There's some pretty big stuff out there in the Universe, but how big is the biggest? According to a team of Hungarian-US scientists led by Prof Lajos Balazs, the largest regular formation in the Universe is a ring of nine galaxies 7 billion light years away and 5 billion light years wide. Though not visible from Earth, the newly discovered feature covers a third of our sky.
The ring was revealed by nine Gamma-Ray Bursts (GRB) originating from the nine galaxies. GRBs are the brightest, most energetic events in the cosmos, putting out as much energy in seconds as the Sun will in its entire lifetime. They're caused by supernovae or hypernovae – supermassive stars collapse into neutron stars or black holes in times ranging from milliseconds to a few hours. Aside from their spectacular deaths, they also help astronomers to measure the distance of other galaxies.
In this case, the observed GRB's indicate that the nine galaxies are positioned in a ring shaped like a shell. They also show that the galaxies are all of a very similar distance from Earth – according to Prof Balazs, there's only a 1 in 20,000 chance that the ring's arrangement is accidental.
If it was visible to us, the ring would cover 36 percent of the sky, making it 70 times bigger than a full moon.
The importance of the ring isn't just that it appears to be a record breaker – it raises questions about the architecture of the Universe. In particular, it casts doubts on the Cosmological Principle. First asserted by Sir Isaac Newton and developed based on observations of the cosmic microwave background radiation and the structure of the early universe in the past century, it states that at the largest scale, the Universe is uniform, so no matter where you are, it looks essentially the same.
According to the team, recent work indicates that the largest structures can't be more than 1.2 billion light years across. This is at odds with the new discovery, as the ring is about five times as big, implying a much more uneven cosmos.
The next step for the team is to see if the processes controlling galaxy formation and large scale structure could have produced the ring without violating the Cosmological Principle. If not, it could require rethinking how the Universe evolved.
"If we are right, this structure contradicts the current models of the universe," says Balazs. "It was a huge surprise to find something this big – and we still don’t quite understand how it came to exist at all."
The team's results were published in the Monthly Notices of the Royal Astronomical Society.
Source: Royal Astronomical Society
