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Scientists Study The ‘Galaxy Zoo’ Using Google Maps And Thousands Of Volunteers
More than two thirds of spiral galaxies, including our own Milky Way, display a central bar that can extend for thousands of light years. These colossal elongated structures are made up of collections of stars and dark matter which are held together by gravity.
The images provide examples of barred galaxies with spiral arms. In the first row, the arms are connected to the ring around the bar. In the second row, the arms are connected at the end of the bar and the third row shows a mixture of the two.
Credit: Ben Hoyle et al./Galaxy Zoo.
The study comes under the Galaxy Zoo project, a citizen science initiative in which more than 200,000 volunteers assisted in classifying a million galaxies through images provided by the Sloan Digital Sky Survey astronomical catalogue. As for the bars, 150 amateur astronomers have recorded their observations on a webpage specifically created for this purpose. The page is currently still active despite being closed to any further data entry.
Ben Hoyle, researcher at the Institute of Cosmos Sciences (University of Barcelona, Spain) and coordinator of the study, stresses to SINC that "this webpage combines Galaxy Zoo classifications with Google Maps technology." More precisely, the team has used the Google Maps Sky interface which allows to see the sky, especially the galaxies, as seen from the Earth's surface.
"In this way we have compiled some 16,000 measurements of the bars of 5000 galaxies, which is a sample a hundred times greater than previous ones. We have also come to many different conclusions, such as the fact that redder galaxies, which are stopping star formation, have longer bars," says Hoyle.
In the electromagnetic spectrum, the colour red comes from older, cooler stars whereas the colour blue is linked to hotter and younger stars. The study also reveals that the bars tend to be redder than the rest of the galaxy, which indicates that they have an older stellar population.
Other conclusions indicate that those galaxies with a larger bulb (a central agglomeration of stars) have longer bars. In addition, barred galaxies are more likely to display spiral arms than unbarred galaxies.
Contacts and sources:
SINC
FECYT – Spanish Foundation for Science and Technology
References: Ben Hoyle, Karen. L. Masters, Robert C. Nichol, Edward M. Edmondson, Arfon M. Smith, Chris Lintott, Ryan Scranton, Steven Bamford, Kevin Schawinski, Daniel Thomas. "Galaxy Zoo: Bar Lengths in Nearby Disk Galaxies". Monthly Notices of the Royal Astronomical Society 415 (4): 3627-3640, 2011. Doi: 10.1111/j.1365-2966.2011.18979.x.
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