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The white dwarf star, 1,300 light-years away, shows astronomers two very different faces: One hemisphere’s surface is made of helium and the other is hydrogen. This has been demonstrated by observations made by an international research team using several large telescopes. The strange phenomenon is likely caused by magnetic fields, the scientists write in the journal “Nature.”
“White dwarfs are extremely dense remnants of normal stars like our sun,” explain Ilaria Caiazzo of the California Institute of Technology and her colleagues. “They put a mass the size of our sun on an Earth-sized object.” In about five billion years, when our sun has exhausted its nuclear fuel store, it will first expand into a red giant star and then turn into such a white dwarf that will gradually cool over billions of years.
Janus shows very strong fluctuations
The star ZTF J203349.8+322901.1, named Janus, named after the two-faced Roman god, first caught the researchers’ attention during observations with the Zwicky Transient Facility at the Observatory on Mount Palomar, California. This telescope looks for obvious, temporary changes in the brightness of stars. Janus shows very strong fluctuations in its brightness every 15 minutes, unusual behavior for white dwarfs. Reason enough for Caiazzo and his colleagues to take a closer look at the object through various telescopes.
Among other things, the Gran Telescopio Canarias on La Palma’s Canary Island and one of the Keck telescopes in Hawaii were used. With the help of special devices – spectrometers – the researchers separated the light from Janus into its spectral colors. In this way, astronomers can learn from which chemical elements a celestial body is made. Because every element emits radiation at very specific wavelengths. These spectral lines act as a kind of fingerprint to identify related elements.
Until now, astronomers only knew about white dwarfs.
The result of the observations was surprising: Janus’ surface consists almost entirely of helium on one side and only hydrogen on the other. Until now, astronomers have only known about white dwarfs whose surface consists of hydrogen or helium.
“With the strong gravity of the white dwarfs, all the heavy elements sink to the bottom, with only hydrogen at the top initially,” the researchers explain. However, when a dwarf star cools below 30,000 degrees, the upper layers are mixed and therefore helium dominates in cooler-surfaced white dwarfs.
“It looks like we caught a white dwarf at this moment of transit with Janus,” says Caiazzo. The question is why this transition is so irregular in the two hemispheres of the star. Scientists suspect magnetic fields are at work here. This is because the magnetic fields of stars are often asymmetrical, meaning they are stronger on one side than the other. Where the magnetic field is stronger, it can block the transition. The team now hopes to use the Zwicky Transient Facility to track down other double-faced white dwarfs and thus trace the origin of the phenomenon.
(SDA)
Source : Blick
I am Dawid Malan, a news reporter for 24 Instant News. I specialize in celebrity and entertainment news, writing stories that capture the attention of readers from all walks of life. My work has been featured in some of the world’s leading publications and I am passionate about delivering quality content to my readers.
