Astronomers using the NASA/ESA Hubble Space Telescope have found a giant arc of light behind SDSS J1156+1911, a cluster of hundreds of galaxies located about 5.4 billion light-years from Earth. The arc is the stretched shape of a more distant galaxy whose light is distorted by the massive cluster’s powerful gravity, an effect called gravitational lensing.
This Hubble image shows the massive galaxy cluster SDSS J1156+1911. The brightest cluster galaxy is visible in the lower middle of the frame. Image credit: NASA / ESA / Hubble / Judy Schmidt, www.geckzilla.com.
Gravitational lensing is one of the predictions of Albert Einstein’s General Theory of Relativity.
The mass contained within a galaxy is so immense that it can actually wrap and bend the very fabric of its surroundings (known as spacetime), forcing the light to travel along curved paths.
As a result, the image of a more distant galaxy appears distorted and amplified to an observer, as the light from it has been bent around the intervening galaxy.
This effect can be very useful in astronomy, allowing astronomers to see galaxies that are either obscured or too distant for us to be otherwise detected by our current instruments.
SDSS J1156+1911 is only roughly 600 billion times the mass of the Sun, making it less massive than the average galaxy.
However, it is massive enough to produce the fuzzy greenish streak seen just below SDSS J1156+1911’s brightest galaxy — the lensed image of a more distant galaxy.
In this Hubble image the light from a distant galaxy, nearly 9.5 billion light-years away, has been warped into a giant arc of light in the galaxy cluster SDSS J1156+1911. Image credit: NASA / ESA / Hubble / Judy Schmidt, www.geckzilla.com.
This cluster was first documented by the Sloan Digital Sky Survey (SDSS), hence its name.
It was also part of the Sloan Giant Arcs Survey (SGAS), which studied data maps covering huge parts of the sky from SDSS.
SGAS found more than 70 extremely distant galaxies that look to be significantly affected by gravitational lensing.
