The lack of black holes in telescopes is caused by biases

Biases in the observation of telescopes explain why black holes with stellar mass greater than 20 times the sun are not detected, although they are known to exist due to the radiation of gravitational waves. It is the conclusion of research on these seemingly disparate results by a team of astronomers led by Peter Jonker of the SRON Netherlands Institute for Space Research.

In 2015, the LIGO facilities detected gravitational waves for the first time. They were emitted by two massive black holes several tens of the mass of the melting sun. This discovery shook the universe, and also the astronomical community, because few astronomers had predicted that such massive black holes would exist, much less that they could merge.

Before gravitational wave detections, our conventional telescopes had found evidence of stellar-mass black holes in about 20 cases. However, none have ever been found that were as massive as those now observed through gravitational wave radiation emitted during fusion. So far, around 50 of these merged black hole pairs have been detected.

Telescopes have yet to find such black holes. Thank you for watching This disparity can be explained in part by the greater volume of the universe that gravitational wave detectors are testing. LIGO-Virgo can find more massive black holes more easily because their waves are stronger relative to those of lighter black holes, implying that these could be rare but noisy events.

But zero detections of such black holes using telescopes? Black holes, or at least their close surroundings, light up when they slowly devour a companion star. By measuring the orbital motion of the hapless star, the mass of the black hole can be determined.

A team of astronomers led by Peter Jonker (The Netherlands SRON Space Research Institute / Radboud University) realized that the telescope’s observations are biased against the detection of massive black holes. These massive black holes can, in principle, be observed if they eat mass from a companion star.

However, the circumstances for those observations have been too difficult in practice, which explains the lack of detection of massive black holes through telescopic observations. Larger black holes are formed by the implosion of massive stars, rather than the explosion of massive stars (“supernova”).

Formed through an implosion, these huge black holes remain in the same place where their predecessor (the massive star) was born, the plane of the Milky Way galaxy. However, that means they remain enveloped in dust and gas…