Hanny's Voorwerp / /, Dutch for Hanny's object, is an astronomical object of unknown nature. It was discovered in 2007 by Dutch school teacher Hanny van Arkel, while she was participating as an amateur volunteer in the Galaxy Zoo project. Photographically, it appears as a bright blob close to spiral galaxy IC 2497 in the constellation Leo Minor.
The object, now referred to as a "voorwerp" (a Dutch word for "object") is about the size of our Milky Way galaxy and has a huge central hole over 16,000 light years across. In the image, the voorwerp is colored green, a false color that is standardly used to represent the presence of several luminous emission lines of glowing oxygen. It has been shown to be at the same distance from Earth as the adjacent galaxy, both about 650 million light-years away.
Star birth is occurring in the region of the object that faces IC 2497. Radio observations indicate that this is due to an outflow of gas arising from the IC 2497's core which is interacting with a small region of Hanny's Voorwerp to collapse and form stars. The youngest stars are several million years old.
A picture of the object appeared on the Astronomy Picture of the Day website in data taken by Dan Smith (Liverpool John Moores University), Peter Herbert (University of Hertfordshire) and Chris Lintott (University of Oxford) on the 2.5 metre Isaac Newton Telescope.
One hypothesis suggests that it 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 the voorwerp. The quasar may have switched off in the last 200,000 years, and is not visible in the available images.
One possible explanation for the missing light-source is that illumination from the assumed quasar was a transient phenomenon. In this case, its effects on the voorwerp would be still visible because of the distance of several tens of thousands of light years between the voorwerp and the quasar in the nearby galaxy: the voorwerp would show a "light echo" or "ghost image," of events that are older than those currently seen in the galaxy.
On 17 June 2010, a group of researchers at the European Very Long Baseline Interferometry Network (EVN) and the UK’s Multi-Element Radio Linked Interferometer Network (MERLIN), proposed another related explanation. They hypothesized that the light comes from two sources: a supermassive black hole at the center of IC 2497, and light produced by an interaction of an energetic jet from that black hole and the gas surrounding IC 2497.
The voorwerp and the neighboring galaxy are the object of active astrophysical research. Observations of IC 2497 with the XMM-Newton and Suzaku X-ray space telescopes to probe the current activity of the supermassive black hole have been arranged.
- Pea galaxy, another class of objects discovered by Galaxy Zoo participants
- Rincon, Paul (5 August 2008). "Teacher finds new cosmic object". BBC News. Retrieved 19 October 2012.
- "Hubble Zooms in on a Space Oddity". European Southern Observatory. Retrieved 11 January 2011.
- What is Hanny's Voorwerp? NASA Astronomy picture of the day June 25, 2008.
- "Stars in their eyes: An armchair astronomer discovers something very odd". The Economist. 2008-06-26. Retrieved 2008-06-30.
- 'Cosmic ghost' discovered by volunteer astronomer Physorg.com August 05, 2008
- "Radio observations shed new light on Hanny's Voorwerp". Astronomy Now Online. June 29, 2010
- Lintott, C. J.; et al. (2009). "Galaxy Zoo: 'Hanny's Voorwerp', a quasar light echo?". Monthly Notices of the Royal Astronomical Society 399: 129. arXiv:0906.5304. Bibcode:2009MNRAS.399..129L. doi:10.1111/j.1365-2966.2009.15299.x.
- Rampadarath, H.; et al. (2010). "Hanny's Voorwerp: Evidence of AGN activity and a nuclear starburst in the central regions of IC 2497". arXiv:1006.4096 [astro-ph.GA].
- Galaxy Zoo's blue mystery (part I) by Janet Raloff at Science News June 19, 2008
- Galaxy Zoo's blue mystery (part 2) Janet Raloff June 20, 2008
- Hanny's Voorwerp (SDSS J094103.80+344334.2) Hanny's Voorwerp at Bill Keel's pages University of Alabama. Accessed June 2008
- Hanny's Voorwerp – Still Alive and Kicking by Tammy Plotner, Universe Today, June 9, 2008
- www.hannysvoorwerp.com Personal website of discoverer Hanny van Arkel
- Astronomers Solve The Mystery of Hanny's Voorwerp, Technology Review
- Gray, Meghan (2009). "Hanny's Voorwerp". Sixty Symbols. Brady Haran for the University of Nottingham.