According to this article, the quasar (black hole) named J0529-4351 is the most luminous object in the known universe, being:

500 trillion times more luminous than the Sun

To put it in terms easier to understand at a human level, how bright would the quasar be if it were within our galaxy? I'm considering that it is either in place of the current black hole in the galactic center of the Milky Way, or somewhere perhaps less shrouded by dust (if it matters).

  • $\begingroup$ FWIW, it has a mass of 17 billion solar masses, which means its Schwarzschild radius is ~46.5 light-hours. That's big, but TON 618 has more than double that mass. $\endgroup$
    – PM 2Ring
    Commented Feb 20 at 19:11
  • $\begingroup$ Are you just asking about the luminosity of the central object, i.e., that 7 light-year diameter accretion disk? Quasar tend to have jets, which can span over a million light-years, which is larger than the Milky Way. $\endgroup$
    – PM 2Ring
    Commented Feb 20 at 19:15
  • $\begingroup$ Actually, small correction - the article you provided says that a lens galaxy magnified the quasar to appear to be 500 trillion L☉. It is thought to be "just" around 11 trillion naturally. $\endgroup$
    – 4NT4R3S
    Commented Feb 20 at 20:10
  • $\begingroup$ @4NT4R3S I got confused by that as well, but it's not talking about J0529-4351 but rather another quasar. $\endgroup$ Commented Feb 20 at 21:36
  • $\begingroup$ @PM2Ring I'm just talking about the luminosity that they reference, whatever the source is. I'm not sure if it is known whether the luminosity is due to the jet or the accretion disk. $\endgroup$ Commented Feb 20 at 21:37

1 Answer 1


The (boldly titled) omnicalculator can do luminosity calculations. At 500 trillion solar luminosities, this object would have an absolute magnitude of -32, and if placed at 26000 light years distance, it would have an apparent magnitude of -17.5 That is much brighter than the moon (about 100 times brighter) but not nearly as bright as the sun (The sun would be 10000 times brighter)

It would, however be no larger in the sky than Venus. So it might be "fair" to compare it to bright stars and planets. It would appear to be a "star" that is about 60000 times brighter than Venus. Or about 4000000 times brighter than Sirus.


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