Citizen Scientists Reveal a Bubbly Milky Way

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Written by Adam Hadhazy

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov

News feature: 2012-062 March 7, 2012

Citizen Scientists Reveal a Bubbly Milky Way

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2012-062&cid=release_2012-062

A team of volunteers has pored over observations from NASA's Spitzer Space Telescope and
discovered more than 5,000 "bubbles" in the disk of our Milky Way galaxy. Young, hot stars
blow these bubbles into surrounding gas and dust, indicating areas of brand new star formation.

Upwards of 35,000 "citizen scientists" sifted through the Spitzer infrared data as part of the
online Milky Way Project to find these telltale bubbles. The volunteers have turned up 10 times
as many bubbles as previous surveys so far.

"These findings make us suspect that the Milky Way is a much more active star-forming galaxy
than previously thought," said Eli Bressert, an astrophysics doctoral student at the European
Southern Observatory, based in Germany, and the University of Exeter, England, and co-author
of a paper submitted to the Monthly Notices of the Royal Astronomical Society.

"The Milky Way's disk is like champagne with bubbles all over the place," he said.

Computer programs struggle at identifying the cosmic bubbles. But human eyes and minds do an
excellent job of noticing the wispy arcs of partially broken rings and the circles-within-circles of
overlapping bubbles. The Milky Way Project taps into the "wisdom of crowds" by requiring that
at least five users flag a potential bubble before its inclusion in the new catalog. Volunteers mark
any candidate bubbles in the infrared Spitzer images with a sophisticated drawing tool before
proceeding to scour another image.

"The Milky Way Project is an attempt to take the vast and beautiful data from Spitzer and make
extracting the information a fun, online, public endeavor," said Robert Simpson, a postdoctoral
researcher in astronomy at Oxford University, England, principal investigator of the Milky Way
Project and lead author of the paper.

The data come from the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire
(GLIMPSE) and Multiband Imaging Photometer for Spitzer Galactic (MIPSGAL) surveys.
These datasets cover a narrow, wide strip of the sky measuring 130 degrees wide and just two
degrees tall. From a stargazer's perspective, a two-degree strip is about the width of your index
finger held at arm's length, and your arms opened to the sky span about 130 degrees. The
surveys peer through the Milky Way's disk and right into the galaxy's heart.

The bubbles tagged by the volunteers vary in size and shape, both with distance and due to local
gas cloud variations. The results will help astronomers better identify star formation across the
galaxy. One topic under investigation is triggered star formation, in which the bubble-blowing
birth of massive stars compresses nearby gas that then collapses to create further fresh stars.

"The Milky Way Project has shown that nearly a third of the bubbles are part of 'hierarchies,'
where smaller bubbles are found on or near the rims of larger bubbles," said Matthew Povich, a
National Science Foundation Astronomy and Astrophysics Postdoctoral Fellow at Penn State,
University Park, and co-author of the paper. "This suggests new generations of star formation are
being spawned by the expanding bubbles."

Variations in the distribution pattern of the bubbles intriguingly hint at structure in the Milky
Way. For example, a rise in the number of bubbles around a gap at one end of the survey could
correlate with a spiral arm. Perhaps the biggest surprise is a drop-off in the bubble census on
either side of the galactic center. "We would expect star formation to be peaking in the galactic
center because that's where most of the dense gas is," said Bressert. "This project is bringing us
way more questions than answers."

In addition, the Milky Way Project users have pinpointed many other phenomena, such as star
clusters and dark nebulae, as well as gaseous "green knots" and "fuzzy red objects." Meanwhile,
the work with the bubbles continues, with each drawing helping to refine and improve the
catalog.

For those interested in counting bubbles and contributing to the Milky Way Project, visit the
following link: www.milkywayproject.org . To learn of other citizen science-based efforts,
check out the Zooniverse: https://www.zooniverse.org/ .

Other authors of the paper include Sarah Kendrew of the Max Planck Institute, Heidelberg,
Germany; Chris Lintott and Arfon Smith, also of the University of Oxford and the Adler
Planetarium in Chicago, Ill.; Kim Arvidsson, also of the Adler Planetarium; Grace Wolf-Chase,
also of the Adler Planetarium and the University of Chicago; Reid Sherman, also of the
University of Chicago; Claudia Cyganowski of the Harvard-Smithsonian Center for Astronomy,
Cambridge, Mass. and a National Science Foundation Astronomy and Astrophysics Postdoctoral
Fellow; Sarah Maddison of Swinburne University, Hawthorn, Australia; and Kevin Schawinski
of Yale University, New Haven, Conn. and an Einstein Fellow.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope
mission for NASA's Science Mission Directorate, Washington. Science operations are conducted
at the Spitzer Science Center at the California Institute of Technology in Pasadena. Caltech
manages JPL for NASA. For more information about Spitzer, visit http://spitzer.caltech.edu
and http://www.nasa.gov/spitzer .

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