|Type of site||Volunteer Scientific Project|
|Available language(s)||English, French, German, Polish, Czech|
|Owner||Galaxy Zoo Team|
|Created by||Galaxy Zoo Team|
|Launched||12 July 2007|
Galaxy Zoo is an online astronomy project which invites people to assist in the morphological classification of large numbers of 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. The third iteration of the project, launched in April 2010, Galaxy Zoo: Hubble, used Hubble Space Telescope survey data. The fourth and current version was launched in summer, 2012, incorporating new images of the Sloan galaxies and images from Hubbel's CANDELS survey. Galaxy Zoo is part of the Zooniverse group of citizen science projects.
Scientists are increasingly finding it difficult to cope with what has been called the "Data Deluge", where modern research is producing vast sets of information. Often the teams involved don't have the time, resources or brainpower to analyse it all. Kevin Schawinski, an astrophysicist at Oxford University and co-founder of Galaxy Zoo, described the problem that led to Galaxy Zoo's creation when he was set the task of classifying the morphology of ~1 million galaxies by eye that had been imaged by the Sloan Digital Sky Survey at the Apache Point Observatory in New Mexico, United States. "I classified 50,000 galaxies myself in a week, it was mind-numbing." According to Chris Lintott – another founder of the project and co-host of the long-running astronomical television programme The Sky at Night – "In many parts of science, we're not constrained by what data we can get, we're constrained by what we can do with the data we have. Citizen science is a very powerful way of solving that problem." The concept was 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. Unlike earlier internet-based citizen science projects such as SETI@home which used spare computer processing power to analyse data, known as distributed or volunteer computing, the active participation of human volunteers was needed to complete the research task. It was hoped that 20–30,000 people would take part, and estimated that one graduate student working 24 hours a day and 7 days a week would take 3–5 years to do the same task.
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." 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."
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. 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. 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.
On 2 August 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.—Galaxy Zoo 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 was actually a bias of the human eye (as seems to be the case).
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. Many more have now been found. There are many pictures of merging, colliding or interacting galaxies.
There is also now a 'science blog', 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 
This 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.
The project closed with some 60 million classifications. The first papers from Zoo 2 are already complete, and much science work continues. Galaxy classification by volunteers continues with Galaxy Zoo Hubble.
An object known as Hanny's Voorwerp, Dutch for Hanny's object, was spotted by a member called Hanny van Arkel and has attracted some scientific interest. This discovery was featured as NASA's Astronomy Picture of the Day on 25 June 2008. It is now thought to be a portion of a gas-cloud, heated by the jet from a black hole.
