Supernova shoots a dying metal star out of the Milky Way at 2 million mph

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• Supernova shoots a dying metal star out of the Milky Way at 2 million mph

When astronomers first saw the white dwarf designated LP 40-365 about 2.000 light-years from Earth in 2017, it was hard not to notice. Opposing the rotation of the Milky Way, the white dwarf was traveling at almost 2 million mph (about 3,2 million km/h), which is about four times as fast as our sun revolves around the galactic core. At this speed, the star is on its way to escape the gravitational pull of the Milky Way and enter intergalactic space. Even more remarkable, according to LiveScience, was its composition, loaded with heavy metals like oxygen, carbon, and magnesium (any atom larger than helium is considered a metal by astronomers). While it wasn't unusual for white dwarfs to have compositions of carbon and oxygen, this star had magnesium and neon, which typically form under the intense energy of a supernova. This prompted researchers at the Boston University (BU) Department of Astronomy to study the star and piece together the puzzle of what sent it across the galaxy to its final destination in the far reaches of intergalactic space. Their findings, published in The Astronomical Journal Letters, point to the catastrophic supernova. White dwarf stars are the hospice stage of a star's life cycle. When a main sequence star runs out of fuel to burn during nuclear fusion, there is not enough external force to support the intense mass of the star and it collapses in on itself. If a star's mass is more than about eight times the mass of the sun, the mass is so great that the result is a neutron star or even a black hole. However, the smallest stars escape this fate. Its collapse triggers a catastrophic explosion known as a supernova, which scatters most of the star's mass into a massive nebula that will help form new stars and solar systems. What remains is a bright and intensely hot layer of the star's core, known as a white dwarf, whose mass is maintained not by fusion but by a quantum phenomenon involving electrons.

The Helix Nebula, with a white dwarf at its center, is the product of a violent supernova (Image credit: X-ray: NASA/CXC; Ultraviolet: NASA/JPL-Caltech/SSC; Optics: NASA/STScI (M. Meixner) / ESA / NRAO (TA Chancellor; Infrared: NASA / JPL-Caltech / K. Su) Although technically dead, with the nuclear fusion phase of the star's life, these stellar corpses will radiate heat and light for another billion years before completely dimming and becoming dwarf, black.In some cases, binary star systems can end with two white dwarfs, and this is where things get interesting.The smaller of the two white dwarfs will begin to consume matter from the larger one, since the more massive white dwarfs are actually smaller.If a white dwarf consumes too much matter, the quantum process that prevents the star from collapsing is further destabilized and the white dwarf erupts again in another violent supernova. This is what the BU researchers believe happened to this star. "Having been partially detonated and surviving is so fun and unique, and it was only in the last few years that we started to think that this type of star might exist," said Odelia Putterman, a BU alumnus, who co-authored the paper. “The star actually dropped the explosion, and we are its rotation upon launch,” Putterman added. What is not known is whether the star was the partner star or a part of the star that went supernova, although in Based on the rate of their rotation, the BU team believes the star is essentially shrapnel from the most massive star that has gone supernova."They are very strange stars," said JJ Hermes, lead author of the paper and associate professor of astronomy at BU "What we're seeing are the byproducts of violent nuclear reactions that occur when a star explodes."