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Mysterious and invisible, black holes are some of the strangest objects in the universe.
Unlike planets or stars, black holes do not have a surface and cannot easily be directly observed.
Instead, black holes are studied by the effects they have on the matter around them.
A black hole is a celestial object with a graviational pull so powerful that nothing
- no matter, no energy, not even the fastest thing we know, light - can escape.
That is why they appear so dark.
The boundary around a black hole, past which nothing can escape, is called the event horizon.
The mass of a black hole determines its gravitational force, which in turn determines the size and
shape of its event horizon.
The more massive a black hole is, the larger its event horizon will be.
Despite the name, a black hole is not empty space.
Instead, an incredible amount of matter is packed into a very small area.
To understand how much material we are talking about, imagine a star ten times more massive
than the sun compressed into a sphere the size of New York City.
Black holes represent the greatest concentration of mass anywhere in the universe.
If we cannot see or directly observe them, how do we know that black holes exist?
One way is to look for their effects on nearby objects.
For example, when a star passes too close to a supermassive black hole, it can be pulled
apart by the black hole's powerful gravitational force in a process called tidal disruption.
Scientists can also look for traces of gas and dust that have been drawn towards a black
hole, or for stars that appear bent or distorted by the immense gravitational forces near the
black hole.
When a black hole swallows up a nearby star, it can create a powerful jet of energy that
can be detected from great distances, called a quasar.
The gravitational forces of black holes are so powerful that they can distort both space
and time.
In fact, scientists believe that time will slow down when you are close enough to a black
hole.
This is because the gravitational force of a black hole can curve space-time, making
it possible for objects to travel through it in a way that bypasses the normal rules
of time.
There are four types of black holes: stellar, supermassive, intermediate, and miniature.
The most common types of black holes are stellar and supermassive.
A stellar black hole is believed to be created at the end of a massive star's life cycle.
For a star to become a black hole, it must be several times more massive than our Sun.
When this huge star dies, its core collapses, triggering a supernova.
The explosion of the supernova blasts leftover material from the star far out into space.
The collapsed core that remains becomes a black hole.
It is believed that there might be millions of these stellar black holes in our galaxy
alone.
Less is known about the formation of supermassive black holes.
Like their name suggests, supermassive black holes are much more massive than stellar black
holes, with some weighing in at billions of times the mass of the Sun.
They are thought to exist at the center of most galaxies, including our own Milky Way
galaxy.
The black hole at the center of the Milky Way is known as Sagittarius A*, with a mass
four million times that of the sun.
Some scientists suggest that supermassive black holes may have been formed from collisions
between stars, black holes, and other materials that accumulated at the center of the galaxy,
continually growing larger as they collect more matter over time.
Although black holes have been predicted for centuries, the first black hole was not discovered
until 1971.
Black holes have since become an important area of study for astronomers and physicists
alike.
The first photograph of a black hole was a major breakthrough in our understanding of
these mysterious objects.
It was taken in 2019 using a network of telescopes called the Event Horizon Telescope.
This photograph has made a huge impact on the scientific community.
It has allowed scientists to confirm some of their theories about black holes and has
sparked new research into them.
Despite all we know about them, black holes remain one of the greatest mysteries in the
universe.
They continue to intrigue scientists and fascinate the public.
Their extreme power and their ability to distort space and time make them difficult to understand
and even harder to observe.
But thanks to new technology and ongoing research, scientists continue to learn more about these
incredible objects every day.