Galaxy Zoo puts new spin on galaxy rotation

BY DR EMILY BALDWIN

ASTRONOMY NOW

Posted: 11 June, 2009

During the International Year of Astronomy’s 100 Hours of Astronomy event in April, Galaxy Zoo volunteers provided more than 2.5 million classifications, smashing the one million target the team had set.

Galaxy Zoo 2 was launched in February this year, building on the success of the original Galaxy Zoo which asked users to classify galaxies, based on their shape, in images taken from the Sloan Digital Sky Survey (SDSS). The latest version asks for more detailed classifications based on details of galaxy bars, spiral arm properties, merging galaxies and more.

M51, The Whirlpool Galaxy, interacts with a smaller galaxy. The Galaxy Zoo team have some 3,000 examples of interacting and merging galaxies in their catalogue. Image: SSDS.

Between Galaxy Zoo 1 and 2, more than 100 million classifications have been recorded – equivalent to one person spending 20 years working on the same data without any sleep. “Without the help and hard work of the Galaxy Zoo volunteers throughout the International Year of Astronomy, our understanding of galaxies wouldn’t be as rich and as colorful,” says IYA New Media chair Pamela Gay.

The latest results show that spiral galaxies which share a neighbourhood (a region defined as 65 million light years
across) are likely to rotate in the same direction – but only if they formed the vast majority of their stars more than 10 billion years ago. The work also confirms that the dramatic merging of two or more galaxies when they collide on the galactic highway is responsible for more recent galaxy evolution, such as disrupting their alignment and triggering bouts of intense star formation.

“It is very exciting to see this result from Galaxy Zoo – now it is time to go back to theory and simulations and understand better what it all means!” says project leader Raul Jimenez.

Earlier Galaxy Zoo results provide support for the theory that spiral galaxies which form in the same environment share the same spin direction, and that later interactions and merger events might randomise these spin directions. The Galaxy Zoo team now have the largest catalogue of merging galaxies, with some 3,000 systems identified from the SDSS.

“With the Zoo 2 target of 40 million classifications in sight, participants in this IYA project will soon truly have made the Universe theirs to discover,” says project principal investigator Chris Lintott.

If you have a few minutes or hours to spare then why not have a go at classifying some of Galaxy Zoo’s weird and wonderful objects and contributing to real scientific research? Visit the Galaxy Zoo at www.galaxyzoo.org

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