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This is not really correct. We can also 'see' (some) black holes through gravitational waves. The gravitational wave observatories were by the way the first ones to directly observe a black hole.

LIGO right?
I guess there are a few others as well...

Ligo and Virgo indeed :)

Good point
I did not know that they knew what the waves were from that they detected.
This is not my field but more of an interest.

It is slightly more subtle. The only phenomenon we know that is capable to produce such waves is the merging of two blackholes. Roughly speaking, this is more or less the same, but in fact, that could be something else that acts as a blackhole (a kind of "smell like a blackhole, live like a blackhole and eat like a blockhole" object). From our human perspective, therefore, this would simply be a blackhole. I don't know if I made this little difference clear enough. Please let me know. (and please apologies for the delay; I was so busy in offline life ;) ).

Its never to late :)

We picked up some waves from two colliding neutron stars that .
That caused some rethinking.
I don’t know that much about and more like a novice

The nice feature with the neutron star event is that it was followed by something visible with gamma rays. We thus had several ways to get information on the same catastrophic cosmic event: the three gravitational wave observatories plus many telescopes.

I only heard bits and pieces and that they thought it was black holes colliding.
I am starting to think that Neutron stars and their many types are worse, more destructive the black holes

They actually saw both: a bunch of black hole events and a single neutron star events.

I did some looking the other day. This is just one of the things I found. Interesting stuff

https://www.npr.org/sections/thetwo-way/2017/10/16/557557544/astronomers-strike-gravitational-gold-in-colliding-neutron-stars