Galaxy Zoo!

By Risa Wechsler | July 12, 2007 2:24 am

So, I’ve been in the throes of grant proposal writing, which as far as I can tell is the worst part of becoming a professor. As such, I’ve been ignoring as much of my email as humanly possible for the past week. Until I got an email from David Weinberg this afternoon, announcing to the SDSS (Sloan Digital Sky Survey) mailing list the arrival of a new web-based galaxy classification project, Galaxy Zoo. The project was started by some scientists with SDSS, including Alex Szalay and Bob Nichol, and others. They had a press release today, and it’s already been covered by the BBC and was picked up by AP, so I think the website has gotten a bit hammered in the first day.

The basic idea here is to harness the collective eyes and brains of the internet to visually classify galaxies by morphology. It turns out that galaxy mophologies are in some ways a lot easier to classify by eye than by computer, just like faces and other complex images. This is one reason that now that surveys include millions of galaxies, morphology studies have not been as popular as other classification schemes based on colors or spectral types. Apparently, galaxy zoo to the rescue!

Here’s the first thing I learned: looking at pictures of galaxies is a lot more fun than writing proposals to the NSF to get funding to think about galaxies.
(Dear Galaxy Zoo: if I don’t get a CAREER grant this year, I blame you!)

There were tools to do this before, and I actually have managed to (finally) look
at a bunch of these Sloan galaxies over the past few years (I’m a theorist who’s never been observing, and normally I only look at fake galaxies in my computer — or real galaxies labeled by just a couple of variables like luminosity and color instead of their infinite structural variety). But the fact that galaxyzoo gives you a goal for looking at each galaxy makes it totally addictive. Plus galaxies are just pretty awesome looking! Even better, each galaxy has a link directly back to the SDSS Sky Server, which has tons of other info about the galaxy, like a spectrum where available, 5 band magnitudes, etc.
Personally, I found myself compelled to look at this information when perplexed about how to classify something. What’s it’s color? Is it star forming? What’s is redshift? All there. (Really, it was all there in the Sky Server before, but this is a pretty cool interface to it because you start by wondering.)

It turns out there’s a lot of cool stuff in the Universe. In just a bit of classifying, I found a couple of cool galaxy interactions (click for more info):
galaxy mergergalaxy merger2

A galaxy that to me looks like the cartwheel galaxy with bad seeing:

My main gripe about the site is that they’ve made the classification pretty simple,
just allowing for 3 types of spirals, counterclockwise, clockwise, and edge on
(none of which are really different types in the classical sense), elliptical galaxies, and mergers.
What was I supposed to do with the cartwheel?
And what about this bloby guy, which has whopping H-alpha and OII emission and the mysterious zwarning “NOT_GAL”? Clearly has no structure but I just couldn’t bring myself to call it an elliptical.

blob with Halpha

Or these very nebulous beauties:
blue specks just barely

I kept wishing for a button that said “This one’s interesting” or allowed me to choose from a menu, including things like “close pair“, “blobby star forming thing“,
scoop of neopolitan ice cream” or “i’ve got a green crayon“.
In all seriousness, I understand the simple scheme, but it does seem like there’s a lot of potential here from a lot of eyes that won’t be realized with it. I wonder whether a lot of this won’t come from the classification statistics, though, i.e., probably many of the interested objects will have less consistent classifications than normal ellipticals or spirals.

To be honest, I think I have exactly the wrong amount of knowledge to do this task effectively as designed — I overanalyze it and think I must know what’s going on, but am clearly just a clueless theorist. Turns out we’re still trying to explain the two most basic parameters.

Anyways, go check it out. A Universe of galaxies awaits at your fingertips!

  • Pingback: Galaxy Zoo « Phase Transitions()

  • theomin

    Just wanted to point out that the url-link of Galaxy Zoo needs to be fixed 😉

  • Quasar9

    lol Risa, love the error message on Galaxy Zoo link
    “You are looking for something that doesn’r exist – (Aren’t we All)”

    Is that a deliberate mistake

    “The hope is that about 30,000 people might take part in a project that could help reveal whether our existing models of the Universe are correct.” – from the BBC link.

    In the meantime here’s a view of The Galactic Plane in the infrared from Akari Results

  • Risa

    Thanks, theomin — Fixed.

  • Kevin Marks

    Sounds like what they need is free tagging as well, so you can call out your descriptive labels, and others, like the Q-shaped galaxy.

