Two spiral galaxies,
satellite view. Photograph: StockTrek/Getty Images
When Dr Chris Lintott, a
researcher in the department of physics at the
University of Oxford, first considered launching a
website to ask the public to help classify photographs
of 1m galaxies, he assumed it would probably take three
or four years to complete. Galaxy Zoo (galaxyzoo.org),
launched in July 2007, was supposed to be a side
project; instead it has turned into the biggest
citizen-science experiment on the web.
Galaxies can be classified
as spiral, elliptical or merging (when two come
together). The Sloan Digital Sky Survey, or SDSS (www.sdss.org),
has images of nearly a million galaxies; what those
images don't have in their raw form is the information
about what class of galaxy is pictured.
Lintott had hoped that each
image would get 10 classifications, or "clicks", and
that the public would prove able to classify galaxies
accurately according to their features. Three weeks and
10m clicks later, he was proved right: the public is
capable of classifying galaxies as well as, or even
better than, professional astronomers. And quickly, too.
"It was like being hit by a tidal wave," says Lintott.
The images have now had
more than 70m clicks in total, allowing Lintott and his
team to go beyond simply sorting galaxies into spiral,
elliptical or merging categories, into further research.
"You can have confidence, as we can say, '100% of people
think that's a spiral galaxy, so it's really, really
spirally'," says Lintott.
His team was allocated
precious time on the IRAM 30m radio telescope in
southern Spain, and was easily able to select just 40
galaxies from the original sample to study, safe in the
knowledge that the scientists had exactly what they
After Galaxy Zoo's initial
success, Lintott wanted to take a closer look at merging
galaxies. At 5pm one Tuesday he posted a spreadsheet
listing a selection to the forums and asked members to
take a look and email him the best. Then he went to the
One "Zooite", Richard
Proctor, a telecoms consultant, spotted the spreadsheet
and thought: "I can build a webpage to do that!" By the
time Lintott logged back in, the web interface was
already in use.
"What was going to be a
quick little study turned into a much larger study of
about 45,000 images," says Proctor. Each image has now
had more than 25 clicks, with four particularly
committed souls having seen every single one. The first
academic paper about those merging galaxies has been
submitted, and Proctor
is listed as a co-author.
It's not the first time
collaborative astronomy has
proved a hit online. The Search for Extraterrestrial
Intelligence (Seti) project created the most powerful
distributed computer ever with its Seti@home project
launched in May 1999, which used spare processing power
on home computers to process data collected from a
specific wavelength to see if aliens were trying to get
in touch. It was used by 5.2 million people and offered,
at its peak, 265 teraflops (a trillion calculations a
second) of processing power.
Clickworkers project in 2000-01, found that ordinary
people were just as good as astronomers at identifying
craters on Mars in photos.
The biggest influence on
Galaxy Zoo, however, is Stardust@home, where users
search for tiny interstellar dust particles within
images returned by the 2006 Stardust mission. Thousands
of users have logged on to the site.
"Stardust@home was a real
inspiration for us," says Lintott. "We thought, 'If
20,000 people will look for dust grains in their spare
time, surely they will look at beautiful pictures of
But unlike those projects,
where the task is set from the top down, the Galaxy Zoo
community has its own ideas about what can be done with
the SDSS data.
"Up until now," says
Proctor, "the professional astronomers have come up with
things that want classifying and we've classified them."
But there are thousands of irregular galaxies - neither
spiral nor elliptical - that the professionals don't
have time to examine. So the community decided to do it
themselves, drafting a list of questions and building a
web interface to make classification easier.
"Once we've got some
results," promises Proctor, "we'll publish them for
everybody to use, and then see if we can find out
anything useful. Given that the biggest study of
irregular galaxies to date looked at around 150, and
we've got 9,000, we must find something!"
Lintott is supportive of
the irregulars project: "They are doing everything
professional astronomers would do," he says. "It's up
there with any work I've done."
It's not just the volume of
research that can be done by collaborating with the
public that's important to Lintott, but also the opening
up of scientific research to anyone with a browser and a
"By making the data
available to everyone," he says, "whatever stage you are
in your learning, you can do research."
And a surprising
cross-section of people are doing just that. Hanny van
Arkel is a Dutch primary school teacher who discovered a
strange object, now called Hanny's Voorwerp (Dutch for
"object"), near a spiral galaxy. "I thought it was fun,"
she says of Galaxy Zoo, "but I didn't expect that it
would become such a big part of my life. I've learned a
lot and it's a good way of participating in science."
Elisabeth Baeten, a Belgian
secretary, is one of only four people who has seen every
image in the galaxy merger project. "I also classify the
irregulars," she says, "and in between I cruise the
universe looking for asteroids and gravitational
In future, it will be much
easier for both scientists and enthusiasts to take part
in such projects. Not only are Lintott and his
colleagues finalising Galaxy Zoo 2, which will examine
galaxies in much more detail, they are also building a
platform that will allow any scientist to upload data
and tap into the vast potential of the internet.
"Our users are clamouring
for stuff to do," says Lintott. "The problem of having
too much data to pay close attention to is not just an
astronomical problem. It's astronomical in scale, but
it's not just us."
The new project will allow
scientists to upload their videos of elephants, pictures
of galaxies, or chemical structures, then specify what
they want done with them. They can either use the
provided templates, or customise their project. Lintott
describes it as the scientific version of the popular
blogging software WordPress.
And there are many uses of
such a platform. Nasa has high-quality images from the
Mars Reconnaissance Orbiter, most of which are simply
filed. And study of the pictures produced by this year's
Lunar Reconnaissance Orbiter will allow scientists to
build a history of asteroid bombardment of the inner
"It's like Nasa does the
map and we'll write the guide book," says Lintott.
Indeed, it would be
possible for anyone to upload data, including amateur
astronomers. "More than a million separate observations
a year are recorded by amateurs," says Lintott. "That's
a huge pile of data that, at the minute, professionals
slowly sort through, but we can hand that back to the
amateurs to analyse.