Black Holes


The universe contains an incredible amount of unusual, strange, and powerful objects, and some of those that baffle scientists are black holes. These are areas that have such extreme densities and gravitational pull that is so strong that they pull everything in and not even light can escape.

Stellar Black Holes

When scientists find a black hole they aren’t actually looking at the black hole, but instead, the light around it that defines its boundaries.

Once thought to be a figment of the imagination of science fiction writers, the discovery of black holes went even further.

Now scientists know that almost every galaxy in the universe has a supermassive black hole at its core that has a mass that’s equal to millions of suns, including our own Milky Way galaxy.

The original black holes are believed to have started to form in the universe not that long after the Big Bang.

Due to the laws of gravity, black holes remain in a single location. This is good news for us and the universe, otherwise we would see black holes wandering around and eating the planets and suns. The orbit that the black hole maintains is extremely close to the solar system where it lives.

Albert Einstein had predicted the existence of black holes in his theory of relativity. He indicated that when a massive star dies there will be a remaining dense core and if the mass of the core is over three times the mass of the sun, the force of gravity will overwhelm all other forces and result in the creation of a black hole.

Stephen Hawking, the famed English theoretical physicist, cosmologist, author, and director of the Centre for Theoretical Cosmology at the University of Cambridge, wrote a few books and did a number of videos on the study of black holes. Yet with all of the research, scientists continue to add new information to a rather confounding topic.

Astronomers can’t see black holes head-on, but must use special instruments that observe the behavior of stars and material near the black holes. Black holes have been divided up into three types: stellar black holes, supermassive black holes, and intermediate black holes.

Black Holes Information:

Black holes have a variety of sizes and both mass and size are the determining factors on what classification it falls into.

Scientists believe that the smallest black hole is around the size of a single atom and yet has the mass of a huge mountain. These are called “primordial black holes.”

The most common black hole type is the “stellar” black hole which is medium-sized. A stellar black hole’s mass can be up to twenty times greater than the sun’s mass and its size can fit inside a sphere with a 10-mile diameter.

Astronomers think that the Milky Way galaxy may have dozens of stellar black holes in it.

The biggest black holes are those defined as “supermassive.” These have a mass that’s greater than the combination of one million suns and they would fit inside a ball the size of the solar system.

Scientists believe that every large galaxy has a center with a supermassive black hole. The one that is in the Milky Way galaxy is called Sagittarius A and has a mass that is equal to four million suns and could fit inside a sphere with a diameter around the size of our sun.

Stellar Black Holes:

Smaller stars that are around three times the mass of the sun may be small, but when they use up all of their fuel they can collapse and turn into white dwarfs or neutron stars. However when a larger star collapses, it will continue the compression process and become a stellar black hole, and these can be deadly.

The core of stellar black holes are smaller but very dense and they can compress three times the sun’s mass into a city size. The “small but deadly” quote is perfect for stellar black holes.

A stellar-mass black hole is formed when a star that has the mass of around 20 solar masses finally uses up all of its fuel that gives it nuclear fusion and then collapses under its own weight.

The process of its collapse causes a supernova explosion that blows out all of the outer layers of the star. However, if the core that’s now crushed has over three times the mass of the sun, there isn’t any force that we know of that will stop it and it can continue to collapse to become a black hole.

Black holes “eat” the dust and gas that is around them and this will make them grow larger. Scientists believe that there are a few hundred million stellar black holes in the Milky Way galaxy.

Supermassive Black Holes:

These black holes dominate the universe and almost all galaxies have a supermassive black hole at its center. These are the strongest black holes, ranging from millions to billions of times the mass of the sun, however they typically have a radius that is small for the intensity of their influence.

Scientists believe that supermassive black holes are created when large groups of smaller black holes merge. These can be in the hundreds or thousands.

Another theory is that when large gas clouds collapse and accrete their mass in fast speeds, they create a supermassive black hole. However, a third theory involves the collapse of a stellar cluster.

Like all black holes, they consume everything around them, and in the case of supermassive black holes, their appetite is huge, giving them the ability to eat entire planets.

Intermediate Black Holes:

In the past, as scientists tried to study black holes, they believed that they were either small or huge. However, newer discoveries are showing that there is a possibility for a mid-sized or intermediate black hole (IMBH).

The theory is that when stars that exist in a cluster collide and start a chain reaction to create intermediate black holes.

If a number of these types of black holes form in the same area they could fall to the galaxy’s center, creating a supermassive black hole.


In 1916, Albert Einstein created his general theory of relativity that predicted black holes.
1967, John Wheeler, an American astronomer, created the term “black hole.”
1971: The discovery of the first black hole.

Most Well-Known Black Holes:

As scientists continue to research black holes, they will categorize and name those that seem to be the most outstanding based on the criteria that they establish.

Sagittarius A*: This is the supermassive black hole that is at the center of the Milky Way galaxy. Its location is in the Sagittarius constellation and its mass is around that of 4 million suns.

Cygnus X-1: this is a stellar-mass black hole that is around 6,500 light-years away. It’s an x-ray source and a binary system that includes a blue supergiant star. Scientists believe that the source of the x-rays are that of the black hole.

Supermassiv Black Holes

Centaurus A: this is a giant spiral galaxy that is in the area of the Centaurus constellation. There are 55 million solar-mass black holes at its center, as well as two streaming jets of material that is spewing out of the galaxy as far as a million light-years away in space at around half the speed of light.

