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The Deepening Mystery of White Dwarf GD 394

12 Aug 2020, 16:00 UTC
The Deepening Mystery of White Dwarf GD 394
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This week, scientists are celebrating the recent conclusion of the primary mission for the Transiting Exoplanet Survey Satellite (TESS). On Monday, we talked about TESS’s ongoing contributions to exoplanet science. But what else has this spacecraft been up to? Today we’re exploring its addition to the mystery of a puzzling white dwarf.
Puzzling Pollution
GD 394 was one of the earliest metal-rich white dwarfs discovered, though others with varying explanations have been detected more recently. In the illustration above, a disintegrating planetesimal accretes onto a white dwarf. [NASA/JPL-Caltech]During TESS’s primary two-year mission, the spacecraft monitored 200,000 stars, discovering more than 2,000 planet candidates. But other targets also fell under the telescope’s scrutiny — including GD 394, an unusual white dwarf located less than 200 light-years away.
GD 394 has challenged our expectations for white dwarfs ever since its discovery in the 1960s. A white dwarf — a hot, dense stellar remnant — has such a strong gravitational pull that heavier elements are expected to rapidly sink to the white dwarf’s center, leaving only lightweight hydrogen, helium, and sometimes carbon and oxygen for us to identify in its atmosphere.
But early observations of GD 394 revealed an object unexpectedly polluted with ...

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