There are likely millions of small black holes lurking undetected near us in space

Black holes 101

At the center of our galaxy, a supermassive black hole churns. Learn about the types of black holes, how they form, and how scientists discovered these invisible, yet extraordinary objects in our universe. This three-minute video from National Geographic tutors the viewer on the basics regarding the universe's most mysterious residents.

The mysterious origins of the universe’s biggest black holes

Think you know everything about black holes? You might be surprised. Thought of as massive vacuum cleaners sucking up everything in their cosmic path, black holes actually accrete matter at an incredibly slow pace. Yet, some black holes existed when the universe was only a few billion years young. Learn more in this BBC report.

The Event Horizon Telescope captured the first photo of a black hole in 2019

Predicted by Einstein in 1916, these invisible objects can be indirectly seen through their accretion discs and X-ray bursts. Over 40 million trillion black holes may be scattered throughout the universe.

What lies inside a black hole remains one of the universe's greatest mysteries

At the center of black holes is a theoretical point of infinite density called a singularity. Alternatively, one theory suggests a black hole's core could form a Planck star—a mind-bogglingly tiny object just a trillionth trillionth trillionth of a meter in size.

How black holes form

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.

Dark matter makes up about 85% of the matter in the universe

Astronomers discovered that galaxies rotate in ways that visible matter alone cannot explain, pointing to the existence of unseen matter. According to current models, the universe has not been around long enough for gravity to have formed galaxies and other large-scale structures unless dark matter were present in quantities five to six times greater than visible matter.

Explaining 'impossible' black holes

When stars collapse, the black holes they form can have the mass of either 50 suns or over 120—but current models claim strongly that no black hole should have a mass that falls in between that range. But in 2019, gravitational wave observatories detected two within it: one at 66 solar masses, the other at 85. The discovery disrupted established science and left researchers questioning the Standard Model of physics.

There may be as many as four types of black holes, categorized by their mass

Three types are known to exist: stellar mass black holes, supermassive black holes, and intermediate black holes. A fourth type—micro black holes—is theoretical and would have the same mass as Mount Everest in a space the size of an atom.

Most of the observable universe's volume consists of voids and supervoids—enormous regions of space with little to no galaxies, stars, or light.

Mars' orbit may provide evidence that dark matter is made of primordial black holes

Physicists at MIT have found that, statistically, one such microscopic black hole should pass through the solar system every decade, which they predict would introduce a detectable wobble in Mars' orbit. Such black holes would have formed in the early universe from collapsing gas clouds and scattered as the universe expanded.

Most of the observable universe's volume consists of voids and supervoids—enormous regions of space with little to no galaxies, stars, or light.

Mapping the universe's 1.3 million quasars

Quasars form the core of active galaxies where supermassive black holes devour unimaginable amounts of matter. You can see a map of all 1.3 million of these objects with this 3D map. It was assembled with data from the Gaia spacecraft and shows how the spread of dark matter across space matches that described by the Cosmic Microwave Background.

Black holes do not 'suck' matter and energy in like a vacuum cleaner

Despite its immense magnitude, the force of gravity exerted by black holes acts in the same way as provided by stars and planets, allowing objects to maintain stable orbits around them. Even in cases where tidal forces and friction cause objects to change their orbit and fall towards a black hole, they are more likely to glance by, be whipped around, and get ejected rather than absorbed.

Sagittarius A* is a massive black hole at the center of our Milky Way galaxy

For years, it was known as a strong source of radio signals, but there wasn't enough data to adequately describe or identify it. Orbital movements of nearby stars would indicate it had 4.6 million times the sun's mass, proving it was a black hole.

Black holes can disrupt the formation of galaxies

A team of astronomers in Munich detected a gas cloud being stretched and torn apart by the supermassive black hole at the center of the Milky Way, preventing matter from coalescing into new stars. Energy released from siphoned gas produced warm winds that may also prevent surrounding gas from coalescing.

According to the physics of black holes, our 4D reality may be a hologram—a projection of information coded on a 2D surface on the edge of the universe.

The first image of a black hole was captured by creating an Earth-sized virtual observatory from a network of eight radio telescopes.

The most mysterious (known) star in the universe

Something massive, with roughly 1,000 times the area of Earth, is blocking the light coming from a distant star known as KIC 8462852. One of astronomers' more intriguing theories: Alien technology. Discovered via NASA's Kepler space telescope and a...

