How massive can black holes get?

August 11, 2015 by Fraser Cain, Universe Today
How Massive Can Black Holes Get?
Labelled image of the M87 Galaxy. Credit: NASA/Chandra

Without the light pressure from nuclear fusion to hold back the mass of the star, the outer layers compress inward in an instant. The star dies, exploding violently as a supernova.

All that's left behind is a black hole. They start around three times the mass of the sun, and go up from there. The more a black hole feeds, the bigger it gets.

Terrifyingly, there's no limit to much material a black hole can consume, if it's given enough time. The most massive are ones found at the hearts of galaxies. These are the supermassive , such as the 4.1 million mass nugget at the center of the Milky Way. Astronomers figured its mass by watching the movements of stars zipping around the center of the Milky Way, like comets going around the sun.

There seems to be at the heart of every galaxy we can find, and our Milky Way's black hole is actually puny in comparison. Interstellar depicted a black hole with 100 million times the mass of the sun. And we're just getting started.

The M87 has a black hole with 6.2 billion times the mass of the sun. How can astronomers possibly know that? They've spotted a jet of material 4,300 light-years long, blasting out of the center of M87 at , and only black holes that massive generate jets like that.

Most recently, astronomers announced in the journal Nature that they have found a black hole with about 12 billion times the mass of the sun. The here generates 429 trillion times more light than the sun, and it shines clear across the Universe. We see the light from this region from when the Universe was only 6% into its current age.

An illustration that shows the powerful winds driven by a supermassive black hole at the centre of a galaxy. The schematic figure in the inset depicts the innermost regions of the galaxy where a black hole accretes, that is, consumes, at a very high rate the surrounding matter (light grey) in the form of a disc (darker grey). At the same time, part of that matter is cast away through powerful winds. Credit: XMM-Newton and NuSTAR Missions; NASA/JPL-Caltech;Insert:ESA

Somehow this black hole went from zero to 12 billion times the mass of the sun in about 875 million years. Which poses a tiny concern. Such as how in the dickens is it possible that a black hole could build up so much mass so quickly? Also, we're seeing it 13 billion years ago. How big is it now? Currently, astronomers have no idea. I'm sure it's fine. It's fine right?

We've talked about how massive black holes can get, but what about the opposite question? How teeny tiny can a black hole be?

Astronomers figure there could be primordial black holes, black holes with the mass of a planet, or maybe an asteroid, or maybe a car… or maybe even less. There's no method that could form them today, but it's possible that uneven levels of density in the early Universe might have compressed matter into black holes.

Those black holes might still be out there, zipping around the Universe, occasionally running into stars, planets, and spacecraft and interstellar picnics. I'm sure it's the stellar equivalent of smashing your shin on the edge of the coffee table.

Astronomers have never seen any evidence that they actually exist, so we'll shrug this off and choose to pretend we shouldn't be worrying too much. And so it turns out, black holes can get really, really, really massive. 12 billion times the of the massive.

Explore further: How much of the universe is black holes?

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5 / 5 (1) Aug 11, 2015
If it can be imagined it exists.
1 / 5 (3) Aug 12, 2015
Once the Black Hole forms no matter can pass the event horizon in a finite interval as measured by any observer above the event horizon therefore the Black Hole can not grow after formation as measured by any observer.

The accretion disc certainly can gain mass.
3 / 5 (1) Aug 12, 2015
Here is a dumb question.

If light cannot escape a black hole, then how is it possible for gravity to escape a black hole ?

4.2 / 5 (5) Aug 12, 2015
Once the Black Hole forms no matter can pass the event horizon in a finite interval as measured by any observer

I think you're confusing two things here:

a) the observation of the crossover
b) the actual crossover

While we can never observe a) because the light emitted in the last few seconds before the crossing over gets stretched into infinity (and very quickly gets redshifted out of any observable wavelength, BTW).
However b) does happen in a finite time relative to the an outside observer. Otherwise a black hole couldn't form in the first place.

5 / 5 (2) Aug 15, 2015
If light cannot escape a black hole, then how is it possible for gravity to escape a black hole ?
Good question. Here's a good answer: http://www.askama...-escape/
1 / 5 (1) Aug 17, 2015
Maybe there really IS an upper limit. Suppose matter is a literally infinite onion of smaller and ever smaller sub-units. Now once we thought only of atoms...then of electrons and protons and other stuff. Then thirty years ago we posited quarks as building blocks of protons, etc. Now we are thinking even quarks have smaller units called preons.. We have neutron stars where atoms have collapsed, and quark stars where protons, neutrons, etc have collapsed. Now we also have black holes...supposedly where preons have collapsed. Now let us posit a truly immense explosion, an ultra hyper nova where the preon/black holes collapse and either tear a hole in the universe or we see an immense energy blast coming from beyond our visible universe, because this event may really set all known physics on its ear. If a hole in the universe, does that lead to a new island universal 'big bang'. Maybe sucking our universe dry in the process?
1 / 5 (1) Sep 22, 2015
The General Relativity Math that predicts **Relatively** frozen time at the event horizon was first measured and the GR prediction verified by Pound in 1960 and later used to adjust the clock rate of global positioning satellites which run quicker than Earth bound clocks due to gravitational time dilation.

In other words, gravitational time dilation has nothing to do with light stretching. In fact if we look at that analogy (light does not and can not actually stretch) in reverse then we see that light from space is infinitely blue shifted to an observer at the event horizon.

If we consider pulses of light, then as the observer descends toward the event horizon, pulses sent to a space observer slow and finally stop. But those pulses received FROM space become more frequent. As the descending observer can not receive pulses before they are sent, the increase in *apparent* frequency can only be explained by the relative clock rate.

'Stretched Light' fails.

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