Galaxy Zoo’s blue mystery (part I)

Nearly a year ago, astronomers at several universities recruited citizen scientists to help them catalog distant galaxies that had recently been photographed as part of the Sloan Digital Sky Survey. A high-school physics teacher in the Netherlands who was participating in this project, known as Galaxy Zoo, appears to have scored a major coup. She brought a weird blue object to the attention of the professional zookeepers, according to a cosmologist associated with the zoo.

That novelty appears to be a quasar whose intense radio emissions have been fueling star births.

Alex Szalay of JohnsHopkinsUniversity, and a project director for the National Virtual Observatory, was today’s keynote speaker, here in Pittsburgh, at the Joint Conference on Digital Libraries. He reflected on how much data had been collected during the Sloan survey, which wrapped up a month ago. Its organizers expected this project, designed to be the most comprehensive photographic imaging of the northern skies, to take some five years. It actually took 16.

In the process, it collected more data than astronomers decided they could ever realistically review and catalog. So they released more than a million never-before-seen images for the public to peruse in the comfort of their own homes. After a bit of online training, each was asked to categorize the type or shape of galaxies in any image they viewed.

“We expected to get several hundred people a day” taking part, Szalay says. In fact, the first day alone there were several million. During the past 11 months, the public has turned in some 40 million galaxy classifications. But the one that has astronomers scratching their heads is the Dutch report of a weird blue object, or Voorwerp. A teacher named Hanny reported the mystery cloud on a Galaxy Zoo blog in mid-August and asked if anyone knew what it might be.

Her request didn’t really catch the eye of scientists until around Christmas, Szalay says. Since then, astronomers have been abuzz over the enigmatic object. They’ve also been filing requests to get viewing time on major telescopes in coming months for a better look.

What initially slowed an evaluation of Hanny’s Voorwerp was that “we didn’t have a spectrum for it, so it could have been literally anywhere from right next door in our galaxy to the edge of the universe,” explained Kevin, another Galaxy Zoo blogger, on Jan. 31. A helpful colleague, astronomer Bill Keel of the University of Alabama, performed that spectral analysis and shared it as a guest GZ blogger. He described the novelty as “a deep blue, irregular cloud, just south of the spiral galaxy IC 2497.”

Piecing together odd bits about that galaxy, the newfound object’s spectra, and some additional crisp imaging of the region, Keel concluded: “The Voorwerp is at almost exactly the same redshift [or distance] as IC 2497, and almost certainly associated with it.” The object’s intense and narrow range of blue emissions, he said, “are what one would see from a star-forming region. But there are some things about it that are strange, and need more work.” Moreover, he added, “Whatever this is, it’s rare.” Galaxy zookeeper Chris Lintott of OxfordUniversity in England scanned for other blue objects in the survey database. Keel said Lintott found none emitting colors close to “what we see here.”

Szalay says Lintott has now formally drafted a proposal to use the Space Telescope, together with Keel to study the Voorwerp. “And we just got a notification, about a week ago,” Szalay told me, “that we’re getting seven orbits [to do this], which will be scheduled at some time in the fall.”

Szalay says other preliminary observations with an ultraviolet satellite have been completed, and Keel has asked to use the Very Large Array radio telescope near Socorro, N.M., for additional glances at this strange celestial object.

Currently, no one is sure what the wispy blue cloud is. But Szalay says it appears to be “radiation emitted by a quasar.” Only one similar object is known, he says: Minkowski’s object.

I’d never heard of it before. But googling the name turned up descriptions suggesting Minkowski’s Voorwerp is a stellar nursery — incubating some 10 million stars. This conglomeration is thought to have formed when a jet of intense radio waves slammed into a patch of dense gas. The source of the radio jet: a black hole at the core of a nearby galaxy (NGC 541).

It’s not yet known whether the new Voorwerp is the same thing, “but it has similarities,” Szalay says.

Whatever it turns out to be, he says the enterprise that uncovered it “blew my mind. You read in the papers that today people are not interested in science.” But the number of GZ recruits, or zooties, confirm that much of the public is not only interested in science, he says, but willing to take part in it.

“This is different from running something on your computer, like SETI@home or the prime-number search,” he maintains. GZ requires that nonscientists actually use their brain power. Not only can this armchair astronomy be fun, he says, but participants “can make a genuine discovery” — as Hanny did.

Look for formal announcements on the new, blue, Minkowski-like object soon from both the zookeepers and Johns Hopkins.