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Friday, 14 April, 2000, 09:13 GMT 10:13 UK
Astronomers see further than ever
The newly discovered quasar has a redshift of 5.8
By BBC News Online science editor Dr David Whitehouse

The most distant object ever seen has been picked up by an automated sky survey camera.

The object is 12 billion light years distant. A light-year is 10 million, million kms (6 million, million miles).

The object is what astronomers call a quasar, a compact yet highly luminous object thought to be powered by the gravitational energy of a supermassive black hole as massive as a billion of our suns.

The quasar was found by a robot telescope in New Mexico making a sensitive survey of vast tracts of the night sky.

Scientists measure an object's distance by how much its light has been affected by the so-called Doppler effect. As the Universe is expanding, the result of its birth in a cataclysmic explosion called the Big bang, an object's light is shifted towards the red end of the spectrum. The greater the redshift, the greater the distance.

Record holders

The newly discovered quasar has a redshift of 5.8, just beating the previous record holder that had a redshift of 5.7.

To date, the Sloan Digital Sky Survey (SDSS) has discovered about a thousand quasars, including eight of the 10 most distant known quasars. Two thirds of these have redshifts greater than 4.5.

Fermilab Visual Media Services
The robot telescope covers large areas of the sky
It is an exciting time for quasar hunters. Just a few weeks ago, two SDSS astronomers, Wei Zheng and Zlatan Tsvetanov, discovered what is now the second most distant SDSS quasar with a redshift of 5.3.

Princeton graduate student Xiaohui Fan spotted the new quasar in the sky survey data gathered last month.

The object's distinctive red colour showed it to be a likely candidate for a very distant quasar. It was then observed by the world's largest telescope, the 10-metre Keck telescope in Hawaii, which measured the quasar's record redshift.

Birth of galaxies

The real significance of the Sloan quasars, says SDSS project scientist James Gunn, is not their record-breaking distance but the size and quality of the sample.

The quality of the survey data will allow scientists to use quasars to chart the birth and formation of galaxies, explore structure on the largest scales, and better understand black holes, he says.

Dr Donald Schneider, a Pennsylvania State University astronomer says that our current understanding of very high redshift quasars is based on samples of a dozen or so objects assembled over many years of observation.

In the past 18 months, he notes, the SDSS has more than doubled the number of known quasars with very high redshifts.

Using this survey, astronomers believe that the number of quasars rose dramatically from a billion years after the Big Bang before falling off sharply at a later time.

Princeton researcher Robert Lupton says the new object's exceptional luminosity provides a wonderful opportunity to study the Universe when the galaxies that we see today were young, perhaps before they had even been born.

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10 Dec 98 | Sci/Tech
The most distant object ever seen
26 May 99 | Sci/Tech
Universe is 12 billion years old
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