Dark stars are hypothetical stars that would have existed in the early universe

Dark matter and dark energy, explained

What is dark energy? What is dark matter? Well, if we knew exactly, we would have a Nobel prize—we know that they exist, though. Scientists have theorized that the former may be a property of three-dimensional space itself, while the latter could be exotic particles that interact with almost nothing. This video from Kurzgesagt explains what we know and what we don't.

Due to dark energy, the universe is expected to end as a dark, sparse place

While the sun is expected to continue shining for another five billion years, the expansion of the universe will cause nearby stars and galaxies to become ever more distant, until they are too far to observe. Once the last old, red, dim stars cool into darkness after trillions of years, the universe will settle into a state of eternal, dark emptiness.

Astronomical models suggest dark matter must be 'cold,' or slow-moving

Theories for what constitutes dark matter have ranged from slow, planet-sized objects to light subatomic particles that travel at high speeds. However, fast-moving candidates would quickly spread across the universe, preventing the gradual gathering of visible matter into the galaxies and galaxy clusters seen today through gravity.

Fritz Zwicky predicted the existence of dark matter and neutron stars

The former resulted from analyzing the motion of galaxies in the Coma Cluster, a subset of the approximately 30,000 galaxies he cataloged during his life. When hypothesizing an origin for observed high-energy particles called cosmic rays, Zwicky and colleague Walter Baade thought they could come from exploding stars, or supernovae—a term he coined—which would leave behind a collapsed star made entirely of neutrons.

Under the Big Rip scenario, dark energy becomes strong enough to tear atoms apart

If the density of dark energy, which produces a repulsive effect through the expansion of space, increases with time, then all structures of matter, including galaxies, stars, planets, and atoms, will be pulled apart once the strength of dark energy surpasses the magnitude of the forces holding those structures together, including the gravitational and electromagnetic forces.

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.

Universes with stronger dark energy may be more common than ours

Research shows that while universes with slightly weaker dark energy form stars more efficiently, universes with stronger dark energy are statistically more common and can still support star formation. This challenges the anthropic logic that our universe must have ideal conditions for life because we exist to observe them.

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.

Watch a simulation of a collapsing star becoming a black hole

When a massive star can no longer release enough energy through fusion in its core to fight off gravitational collapse, the dense core collapses first, producing an event horizon that traps light within it, including some light produced within the star at the time of collapse. As more material falls into the growing event horizon, the star will appear to eclipse itself from the inside.

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

Cloud 9 is a dark-matter-dominated failed galaxy

Identified in 2023, the starless, gas-rich object is the first of its kind seen by astronomers and provides a window into the early stages of galactic formation without observations relying on visible matter as a proxy. The existence of such REHLICs, or Reionization-Limited-H I Clouds, was predicted by cold dark matter cosmological models.

View the composition of the universe, dominated by dark energy and dark matter

About 95% of the observable universe is made of substances whose composition is unknown, but most of what remains (4%) is in the form of clouds of hydrogen and helium, followed by gases and plasma within stars (0.5%) and neutrinos created in nuclear reactions (0.3%).

It may be possible to create dark matter in particle accelerators

In high-energy collisions, exotic forms of matter can be produced by directly converting energy into mass according to *E = mc*². Even though a dark matter particle would not be directly observable, its creation would result in unaccounted-for mass, which can be compared to potential dark matter candidates for indirect detection.

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

Our solar system is currently traveling through a 'dark matter hurricane'

The phenomenon refers to a stream of cosmic debris, including stars and dark matter, leftover from a small galaxy that passed too close to the Milky Way and was torn apart. There are over 30 such streams known in our galaxy, and the stream intersecting the solar system is predicted to continue to do so for millions of years.

Axions, a hypothetical subatomic particle, are a leading dark matter candidate

Among the possibilities for what makes up dark matter, some physicists champion axions, which could clump into galaxy-scale quantum states. These states would act as massive, unified superparticles that could explain the observational evidence for the universe's missing matter.

Simulate the distribution of dark matter within a galaxy

By modifying the dark matter density at different distances from the center of a simulated galaxy, you can plot the resulting orbital speed of stars. Preset data enables you to replicate astrophysicists' work in determining the dark matter concentration that best fits observed structures.

