Tuesday, October 27, 2009

The Color of Your Galaxy May Vary

From yesterday's Astonomy Picture of the Day comes a striking image from the Galaxy Zoo web site. The image is also of interest because it is only one image of many thousands of images viewed by many thousands of online volunteers. These volunteers among other things, classified the shape of the galaxies for subsequent analysis and research purposes.

Crowdsourcing comes to astronomy research via distributed classification of galactic images.

But note the color of the galaxy you are evaluating may vary.

From the main page of the Galaxy Zoo 2 project comes the following background about the project:

The original Galaxy Zoo was launched in July 2007, with a data set made up of a million galaxies imaged with the robotic telescope of the Sloan Digital Sky Survey. With so many galaxies, the team thought that it might take at least two years for visitors to the site to work through them all. Within 24 hours of launch, the site was receiving 70,000 classifications an hour, and more than 50 million classifications were received by the project during its first year, from almost 150,000 people.

And all of these classifications have provided results. A number of publications based on these collective classifications have appeared in or have been submitted to the Monthly Notices of the Royal Astronomical Society. But then really, how else do you classify the shape of one million galaxies? Not sometheing a small group of research astronomers could ever hope to achieve. But with the web you can have multiple classifications per galaxy. As a fan of web-based experiments this is a great project with real results.

As for color? The FAQ lists a couple questions specifically about color:

Q. I have noticed the colours seem to vary between spirals and ellipticals. Can we use this to help with our classifications?
A: Well spotted. Massive stars are blue, and also short lived (by astronomical standards, anyway) so we only see them where star formation has occured recently. That tends to be in spiral galaxies, but beware! We're trying to classify galaxies by shape, not by colour; one of the major results from Galaxy Zoo is that colour and shape are more independent than people believed, so we need to be careful. Classify what you see and ignore the colours!

Q. Why don't you just show us black and white images, then?
A: We tested for any difference in classifications between showing people colour and showing people monochrome images in the original Galaxy Zoo, and found that it was only small. We also discovered that our users really like looking at coloured galaxies, and we aim to please.

Which is to say, galaxy color may vary but any color galaxy is peferable to a monochrome galaxy.