Hanny's Voorwerp


Hanny's Voorwerp is a very rare type of astronomical object called a quasar ionization echo. It was discovered in 2007 by Dutch school teacher Hanny van Arkel, while she was participating as a volunteer in the Galaxy Zoo project. Photographically, it appears as a bright blob close to spiral galaxy IC 2497 in the constellation Leo Minor.

One hypothesis suggests that HsV consists of remnants of a small galaxy showing the impact of radiation from a bright quasar event that occurred in the center of IC 2497 about 100,000 years before how it is observed today. The quasar event is thought to have stimulated the bright emission that characterizes HsV. The quasar might have switched off in the last 200,000 years and is not visible in the available images. This might well be due to a process known as AGN feedback. Read more

In the News ...

Amateur astronomer spies gassy "cosmic ghost"   MSNBC - August 5, 2008
A greenish blob of gas known as Hanny's Voorwerp is thought to be a light echo from the bright, stormy center of a distant galaxy that has now gone dim. A Dutch primary school teacher and amateur astronomer has discovered what some are calling a "cosmic ghost," a strange, gaseous object with a hole in the middle that may represent a new class of astronomical object. The teacher, Hanny van Arkel, discovered the object while volunteering in the Galaxy Zoo project, which enlists the help of members of the public to classify galaxies online. "At first, we had no idea what it was. It could have been in our solar system, or at the edge of the universe," Yale University astrophysicist Kevin Schawinski, a member and co-founder of the Galaxy Zoo team, said in a statement.

The find, nicknamed "Hanny's Voorwerp" (Dutch for object), soon had scientists training their telescopes on the object. "What we saw was really a mystery," Schawinski said. "The Voorwerp didn't contain any stars." Made entirely of very hot gas, the eerie green object is illuminated by remnant light from the nearby galaxy IC 2497. "We think that in the recent past the galaxy IC 2497 hosted an enormously bright quasar," Schawinski said. He said light from the past still illuminates the ghostly object, even though the quasar shut down some 100,000 years ago and the galaxy's black hole went quiet. "It's this light echo that has been frozen in time for us to observe," said Chris Lintott, a co-organizer of Galaxy Zoo at Oxford University in the United Kingdom, said in a statement. Researchers will soon use the Hubble Space Telescope to get a closer look.

Teacher finds new cosmic object   BBC - August 5, 2008
A new class of cosmic object has been found by a Dutch schoolteacher, through a project which allows the public to take part in astronomy research online. Hanny Van Arkel, 25, came across the strange gaseous blob while using the Galaxy Zoo website to help classify galaxies in telescope images. Astronomers subsequently confirmed that the object was one-of-a-kind.

What is Hanny's Voorwerp?   NASA - June 25, 2008
What is that green thing? A volunteer sky enthusiast surfing through online Galaxy Zoo images has discovered something really strange. The mystery object is unusually green, not of any clear galaxy type, and situated below relatively normal looking spiral galaxy IC 2497. Dutch schoolteacher Hanny van Arkel, discovered the strange green "voorwerp" (Dutch for "object") last year. The Galaxy Zoo project encourages sky enthusiasts to browse through SDSS images and classify galaxy types. Now known popularly as Hanny's Voorwerp, subsequent observations have shown that the mysterious green blob has the same distance as neighboring galaxy IC 2497. Research is ongoing, but one leading hypothesis holds that Hanny's Voorwerp is a small galaxy that acts like a large reflection nebula, showing the reflected light of a bright quasar event that was visible in the center of IC 2497 about 100,000 years ago. Pictured above, Hanny's Voorwerp was imaged recently by the 2.5-meter Isaac Newton Telescope in the Canary Islands by Dan Smith, Peter Herbert and Chris Lintott (Univ. Hertfordshire). Other collaboration members include Matt Jarvis, Kevin Schawinski, and William Keel.