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Astronomers shed light on black holes

Edinburgh astronomers may have found a new way to map quasars - bright areas of energy surrounding black holes.

An international team of scientists has discovered that when a nearby star moves in front of a distant quasar, it acts like a magnifying glass, revealing details that would otherwise be undetectable.

Findings of the study, led by the University, are being presented at a Royal Astronomical Society National Astronomy Meeting this week.

Telescope study

Until recently, quasars were a mystery to astronomers, despite being among the most powerful and important objects in the universe.

Professor Andy LawrenceSchool of Physics and Astronomy

A large scale survey was conducted using the PanSTARRS telescope in Hawaii and the Liverpool Telescope in La Palma.

The team was monitoring millions of galaxies, hunting for a predicted phenomenon where a star is shredded by a giant black hole in the centre of the galaxy.

Instead, the scientists noticed that patches of sky observed in previous surveys were found to have become brighter than before.

Magnifying effect

The new bright spots look like quasars, caused by gas falling into a giant black hole inside a galaxy, releasing energy and light. However, the quasars seemed to be at the wrong distance.

They found huge distances to the quasars - typically 10 billion light years away - whereas the galaxies seen before the flare-up are about 3 billion light years distant.

They believe their observations show distant quasars seen through a foreground galaxy.

A single star in a foreground galaxy passing exactly in front of the distant quasar can focus the light, making the background quasar seem temporarily brighter.

Researchers say their fresh insight into how quasars can be closely observed will help them capture more images and so better understand the nature of quasars, galaxies and black holes.

We hope our findings will help future studies to improve our knowledge of quasars and their associated galaxies and black holes.

Professor Andy LawrenceSchool of Physics and Astronomy