Dark comets appear to be rocky asteroids but move like comets

Cometary orbits are known to exhibit accelerations independent of gravity that result from forces related to the release of gases. Dark comets exhibit this behavior but lack visible clouds of frozen material that have turned into a gas—the coma the comets display—indicating minor quantities of escaping subsurface ice.

Attempts to 'fix' black hole physics have led scientists to theorize new types

Along with their spin and charge, mass is used to categorize black holes as supermassive, intermediate, or stellar-mass. However, ongoing research suggests various additional types may exist, including primordials that formed one second into the universe's birth, fuzzballs—tangles of vibrating strings—and gravastars, which have a shell of dense matter around repulsive vacuum energy.

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

Quasars are extremely luminous cores of distant galaxies

Discovered in the 1950s through their intense radio signals, they are fueled by supermassive black holes with prominent accretion disks. The disks emit extreme radiation that heats and expels gas, halting star formation and altering the future of their host galaxies.

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...

Type Ia supernovae are 'standard candles' used to accurately measure cosmic distances

These explosions are caused by white dwarfs—remnants of low-mass stars—that reignite and explode, with every explosion brightening and dimming in the same way. By comparing them, astronomers have mapped the locations of galaxies alongside velocity data to determine the universe's expansion rate across time and the existence of dark energy.

Light echoes are expanding shells of reflected starlight

Just as sound waves reveal the location of obstacles by reflecting off them, pulses of light emitted by stars illuminate rings of interstellar dust, giving the appearance of ejected material as the light travels outward.

Voids in the northern and southern lights are known as black auroras

Appearing as dark rings or blobs against the illuminated sky, black auroras occur when there are holes in Earth's ionosphere—the upper atmospheric layer of charged particles created by solar ultraviolet rays. In these gaps—also known as anti-auroras—electrons ascend up into space, rather than spiraling into the atmosphere to collide with atmospheric gases and produce light.

Antimatter engines would have the greatest energy output of all machines

These devices would annihilate matter with antimatter, converting mass into pure energy. A teacup of fuel would release energy equivalent to that of a hydrogen bomb, but stabilizing and storing that much antimatter remains a challenging task. Alternatively, hybrid systems would utilize small amounts of antimatter to initiate nuclear reactions.

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.

Understanding why charged particles from the sun protect Earth from more dangerous particles

The solar wind engulfs the solar system in a protective bubble called the heliosphere, which was first theorized in the late 1950s based on studies of cosmic rays—high-energy particles traveling through space at near light speed. The heliosphere shields the solar system from much of this ionizing radiation originating elsewhere in the Milky Way.

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.

Shooting stars, or meteors, are fragments of asteroids and comets that burn up as they enter Earth's atmosphere, creating streaks in the sky called meteor showers.

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.

Planeterrellas create artificial auroras that mimic the atmospheric displays of light by setting up an electric field between two metal balls in a jar filled with a small amount of air.

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

How fusion—which releases energy when two lighter atoms combine to form a heavier atom—differs from fission

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.

Massive blooms of microscopic plankton called dinoflagellates produce the neon blue light seen in glowing tides.

Dirty lightning is a thunderstorm created from friction between rising and falling flows of ash and smoke during volcanic eruptions.

After NASA's Voyager 1 captured Earth as a single pixel as it left the solar system in 1990, astronomer Carl Sagan used the image to reflect on humanity's fragility and the responsibility to protect 'the only world we've ever known.'

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.

One disco producer saw 'Star Wars' four times on its opening weekend and was so inspired that he recorded the album 'Star Wars and Other Intergalactic Funk,' which produced a chart-topping single.

In 1945, Surrealist artist Salvador Dalí and legendary animator Walt Disney began collaborating on a short film that was not completed until 2003, years after both men had died.

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

The Dracula character, now seen as the vampire archetype, was inspired by a seafood-induced nightmare its creator experienced.

The original copy of the Declaration of Independence is not a pristine document, and even features a smudged anonymous handprint in the bottom left corner.

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.

Indefinite cloning of some endangered species may not sustain their longevity because cloning success rates decrease as genetic mutations accumulate.

Apeirophobia is an overwhelming fear of living forever, perhaps stemming from the brain's inability to conceptualize an infinite life.

Read a deep dive on the 'all-purpose healing' peptide BPC-157.

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

The word 'jazz' evolved from 'jasm,' 19th-century American slang for 'energy'