Black Holes - Everything You Need To Know - Modul Cititor
Black Holes - Everything You Need To Know - Modul Cititor
Black Holes - Everything You Need To Know - Modul Cititor
Black holes are some of the most fascinating objects in space.(Image credit:
solarseven via Getty Images )
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Black holes are some of the strangest and most fascinating objects in
space. They're extremely dense, with such strong gravitational
attraction that not even light can escape their grasp.
The Milky Way could contain over 100 million black holes, though
detecting these gluttonous beasts is very di cult. At the heart of the
Milky Way lies a supermassive black hole — Sagittarius A*. The
colossal structure is about 4 million times the mass of the sun and
lies approximately 26,000 light-years away from Earth, according to a
statement from NASA.
The rst image of a black hole was captured in 2019 by the Event
Horizon Telescope (EHT) collaboration. The striking photo of the
black hole at the center of the M87 galaxy 55 million light-years from
Earth thrilled scientists around the world.
Black holes are expected to form via two distinct channels. According
to the rst pathway, they are stellar corpses, so they form when
massive stars die. Stars whose birth masses are above roughly 8 to
10 times mass of our sun, when they exhaust all their fuel — their
hydrogen — they explode and die leaving behind a very compact
dense object, a black hole. The resulting black hole that is left behind
is referred to as a stellar mass black hole and its mass is of the order
of a few times the mass of the sun.
Not all stars leave behind black holes, stars with lower birth masses
leave behind a neutron star or a white dwarf. Another way that black
holes form is from the direct collapse of gas, a process that is
expected to result in more massive black holes with a mass ranging
from 1000 times the mass of the sun up to even 100,000 times the
mass of the sun. This channel circumvents the formation of the
traditional star, and is believed to operate in the early universe and
produce more massive black hole seeds.
The black hole solution was found was by Karl Schwarzschild in 1915,
and these regions — black holes — were found to distort space
extremally and generate a puncture in the fabric of spacetime. It was
unclear at the time if these corresponded to real objects in the
universe. Over time, as other end products of stellar death were
detected, namely, neutron stars seen as pulsars it became clear that
black holes were real and ought to exist. The rst detected black hole
was Cygnus-X1.
Black holes do not die per se, but they are theoretically predicted to
eventually slowly evaporate over extremely long time scales.
The rst black hole ever discovered was Cygnus X-1, located within
the Milky Way in the constellation of Cygnus, the Swan. Astronomers
saw the rst signs of the black hole in 1964 when a sounding rocket
detected celestial sources of X-rays according to NASA. In 1971,
astronomers determined that the X-rays were coming from a bright
blue star orbiting a strange dark object. It was suggested that the
detected X-rays were a result of stellar material being stripped away
from the bright star and "gobbled" up by the dark object — an all-
consuming black hole.
At the center of the Milky Way lies a supermassive black hole Sagittarius A* (Sgr
A*). (Image credit: NASA/UMass/D.Wang et al., IR: NASA/STScI)
Following the release of the rst image of a black hole in 2019, astronomers
captured a new polarized view of the black hole. (Image credit: EHT
Collaboration)
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 supermassive 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.
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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.
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 elds 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.
ESO's black hole anatomy diagram shows what a black hole looks like and labels
the different components. (Image credit: ESO)
When a star burns through the last of its fuel, the object may collapse,
or fall 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.
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.
Scientists once thought that black holes came in only small and large
sizes, but 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 supermassive black
hole.
Research, from 2018, suggested that these IMBHs may exist in the
heart of dwarf galaxies (or very small galaxies). Observations of 10
such galaxies ( ve 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.
There are two theories on how binary black holes form. The rst
suggests that the two black holes in a binary form at about the same
time, from two stars that were born together and died explosively at
about the same time. The companion stars would have had the same
spin orientation as one another, so the two black holes left behind
would as well.
Under the second model, black holes in a stellar cluster sink to the
center of the cluster and pair up. These companions would have
random spin orientations compared to one another according to LIGO
Scienti c Collaboration. LIGO's observations of companion black
holes with different spin orientations provide stronger evidence for
this formation theory.
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 re, 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 de nitely is not. Instead,
objects fall into them just as they fall toward anything that exerts
gravity, like the Earth.
The rst 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 terri c fodder for science ction 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.
Additional resources
Dive deeper into the mystery of black holes with NASA Science.
Watch videos and read more about black holes from NASA's
Hubblesite. Discover more about black holes with the National
Science Foundation.
Bibliography
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