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Astronomers have discovered a white dwarf with two faces, one facet dominated by hydrogen and the opposite by helium. Appropriately sufficient, they’ve dubbed it Janus after the two-faced Roman god of transition and duality.
“The floor of the white dwarf utterly adjustments from one facet to the opposite,” mentioned Ilaria Caiazzo, a postdoctoral scholar at Caltech who led a research describing the findings within the journal Nature. “Once I present the observations to individuals, they’re blown away.”
White dwarfs are the remnants of stars like our Solar which have used up their nuclear gasoline, swelling to turn into crimson giants earlier than blowing off their outer layers. The cores then collapse, forming slowly cooling planet-size dwarf stars.
Heavier components sink into the inside whereas lighter components like hydrogen float to the highest. Over time, because the dwarf cools, the supplies combine collectively and in some instances, helium can turn into extra prevalent.
The Janus dwarf was found by the Zwicky Transient Facility at Caltech’s Palomar Observatory close to San Diego, California. Caiazzo was trying to find extremely magnetised white dwarfs when her group took a better have a look at a candidate that confirmed fast brightness adjustments.
Utilizing the CHIMERA instrument at Palomar and the HiPERCAM on the Gran Telescopio Canarias within the Canary Islands, they discovered it was rotating on its axis as soon as each quarter-hour. Subsequent spectroscopic observations utilizing the W.M. Keck Observatory in Hawaii confirmed one facet was dominated by hydrogen and the opposite facet by helium.
Baffled, the group got here up with two potential explanations, each involving the dwarf’s magnetic subject.
“Magnetic fields round cosmic our bodies are typically uneven, or stronger on one facet,” Caiazzo mentioned. “Magnetic fields can forestall the blending of supplies. So, if the magnetic subject is stronger on one facet, then that facet would have much less mixing and thus extra hydrogen.”
One other chance: the magnetic fields might change the stress and density of the gases. Stated co-author James Fuller, professor of theoretical astrophysics at Caltech: “The magnetic fields might result in decrease gasoline pressures within the environment, and this may occasionally permit a hydrogen ‘ocean’ to kind the place the magnetic fields are strongest.”
“We don’t know which of those theories are appropriate, however we will’t consider some other method to clarify the uneven sides with out magnetic fields.”
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