determined was related to a detected change in the star’s magnetic field. A new study that detailed the observation appeared this Monday en The Astrophysical Journal Letters.

“It is well known that some white dwarfs—slowly cooling embers of stars like our Sun—are cannibalizing fragments of their planetary systems. We have now discovered that the star’s magnetic field plays a key role in this process, resulting in a scar on the surface of the white dwarf,” said the study’s lead author, Dr. Stefano Bagnulo, an astronomer at the Armagh Observatory and Planetarium in Northern Ireland. it’s a statement.

The white dwarf, called WD 0816-310, is an Earth-sized remnant of a star that was once like our sun but larger. The stellar object acquired a noticeable dark mark on its surface, which turned out to be a concentration of metals.

“We have shown that these metals come from a planetary fragment as large as or possibly larger than Vesta, which is regarding 500 kilometers in diameter and is the second largest asteroid in the Solar System,” said study co-author Jay Farihi, a professor of astrophysics at University College London, in a statement.

A magnetic connection

While working with the Very Large Telescope, the team relied on its FORS2 instrument, considered a “Swiss army knife” instrument by researchers, to determine how the metal became part of the star. FORS2 is the acronym for Focal Reducer/low dispersion Spectrograph 2.

As astronomers observed the star, they noticed that the concentration of the metal they detected changed as the star rotated. Instead of being dispersed across the star’s surface as astronomical theory predicts, the metal was concentrated in a single area, study co-author John Landstreet, professor emeritus of physics and astronomy at Western University in Canada, said in a statement. .

The strength of the metal detection also matched the observed changes in the star’s magnetic field, leading the team to determine that the metal scar was located at one of the star’s magnetic poles.

The star’s magnetic field attracted metals toward the star, which led to the presence of the scar, the finding suggests.

“This scar is a concentrated patch of planetary material, held in place by the same magnetic field that has guided the falling fragments,” said Landstreet, also affiliated with the Armagh Observatory and Planetarium. “You’ve never seen anything like this before.”

A peculiar star

Previous observations of white dwarfs have shown that dead stars have surfaces scattered with metals. The metallic features likely came from planets or asteroids that came too close to the star, much like comets that fly close to the sun in our solar system.

But WD 0816-310 presents a completely different scenario orchestrated by the star’s magnetic field. The process is similar to how auroras create bright displays near Earth’s poles when energetic particles from the sun collide with Earth’s atmosphere.

The study’s authors said their observations show the dynamic actions that can take place within other planetary systems, even following the host star dies.

In regarding 5 billion years, Our sun is expected to become a white dwarf. But first, the golden orb will become a red giant, swelling and expanding as it releases layers of material. Red giants form when stars have exhausted their supply of hydrogen for nuclear fusion and begin to die.

As a red giant, the sun is likely to evaporate the solar system’s inner planets, such as Mercury and Venus, although Earth’s fate remains uncertain, according to the NASA.

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