How a companion star can reveal an invisible black hole

A companion star can reveal a black hole

≈2 solar masses

Astronomers can estimate the mass of an unseen object by watching a nearby star orbit it. If the hidden object is much heavier than the roughly two-solar-mass limit for neutron stars, it is generally thought to be a black hole.

Most of China’s people live in the east

Only 6.5% Lived West

In 2020, only 6.5% of China’s population lived west of the Heihe–Tengchong Line, even though that area covers about 64% of the country. Most of China’s people are packed into the much smaller eastern part.

A fly can locate a singing cricket with ears on its abdomen

A female cricket fly finds singing male crickets using two hearing organs on its abdomen. The two ears can respond only about 50 billionths of a second apart, yet that tiny difference is enough to tell the fly which direction to move before it attacks the cricket as a parasite.

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How a companion star can reveal an invisible black hole

A companion star can reveal a black hole

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