Black Holes
Black holes have long fascinated the imagination yet challenged
discovery. Their extreme gravity, so strong light cannot escape, make
them exceptionally difficult to see. Nearly a century after scientists
suggested black holes might exist, the world has tools to see them in
action.
The US National Science Foundation is at the forefront of these efforts,
supporting researchers studying black holes; facilities such as the Laser
Interferometer Gravitational-Wave Observatory, the Event Horizon
Telescope, and the international Atacama Large
Millimeter/submillimeter Array; and providing time on supercomputers
so data can be analyzed.
With a seemingly endless supply of weird and wow, these facts will
blow your mind.
1. There are likely millions of black holes in our galaxy, and we will
probably never know where they are
There are probably millions of black holes in the Milky Way alone,
orbiting like the stars, but we cannot see them. Black holes are
extremely dense pockets of matter, objects of such incredible mass and
miniscule volume that they drastically warp the fabric of space-time.
These monsters of the universe are nearly undetectable unless they are
feeding on space stuff or tugging on nearby stars. That means one
hungry black hole could be zipping right through our solar system
without us knowing, but that's highly unlikely.
2. If you fell into a black hole, you would never escape
If you got really close to a black hole, you would get sucked in and
never escape. Anything that passes too close, from a wandering star to a
photon of light, or even a human, gets captured. Scientists call this point
of no return around a black hole the event horizon. The closest known
black hole to Earth is believed to be 1,000 light-years away, so don't fret
— we are not getting sucked in.
3. If you fell into a stellar-size black hole, you could turn into human
spaghetti
Yes, it's as gross as it sounds. A stellar-size black hole's gravity field is
extreme and can vary enormously over small distances. If you fell in,
your feet would immediately get pulled way more than your head, and
you would stretch — a lot. This super stretching effect is
called spaghettification. Consider this a public service announcement to
stay away from stellar-size black holes.
4. A black hole could fit in your pocket
Scientists believe there are four kinds of black holes: primordial, stellar-
mass, intermediate-mass and supermassive.
Primordial black holes: Many scientists believe these tiny black
holes formed from the condensation of raw materials in the early
cosmos and emerged soon after the Big Bang. Most were
extremely tiny, about the size of an atom or smaller. While the
smallest have likely evaporated, the larger primordial black holes
may still exist — though, even those have remained undetected.
Stellar-mass black holes: The most common black holes form
from the result of a supernova, the catastrophic death of a massive
star. Most stellar-mass black holes are roughly five to 10 times
more massive than the sun, but the NSF-supported Laser
Interferometer Gravitational-Wave Observatory has detected
several with masses up to 100 times that of the sun.
Intermediate-mass black holes: Black holes that range from about
a hundred to hundreds of thousands solar masses are called
intermediate-mass black holes. Astronomers have spotted evidence
for a handful of candidates but were only recently able to confirm
their existence. Scientists believe there are several scenarios that
may explain their formation. They might have formed in
environments dense with stars or from mergers of stellar-mass
black holes or something completely different.
Supermassive black holes: Supermassive black holes are huge,
ranging from millions to billions of times the mass of the sun and
appear to be in the center of almost all galaxies. The supermassive
black hole at the center of the Milky Way is , commonly known as
Sgr A*, with a mass of over 4 million suns. An important area of
modern astrophysics is determining how supermassive black holes
came to be: Were they formed with such high masses, or did their
mass build up over time? Understanding these questions can give
insights into the cosmic origins of our galaxy.
The first image of Sgr A*, the supermassive black hole at the center of our galaxy. It’s the first
direct visual evidence of the presence of this black hole and was captured by the Event Horizon
Telescope.
Credit: EHT Collaboration
5. For the first time in human history, we know what a black hole
looks like
The NSF-supported Event Horizon Telescope captured the first image of
a black hole called M87* in 2019, and its mass is the largest known —
6.5 billion times the mass of the sun. In 2022, scientists released the
second image ever captured of a black hole; the one at the center of the
Milky Way dubbed Sgr A*. To capture images of black holes, an
international collaboration of scientists connected telescopes from
around the planet into an array that worked together as a super telescope,
enabling them to capture the region around the black hole and the pitch-
black void at its heart, where the black hole lives.
What are black holes made of?
Don't let the name fool you: a black hole is anything but empty space.
Rather, it is a great amount of matter packed into a very small area -
think of a star ten times more massive than the Sun squeezed into a
sphere approximately the diameter of New York City.
What can destroy black hole?
Eventually, in theory, black holes will evaporate through Hawking
radiation. But it would take much longer than the entire age of the
universe for most black holes we know about to significantly evaporate.
Black holes, even the ones around a few times the mass of the Sun, will
be around for a really, really long time!
