Quasar wall's size surprises astronomers

Measuring some 4 billion light years across, the chain of "quasars" more than doubles the size of previous record sizes for cosmological structures.

A string of fiery galaxies has taken the title of largest structure yet seen in the universe, astronomers report.

Measuring some 4 billion light years across, the chain of "quasars" — fiery central regions of infant galaxies — more than doubles the previous record sizes for cosmological structures. The wall of quasars resides roughly 9 billion light-years (one light-year is about 5.9 trillion miles) from Earth, reports a team led by Roger Clowes of University College London in the Monthly Notices of the Royal Astronomical Society.

"Even traveling at the speed of light, it would take 4 billion light-years to cross," Clowes says in a statement. "(W)e can say quite definitely it is the largest structure ever seen in the entire universe.

"The discovery of this large structure is certainly fascinating," says astronomer Margaret Geller of the Harvard Smithsonian Center for Astrophysics, by e-mail. "It will be very interesting to see how it compares with structures identified in the same way in simulations."

In the study, the team notes the size of the structure challenges theories about the "cosmological principle," which states stars and galaxies should be distributed more or less evenly across the universe.

However Geller, a pioneer in the study of large galactic structures, is more cautious.

"Is the structure larger than models predict? The answer may well be yes," she says. "Does it show that the cosmological principle is wrong? Probably no. This structure is still small compared with the universe as a whole. It may simply mean that the scale where the principle applies is simply larger than we thought."

The coloured background indicates the peaks and troughs in the occurrence
 of quasars at the distance of the LQG. Darker colours indicate more quasars,
 lighter colours indicate fewer quasars. The LQG is clearly seen as a long chain
 of peaks indicated by black circles. (The red crosses mark the positions of
 quasars in a different and smaller LQG).
(Photo: R. G. Clowes / UCLan)

- usatoday.com


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