Mystery Gravitational Lens Hints at Possible Primordial Black Holes, Dark Matter

Bild: NASA/public domain
At the very least, the new discovery offers a novel way of magnifying the distant cosmos.

By Michael Byrne | MOTHERBOARD

Astronomers have an unexpected new tool for spying on distant galaxies. It comes in the form of, well, we don’t really know yet. It could be a primordial black hole, or possibly a wayward cluster of stars. We do know that its effect is a powerful gravitational lens, a phenomenon in which a gravitational field around a stellar body, like a star, deflects distant light sources.

The finding is described this month in the Astrophysical Journal by researchers at Caltech, Aalto University in Finland, and elsewhere. (An open-access preprint can be found at arXiv.) If the findings are confirmed, the lens could offer „a new and powerful probe of cosmological matter distribution,“ which could even include elusive dark matter, according to the paper.

First, let’s dig into what exactly a gravitational lens is. A key feature of the universe is that gravity bends light. For example, that’s what’s going on in a black hole. In a black hole, light is bent to infinity so it can’t escape its own gravitational field. With other cosmic gravitational sources, the effect isn’t as terminal, but can still be pretty extreme. It’s easiest to just see it:

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