M87: at the center of this elliptical galaxy sits a black hole that has the mass of 3.5 billion suns. The black hole is enveloped in material that is superheated and it has a jet of the material that streams away extending out from the core 5,000 light-years.


There are three layers to black holes: the outer layer, the inner event horizon, and the singularity.

The event horizon is the edge or boundary near the black hole’s mouth and this is the place that light loses any escape ability. The event horizon has constant gravity. Anything that crosses the event horizon will never be able to leave.

The singularity is the black hole’s inner region and this is where its mass exists. This is a location that is the single point in space-time with the mass concentration of the black hole.

Classical physics dictates that nothing can escape a black hole, however, when the concepts of quantum mechanics are added, this idea can change a bit.

Quantum mechanics indicates that each particle has an antiparticle, and this antiparticle has the opposite electric charge and the same mass as the particle.

When the two particles meet, the antiparticle and particle pairs can destroy each other. When one of these pair meetings occurs just beyond the black hole’s event horizon, there is a possibility that one can be drawn into the black hole and the other one is ejected.

Most Well Known Black Holes

The resulting condition is that the black hole can experience a reduction that causes it to decay. The quantum mechanics theory isn’t accepted under classical mechanics.

The problem with black holes is that they are very massive, but their density is so great that their size is smaller than the mass.

They have extremely powerful gravitational forces, so powerful that almost nothing can escape their gravity. Physics shows that even light becomes trapped in their grasp.

When scientists “view” a black hole they aren’t really seeing the black hole. Instead, they are seeing the light around it, including the stars and other objects such as gas and dust that are near the black hole. The area that doesn’t have any light is the black hole.

When a galaxy has a supermassive black hole at its center, it is usually camouflaged by the thick gas and dust that surrounds it, and this can block the emissions that are the signs of the existence of a black hole.

The gravitational forces of a black hole are so strong that they can bend light, distort time, and warp space.

When some matter is pulled toward a black hole it is ricocheted off of the edge area of the black hole known as the “event horizon” and can be thrown outward instead of pulled into the opening.

This causes jets of material that are very bright to go at incredibly fast speeds, and they are so bright that they can be seen from distances.

It’s fair to say that scientists continue to work to comprehend how black holes function.

Interesting Information:

  • When scientists want to observe a black hole they have to rely on the light, x-rays, or other forms of electromagnetic radiation that is being thrown outside of the black hole so that they know where it is.
  • If a black hole passes through an interstellar matter cloud it will draw the matter toward it with its gravitational force. This process is called “accretion.”
  • The accretion process also happens if a star gets too close to a black hole. In the case of a star, it will draw it in and then the star will be torn apart.
  • The matter that is attracted to the black hole heats up and accelerates, emitting x-rays that expand out into space. These x-rays can be viewed with special telescopes.
  • Scientists are learning that black holes may influence that areas around them with the emission of gamma ray bursts, the destruction of stars that leave leftovers that may spark the birth of new stars while ceasing the growth of stars in other areas.
  • The gravitational pull of a black hole can sometimes be so strong that it pulls a star’s outer gases and then grows a disk around itself called an “accretion disk.”

Exploration and Research:

In 2004, NASA’s Swift telescope made the observation of some incredibly fleeting and powerful light flashes called gamma ray bursts.

Later exploration by NASA’s Hubble Space Telescope and Chandra Space telescope collected enough information to show a black hole’s event “afterglow.”

These discoveries led scientists to conclude that the explosions measured were the result of the collision of a black hole and a neutron star, which then created another black hole.

Both the Chandra Space Telescope and XMM-Newton have confirmed that the mid-sized black holes do exist.

In 2014, astronomers at the University of Durham in the United Kingdom found what they identified as an intermediate-mass black hole that was within a spiral galaxy’s arm.

In 2015 scientists began to detect gravitational waves in space. These were predicted by Albert Einstein’s general theory of relativity and are ripples in the fabric of space.

LIGO detectors (The National Science Foundation’s Laser Interferometer Gravitational-wave Observatory) that are in Louisiana and Washington observed the gravitational waves.

They found that the source of the waves was the result of a merger that happened 1.3 billion years ago between two orbiting black holes that spiraled into each other. Since that discovery, LIGO as well as other facilities now know what to look for and have seen a lot of these same types of black hole mergers.

The EHT (Event Horizon Telescope) is an international collaboration that involves a network of eight ground-based telescopes into a single Earth-sized dish. In 2019, the EHT caught a black hole image for the first time.

This is the famous M87 black hole that’s around 55 million light-years away and has a mass that weighs over 6 billion sun masses. It looked like a dark circle that had a silhouette of an orbiting disk of glowing hot matter.

Facts about Black Holes for Kids:

  • Black holes were first suggested in the 18th century, but were considered to be a mathematical curiosity until 1964 when scientists found the first black hole that they named Cygnus X-1.
  • Black holes don’t have the ability to emit any radiation on their own. The radiation that is used to detect them is given off as the accretion disk when it draws material from other objects that pass nearby.
  • Once trapped by a black hole, the material that spirals into a black hole enters the accretion disk which consists of dust, gas, planets, and stars that fall into the black hole’s orbit.
  • The event horizon of a black hole is also known as the “point of no return” because it’s the place where the black hole’s gravity overtakes the material’s momentum and spins it around the accretion disk. Once an item crosses the event horizon, there is no known power that can pull it out.
  • The intense influence of a black hole’s gravity can distort space and time within the neighborhood that it exists. The closer an object gets to a black hole, the slower that time will run.