As follow-up question for my previous question I'm thinking about the search for the electromagnetic (EM) counterpart of a gravitational wave (GW). Is it possible to search for those events with 'normal' telescope, the ones (professional) amateur astronomers have? What I mean with a (professional) amateur astronomer is: a telescope with an aperture of 10" or more (remote) and the ability to do long exposures.

Is that equipment capable of detecting the EM counterpart of a gravitational wave (in theory)? Thanks in advance!

EDIT: I'm not sure if there is an EM counterpart in the visible light at all. Is this the case? Can such an event, that triggers a detectable GW, been seen in the visible light (by extension: with 'amateur' telescopes as stated above)?

  • $\begingroup$ Can you define what this "EM counterpart" is theorized to be? $\endgroup$ Jun 29, 2020 at 14:59
  • $\begingroup$ Wikipedia has a list of GW observations. None have been in our galaxy. The closest on that list, GW170817, is at 40 Mpc. $\endgroup$
    – PM 2Ring
    Jun 29, 2020 at 16:38
  • $\begingroup$ @CarlWitthoft When an explosive event happens that causes a detectable GW, there is an energy release in the EM too. Gamma radiation, visible light, everything in the spectrum. This is what I mean by "EM counterpart". The release in energy in the EM of the source. $\endgroup$ Jun 29, 2020 at 18:08
  • $\begingroup$ @PM2Ring That doesn't help. Stars are likely not to be seen in such distances, but the EM counterpart of such explosive events is rather energetic, thus of a very magnitude. However, I'm not sure if there is a(n) (big) energy release in the visible light, so I'll change my question a little bit! Thanks anyways. $\endgroup$ Jun 29, 2020 at 18:10
  • $\begingroup$ It seems that neutron star collisions emit quite a lot of EM radiation, as do black hole collisions taking place in an area rich in dust and gas (like the accretion disk of a much bigger black hole) but black hole collisions in empty space emit almost none. $\endgroup$ Jun 29, 2020 at 22:13

1 Answer 1



The Neutron star merger GW170817 had an optical counterpart (SSS 17a) The optical magnitude peaked at about +18, this is beyond the abilities of most amateur set ups.

Black hole mergers may be intrinsically more energetic, but less bright in the electromagnetic spectrum, as the black holes don't have a surface to interact electromagnetically.

However each gravitational wave detection is examined to see if there is a corresponding gamma ray burst, or optical transient. Combining results of gravitational, neutrino and optical observations has been called "multi messenger astronomy".

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    $\begingroup$ Also not with exposure times of 3 minutes or (much) more for example? I don't know enough of how long exposures can make higher magnitude better visible. With which kind of telescopes is it then observed? $\endgroup$ Jun 29, 2020 at 19:10

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