🌅 This Galaxy Is Made Almost Entirely of Dark Matter

SOURCE

Li et al. (2025)

WHAT TO KNOW

• Astronomers using NASA’s Hubble Space Telescope, Europe’s Euclid space observatory, and Japan’s Subaru Telescope spotted a nearly invisible “ghost galaxy” the team estimates is made of 99.9% dark matter. The object, called Candidate Dark Galaxy-2 (CDG-2), is located in the Perseus Cluster, a group of thousands of galaxies about 240 million miles away from Earth.

WHY IT MATTERS

• Most galaxies brim with billions of stars that light up the universe across vast cosmic distances. However, a small group of galaxies—called low-surface-brightness galaxies—have so few stars that dark matter makes up most of their mass, causing them to barely glow at all. CDG-2 is one such galaxy and also one of the most dark matter-dominated galaxies ever discovered. Studying the object should help astronomers better understand how so-called “dark galaxies” form.

CONNECT THE DOTS

• Dark matter is an invisible form of matter that doesn’t reflect, emit, or absorb light. It makes up most of the matter in the universe and acts as the “glue” binding everything together. Earlier this year, astronomers released the largest and most detailed map of dark matter ever created, revealing how it overlaps and intertwines with regular matter, and providing new details about its role in shaping the early universe.