Galaxy Zoo

Galaxy Zoo

URL	http://www.galaxyzoo.org
Commercial?	No
Type of site	Volunteer Scientific Project
Registration	Yes
Available language(s)	English, Polish
Owner	Galaxy Zoo Team
Created by	Galaxy Zoo Team
Launched	12 July 2007

Galaxy Zoo is an online astronomy project which invites members of the public to assist in classifying over a million galaxies. It is an example of citizen science as it enlists the help of members of the public to help in scientific research. An improved version — Galaxy Zoo 2 — went live on 17 February 2009.

Origins

The project is inspired by Stardust@home, where the public was asked by NASA to search images obtained from a mission to a comet for interstellar dust impacts. Galaxy Zoo is a collaboration between researchers at many institutions, including Oxford University, Portsmouth University, Nottingham University, Johns Hopkins University, Yale University, University of California, Berkeley and Fingerprint Digital Media, Belfast.

Importance of volunteers

Computer programs have been unable to reliably classify the galaxies. According to a member of the team behind the project, Kevin Schawinski, "The human brain is actually much better than a computer at these pattern-recognition tasks."Without human volunteers, it would take researchers years to process the photographs, but it is estimated that with as few as 10,000 to 20,000 people giving up time to classify the galaxies, the process could be complete in one month.

No knowledge of astronomy is required. In the site's tutorial, would-be volunteers are shown spirals, ellipticals etc., and can try guessing before being shown the correct answer. Also shown are pictures of stars and satellite trails, which the robot telescope would have recorded without being able to classify them. Volunteers are then tested on some additional pictures and signed up if they get a reasonable number of correct results.

Previously unseen images

Chris Lintott, another member of the team behind the project commented that, "One advantage is that you get to see parts of space that have never been seen before. These images were taken by a robotic telescope and processed automatically, so the odds are that when you log on, that first galaxy you see will be one that no human has seen before."^[1] This was confirmed by Schawinski, "Most of these galaxies have been photographed by a robotic telescope, and then processed by computer. So this is the first time they will have been seen by human eyes."^[2]

Original purpose

Galaxy Zoo volunteers were asked to judge from the images whether the galaxies are elliptical or spiral and, if spiral, whether they are rotating in a clockwise or anti-clockwise direction. The images were taken automatically by the Sloan Digital Sky Survey using a digital camera mounted on a telescope at the Apache Point Observatory in New Mexico, United States. It is hoped this census will provide valuable information about how different kinds of galaxies are distributed, allowing scientists to determine whether existing galactic models are correct^[3]. It is an example of citizen science.

Theorists believe that spiral galaxies can merge and become ellipticals, and also that ellipticals can become spirals if they receive more gas or stars.^[4] In addition, Professor Michael Longo of the University of Michigan has claimed that the rotation of spiral galaxies is not random, which would force a major rethink of cosmology if it were correct. This is based on a survey of 1,660 galaxies: a much larger sample could support or disprove it.^[5]

Progress

On August 2, 2007, Galaxy Zoo issued its first newsletter which explained that 80,000 volunteers had already classified more than 10 million images of galaxies, meeting the goals for the first phase of the project. The aim now is

To have "each and every galaxy classified by 20 separate users. The importance of multiple classifications is that it will enable us to build an accurate and reliable database, that will meet the high standards of the scientific community. For the first time, we'll be able to separate not only spirals from ellipticals, but obvious spirals from fainter, fuzzier things. No-one has ever been able to do this before. (Newsletter).

This target was later raised to 30, in light of the continuing enthusiasm of the volunteers. The final datasets contain 34,617,406 clicks done by 82,931 users. Work was then done to test for bias, by presenting images in black-and-white and / or photographically reversed. This is needed to check whether the apparent surplus of anti-clockwise spirals^[6] was actually a bias of the human eye (as seems to be the case).^[7]

Forums and Blogs

There is also an active forum attached to Galaxy Zoo, where volunteers post the more striking images and discuss what they are. There are already some interesting (unofficial) results. Ring galaxies turn out to be much more common than was believed. Only two known galaxies were 'three legged' - possessing three well-defined spiral arms. A lot more have now been found.^[8]. There are many pictures of merging, colliding or interacting galaxies.^[9]

There is also now a 'science blog',^[10], an official summary of what the 'zoo' has achieved so far. There is a current project seeking volunteers to review a set of possible merging galaxies.

Galaxy Zoo 2

After several months 'beta-testing', this is now live and offers a much more detailed classification system. The sample consists of some 250,000 of the brightest galaxies from the Galaxy Zoo. Galaxy Zoo 2 allows for a much more detailed classification, by shape and by the intensity or dimness of the galactic core, and with a special section for oddities like mergers or ring galaxies. The sample also contains fewer optical oddities and orange blobs.

Discoveries

An object known as Hanny's Voorwerp^[11], Dutch for Hanny's object,^[12] was spotted by a member called Hanny van Arkel and has attracted some scientific interest.^[13] This discovery was featured as NASA's Astronomy Picture of the Day on June 25, 2008.^[14] It is now thought to be a portion of a gas-cloud, heated by the jet from a black hole.^[15]

Eleven scientific papers based on the overall data classifications are now completed and five have already been published, with more to follow. One of these concerns the evolution of 'red and dead' spiral galaxies into ellipticals.^[16]

It has recently been confirmed that "spiral galaxies which share a neighbourhood (a region defined as 65 million light years across) are likely to rotate in the same direction – but only if they formed the vast majority of their stars more than 10 billion years ago." ^[17] (This is distinct from the idea of a bias in the much vaster area of the entire survey, which does not seem to be true.)

A number of telescopes are being used to follow up on Galaxy Zoo object discoveries, including Kitt Peak in Arizona and the IRAM millimeter dish in Spain.

See also

• Crowdsourcing
• Peas (Astronomy), a class of objects discovered by Zoo participants

References

External links

• Galaxy Zoo
• Galaxy Zoo Forum
• The official blog of the Galaxy Zoo project
• Original Blog of the most interesting galaxies found on Galaxy Zoo superseded by the official blog above
• Sloan Digital Sky Survey - Famous Places
• Another blog of images from the Sloan Digital Sky Survey
• Radio station featuring interviews from the team
• Galaxy Zoo: The large-scale spin statistics of spiral galaxies in the Sloan Digital Sky Survey (Astrophysics paper, downloadable)
• Galaxy Zoo : Morphologies derived from visual inspection of galaxies from the Sloan Digital Sky Survey (Astrophysics paper, downloadable)
• Galaxy Zoo: the independence of morphology and colour (Astrophysics paper, downloadable)
• How do you count the stars? - a BBC short newsfilm