In order to give you a realistic idea of the volume of space occupied by a
supermassive black hole, NASA has
released a new animation.
These galaxies serve as the gravitational heart around which stars twirl in
an orbital dance that lasts for eons. They are the behemoths of the
universe. On the lower end of the spectrum, they begin at around 100,000
times the mass of the Sun, and at their maximum, they may reach tens of
billions of solar masses.
All right, these are abstract numbers, but it's difficult to imagine how
big these things really are. One of the great mysteries of the universe is
how things came to be the way they are, despite the fact that we do have
some theories.
There are more than 100 supermassive black holes, according to direct
observations, many of which were made with the aid of the Hubble Space
Telescope, says theoretical astronomer
Jeremy Schnittman
of NASA's Goddard Space Flight Center. How do they become so large? The
center black holes of merging galaxies may eventually combine as well.
The black holes themselves could not even be that large. The universe's
black holes are the densest things we are aware of. They are so small that
the only mathematical term we can use to describe them is a singularity,
which is a one-dimensional point with infinite density. They are so dense
that space-time is gravitationally bent around them, creating what is
essentially a closed sphere. Not even light has enough speed to escape from
that sphere.
When we discuss a black hole's dimensions, we are referring to its event
horizon, which is the border. The Schwartzschild radius—the circumference of
the sphere enclosed by the event horizon—increases with black hole mass. For
instance, the Sun's
Schwartzschild radius would be just 2.95 kilometers (1.8 miles) if it were a black hole.
As far as we are aware, the tiniest black holes, which are objects produced
from the collapsing core of a huge star at the end of its existence, start
at around
five times the mass
of the Sun. These black holes have stellar masses.
The maximum mass of stellar mass black holes is about 65 times that of the
Sun because the massive precursor stars that would give rise to these larger
objects pass away in a
pair-instability supernova, which completely destroys the core and leaves nothing behind for the
black hole to collide with.
However, black holes with stellar masses greater than 65 solar masses have
been observed. They can arise from the merger of two black holes, which
produces a mass-combining object. However, there is a significant gap
between these and the supermassive and ultramassive black holes. Really
literally. In the mass range between stellar mass black holes and
supermassive ones, there have been very few black holes found.
However, there is also a wide variety among supermassive black holes.
Starting with a black hole in a dwarf galaxy designated J1601+3113, which
has a black hole with a mass of about 100,000 solar masses, NASA's new
animation provides a truly astounding look at that range. Its Schwarzschild
radius would be little smaller than half the size of the Sun as a result. In
the movie, this shadow seems to be almost the same size as the Sun because
the black hole's shadow spreads into the area surrounding its event horizon,
creating a darker region nearly twice its size.
Also visible is Sagittarius A*, the about 4.3 million solar mass
supermassive black hole at the heart of our own galaxy. There is also M87*,
the first black hole to be seen, which has a mass 5.37 billion Suns, which
is substantially higher.
The same galaxy, NGC 7727, likewise has two black holes hanging at its
core. NGC 7727 was formerly composed of two galaxies. The two black holes at
the galactic cores, measuring in at 154 million and 6.3 million solar
masses, respectively, have now merged and have descended to the heart of the
newly joined galaxy, where they will eventually also merge.
These black holes are a significant hint that, according to scientists,
reveals one method of supermassive black hole growth. Their mergers ought to
result in gravitational waves. These mergers happen too seldom for our
existing tools to pick them up, though.
The monster referred to as TON-618 is one of the biggest black holes that
we are aware of in the Universe. Its mass was estimated by experts to be a
staggering 66 billion solar masses in 2004. Around 50 billion solar masses is one theoretical upper limit for the mass of black holes, but the universe
is pretty good at defying theories.
The black hole's Schwarzschild radius would be more than 1,300 astronomical
units at such mass. To put things in perspective, Pluto is located around 40
astronomical units from the Sun in its orbit. The Solar System would be
completely engulfed by this object.