Here is the list of studies derived from the project with related information (the accepted and published are in green). One of these concerns the evolution of 'red and dead' spiral galaxies into ellipticals.
Galaxy Zoo: The large-scale spin statistics of spiral galaxies in the Sloan Digital Sky Survey
|Kate Land, Anze Slosar, Chris J. Lintott, Dan Andreescu, Steven Bamford, Phil Murray, Robert Nichol, M. Jordan Raddick, Kevin Schawinski, Alex Szalay, Daniel Thomas, Jan Vandenberg||Submitted 21 March 2008
Accepted 19 May 2008
Published MNRAS Vol. 388 Issue 4
|Galaxy Zoo : Morphologies Derived from Visual Inspection of Galaxies from the Sloan Digital Sky Survey||Chris J. Lintott, Kevin Schawinski, Anze Slosar, Kate Land, Steven Bamford, Daniel Thomas, M. Jordan Raddick, Robert C. Nichol, Alex Szalay, Dan Andreescu, Phil Murray, Jan VandenBerg||Submitted 16 April 2008
Accepted 4 July 2008
Published MNRAS Volume 389 Issue 3
pp. 1179 – 1189
|Galaxy Zoo: The Dependence of Morphology and Colour on Environment||Steven P. Bamford, Robert C. Nichol, Ivan K. Baldry, Kate Land, Chris J. Lintott, Kevin Schawinski, Anze Slosar, Alexander S. Szalay, Daniel Thomas, Mehri Torki, Dan Andreescu, Edward M. Edmondson, Christopher J. Miller, Phil Murray, M. Jordan Raddick, Jan Vandenberg||Submitted 16 May 2008
Accepted 13 November 2008
Published MNRAS Volume 393 Issue 4
pp. 1324 – 1352
|Galaxy Zoo: A Sample of Blue Early-type Galaxies at Low Redshift||Kevin Schawinski, Chris J. Lintott, Daniel Thomas, Marc Sarzi, Dan Andreescu, Steven P. Bamford, Sugata Kaviraj, Sadegh Khochfar, Kate Land, Phil Murray, Robert C. Nichol, M. Jordan Raddick, Anze Slosar, Alex Szalay, Jan VandenBerg, Sukyoung K. Yi||Submitted 14 June 2008
Accepted 19 March 2009
Published MNRAS Volume 396 Issue 2
pp. 818 – 829
|Galaxy Zoo: 'Hanny's Voorwerp', a Quasar Light Echo ?||Chris J. Lintott, Kevin Scawinski, William Keel, Hanny van Arkel, Edward Edmondson, Daniel Thomas, Nicola Bennert, Daniel J.B. Smith, Peter D. Herbert, Matt J. Jarvis, Dan Andreescu, Steven P. Bamford, Kate Land, Phil Murray, Robert C. Nichol, M. Jordan Raddick, Anze Slosar, Alex Szalay, Jan Vandenberg||Submitted 15 July 2008
Accepted 23 June 2009
Published MNRAS Volume 399 Issue 1
pp. 129 – 140
|Galaxy Zoo: Chiral Correlation Function of Galaxy Spins||Anze Slosar, Kate Land, Steven Bamford, Chris J. Lintott, Dan Andreescu, Phil Murray, Robert Nichol, M. Jordan Raddick, Kevin Schawinski, Alex Szalay, Daniel Thomas, Jan Vandenberg||Submitted 12 September 2008
Accepted 22 October 2008
Published MNRAS Volume 392 Issue 3
pp. 1225 – 1232
|Galaxy Zoo: Disentangling the Environmental Dependence of Morphology and Colour||Ramin A. Skibba, Steven P. Bamford, Robert C. Nichol, Chris J. Lintott, Dan Andreescu, Edward M. Edmondson, Phil Murray, M. Jordan Raddick, Kevin Schawinski, Anze Slosar, Alexander S. Szalay, Daniel Thomas, Jan Vandenberg||Submitted 20 November 2008
Accepted 29 June 2009
Published MNRAS Volume 399 Issue 2
pp. 966 – 982
|Galaxy Zoo: The Fraction of Merging Galaxies in the SDSS and Their Morphologies||D. W. Darg, Sugata Kaviraj, Chris J. Lintott, Kevin Schawinski, Marc Sarzi, Steven P. Bamford, J. Silk, R. Proctor, Dan Andreescu, Phil Murray, Robert C. Nichol, M. Jordan Raddick, Anze Slosar, Alex S. Szalay, Daniel Thomas, Jan Vandenberg||Submitted 28 November 2008
Accepted 8 September 2009
Published MNRAS Volume 401 Issue 2
pp. 1043 – 1056
|Galaxy Zoo: An Unusual New Class of Galaxy Cluster||Marven F. Pedbost, Trillean Pomalgu, the Galaxy Zoo Team||Submitted[where?] March 2009||astro-ph|
