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Dublin: 31.03.2015 09.26AM
Artist's rendering of galaxy BX442 and companion. Image from Dunlap Institute for Astronomy & Astrophysics; Joe Bergero
Astronomers in the US are claiming to have discovered a spiral galaxy that appears to have formed a billion years before other spirals. The galaxy is apparently 10.5bn light-years from Earth, which would place it at a time when the universe was only 3bn years old and spirals were extremely rare, according to the scientists.
Nature has today published their findings.
The team was led by an astronomer at the Dunlap Institute for Astronomy & Astrophysics, at University of Toronto, David Law, while the other astronomers involved hailed from UCLA, Caltech, UC Riverside, Steward Observatory and UW Milwaukee. The Space Telescope Science Institute provided principal funding for the work.
The researchers said they detected the galaxy, which they have identified as BX442, in images they obtained using the Hubble Space Telescope. The astronomers also used the Keck II telescope in Hawaii to sample light from different parts of the galaxy.
They said these samples revealed that the galaxy's internal moving parts were moving at different speeds relative to us. Thus, the astronomers said it revealed that the BX442 galaxy is a spiral disk, which rotates roughly as fast as our own Milky Way galaxy, but forming stars more rapidly.
HST/Keck false colour composite image of galaxy BX442. Image from David Law, Dunlap Institute for Astronomy & Astrophysics
"The fact that this galaxy exists is astounding. Current wisdom holds that such grand-design spiral galaxies simply didn't exist at such an early time in the history of the universe," said Law.
He said most galaxies in the 3bn-year-old universe are "clumpy and irregularly shaped".
"Seeing this galaxy amongst the irregular, young galaxies of that epoch is like seeing a fully formed adult in a room of grade-school children," added Law.
However, while the scientists have confirmed the spiral structure and rotation of this galaxy, they are still mystified as to the reason for its spiral structure that has been formed so much earlier than other galaxies.
Kinematic velocity and velocity dispersion maps of BX442. Image from David Law; Dunlap Institute for Astronomy & Astrophysics