Did we just see a primordial black hole at the Milky Way’s edge?

Is this a moon-sized primordial black hole adrift in the Milky Way?

A blip of light in the outer reaches of the Milky Way might be a bizarre black hole born at the beginning of time itself—and the long-sought solution to the mystery of dark matter. Astronomers are calling it “Phoebe”

What if dark matter isn’t some exotic particle that stubbornly eludes discovery but is instead swarms of tiny “primordial” black holes born in the first second of the universe?

Once derided as fringe science, this bizarre idea is having a very real comeback as searches for dark matter continue coming up empty . Yet actual evidence for the existence of primordial black holes remains scarce , potentially making them just another cosmic case of wishful thinking—unless, that is, scientists have finally spotted one.

In two papers posted to the preprint server arXiv.org on May 19, researchers led by Renee Key of Swinburne University of Technology in Australia say they’ve done exactly that. Their potential primordial black hole (PBH) would be an object three times as massive as Earth’s moon, briefly glimpsed as it drifted through the Milky Way’s halo —our galaxy’s star-sparse outskirts thought to host most of its dark matter.

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The result is controversial, and Key acknowledges there are “weaknesses with our data.” But the possibility of an epochal discovery that radically changes our understanding of the universe’s history and solves one of the greatest mysteries in modern astrophysics is too alluring to ignore. And even if the claim evaporates with further scrutiny, it still highlights how scientists are needing to think outside the box as the hunt for dark matter continues to flounder.

First proposed in the 1960s, PBHs were explored in detail by physicist Bernard Carr and the late physicist Stephen Hawking in the 1970s. Carr and Hawking suggested that, in the first quadrillionth of a second after the big bang, especially matter-dense regions of the expanding universe could have collapsed under their own gravity, leading to the formation of countless black holes with a wide range of masses, from lighter than subatomic particles to much heavier than stars.