|Galaxy Zoo: The Properties of Merging Galaxies in the Nearby Universe – Local Environments, Colours, Masses, Star-formation Rates and AGN Activity||D. W. Darg, Sugata Kaviraj, Chris J. Lintott, Kevin Schawinski, Marc Sarzi, Steven P. Bamford, J. Silk, Dan Andreescu, P. Murray, R. C. Nichol, M. Jordan Raddick, Anze Slosar, Alex S. Szalay, Daniel Thomas, Jan Vandenberg||Submitted 16 March 2009
Accepted 25 September 2009
Published MNRAS Volume 401 Issue 3
pp. 1552 – 1563
|Galaxy Zoo Green Peas: Discovery of A Class of Compact Extremely Star Forming Galaxies||Caroline Cardamone, Kevin Scawinski, Marc Sarzi, Steven P. Bamford, Nicola Bennert, C.M. Urry, Chris J. Lintott, William C. Keel, John Parejiko, Robert C. Nichol, Daniel Thomas, Dan Andreescu, Phil Murray, M. Jordan Raddick, Anze Slosar, Jan Vandenberg||Submitted 10 April 2009
Accepted 9 July 2009
Published MNRAS Volume 399 Issue 3
pp. 1191 – 1205
|Galaxy Zoo: A Correlation Between Coherence of Galaxy Spin Chirality and Star Formation Efficiency||Raul Jimenez, Anze Slosar, Licia Verde, Steven P. Bamford, Chris J. Lintott, Kevin Scawinski, Robert Nichol, Dan Andreescu, Kate Land, Phil Murray, M. Jordan Raddick, Alex Szalay, Daniel Thomas, Jan Vandenberg||Submitted 9 June 2009
Accepted 11 January 2010
Published MNRAS Volume 404 Issue 2
pp. 975 – 980
|Galaxy Zoo: Reproducing Galaxy Morphologies Via Machine Learning||Manda Banerji, Ofer Lahav, Chris J. Lintott, Filipe B. Abdalla, Kevin Scawinski, Steven P. Bamford, Dan Andreescu, Phil Murray, M. Jordan Raddick, Anze Slosar, Alex Szalay, Daniel Thomas, Jan Vandenberg||Submitted 4 August 2009
Accepted 17 March 2010
Published MNRAS Volume 406 Issue 1
pp. 342 – 353
|Galaxy Zoo: Dust in Spirals||Karen L. Masters, Robert C. Nichol, Steven P. Bamford, Moein Mosleh, Chris J. Lintott, Dan Andreescu, Edward M. Edmondson, William C. Keel, Phil Murray, M. Jordan Raddick, Kevin Schawinsky, Anze Slosar, Alex S. Szalay, Daniel Thomas, Jan Vandenberg||Submitted 17 August 2009
Accepted 12 January 2010
Published MNRAS Volume 404 Issue 1
pp. 792 – 810
|Galaxy Zoo: Exploring the Motivations of Citizen Science Volunteers||M. Jordan Riddick, Georgia Bracey, Pamela Gay, Chris J. Lintott, Kevin Scawinski, Alex Szalay, Jan Vanderberg||Submitted 1 June 2009
Accepted 24 August 2009
Published Astronomy Education Review Volume 9 Issue 1
|Galaxy Zoo: Passive Red Spirals||Karen L. Masters, Moein Mosleh, A. Kathy Romer, Robert C. Nichol, Steven P. Bamford, Kevin Schawinsky, Chris J. Lintott, Dan Andreescu, Heather C. Campbell, Ben Crowcroft, Isabelle Doyle, Edward M. Edmondson, Phil Murray, M. Jordan Raddick, Anze Slosar, Alex S. Szalay, Jan Vandenberg||Submitted 19 October 2009
Accepted 10 February 2010
Published MNRAS online.
|Revealing Hanny's Voorwerp: radio observations of IC 2497||G. I. G. Jozsa, M. A. Garrett, T. A. Oosterloo, H. Rampadarath, Z. Paragi, Hanny van Arkel, Chris Lintott, William C. Keel, Kevin Scawinski, Edd Edmondson||Published Astronomy & Astrophysics
- A&A 500, L33–L36 (2009)
|Galaxy Zoo: The Fundamentally Different Co-evolution of Supermassive Black Holes and Their early- and late-type Host Galaxies||Kevin Schawinsky, C. Megan Urry, Shanil Virani, Paolo Coppi, Steven P. Bamford, Ezequiel Treister, Chris J. Lintott, Marc Sarzi, William C. Keel, Sugata Kaviraj, Carolin N. Cardamone, Karen L. Masters, Nicholas P. Ross, Dan Andreescu, Phil Murray, Robert C. Nichol, M. Jordan Raddick, Anze Slosar, Alex S. Szalay, Daniel Thomas, Jan Vandenberg||Submitted 5 August 2009
Accepted 20 January 2010
Published Astrophys. J.
