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Gravity is the weird and mysterious glue that binds the Universe, but that’s not the limit of its charms. We can also take advantage of the way it distorts spacetime to see distant objects that would otherwise be much more difficult to distinguish.
It’s called the gravitational lens, an effect predicted by Einstein, and it’s beautifully illustrated in a new version of the Hubble Space Telescope.
In the center of the image (below) is a shiny and almost perfect ring with what appear to be four light dots strung along it, wrapping around two more dots with a golden glow.
(ESA / Hubble & NASA, T. Treu; Acknowledgments: J. Schmidt)
It’s called an Einstein ring, and these bright spots are not six galaxies, but three: the two in the middle of the ring and a quasar behind, its light distorted and amplified as it passes through the gravitational field of the first two planes. galactic.
Because the mass of the two foreground galaxies is so high, it causes a gravitational curvature of spacetime around the pair. Any light that then passes through this space-time follows this curvature and enters our telescopes smeared and distorted – but also magnified.
Illustration of the gravitational lens. (NASA, ESA & L. Calçada)
It turns out to be a really useful tool for probing both the far and near expanses of the Universe. Anything that has sufficient mass can act as a gravitational lens. It can mean one or two galaxies, as we see here, or even huge galaxy clusters, which produce a wonderful mess of light trails from the many objects behind them.
Astronomers scanning deep space can reconstruct these smears and replicated images to see in much more detail the distant galaxies thus focused. But that’s not all the gravitational lens can do. The strength of a lens depends on the curvature of the gravitational field, which is directly related to the mass around which it is curving.
So, gravitational lenses can allow us to weigh galaxies and galaxy clusters, which in turn can help us find and map dark matter – the mysterious and invisible source of mass that generates additional gravity that cannot not be explained by the elements of the Universe that we can actually detect.
A little closer to home, gravitational lenses – or microlenses, to be more precise – can help us find objects in the Milky Way that would be too dark for us to see otherwise, like stellar mass black holes. .
And it gets smaller. Astronomers have successfully detected rogue exoplanets – those not attached to a host star, roaming the galaxy, cold and lonely – from the magnification that occurs when such exoplanets pass between us and distant stars. And they even used gravitational microlenses to detect exoplanets in other galaxies.
It’s pretty crazy what the Universe has up its gravitational sleeves.
You can download a paper version of the above image from the ESA website.
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