Citizen astronomers help locate perplexing new galaxy


Radio-optical overlay image of galaxy J1649+2635. The yellow is visible light. The blue is the radio image, including the presence of jets.
MAO ET AL NRAO/AUI/NSF SLOAN DIGITAL SKY SURVEY

An unusual spiral galaxy which ejects jets of sub-atomic particles from its core has been located with the help of citizen astronomers.

Spiral galaxies with jets are extremely rare - only four have been found so far. Astronomers do not yet understand how the jets have come about in a galaxy of this type. The galaxy, named J1649+2635, is nearly 800 million light years from the Earth. Astronomers hope the galaxy may yield information about the early Universe.

"The conventional wisdom is that such jets come only from elliptical galaxies that formed through the merger of spirals. We don't know how spirals can have these large jets," said Minnie Mao, of the National Radio Astronomy Observatory (NRAO).

"In order to figure out how these jets can be produced by the 'wrong' kind of galaxy, we realised we needed to find more of them," she said.

The first jet-emitting spiral galaxy was found in 2003 when astronomers combined a radio-telescope image from the Karl G. Jansky Very Large Array (VLA) and a visible-light image of the same object from the Hubble Space Telescope.

To find another of these exotic galaxies, astronomers sought help from volunteer scientists who participate in an online project called Galaxy Zoo, which classifies galaxies captured by the visible light Sloan Digital Sky Survey. So far, some 150,000 Galaxy Zoo participants have identified about 700,000 galaxies. Each galaxy image is inspected by many volunteers who classify them as elliptical, spiral, or other types.

J1649+2635 was found by taking a subset of 35,000 images of spiral galaxies and cross-matching them with galaxies in a catalogue that combines data from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty Centimetres survey.

J1649+2635 is also the first example of a "grand design" spiral galaxy with a large "halo" of visible-light emission surrounding it.

"This galaxy presents us with many mysteries. We want to know how it became such a strange beast," Mao said. "Did it have a unique type of merger that preserved its spiral structure? Was it an elliptical that had another collision that made it re-grow spiral arms? Is its unique character the result of interaction with its environment?"

"We will study it further, but in addition, we need to see if there are more like it," Mao said.

"We hope that with projects like the Galaxy Zoo and another called Radio Galaxy Zoo, those thousands of citizen scientists can help us find many more galaxies like this one so we can answer all our questions."

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