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Astronomers ask public to find star clusters in Hubble images

Evan Skillman and Lucy Fortson
Evan Skillman and Lucy Fortson

You could advance science simply by looking at beautiful pictures from space. An international team of astronomers is seeking volunteers to explore Andromeda, the galaxy next door. The newly launched Andromeda Project will use people power to examine thousands of Hubble Space Telescope images of the galaxy to identify star clusters that hold clues to the evolution of galaxies. University of Minnesota researchers are part of the project.

Anyone can take part by going to No special skills are needed, and volunteers can be classifying clusters and helping the scientists within minutes of going to the website.

"We want to get people excited about participating. We’re hoping for thousands of volunteers," says Anil Seth, an organizer of the Andromeda Project and an assistant professor of physics and astronomy at the University of Utah. "I love looking through these amazing Hubble Space Telescope images of Andromeda, the closest big spiral galaxy to our Milky Way galaxy. The Andromeda Project will give lots of people the opportunity to share in that amazement."

Star clusters are groups of hundreds to millions of stars that formed from gas at the same time, so all the stars have the same age. A goal of the Andromeda Project is to study the history of the galaxy, and these clusters play an important role, the researchers said.

Star clusters are hard to find using computers because the number and color of stars in a cluster varies, and the clusters appear against very different backgrounds, from the busy center of the galaxy to its tenuous outskirts. Eight scientists spent more than a month each searching through 20 percent of the available Hubble images just to find 600 star clusters. This is less than a quarter of the 2,500 star clusters they believe exist in the full set of Hubble images of Andromeda, also known as galaxy M31.

To obtain faster results, the scientists want to "crowdsource" the problem and enlist volunteers from all walks of life to identify the star clusters in more than 10,000 images.

Registration isn't required, and a simple online tutorial helps volunteers quickly learn how to recognize and mark star clusters. The volunteers might even discover new information.

"There is the likely possibility that this project will discover something unique in Andromeda. It has happened before in citizen science projects," said Evan Skillman, a professor of physics and astronomy in the University of Minnesota’s College of Science and Engineering and co-author of the successful Hubble Space Telescope proposal.

The Andromeda Project joins several research projects on the Zooniverse portal, which was co-founded by Lucy Fortson, professor of physics and astronomy in the University of Minnesota’s College of Science and Engineering. Other projects range across fields as diverse as climate change, archaeology, marine biology and cancer research.

"The Andromeda Project is another example of projects involving University of Minnesota researchers using the cutting-edge technique of crowdsourcing to overcome major research challenges," Fortson said.

The Andromeda Project is a collaboration that includes scientists and website developers at the University of Utah, University of Washington, Adler Planetarium in Chicago, Oxford University, University of Minnesota, University of Alabama and the European Space Agency.

About 400 volunteers participated in a recent test of the new website.

About Andromeda
Pioneer astronomer Edwin Hubble observed Andromeda in the 1920s, confirming galaxies exist beyond the Milky Way and contain billions of stars.

Andromeda is about 2.4 million light-years away from Earth, or 14 billion billion miles (billion billion twice is correct). There are other, closer galaxies, but Andromeda is the closest big spiral galaxy like our own Milky Way.

Andromeda contains hundreds of billions of stars, and has a diameter of about 160,000 light-years, or about 940 million billion miles. The star clusters in Andromeda are typically about 20 light-years across, which equals 118 trillion miles—tiny compared to the diameter of the galaxy.

The Hubble images used in the Andromeda Project are part of a larger effort involving about 20 institutions and known as the Panchromatic Hubble Andromeda Treasury (PHAT) survey.

The Hubble Space Telescope began collecting the PHAT images in 2010. Since then it has spent nearly two months making hundreds of orbits of Earth while taking pictures of the least dusty third of Andromeda. If all goes well, the Hubble will send the last batch of images back to Earth next summer.