Try to catch the 'sound' of black holes in gravitational wave detector data

In "Black Hole Hunter," users try to listen for gravitational wave signals from black holes in four sample data files that include substantial background noise. With each level, learn more about black holes while being faced with ever-quieter signals.

According to the physics of black holes, our 4D reality may be a hologram—a projection of information coded on a 2D surface on the edge of the universe.

The entire observable universe in one map

Scientists believe we’ve only discovered about 5% of the universe. Here’s a map of what we’ve found so far, visualized using a log scale.

There may be as many as 300 million potentially habitable planets in our galaxy

The estimate comes from a study using data from the Kepler space telescope—a project aimed at finding exoplanets—and considers exoplanets similar in size to Earth around sun-like stars. These have a greater potential to possess liquid water.

Collisions between cosmic rays and atmospheric particles dwarf particle accelerators

According to Einstein's model of gravity, confining immense energy into a sufficiently small region would warp space-time enough to create a black hole. If accelerators actually did create black holes, then trillions more would be produced daily in the atmosphere, where collisions are millions of times more energetic.

Edwin Hubble showed that the universe is full of galaxies and is expanding

In the 1920s, Hubble showed that the Andromeda "nebula" was another galaxy. He later discovered that galaxies move away from us at speeds proportional to their distance—a breakthrough now known as the Hubble-Lemaître law, foundational to Big Bang cosmology.

Hawking radiation shows black holes slowly evaporate through quantum effects.

Hawking radiation is Stephen Hawking's theoretical prediction that black holes emit radiation and eventually evaporate. Applied to known black holes, their radiation is so weak that it would take vastly longer than the current age of the universe for them to disappear.

There are trillions of pieces of space trash that are too small to be tracked

Although scientists monitor more than 24,000 pieces of large orbital debris, space junk can be as small as a paint fleck. The density of this trash is steadily increasing with the growth of the space industry on Earth.

Only 40% of city-destroying asteroids have been detected

Statistical modeling shows that while we have identified the majority of extinction-level asteroids, smaller asteroids that can cause significant damage remain elusive. Some asteroids, like the one that exploded over Chelyabinsk in 2013, can't be detected ahead of time since they come from the sun's direction.

Explore our favorite visualization of the immense scale of space, from an astronaut to the size of the observable universe

Some stars take longer to form than the current age of the universe

The first stars only burned for millions of years, providing the universe's first heavy elements. Some in the current population will burn for trillions of years, delaying the appearance of black dwarfs and other exotic cold stars.

Neutron stars, the remains of some massive stars after they explode in a supernova, are the densest directly observable objects in the universe.

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

Explore the known asteroids, comets, and spacecraft involved in asteroid studies within our solar system with 'Eyes on Asteroids,' a 3D visualization from NASA.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

Stars appear to twinkle because turbulence in the motion of molecules in Earth's atmosphere causes light to bend and wiggle rapidly on its way to the surface—a phenomenon called scintillation.

SpaceX's S-1 or 'prospectus' revealed many previously unknown details about the company, including its unprofitability despite doing $18.7B in revenue in 2025, exactly how many voting shares Elon Musk will have in the company (roughly 85%), and more.

Roughly 43 million US borrowers owe roughly $1.7T in student debt, the second-largest source of consumer debt behind mortgages.

Hedge funds, the private investment firms that trade a wide swath of financial assets, make money by imposing steep fees on investors and from the fund's investment performance.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens.

In 1963, a basement renovation in Turkey revealed a passageway to a hidden, multilevel underground city that once housed as many as 20,000 people

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Before humans, the Soviet Union and the United States sent animals—including apes, dogs, and cats—to space during the Space Race.

Discover the catastrophic consequences of a failure of the US electrical grid—something that is more likely than many Americans think.

Browse a detailed visual analysis of over 200,000 similes—comparisons that often use 'like' or 'as'—from popular fiction to see how frequently writers the same idiomatic expressions.

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

A 2019 Facebook event called on attendees to "Storm Area 51, They Can't Stop All of Us," resulting in countless memes, the creation of a music festival, and eventually the arrests of those who did try to approach the area.

Scientists have struggled to pin down Ebola's natural reservoir species for decades, but the available evidence suggests that it's very likely fruit and insect-eating bats found in Africa.

In 2009, the nation was gripped by the story of a missing young boy who was believed to be floating over Colorado in a homemade balloon, until it was revealed that he was at home the whole time.

44% of Americans say they pray at least once a day—discover how your state's religiosity stacks up against the rest of the country.