Astronomers predict an unseen class of star-like bodies called “dark dwarfs” near our galaxy’s center. A new study suggests these objects could shine thanks to annihilating dark matter, not nuclear fusion. Dark matter makes up about a quarter of the universe and interacts via gravity. If WIMP-like dark matter particles collect in a brown dwarf, they would annihilate and heat it, causing a faint glow. Dark dwarfs would be too light to fuse hydrogen, but would keep lithium-7 in their atmospheres, offering a signature. This prediction comes from a JCAP study. The discovery of one could reveal dark matter’s nature.

Predicted Dark Dwarf Properties

According to the paper, sub-stellar objects just below the hydrogen-burning threshold would be powered by dark matter. The authors find that the minimum mass for hydrogen fusion shifts above ∼0.075 M⊙ in dense dark-matter environments, so lighter brown dwarfs instead become stable dark-matter–powered stars (‘dark dwarfs’) via WIMP annihilation inside them. They predict such objects only appear in regions with extremely high dark-matter density, like the Galactic center (ρ_DM ≳ 10^3 GeV/cm^3), because further out the halo is too tenuous. Crucially, dark dwarfs should retain lithium-7 in mass ranges where ordinary brown dwarfs burn it away, providing a clear observational signature.

Observational Prospects and Implications

Sakstein notes that powerful telescopes like the James Webb Space Telescope might even already detect extremely cold objects like dark dwarfs near the galactic center. Alternatively, astronomers could survey brown dwarf populations for a rare sub-class with anomalous lithium content. Notably, even one confirmed dark dwarf would strongly favor heavy, self-annihilating dark matter.

Sakstein explains that finding dark dwarfs would provide “compelling evidence” for dark matter that is massive and interacts with itself – essentially WIMPs or similar particles. He notes that lighter candidates (like axions) would not produce such stars, so a dark dwarf discovery would disfavor those models. While not a proof of WIMPs, a dark dwarf detection would imply dark matter behaves like WIMPs (heavy and weakly interacting). Indeed, future surveys and JWST observations will also test these predictions.

In early July 2025, NASA astronaut Nichole “Vapor” Ayers snapped a rare image of a giant red “sprite” phenomenon erupting above a thunderstorm, as she orbited 250 miles (400 km) above Earth. Sprites are brief, luminous columns caused by powerful lightning discharges far below. Ayers noted that having the ISS vantage makes for a “great view above the clouds” and helps scientists analyze these elusive events. This sprite appeared over storm clouds spanning Mexico and the southern U.S. on July 3, 2025. The sighting coincides with NASA’s Spritacular citizen-science project, which crowdsources photos of sprites and other upper-atmosphere flashes.

Rare ‘Sprite’ Phenomenon Explained

According to NASA, sprites are one of the “least understood” and most visually striking upper-atmosphere phenomena. They are brief columns of red light that flash high above thunderclouds, triggered by powerful lightning strikes. Data show sprites often form around 50 miles (80 km) altitude above Earth. These fleeting bursts take varied shapes – tendrils, plumes or towering columns of red light.

In Ayers’s photo, the sprite looks like an inverted scarlet umbrella extending into the sky. Each sprite flash lasts only a few milliseconds, so every image provides valuable data. Observations from orbit and the ground are steadily building a clearer picture of these mysterious storm-driven events. For example, NASA’s Juno mission even recorded sprite-like flares in Jupiter’s atmosphere, suggesting similar lightning processes on other worlds.

Crowdsourcing Sprites

To gather more data on sprites, NASA launched the Spritacular citizen-science project. Through Spritacular, volunteers with cameras can submit photos of upper-atmosphere flashes for research. The project’s website reports over 800 volunteers from 21 countries have uploaded about 360 sprite sightings since its 2022 launch. Each contribution helps scientists map where and how sprites occur. Ayers’s ISS photo adds a valuable perspective that complements citizen reports.

Space.com notes that multiple ISS crew members have begun photographing sprites from orbit, bolstering the data. Spritacular principal investigator Dr. Burcu Kosar says the project “will bridge the gap” between casual observers and researchers. NASA scientists say many questions about how and why sprites form “remain unanswered”, so more images could soon help decode the mystery.

Almost half of the matter of the universe is yet hidden from observation, literally unknown to us. Scientists have discovered the fast radio waves and faint X-rays, where all the unfathomable data is located. In a study published in Nature Astronomy on June 16, 2025, which used fast radio bursts (FRBs) in order to track the ordinary matter distribution across the universe within the nearby galaxies and in space. Another study used X-ray data to determine the long, hot gas filament that combines the four galaxy clusters. This study was published in Astronomy and Astrophysics.

A Cosmic Mystery: Where Is the Missing Matter?

As per NASA, ordinary matter includes everything which is visible and tangible, such as people, stars and planets. It is comprised of neutrons, protons or brayons. However, this accounts for around 15% of the total matter in the universe; the remaining is dark matter. Half of the baryonic matter is considered missing, and the reason for it is too diffuse to find it directly. This is scattered matter around the cosmos as a fine mist.

What Counts as Ordinary Matter

This hidden matter has been mapped using FRBs, intense millisecond-long pulses from galaxies located far away. With the help of 70 FRBs, which included one from 9 billion light years away, the scientists determined that around 76% of the ordinary matter lies within the galaxies, 15% around them in halos and other inside the galaxies.

A Unified Picture of the Universe’s Baryonic Matter

One more team examined the faint X-ray emissions to visualise matter from a 23 million light-year-long gas filament. Through noise filtering and analysing X-ray photons, the team found the gas to be over 10 million degrees Celsius with 10 protons per cubic meter, aligning with what models had suggested after predicting.

Implications for Galaxy Formation and Future Research

Altogether, these studies offer a clear picture of how and where ordinary matter exists in the universe. As scientists now combine methods like X-ray detection and FRB mapping, they are confident in the galaxy formation and other major cosmic secrets in depth.