Why don’t planet hunters find black holes?

AI Thread Summary
Over 200 planets have been discovered using the radial velocity technique, but black holes remain elusive in planet-hunting efforts. When a star orbits a black hole, it typically forms an X-ray binary, where matter is drawn into an accretion disc, emitting X-rays. This process results in significant periodic Doppler shifts in stellar spectral lines, which could indicate the presence of a black hole. However, black holes are much rarer than planets, making their detection more challenging. Consequently, astronomers often rely on X-ray emissions rather than traditional planet-hunting methods to identify black holes.
jimgraber
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Over 200 planets have been discovered by the radial velocity technique. Why no black holes? For similar periods, the signal amplitude should be much greater.
TIA.
Jim Graber
 
Astronomy news on Phys.org
I'm no expert in this area, but I believe that such systems (a star orbiting a black hole) would inevitably become what are known as "X-ray binaries", as matter is drawn from the star into a hot X-ray-emitting accretion disc around the black hole. The stellar spectral lines in such systems are indeed subject to enormous periodic Doppler shifts. I'm not sure how X-ray binaries are normally discovered though...
 
BHs are not nearly as common as planets
while they would really bounce a star's orbit
just looking for X-rays is a more common way to find them

V4641 Sgr is 1600 light years away at the closest found
 

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