Dead star “cannibal” is seen with scar after consuming part of planet

Astronomers have spotted the rare image that proves that a dead star consumed a fragment of the planet that orbited it: a metallic scar on its surface. The novelty shows the dynamic nature of planetary systems, even in the final stages of a star's life cycle.

This discovery, according to scientists, could also predict the eventual fate of our own solar system.

Planets form from swirls of gas and dust called a “protoplanterian disk.” These swirls surround a newly formed star. As the star ages and dies, it may consume the very planets and asteroids that contributed to its creation.

In this way, it is as if the star were “cannibalistic”.

Astronomers observed the dead star, known as a white dwarf, located about 63 light-years away from Earth, using the giant telescope at the European Southern Observatory in Chile. With the observation, it was possible to identify the metallic feature on the star's surface, which, according to the researchers, is related to a change in the star's magnetic field. A new study with details of the observation was published in the scientific journal “The Astrophysical Journal Letters” this Monday (26).

“It is known that some white dwarfs – which slowly cool embers from stars like our Sun – cannibalize pieces of their planetary systems. Now, we have 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,” explained the study's lead author, Stefano Bagnulo, an astronomer at the Armagh Observatory and Planetarium in Northern Ireland, in communicated.

The white dwarf, called WD 0816-310, is the remnant of a star that was once similar to our Sun but larger. The remains today are similar in size to Earth. The stellar object acquired a dark mark on its surface, which turned out to be a concentration of metals.

“We demonstrate that these metals originate from a planetary fragment as large 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 Professor of Astrophysics from University College London, Jay Farihi.

A magnetic connection

While working with the telescope, the team of scientists used the FORS2 instrument, considered a “Swiss Army knife” by researchers, to determine how the metal became part of the star. FORS2 is the abbreviation for Focal Reducer/Low Dispersion Spectrograph 2.

As astronomers observed the star, they noticed that the concentration of the detected metal changed as the star rotated. Instead of spreading across the surface of the star, as predicted by astronomical theory, the metal was concentrated in one area, as reported by one of the study's co-authors, professor emeritus of physics and astronomy at Western University in Canada, John Landstreet. .

The strength of the metal detection was also synchronized with the observed changes in the star's magnetic field, which led the team to determine that the metal scar was located at one of the star's magnetic poles.

According to the study, the star's magnetic field pulled the metals toward the star, which caused 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, also affiliated with the Armagh Observatory and Planetarium. “Nothing like this has been seen before.”

A peculiar star

Previous observations of white dwarfs have shown that dead stars have surfaces packed with metals. The metallic features are likely to come from planets or asteroids that have come too close to the star – just like comets that fly close to the Sun in our solar system.

But the star WD 0816-310 presents an entirely different scenario, one that was orchestrated by the star's magnetic field. The process is similar to the way auroras create bright displays near Earth's poles as energetic particles from the Sun collide with Earth's atmosphere.

The study authors said their observations show the dynamic actions 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 will likely evaporate the solar system's inner planets such as Mercury and Venus, although Earth's fate remains uncertain, according to NASA.