We know that there are massive black holes and yet our telescopes can’t find them, so how is that possible?

Now it appears that an international team of researchers has figured this out: it has everything to do with the fact that our telescopes are biased against these massive black holes.

It’s 2015 when specially developed detectors on Earth detected a gravitational wave for the first time. In addition to the great joy that they were finally able to detect the gravitational waves predicted by Einstein, astronomers are also amazed. The wave appears to have originated during a collision between two black holes of a type we did not know existed until then. With a mass of several tens of solar masses, both black holes can be classified as heavy black holes. Astronomers have never observed this with their conventional telescopes (see box).

Black holes arise when stars reach their exploding ends. It’s quite compact, but has tremendous appeal. As a result, nothing can escape the grip of the black hole. Not even the light. This means we can’t see black holes either. But conventional telescopes can indirectly observe black holes when they are pointed by a star. When a black hole steals material from that star, it releases electromagnetic radiation, which reveals the presence of a black hole near the star. The mass of this black hole can also be determined based on the orbit of the companion star. In this way, researchers had already detected quite a few bright black holes before 2015. But a supermassive black hole has never been seen before, as attested by gravitational waves. And in 2021 that hasn’t changed yet; Although we’ve already collected quite a few gravitational waves caused by these supermassive black holes, the counter for the number of supermassive black holes observed with conventional telescopes is still zero.

bias, tendency
how is that possible? An international team of researchers – led by Dutch astronomer Peter Juncker – thinks they’ve discovered it now. According to them, conventional telescopes have a bias against supermassive black holes. In other words, our telescopes have a blind spot. And massive black holes are right in the middle of that.

dusty
Juncker and colleagues say in the journal that supermassive black holes can also be observed through their companion star Astrophysical Journal. Only conditions are working against our telescopes. It is said that massive black holes are made of stars that explode from within rather than exploding. As a result, the resulting massive black holes lie in the plane of the Milky Way, enveloped by dust. On the other hand, the lighter black holes – which our telescopes have already observed – arise from the explosion of a star where they are ejected directly from the plane of the Milky Way and are no longer obscured by dust.

The supervisor is too far away
But a dusty environment containing massive black holes is not the only reason why our telescopes cannot detect these massive black holes. Juncker and colleagues argue that the ancestors of heavy black holes are also very large, so a companion star is by definition somewhat further away. When this precursor explodes, the distance to the companion remains unabated and the resulting supermassive black hole is difficult to extract matter from that companion star. This makes it even more difficult for our telescopes – which can also see massive black holes only when they “eat” – to find them.

Juncker and his colleagues’ reasoning suggests that we don’t have a chance and we can never, ever, observe massive black holes. But this is not true. The James Webb Space Telescope will be launched next month. This infrared telescope can see directly through dust in the Milky Way’s disk and – if Juncker and his colleagues’ reasoning is correct – should have a much better chance of detecting a supermassive black hole.