I would like to know how many known quasars there are in the Universe as well as x-ray binary black holes (not Neutron stars) but I don't seem to be able to.

I also want to know how many black holes have been found via gravitational wave detections but I think the answer to this question is 3.

Do you guys know any credible sources that list the objects in the sky via category and gives detailed info of how we found them (x-ray binary or gravitational waves or quasars).

  • $\begingroup$ Not really helpful, but for stuff within the Milky Way: usno.navy.mil/USNO/astrometry/optical-IR-prod/nomad and gea.esac.esa.int/archive $\endgroup$
    – user21
    Commented Jul 23, 2017 at 15:25
  • 1
    $\begingroup$ Another not so helpful comment, but I thought you might like to see this chart which was produced by LIGO after the 3rd confirmed detection of gravitational waves. Technically they found 6 but those have now merged to become 3 :) Note: LVT151012 was detected with <5 sigma confidence so is not considered a confirmed detection. $\endgroup$
    – Dean
    Commented Jul 24, 2017 at 11:09

2 Answers 2


Lists of astronomical sources are called "catalogues" and other answers have already mentioned the NGC catalogue of galaxies and nebulae. However, you asked about quasars and black hole x-ray binaries.

I say "sources" because the catalogues normally list what can be observed, rather than what can be inferred. For black holes, this is significant, as we can rarely observe black holes directly, but we can infer their existence from the effects that they have on other matter.

For quasars, there are several catalogues. None claim to be complete, as new discoveries happen all the time. The MILLIQUAS catalogue is a compendium of 460,222 type-I QSOs and AGN. It also contains about a million "Quasar candidates". (sources that may be quasars, 80% confidence)

For Black hole binaries, the difficulty is proving that the object is indeed a black hole. This usually requires calculating the mass of the accreting object, which is not always easy. The X-ray catalogues are classified by the mass of the normal stellar component. The High Mass x-ray binary catalogue notes objects that are "black hole candidates". It is in no way a definitive list, since no such list exists.


There are actually numerous lists, categorised in all sorts of ways.

Depending on what level you are approaching this, I'd suggest Wikipedia's list may be your best entry point.

If you want raw data, the NGC 2000 list is the way to go.


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