The Most Distant Quasar Ever Discovered

From ESO-Cast and the European Southern Observatory. Astronomers have discovered the most distant quasar found to date. This brilliant beacon, powered by a black hole with a mass two billion times that of the Sun, is by far the brightest object yet discovered in the early Universe.

Quasars are extremely bright, distant galaxies thought to be powered by supermassive black holes at their centers. These powerful beacons may help astronomers to probe the era when the first stars and galaxies were forming.

The quasar that has just been found is seen as it was only 770 million years after the Big Bang, at redshift 7.1. It took 12.9 billion years for its light to reach us.

Although more distant objects have been confirmed, such as a gamma-ray burst at redshift 8.2, and a galaxy at redshift 8.6, the newly discovered quasar is hundreds of times brighter than these. Among any other object bright enough to be studied in detail, this is the most distant by a large margin.

The next most-distant quasar is seen as it was 870 million years after the Big Bang (redshift 6.4). Similar objects further away cannot be found in visible-light surveys because their light, stretched by the expansion of the Universe, falls mostly in the infrared part of the spectrum by the time it gets to Earth. The European UKIRT Infrared Deep Sky Survey (UKIDSS) which uses the UK’s dedicated infrared telescope in Hawaii was designed to solve this problem. The team of astronomers hunted through millions of objects in this database to find those that could be the long-sought distant quasars, and eventually struck gold.

It took astronomers five years to find this quasar. Its distance was determined from observations made with ESO’s Very Large Telescope (VLT) and instruments on the Gemini North Telescope. Because the object is comparatively bright it is possible to take a spectrum of it (which involves splitting the light from the object into its component colors). This technique allowed the astronomers to find out quite a lot about the quasar.

These observations showed that the mass of the black hole at the center of the quasar is about two billion times that of the Sun. This very high mass is hard to explain so early on after the Big Bang. Current theories for the growth of supermassive black holes predict a slow build-up in mass as the compact object pulls in matter from its surroundings.

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