The early universe was a rough-and-tumble place. Galaxies smashed together with much more regularity than they do today, and the insides of galaxies were chaotic, clumpy pods of stars. It was no place for an orderly, delicate swirl of a galaxy like the Milky Way or Andromeda.

By scanning hundreds of galaxies that existed just a few billion years after the big bang, however, a group of astronomers has turned up a diamond in the cosmic rough. The researchers found a rare early galaxy with pronounced spiral arms, which they reported in the July 19 Nature. (Scientific American is part of Nature Publishing Group.) And that galaxy's unique circumstances may help explain why spirals are so infrequent at that epoch. The newfound galaxy, known as BX 442, was identified in Hubble images as a spiral that existed three billion years after the big bang. It appears to fit the bill for a variety called a grand-design spiral, in which pronounced spiral arms lend a well-defined shape to the galaxy's disk of stars.

Spirals are common in the modern universe, but as astronomers gaze across the cosmos at objects farther and farther away—and hence further and further back in time—spiral structure starts to peter out. Instead of orderly swirls, astronomers see lumpy, blobby galaxies going through the cosmic equivalent of an awkward phase. But somehow a regular spiral structure was imprinted on BX 442, perhaps by a recent grazing encounter with a much smaller galaxy. “What seems to set it apart, as best as we can tell, is that it has this little companion galaxy off to the side,” says lead study author David Law, an astrophysicist at the University of Toronto. If the companion galaxy were the trigger, the spiral arms would “probably fade away within about 100 million years or so,” Law says. The transitory nature of a spiral structure at that epoch could explain why spirals are so rare.

BX 442 could have also generated its own spiral structure without a nudge from its neighbor. Clumps of stars and gas within a galaxy can cause spirals to form, and BX 442 appears to contain at least one large clump along one of its spiral arms.

It may be that numerous different mechanisms can shape a spiral galaxy. Many more examples from different cosmic epochs should be accessible for study once next-generation observatories, such as NASA's James Webb Space Telescope, come online.

COMMENT AT ScientificAmerican.com/oct2012

This article was originally published with the title Primordial Pinwheel.

1 Comments

1. 1. vinodkumarsehgal 08:08 AM 9/22/12

   The article states that spiral of galaxy BX442 was identified by Hubble and it existed some 3 billion years after BB i.e galaxy in its spiral form existed some 10.72 billion years ago. A question arises: what is meant by the age of a galaxy? Can a galaxy be formed within a day that we may specify its age precisely. Formation of a galaxy is a continuous evolving process which may run into billion of years.
   
   In our MW itself, oldest globular star has been estimated at about 13 billion years while our Sun has been estimated to be only 4.6 billion years old. So where is the parallel? So what is the universal reference benchmark for fixing the age of a galaxy when different parts of galaxy are formed at different times spread over a wide range. If there is no universal reference, do astronomers estimate the age of a galaxy based upon age of a star/cluster of stars based upon luminosity and spectroscopy. But this method will not give the correct estimate of the age of galaxy when age of different stars and star clusters vary in a wide range
   
   
   How spirals are formed in a galaxy is an intriguing issue which has entailed the energy of astronomers over long period but still there is no satisfactory answer. However, instead of studying BX442, why not to study own host MW and Andromeda which are even more old than BX442 and also have well build stable spirals

   Reply | Report Abuse | Link to this