Dead ‘cannibal’ star spotted with traces of metal after swallowing up part of planet

(CNN) — Astronomers have spotted an unusual sign that a dead star is eating up pieces of a planet orbiting it. It is a metallic mark on the surface of the star. Scientists say this revelation highlights the dynamic nature of planetary systems even in the final stages of a star’s life cycle, and may predict the ultimate fate of our own solar system.

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

Astronomers using the European Southern Observatory’s Very Large Telescope in Chile spotted a dead star, known as a white dwarf, located about 63 light-years from Earth. The observation revealed a metallic feature on the star’s surface, which the researchers found to be related to observed changes in the star’s magnetic field. A new study detailing the observation was published Monday in The Astrophysical Journal Letters.

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

The white dwarf, called WD 0816-310, is the remains of an Earth-sized star that was once similar to our Sun but larger. A noticeable dark mark formed on the surface of the stellar object, which appeared to be a concentration of metals.

“We show that these metals come from a fragment of a planet as large as or possibly larger than Vesta, which is about 500 kilometers in diameter and is the second largest asteroid in the Solar System,” said study co-author and Professor Jay Farihi. ” In a statement from the Professor of Astrophysics at University College London.

a magnetic connection

Working with the Very Large Telescope, the team relied on its FORS2 instrument, which researchers consider a “Swiss Army knife” instrument, to determine how the metal became part of the star. FORS2 is short for Focal Reducer/Reduced Dispersion Spectrograph 2.

As astronomers observed the star, they noticed that the concentrations of the metals they detected changed as the star rotated. Rather than being scattered across the surface of the star, 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 observed changes in the star’s magnetic field, helping the team determine that the trace of metal was located at one of the star’s magnetic poles.

The discovery suggests that the star’s magnetic field attracted metals to the star, leading to the appearance of the scar.

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

a unique star

Previous observations of white dwarfs have shown that metals are scattered across the surface of dead stars. The metallic features probably came from planets or asteroids that flew 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, driven by the star’s magnetic field. This 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 authors said their observations reflect dynamical processes that can occur within other planetary systems even after the host star dies.

In about 5 billion years, our Sun is expected to become a white dwarf. But first, the golden sphere will become a red giant, swelling and expanding as it sheds layers of material. Red giants form when stars exhaust 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, according to NASA, although Earth’s fate remains uncertain.