In 2007, a Dutch schoolteacher named Hanny van Arkel was just one of thousands helping Hubble to classify galaxies online at GalaxyZoo.org when she discovered a space oddity that rocked the astronomy world. Now UA astronomy professor William Keel is leading the investigation to discover what exactly it is.
On Jan. 11, Keel presented his research to the annual meeting of the American Astronomical Society in Seattle.
Named after its discoverer, Hanny’s Voorwerp is a glowing, green blob located approximately 650 light-years away from Planet Earth, Keel said. He added the voorwerp is part of a ribbon of gas that wraps around the nearby galaxy, IC 2947. A quasar in the core of this galaxy shot out a powerful spotlight, illuminating the section of the gas cloud we now know as the voorwerp. Glowing oxygen accounts for it’s bright green hue.
The quasar must have turned off, said Keel, because we can no longer see its brightness within IC 2947. However, because of the distance between Hanny’s Voorwerp and IC 2947 – 44,000 light-years from edge to core, respectively – the light of the quasar is still reflected on the section of gas. This creates what is called a “light echo” or “ghost image,” and it allows for astronomers to be historians of space because they can see reflections of the past.
“We just missed catching the quasar, because it turned off no more than 200,000 years ago, so what we’re seeing is the afterglow from the quasar,” Keel said. “This implies that it might flicker on and off, which is typical of quasars, but we’ve never seen such a dramatic change happen so rapidly. Left to itself [the voorwerp] should cool and fade away in only a few thousand years, yet here the whole thing is, 100,000 light-tears across, glowing madly.”
A theory suggests that the dark spot in the middle of the voorwerp is caused by something that blocked the beam of the quasar, not allowing any light to pass through.
Assistant professor of astronomy and astrophysics, Jimmy Irwin, explained the phenomenon.
“Sort of like if a small bug is crawling on the surface of a light bulb, then if the light from the bulb is projected onto the ceiling, the shadow of the bug will be huge,” Irwin said.
Keel calls his investigations on the voorwerp one of his most interesting research projects, not just because of the nature of the voorwerp, but because of how it was discovered in the first place.
“One of the interesting points is the science – this discovery has shown us how we can trace the behavior of quasars up to a couple of hundred thousand years before our usual direct view, and we see surprises doing so,” Keel said. “The other is a ringing endorsement of the partnership embodied by citizen science in the Internet age, allowing unexpected discoveries that take so many eyes and brains poring over huge data sets.”
Galaxy Zoo has the purpose of allowing anyone with a computer and an interest in astronomy to take upon the daunting task of classifying over a million galaxies. Galaxy Zoo presents images taken from the Hubble Telescope as well as others.
“One of the most exciting discoveries from the original Galaxy Zoo was something we never expected,” said Galaxy Zoo, referring to Hanny’s Voorwerp on “The Story So Far” section of their website. “Computers will slowly get better at classifying galaxies, but looking at an image and asking ‘what’s that odd thing?’ remains uniquely human.”
“The Zoo team started off worried about the complexity of the material that people were dealing with, but the participants have run out ahead of us over and over again, teaching themselves database query languages and scripting tools so they can pull out even more data on objects they’ve become interested in,” Keel said.
Keel is still up to solving the mystery of the voorwerp. He analyzes data from Hubble and other telescopes, does calculations on this data, and is looking more into the structure and internal motions of the voorwerp.
Irwin says that Keel’s research is making headlines – David Letterman even made a jab at Hanny’s Voorwerp.
“His research can’t help but raise the visibility of UA to high school and undergraduate students looking for a college or graduate school, regardless of whether they want to get their degree in astronomy or another science field,” Irwin said.
Keel remains enthralled by the idea of “citizen science,” and how something as rare and mysterious as Hanny’s Voorwerp can be found by anyone with no scientific background or experience, simply an interest in space. He emphasizes the simplicity – and importance – of curiosity for outer space.
“I’ll always advertise www.galaxyzoo.org,” Keel said. “Not only is there no telling what you might find, but you can’t miss a new appreciation for the beauty and complexity of the universe.”
