Dark matter 'missing' in a galaxy far, far away

Galaxies and dark matter go hand in hand; you typically don't find one without the other. So when researchers uncovered a galaxy, known as NGC1052-DF2, that is almost completely devoid of the stuff, they were shocked.

"Finding a galaxy without dark matter is unexpected because this invisible, mysterious substance is the most dominant aspect of any galaxy," said lead author Pieter van Dokkum of Yale University. "For decades, we thought that galaxies start their lives as blobs of dark matter. After that everything else happens: gas falls into the dark matter halos, the gas turns into stars, they slowly build up, then you end up with galaxies like the Milky Way. NGC1052-DF2 challenges the standard ideas of how we think galaxies form."

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Credit: Gemini Observatory/NSF/AURA/Keck/Jen Miller

Composite color image of NGC1052-DF2 constructed from observations using the Gemini Multi Object Spectrograph (GMOS) on Gemini North on Hawai'i's Maunakea. The ultra-diffuse galaxy was observed using deep imaging in two filters (g' and i').

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NASA's Hubble Space Telescope took an image of a bizarre, ghostly looking galaxy called NGC 1052-DF2 that astronomers calculate to have little to no dark matter. This is the first galaxy astronomers have discovered to be so lacking in dark matter, which is thought to comprise 85% of our universe's mass.