When Tides Turn White Dwarfs Hot

Image of the Sirius system taken by the Hubble Space Telescope. The arrow points to Sirius B, the closest white dwarf to Earth (Credit : NASA, ESA, STSCI)

White dwarfs are stellar corpses, the slowly cooling remnants of stars that ran out of fuel billions of years ago. Our Sun will eventually share this fate, collapsing into a compact object so dense that the heavier it becomes, the smaller it shrinks. This rather strange property is just one of the aspects of white dwarfs that makes them utterly fascinating and occasionally, utterly baffling. Sometimes we find white dwarfs as part of binary systems and they are usually cool and gently radiating their energy out into space. A team of astronomers have recently discovered a peculiar class of these binary systems that defies expectations. The pair of white dwarfs are orbiting each other faster than once per hour and exhibiting temperatures between 10,000 and 30,000 degrees Kelvin, significantly hotter than expected and twice their usual size.

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