The Closest Black Hole to Earth May Not Actually be a Black Hole After All
upstart writes in with an IRC submission for nutherguy:
The closest black hole to Earth may not actually be a black hole after all:
An object identified earlier this year as the closest black hole we've ever discovered may have just been demoted. After reanalyzing the data, separate teams of scientists have concluded that the system in question, named HR 6819, does not include a black hole after all.
Instead, they have found that it's likely just two stars with a slightly unusual binary orbit that makes it difficult to interpret.
[...] After conducting careful calculations, a team of astronomers concluded that the B3 III star could be orbiting another, third object, one that couldn't be seen. A black hole.
But, other astronomers argue, that's far from the only possibility. What if we have miscalculated the masses of the stars?
[...] They carefully studied the hydrogen emission in the system's spectrum, and found that the hydrogen disc around the Be star did indeed display a 40-day periodicity in both Doppler shift and emission line shape. This is consistent with the B3 III star's orbit - just as would be expected if the system were an unequal-mass binary.
"This indicates," they wrote, "that HR 6819 is a binary system consisting of a massive Be star and a low-mass companion that is the stripped down remnant of a former mass donor star in a mass transfer binary."
[...] So the future looks grim for the black hole interpretation, although it's not settled quite yet. Future observations could help resolve any lingering questions. But, Gies and Lang argue, the binary system could be more interesting than a black hole.
Journal References:
Douglas R. Gies and Luqian Wang. The H Emission Line Variations of HR 6819 - IOPscience, The Astrophysical Journal Letters (DOI: https://iopscience.iop.org/article/10.3847/2041-8213/aba51c
J. Bodensteiner, T. Shenar, L. Mahy, et al. Is HR 6819 a triple system containing a black hole? - An alternative explanation [open], Astronomy & Astrophysics (DOI: 10.1051/0004-6361/202038682)
El-Badry, Kareem, Quataert, Eliot. A stripped-companion origin for Be stars: clues from the putative black holes HR 6819 and LB-1, (DOI: https://arxiv.org/abs/2006.11974)
Previously:
Closest Black Hole to Earth Found "Hiding in Plain Sight"
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