Dark Matter and Dark Energy: What Makes Up 95% of the Universe

According to NASA, the universe is made of three ingredients: normal visible matter at about 5%, dark matter at about 27%, and dark energy at about 68%. The European Space Agency (ESA) puts the combined share of dark matter and dark energy at 95% of the universe, with ordinary matter — the atoms that make up stars, planets and everything measurable with light — filling the remaining sliver.

What is dark matter?

Dark matter is a form of matter that has mass and gravity but does not emit, absorb or reflect light, according to NASA. Because it cannot be seen directly, scientists infer its presence from its gravitational effects on visible matter. NASA describes it as the substance that keeps galaxies from flying apart.

The idea dates to 1933, when Swiss astronomer Fritz Zwicky found that galaxies in the Coma Cluster moved too fast to be held together by their visible mass alone, per NASA's account. In the 1970s, astronomer Vera Rubin strengthened the case by showing that stars at the outer edges of spiral galaxies orbit at speeds that visible matter's gravity cannot explain.

ESA notes that a typical galaxy's missing, unseen mass is about ten times larger than the mass of the stars astronomers can actually observe in it. One of the clearest pieces of evidence is the Bullet Cluster, where NASA says 2006 observations showed the distribution of mass detected through gravitational lensing — the bending of light by gravity — did not line up with the hot gas visible in X-rays, indicating an unseen mass component.

What is dark energy?

Dark energy is NASA's term for a mysterious pressure that appears to be accelerating the expansion of the universe, pushing galaxies apart from one another at an increasing rate. ESA says the accelerating expansion was a surprise discovery in the 1990s, and its cause remains unknown: it could be a constant property of empty space, a force that changes over time, or a sign that current theories of gravity need revision.

ESA cites estimates from its Planck mission showing dark energy contributing about 68% of the universe's total matter-energy content — a figure consistent with NASA's broader breakdown of roughly 68% dark energy, 27% dark matter and 5% ordinary matter.

Why this is being studied right now

In April 2026, the Dark Energy Spectroscopic Instrument (DESI) announced it had completed its originally planned five-year survey ahead of schedule, mapping more than 47 million galaxies and quasars — beyond its original 34-million target — plus 20 million Milky Way stars, producing what the collaboration called the largest high-resolution 3D map of the universe made to date, according to DESI's own announcement.

Analysis of DESI's first three years of data found hints that dark energy may not be a fixed cosmological constant but could instead change in strength over cosmic time, the collaboration said. Full dark energy results from DESI's complete five-year dataset are expected in 2027, and the survey will keep observing through 2028, expanding its sky coverage by roughly 20%.

On the dark matter side, scientists with the LUX-ZEPLIN (LZ) experiment — a liquid-xenon detector operated by roughly 250 researchers from 38 institutions at the Sanford Underground Research Facility in South Dakota — reported a single unexplained particle interaction detected on June 16, 2023, presented in 2026 at the TeV Particle Astrophysics conference in Japan, as reported by Al Jazeera.

Researchers involved, including Rick Gaitskell, said the team does not want to get ahead of the data and still must rule out background noise before treating the signal as a genuine dark matter detection, according to the same report.

How scientists plan to narrow it down

NASA's Nancy Grace Roman Space Telescope is designed to probe dark energy using three methods: tracking patterns called baryon acoustic oscillations left over from the early universe, observing thousands of Type Ia supernovae across cosmic history, and measuring weak gravitational lensing to map how matter — including dark matter — is distributed, according to NASA's mission description.

ESA's Euclid mission is pursuing a parallel goal: mapping the distribution of galaxies over the past 10 billion years across more than a third of the sky, aiming to measure the universe's expansion rate to better than 10% accuracy and test Einstein's general relativity to within 2% precision, per ESA.