A black hole is a dead collapsed star with all its mass, that's why it has such a massive gravitational pull.
this post was submitted on 13 Aug 2026
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Yes, black holes absolutely have mass. That's really all they have.
And yes, black holes and stars can attract each other by gravity. Our galaxy has a fuckoff massive black hole at the center, and all the stars in the galaxy including our sun orbit that black hole.
There are also cases of black holes attracting each other and merging. One of these is the reason we know gravitational waves are possible.
Mass, charge and spin are the attributes we can currently assign to a black hole
Huh. Didn't realize they had charge. As in electromagnetic charge?
Yes the total electrical charge of the particles consumed is conserved
And also some measure of radiation, right? Hawking radiation? Whatever that is?
Hawking radiation is not a confirmed effect and it is unique to event horizons not black holes. A naked singularity would have mass spin and charge but no hawking radiation. There are many types of event horizons and all of them have hawking radiation.
Ah-ha, I see. Thanks for that.
There are many types of event horizons
Really. That is intriguing!
I can comprehend gravitational waves and the crazy precision needed to measure them, but I've still never been able to understand how they determine the objects that merge to cause the waves.
I see articles about having detected things like "two supermassive black holes", "a supermassive black hole and a neutron star", or "one massive black hole and an abnormally large poodle" colliding. I have no idea how they feel they have any real knowledge of what objects at what sizes led to the waves from simply being able to see the relative size of the waves and now long they last.
I believe most of the time they run models with the known parameters and use that to decide what the objects were. It also seems that we appear to understand what different wave patterns look like and know what the source objects tend to be. Other times I believe they can figure out what one object was but not the other and just kinda have to guess at it. I would also suspect that once they determine the location in the sky where the event happened they can check and see if there are any past observations of that area of the sky by other telescopes and just look and see what was there previously.
I'm sure I'm greatly simplifying this, but that's what I turned up with a bit of reading on the LIGO website for Gravitational Wave Sources and Types.
Edit: typos
With the interferometers they can estimate the mass of the 2 objects entering in collision and the resulting one.
Since there are multiple interferometers, they can also point to the region of the sky it happens. The "alert" can be picked up by other observatories which can look there on all frequencies.
Depending on if there is an explosion or not they can confirm if the objects were neutron stars or black hole (the details are a bit fuzzy on my head for the black hole / neutron star merger).
This isn't really a mystery. Yes they all have mass. Yes they all pull on each other, as do all things with mass (which is basically all things, btw).
Its mass can be measured just like any other object. We can't see a black hole, but we can see things around it and how they are affected, and using physics determine what mass would be needed. If the Sun magically became a black hole, it would have the same mass and the planets would orbit the same. So we could measure how they go around it and come up with the mass at the center.
One way (I believe) to measure a black hole indirectly is to see how it bends light images from things behind it. Same thing, we can calculate how much mass would be needed to bend that image's light path.
The second question, a star can pull a black hole, it's just a matter of the two masses. Usually you'll find the black hole is much larger, but in theory a small black hole could orbit a large star.
I think our universe could be inside a black hole in a larger universe.