Metallic Scar Found on Cannibalistic Star
As a star resembling our sun nears the conclusion of its lifecycle, it may devour neighboring planets and asteroids that originated alongside it. Recently, using the European Southern Observatory’s Very Large Telescope (ESO’s VLT) in Chile, researchers have detected a unique imprint on the surface of a white dwarf star, marking this occurrence for the first time. These findings have been published in The Astrophysical Journal Letters.
“It’s widely recognized that certain white dwarfs—dimming remnants of stars akin to our sun—are gradually absorbing fragments from their planetary systems. Now, we’ve uncovered the pivotal role of the star’s magnetic field in this process, resulting in a distinct mark on the surface of the white dwarf,” explains Stefano Bagnulo, an astronomer at Armagh Observatory and Planetarium in Northern Ireland, UK, and the lead author of the study.
Metallic Concentration on White Dwarf Surface
The observed scar consists of a concentration of metals etching the surface of the white dwarf WD 0816-310, which remains as the remnant of a star similar in size to, though somewhat larger than, our sun.
“We’ve confirmed that these metals stem from a planetary fragment as substantial as, or possibly larger than, Vesta, which measures around 500 kilometers across and is the second-largest asteroid in the solar system,” notes Jay Farihi, a professor at University College London, UK, and a co-author of the study.
Additionally, the observations shed light on the origin of the star’s metal scar. As the star rotated, the team detected fluctuations in metal intensity, suggesting concentration in a specific region on the white dwarf’s surface rather than uniform distribution.
Magnetic Field Influence on Metal Scar Formation
They observed shifts in the white dwarf’s magnetic field, aligning with these changes, indicating the metal scar’s placement on one of its magnetic poles. This suggests that the magnetic field guided metals onto the star’s surface, forming the scar. Astronomers have previously observed many white dwarfs with scattered surface metals. These metals originate from disrupted planets or asteroids that approach the star, mirroring comet orbits in our solar system.
However, for WD 0816-310, the team believes that the white dwarf’s magnetic field ionized and directed vaporized material onto its magnetic poles.This process bears similarities to the formation of auroras on Earth and Jupiter.
Insights from Co-author John Landstreet
Remarkably, theory did not predict the uniform distribution of the material across the star’s surface. Instead, this scar represents a concentrated area of planetary material, held in position by the same magnetic field that guided the incoming fragments,” explains co-author John Landstreet, a professor at Western University, Canada, affiliated with the Armagh Observatory and Planetarium. “This is unprecedented.”
To reach these conclusions, the team utilized the FORS2 instrument on the VLT, which enabled them to detect the metal scar and link it to the star’s magnetic field.
“ESO possesses the unique blend of capabilities required to observe faint objects such as white dwarfs and accurately measure stellar magnetic fields,” notes Bagnulo. Additionally, the team relied on archival data from the VLT’s X-shooter instrument to corroborate their findings.
By leveraging observations like these, astronomers can uncover the overall composition of exoplanets, i.e., planets orbiting stars outside our solar system. This distinctive study also demonstrates how planetary systems can remain dynamically active even after the “death” of their parent star.
Read the original article on: Phys Org
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