One in a million: hordes of galaxies are awaiting classification as spiral or elliptical.Sloan Digital Sky Survey

An experiment launching today is offering the chance to help unravel the mysteries of galaxy formation. All you need is a computer and a pair of eyes.

The project, called Galaxy Zoo, is recruiting volunteers to help with the largest galaxy census ever carried out. Around a million galaxies will be scrutinized by keen pairs of eyes to categorize them into different types.

The results will help to answer questions about how galaxies form and may reveal galactic patterns spanning the entire Universe.

Cooperative brains

The idea of scientists analysing data on other people's computers is not new. There are a host of such 'distributed computing' experiments, seeking everything from alien life to new cancer drugs.

But these projects use the spare time of volunteers' computers. Galaxy Zoo is different: it uses volunteers' brains.

Galaxy Zoo's website hosts around a million images captured by the Sloan Digital Sky Survey, a project to map around a quarter of the sky. The team, based at the University of Oxford, UK, is aiming to assign each image to one of two main types of galaxy: spiral, like our own Milky Way, or elliptical.

That involves recognizing the presence or absence of the swirling arms that characterize spiral galaxies, and judging whether they are spinning clockwise or anti-clockwise. "The human brain is actually much better than a computer at these pattern-recognition tasks," says team member Kevin Schawinski.

Opening the project to amateurs saves the astronomers the mind-numbing job of studying all the galaxies themselves, and it means that the project could be completed in months rather than years.

Spotting patterns

Taking part involves a brief online tutorial explaining the different galactic types, followed by a short test to prove that you know what you're doing. After that you're off, looking at galaxies that have probably never been seen before.

"Most of these galaxies have been photographed by a robotic telescope, and then processed by computer," says Schawinski. "So this is the first time they will have been seen by human eyes."

Humans are also better than computers at spotting unusual galaxies, such as those that are shifting from one stage to another, or merging with other galaxies. Such finds could offer clues as to how different galaxies form.

Mapping the distribution of spinning spiral galaxies could also help cosmologists who study the Universe's formation to work out whether galaxies in certain areas of the sky are more likely to be spinning in a certain direction.

Previous studies suggested that galaxies in one portion of the sky are more likely to be spinning clockwise, whereas galaxies in the opposite direction are turning anti-clockwise, says Schawinski's colleague Kate Land.

This raises the prospect that galaxies might be turning on a magnetic 'axis' running through our portion of the Universe, meaning that we see those on one side as turning one way and those on our other side as spinning another.

Only a few hundred galaxies have been studied so far, however, meaning that this observation is not reliable. If the Galaxy Zoo project finds a similar pattern, it will give cosmologists the headache of coming up with a theoretical explanation.

"If galaxies are turning in the same direction it will be very interesting, although it will make things hard," Land says. Things would be much easier to explain if the distribution of clockwise and anti-clockwise spiral galaxies is random, she adds. "If we don't find [a pattern] everyone will be very pleased."

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