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Hanny's Voorwerp

Coordinates: Sky map 9h 41m 4.116s, +34° 43′ 58.458072″
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Hanny's Voorwerp (/ˈfʊərvɛərp/), Dutch for Hanny's object,[1] 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.

Description

The voorwerp does not contain any stars and has a huge central hole over 16,000 light years across. A picture of it appeared on the Astronomy Picture of the Day website[2] 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. The voorwerp is unusually green for an astronomical object, owing to the presence of several luminous emission lines. It has been shown to be at the same distance from Earth as the adjacent galaxy, both about 700 million light-years away.

The voorwerp's light spectrum shows that it contains hot, highly ionized gas.[2]

Hypotheses

One hypothesis suggests that it consists of remnants of a small galaxy reflecting a bright quasar event that occurred in the centre of nearby IC 2497 about 100,000 years previously.[3] The quasar event is thought to have stimulated the bright emission that characterises the voorwerp. It remains unclear why the expected quasar 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,"[4] 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.[5] The 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.

Further Study

The voorwerp and the neighboring galaxy are the object of active astrophysical research.[6] Observations of IC 2497 with the XMM-Newton[2] and Suzaku X-ray space telescopes to probe the current activity of the supermassive black hole have been arranged.[7]


On Jan 10, 2011 it was reported that the Hubble Space Telescope had been used to look at it better. Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys have uncovered star birth in a region of the green object that faces the spiral galaxy IC 2497, located about 650 million light-years from Earth. Radio observations have shown an outflow of gas arising from the galaxy’s core. The new Hubble images reveal that the galaxy’s gas is interacting with a small region of Hanny’s Voorwerp, which is collapsing and forming stars. The youngest stars are a couple of million years old.[3]

See also

  • Pea galaxy, another class of objects discovered by Galaxy Zoo participants

References

  1. ^ "Teacher finds new cosmic object", BBC, 5 August 2008
  2. ^ a b What is Hanny's Voorwerp? NASA Astronomy picture of the day June 25, 2008.
  3. ^ "Stars in their eyes: An armchair astronomer discovers something very odd". The Economist. 2008-06-26. Retrieved 2008-06-30. {{cite news}}: Cite has empty unknown parameter: |coauthors= (help)
  4. ^ 'Cosmic ghost' discovered by volunteer astronomer Physorg.com August 05, 2008
  5. ^ "Radio observations shed new light on Hanny's Voorwerp". Astronomy Now Online. June 29, 2010
  6. ^ "Galaxy Zoo: 'Hanny's Voorwerp', a quasar light echo?". Monthly Notices of the Royal Astronomical Society. Retrieved 2009-08-29.
  7. ^ [1]


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