Black holes
Do you know that stars also die? What
happens when a star dies? Yes! Stars can die; when a star dies they form a massive whole called the Black holes. When a star has exhausted
the internal thermonuclear fuels in its core at the end of its life, the core
becomes unstable and gravitationally collapses inward upon itself, and the
star's outer layers are blown away leading to the creation of black hole.
The existence of black hole was first predicted by ALBERT Einstein in
1916, through his general theory of relativity. The term "black hole" was
coined many years later in 1967 by American astronomer John
Wheeler. After
decades of black holes being known only as theoretical objects, the first
physical black hole ever discovered was spotted in 1971.
Then, in 2019 the Event Horizon Telescope (EHT) collaboration released the first image ever
recorded of a black hole. The EHT saw the black hole in the center of galaxy M87 while the telescope
was examining the event horizon, or the area past which nothing can escape from
a black hole. The image maps the sudden loss of photons (particles of light).
It also opens up a whole new area of research in black holes, now that
astronomers know what a black hole looks like.
There are four types
of black holes: stellar, intermediate, supermassive, and miniature. The
most commonly known way a black hole forms is by stellar death.
Black holes are some of the strangest and most
fascinating objects in outer space. They're extremely dense; with such strong
gravitational attraction that even light cannot escape their grasp if it comes
near enough.
Stellar
black holes — small but deadly
When
a star burns through the last of its fuel, the object may collapse, or fall
into itself just like the roof of a building collapsing into itself. For
smaller stars (those up to about three times the sun's mass), the new core will
become a neutron star or a white dwarf. But when a larger star collapses, it
continues to compress and creates a stellar black hole.
Black holes formed by the
collapse of individual stars are relatively small, but incredibly dense. One of
these objects packs more than three times the mass of the sun into the diameter
of a city. This leads to a crazy amount of gravitational force pulling on
objects around the object. Stellar black holes then consume the dust and gas
from their surrounding galaxies, which keeps them growing in size.
According
the Harvard-Smithsonian Center for
Astrophysics," the Milky Way contains a few hundred
million" stellar black holes.
Super
massive black holes — the birth of giant
Imaging
a hole whose size is over millions and billions the size of the sun! Super
massive black holes are enormous black holes whose size is over millions or even billions of times as
massive as the sun, but are about the same size in diameter. Such black holes
are thought to lie at the center of pretty much every galaxy, including
the Milky Way.
Scientists aren't certain how such
large black holes spawn. Once these giants have formed, they gather mass from
the dust and gas around them, material that is plentiful in the center of
galaxies, allowing them to grow to even more enormous sizes.
Super massive black holes may be the result of hundreds or thousands of
tiny black holes that merge together. Large gas clouds could also be
responsible, collapsing together and rapidly accreting mass. A third option is
the collapse of a stellar cluster, a group of stars all falling together.
Fourth, super massive black holes could arise from large clusters of dark matter. This is a substance that we can observe through its
gravitational effect on other objects; however, we don't know what dark matter is composed of because it does not emit light and cannot be
directly observed.
Intermediate
black holes — stuck in the middle
Scientists once thought that black holes came in only small and large
sizes, but recent research has revealed the possibility that midsize, or intermediate,
black holes (IMBHs) could exist. Such bodies could form when stars in a cluster
collide in a chain reaction. Several of these IMBHs forming in the same region
could then eventually fall together in the center of a galaxy and create a
super massive black hole.
In 2014, astronomers found what appeared to be an intermediate-mass black hole in the arm of a spiral galaxy.
"Astronomers
have been looking very hard for these medium-sized black holes," study
co-author Tim Roberts, of the University of Durham in the United Kingdom, said
in a statement. "There have been hints that they exist, but IMBHs
have been acting like a long-lost relative that isn't interested in being
found."
Newer
research, from 2018, suggested that these IMBHs may exist in the heart
of dwarf galaxies (or very small galaxies). Observations of 10 such
galaxies (five of which were previously unknown to science before this latest
survey) revealed X-ray activity — common in black holes — suggesting the
presence of black holes of from 36,000 to 316,000 solar masses. The information
came from the Sloan Digital Sky Survey, which examines about 1 million
galaxies and can detect the kind of light often observed coming from black
holes that are picking up nearby debris.
What
do black holes look like?
Black holes are strange regions where gravity
is strong enough to bend light, warp space and distort time.
Black holes have three
"layers": the outer and inner event horizon, and the singularity.
The event horizon of a black hole is
the boundary around the mouth of the black hole, past which light cannot
escape. Once a particle crosses the event horizon, it cannot leave. Gravity is
constant across the event horizon.
The
inner region of a black hole, where the object's mass lies, is known as
its singularity,
the single point in space-time where the mass of the black hole is
concentrated.
Scientists can't see black
holes the way they can see stars and other objects in space. Instead, astronomers
must rely on detecting the radiation black holes emit as dust and gas are drawn
into the dense creatures. But super massive black holes, lying in the center of
a galaxy, may become shrouded by the thick dust and gas around them, which can
block the telltale emissions.
