Holland Ford: Massive cluster of galaxies acts like a lens

Located two billion light-years away, Abell 2218 is an example of a huge galaxy cluster that can bend light, thereby acting as a ‘telescope’ for astronomers. It works because the gravity of a large mass in space – like a galaxy cluster – bends and focuses the light from galaxies that lie behind it.

Located two billion light-years away, Abell 2218 is an example of a huge galaxy cluster that can bend light, thereby acting as a ‘telescope’ for astronomers. It works because the gravity of this cluster bends and focuses the light from galaxies that lie in the space behind it, at an even-greater distance. Astronomers are able to peer behind Abell 2218 to see some of the first galaxies ever to form.

Astronomers are always curious about the first galaxies ever to form in our universe.

Because these galaxies are now so far away from Earth, 12 billion light-years away, they’re vanishingly faint. Even the largest earthly telescopes can’t see them clearly.

Holland Ford is an astronomer at Johns Hopkins University. He told EarthSky about using what he calls a ‘cosmic telescope’ to search for the first galaxies. And, he explained, it’s not a telescope like anything we know on Earth.

Holland Ford: What we call a ‘cosmic telescope’ is a very massive cluster of galaxies at distances anywhere from a few billion light-years to several billion light-years. The gravitational field from them bends space and time, and the result of that bending of space and time, is that the cluster acts like a lens.

In other words, these galaxy clusters – between us and the earliest galaxies – act to magnify our view of the universe as it was shortly after the Big Bang. This technique is helping astronomers catch glimpses of the first galaxies ever to form.

Ford said these galaxies are smaller than our own Milky Way galaxy, not as luminous, and lacking our Milky Way’s winding spiral arms.

Holland Ford: I grew up in western Oklahoma, in a very small town. So light pollution was minimal. At night, we would see a magnificent sky. And I think it was just the availability, the accessibility, of the night sky that inspired me to become an astronomer.

Our thanks today to Research Corporation, a foundation for the advancement of science.

Our thanks to:
Holland Ford
Johns Hopkins University

Jorge Salazar