    Flickr’s galaxy tag clusters are amusing:

    but this one seems to have found the ones you like:

  • Bruce

    Yep, well, I already did a couple dozen today so we’re pretty well close to finishing by late next week.
    Always happy to help out.

  • Coin

    and the mysterious zwarning NOT_GAL

    If I had to hazard a guess as to what that’s short for, I’d go with “not a galaxy”. Hmm..

  • Paul Valletta

    Has anyone seen the “circus bear riding a unicorn” ?

    fugure four Cygnus, if one angles the image so that the top left corner and bottom right corner are vertical, then you can clearly see an amazing acrobat!

    Just cant imagine how our ancestors, who gave amazing names to constellations and such, could have missed that one?

  • Paul Valletta

    It would be interesting to find out those who see “circus bear atop a unicorn”, or ” big bad wolf attacking a horse, whos legs have clearly collapsed” ?

  • Troy

    I’ve made a blog for the purpose of exhibiting any really cool galaxies that anybody sees through Galaxy Zoo:

    Please come and send in links to photos of the most-interesting galaxies!

  • Ben

    Great, now that I’ve finally figured out how to do visual morphological classification, now SDSS is trying to put me out of work (or “render redundant” in the British phrase) by outsourcing classification to a bunch of unpaid Web 2.0ers.

    Seriously, I think the project is trying to do something limited, which is to classify which way galaxies are rotating (CW or CCW) to look for very large scale spin alignments. This is a low percentage project in some sense (as in, even if they turn up a signal, hordes of theorists will refuse to believe it at first). It’s likely that they didn’t want to assign a bunch of untrained classifiers the task of finding unusual or interesting objects. Your point may be that they should be trusting their audience more.

  • Risa

    Hey Ben — I agree, they do seem to sort of be pushing this angle in the website and press. Frankly that seems a bit silly to me, since I agree, there’s almost no way theorists would believe it if they do find a result. However, I do think they have much broader goals, one of the participants told me that they have a number of projects in galaxy formation and cosmology intended. But yes, I think if they are going to do it they should trust people more. In particular, I think it’s silly to trust *individuals* much, but I’m guessing they can pretty easily get 10 classifications per galaxy (apparently, they had 300,000 classified after one day) — and then it makes sense to have more categories. Fewer categories in some sense makes things *less* reliable, since I get all confused about e.g. putting star forming blobby looking things in the same category as classic massive ellipticals.

  • Ben

    Risa – Now that I’ve read their tutorial more carefully, it looks like they mention irregular galaxies, but they put them in the “Star/Don’t Know” class (!) That’s probably where blobby things were intended to go, but it seems like an unfortunate choice. It’s somewhat odd that they force you to choose spirals being clockwise, anti-clockwise, or edge-on, since it’s entirely possible to have a disk galaxy whose spiral pattern is indistinct at SDSS resolution. I took their test and got 15/15 (not that I’m boasting or anything) but there was one disk where I was guessing at the sense of the spiral.

    A greater value of this method than spins, I think, would be to find rare and interesting objects.
    However, one problem with having Web 2.0 classify for unusual objects is that you have to teach the classifiers what is unusual. Maybe they’ll learn after looking at 1000 galaxies Mergers are one example, which they already do have a button for. Although I already know of a student who’s gone through SDSS looking for mergers (and I’m trying to do it automatically), so in the fullness of time it would be interesting to compare the results.

  • Matt

    Hey. I found a set of Hoag objects/polar ring galaxies (one even merging), but how the hell was I meant to classify those suckers; Just about all you can do is send them in via email.

    Amazing though.

  • 1234567890

    You can submit interesting finds to this Flickr group.

  • Paul

    I visit GalaxyZoo between reviewing proposals at NSF! And no, I’m not in the astronomy division, so you can’t blame any declines on me…

    Can’t wait for the “My Galaxies” function to be enabled, or the brief glimpse we got of “My Statistics” (since disappeared…).

  • mollishka

    The whole CW or CCW thing does seem…. odd, though if people consistently say the same chirality, perhaps the sprial classification is more believable? “Does it have a bar?” seems more straightforward, although again difficult with the SDSS resolution.

    Mmmm, galaxies…

  • mollishka

    Potentially relevant (though not from any of the GalaxyZoo crowd):

  • Pingback: Apparent Brightness · The Galaxy Zoo()

  • Pingback: Find your own Supernovae! | Cosmic Variance | Discover Magazine()


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