Sometimes, as matter is drawn toward a
black hole, it ricochets off the event horizon and is hurled outward, rather
than being tugged into the maw. Bright jets of material traveling at
near-relativistic speeds are created. Although the black hole remains unseen,
these powerful jets can be viewed from great distances.
The Event Horizon Telescope's image
of a black hole in M87 (released
in 2019) was an extraordinary effort, requiring two years of research even
after the images were taken. That's because the collaboration of telescopes,
which stretches across many observatories worldwide, produces an astounding
amount of data that is too large to transfer by internet.
With time, researchers expect to image other black holes and build up a
repository of what the objects look like. The next target is likely Sagittarius
A*, which is the black hole in the center of our own Milky Way galaxy. Sagittarius
A* is intriguing because it is quieter than expected, which may be due to magnetic fields smothering its activity, a 2019 study reported. Another study
that year showed that a cool gas halo surrounds
Sagittarius A*, which
gives unprecedented insight into what the environment around a black hole looks
like.
Weird
facts about black holes
·
If you fell into a black hole, theory has
long suggested that gravity would stretch you out like spaghetti, though your
death would come before you reached the singularity. But a 2012 study
published in the journal Nature suggested that quantum effects would cause
the event horizon to act much like a wall of fire, which would instantly burn
you to death.
·
Black holes don't suck. Suction is caused by
pulling something into a vacuum, which the massive black hole definitely is
not. Instead, objects fall into them just as they fall toward anything that
exerts gravity, like the Earth.
·
The first object considered to be a black
hole is Cygnus X-1. Cygnus X-1 was the subject of a 1974 friendly wager
between Stephen Hawking and fellow physicist Kip Thorne, with
Hawking betting that the source was not a black hole. In 1990, Hawking conceded
defeat.
·
Miniature black holes may have formed
immediately after the Big Bang. Rapidly expanding space may have squeezed some
regions into tiny, dense black holes less massive than the sun.
·
If a star passes too close to a black hole,
the star can be torn apart.
·
Astronomers estimate that the Milky Way has
anywhere from 10 million to 1 billion stellar black holes, with masses roughly
three times that of the sun.
·
Black holes remain terrific fodder for
science fiction books and movies. Check out the movie "Interstellar,"
which relied heavily on Thorne to incorporate science. Thorne's work with the
movie's special effects team led to scientists' improved
understanding of how distant stars might appear when seen near a
fast-spinning black hole.
10 FUN FACTS ABOUT BLACK HOLES!
1. You Can’t
Directly See a Black Hole.
A black hole is called a
black hole because of it’s color, especially since light can’t escape. What we
can see, though, is the effects of a black hole. Analyzing the surrounding area
of a black hole, we can see its effects upon its environment. For example, a
star that’s close enough to a black hole can be seen being ripped apart.
2. Our Milky Way
Probably Has a Black Hole.
But, don’t be alarmed,
Earth isn’t in danger! The major black hole that astronomists believe to be
within our Milky Way is light years away from Earth.
3. Dying Stars
Lead to Stellar Black Holes.
The death of large stars
lead to black holes, because a star’s gravity will overwhelm the star’s natural
pressure that it maintains to keep its shape. When the pressure from the
nuclear reactions collapses, gravity overwhelms and collapses the star’s core,
and the star’s other layers are thrown off into space, and this process is also
known as a supernova. The remainder of the core collapses, a spot overcome by
density and without volume – a black hole.
·
4. There are Three Categories of Black Holes.
·
Primordial Black holes – These are the
smallest of black holes and range from an atom’s size to a mountain’s mass.
·
Stellar Black Holes – These are the most
common of black holes and they can be up to 20 times more massive than the Sun.
There are also a variety of these all over the Milky Way.
·
Supermassive Black Holes – These are the
largest of black holes, being more than 1 million times more massive than the
Sun.
·
Black Holes Are Funky.
·
Say
someone falls into a black hole and there’s an observer that witnesses this.
The person who fell into the black hole’s time slows down, relative to the
person watching. This is explained by Einstein’s Theory of General Relativity,
which states that time is affected by how fast you are going when you’re at
extreme speeds close to light.
·
The First Black Hole Wasn’t
Discovered Until X-Ray Astronomy was Used.
·
Cygnus
X-1 was the first black hole discovered in the 1960’s, and it’s 10 times more
massive than the Sun.
·
The Closest Black Hole is
Probably Not 1,600 Light-Years Away.
·
V4647
Sagitarii was thought to be 1,600 light-years away, but is further away than
expected. Scientists now believe that this black hole is about 20,000 light
years away.
·
We Don’t Know if Wormholes Exist.
·
We
don’t know if this event exists, since we don’t know too much about physics,
but that also means that anything may be possible.
·
Black Holes Are Only Dangerous if
You Get Too Close.
·
Black
holes are safe to observe from a lengthy distance, but not if you get too
close, which also means that it’s unlikely for a black hole to consume an
entire universe.
·
Black Holes Are Constantly Used
in Science Fiction.
