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This Galaxy Has Almost No Dark Matter—and Scientists Are Baffled
If astronomers really have found an "undark" galaxy, it’s a strong clue that dark matter is real.
An unusual galaxy far, far away is stumping astronomers not because of what’s there, but because of what’s missing.
About 65 million light-years away, the galaxy called NGC1052-DF2 is dim and diffuse, coming in at about one two-hundredths the mass of our Milky Way.
Normally, not all of a galaxy’s mass is visible. In addition to a mix of ordinary matter—like stars and planets and manatees—galaxies are expected to contain dark matter, an invisible substance that makes up most of the mass in the universe. Although we can’t directly observe it, we know dark matter is there because we can see how its gravity affects ordinary matter.
Based on the ratio in other galaxies, an isolated galaxy like NGC1052-DF2 should have
