It has been confirmed that there is a galaxy composed almost entirely of dark matter

It’s just astronomers It has identified what appears to be a cosmic anomaly: a faint galaxy with so few visible stars that, by calculations, up to 99.9 percent of its mass is dark matter. The remaining 0.1 percent is traditional material.

This galaxy is located about 300 million light-years away, and is practically invisible. Only four globular clusters stand out, which are small clusters of stars that look like isolated neighborhoods in the middle of nowhere. For many years, these star groups in the Perseus cluster were considered independent objects.

The Dark Galaxy-2 filter can only be seen through four globular clusters that contribute 16 percent of its total brightness. Scientists believe that 99.9% of this galaxy is dark matter.

NASA/ESA

Now, after comprehensive analysis, a study published in The Astrophysical Journal Letters provides strong evidence that these globular clusters are part of the same dark matter-dominated galaxy. Provisionally named CDG-2 (Candidate Dark Galaxy 2), it is the first galaxy to be detected solely by its brightest fragments.

The researchers combined data from the Hubble, Euclid, and Subaru telescopes, three of the most powerful observatories available. The combined readings reveal a very faint glow around the four globular clusters. This residual light is a clear sign of an underground galaxy so faint that the three telescopes missed it on their own.

More than meets the eye

Preliminary analysis suggests that CDG-2 has a total luminosity equivalent to about 6 million suns, and the four globular clusters contribute about 16% of this luminosity, an unusually large share. This distribution indicates that despite the low luminosity, the galaxy is a gravitationally bound system, meaning a dense halo of dark matter exists. Astronomers estimate that this invisible structure represents between 99.94 to 99.98 percent of CDG-2’s total mass.

According to current models, dark matter makes up about 27% of the universe’s total energy density and about 85% of its matter. Although the exact nature of what constitutes dark matter remains unclear, because it neither emits nor reflects light, scientists infer its existence from the effects of gravity on radiation, visible matter, and the large-scale structure of the universe.

Dark matter is so widespread throughout galaxies that its presence explains the stability and motion of stars in systems like the Milky Way. For example, current models suggest that our galaxy is embedded in a halo composed of about 90 percent dark matter.

However, CDG-2’s case is extreme: an almost starless galaxy, almost entirely surrounded by an invisible halo. These types of systems, called “dark galaxies,” are beginning to appear in the astronomical record. Beyond their rarity, scientists value them because they serve as natural laboratories for exploring the nature of dark matter and testing current models of galaxy formation.

This story originally appeared on WIRED in Spanish It was translated from Spanish.