Natural Telescope

A team of international astronomers used NASA’s Fermi observatory to come up with the first ever measurement of a gravitational lens. A gravitational lens is a type of a natural telescope that is formed when a rare cosmic alignment allows the gravity of a massive object to bend and amplify light from a more distant source.

In September 2012, the Large Area Telescope of Fermi detected a series of bright gamma ray flares from a source known as B0218+357 located around 4.35 billion light years from the earth in the direction of a constellation called Triangulum. These flares were a key in calculating lens measurement in a known gravitational lens system. The B0218+357 is classified as a Blazar by astronomers, a type of galaxy noted for its intense emission and unpredictable behaviour.

The Blazar holds a supersized black hole in its heart and as matter moves towards it, some of it blasts outwards leaving behind jets of particles travelling at the speed of light in opposite directions. The gravity of B0218+357 bends light into different paths allowing astronomers to see Blazar’s background as dual images. With just a third of an arc second (less than 0.0001 degree) between them, the B0218+357 images holds the record for the smallest separation of any lensed system known. The accomplishment opens avenues for research including a new way to probe emission regions near supermassive black holes and find other gravitational lenses using the data obtained.