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A Planet That Never Existed & Musical Black Holes

25 Apr 2020, 08:58 UTC
A Planet That Never Existed & Musical Black Holes
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Welcome back to another week in Astronomy for #ScienceFromHome. My favourite stories this week are about A Planet That Never Existed & Musical Black Holes.

In 2008, researchers detected the light of a planet around the nearby Fomalhaut star, only 25 light years away. This was the first visual detection of an exoplanet. It was so significant that the exoplanet was given a proper name, Dagon, after a Middle-Eastern god. But the planet never existed.

What was spotted was a much rarer event. Two objects roughly 200 kilometers in diameter hit each other. The collision stayed visible for a while, planet-like at first but as the debris expanded, it disappeared.

The second story is about the first detection of gravitational waves from a collision of black holes of different masses. So far all black hole mergers detected were between objects of roughly the same size. These have a ratio of 3.6. One is thirty times the mass of the Sun and one is eight times the mass of the Sun.

The disparity also allowed for the first observations of the “overtones” in the signal, and for these black holes it was pretty musical. The difference between the main frequency ...

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