Volume 711 Issue 1
pp. 284 – 302
|Galaxy Zoo: Bars in Disk Galaxies||Karen L. Masters, Robert C. Nichl, Ben Hoyle, Chris J. Lintott, Steven Bamford, Edward M. Edmondson, Lucy Fortson, William C. Keel, Kevin Schawinsky, Arfon Smith, Daniel Thomas.||Submitted February 2010
Accepted 7 October 2010
Published MNRAS Volume 411 Issue 3
pp. 2026 – 2034
|The Sudden Death of the Nearest Quasar||Kevin Schawinski, Daniel A. Evans, Shanil Virani, C. Megan Urry, William C. Keel, Priyamvada Natarajan, Chris J. Lintott, Anna Manning, Paolo Coppi, Sugata Kaviraj, Steven P. Bamford, Gyula I. G. Jozsa, Michael Garrett, Hanny van Arkel, Pamela Gay, Lucy Fortson.||Submitted 24 August 2010
Accepted 12 October 2010
Published Astrophys. J. Letters
Volume 724 Issue 1
|Galaxy Zoo: Multi-Mergers and the Millennium Simulation||D. W. Darg, S. Kaviraj, C. J. Lintott, K. Schawinski, J. Silk, S. Lynn, S. Bamford, R. C. Nichol.||Submitted to MNRAS[when?]||astro-ph|
|Galaxy Zoo: Bar Lengths in Nearby Disk Galaxies||Ben Hoyle, Karen. L. Masters, Robert C. Nichol, Edward M. Edmondson, Arfon M. Smith, Chris Lintott, Ryan Scranton, Steven Bamford, Kevin Schawinski, Daniel Thomas.||Accepted in MNRAS[when?]||astro-ph|
|The Galaxy Zoo survey for giant AGN-ionized clouds: past and present black-hole accretion events||William C. Keel, S. Drew Chojnowski, Vardha N. Bennert, Kevin Schawinski, Chris J. Lintott, Stuart Lynn, Anna Pancoast, Chelsea Harris, A.M. Nierenberg, Alessandro Sonnenfeld, Richard Proctor||Accepted in MNRAS[when?]||astro-ph|
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." (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 November 2010 announcement based on Galaxy Zoo: Bars in Disk Galaxies suggests that bars help to slow or stop star formation in spirals, by some unknown mechanism. This is based on the observation that red spirals are about twice as likely to host bars as blue spirals.
See also 
- "Experts want EU to tackle scientific data deluge". EurActiv.com. 7 October 2010. Retrieved 25 August 2011.
- "Supercomputers: 'Data Deluge' Is Changing, Expanding Supercomputer-Based Research". Science Daily. 24 April 2011. Retrieved 25 August 2011.
- Pinkowski, Jennifer (28 March 2010). "How to Classify a Million Galaxies in Three Weeks". Time. Retrieved 21 July 2011.
- McGourty, Christine (11 July 2007). "Scientists seek galaxy hunt help". BBC News. Retrieved 12 July 2007.
- Hopkin, Michael (11 July 2007). "See new galaxies – without leaving your chair". Nature. doi:10.1038/news070709-7. Retrieved 12 July 2007.
- "Galaxy Zoo opens". inthenews.co.uk. 11 July 2007. Retrieved 12 July 2007.
- "Galaxy Zoo - The Science, page 1". Galaxy Zoo. Retrieved 21 July 2011.
- "Galaxy Zoo – The Science, page 2". Galaxy Zoo. Retrieved 21 July 2011.
- "Why record the galaxy rotation?". Galaxy Zoo. Retrieved 21 July 2011.
- Plait, Phil (10 January 2008). "Galaxy zoo finds people are screwed up, not the Universe". Discover. Retrieved 21 July 2011.
- "Three legged well defined spiral galaxy". Galaxy Zoo. Retrieved 21 July 2011.
- "Biggest cosmic trainwrecks – Mergers". Galaxy Zoo. Retrieved 21 July 2011.
- "Official Blog of the Galaxy Zoo project". Galaxy Zoo. Retrieved 21 July 2011.
- "Galaxy Zoo 2". Galaxy Zoo. Retrieved 21 July 2011.
- Raloff, Janet (20 June 2008). "Galaxy Zoo's blue mystery (part 2)". Science News. Retrieved 21 July 2011.
- Rincon, Paul (5 August 2008). "Teacher finds new cosmic object". BBC News. Retrieved 21 July 2011.
- "Voorwerp fever". Galaxy Zoo. Retrieved 21 July 2011.
- "What’s the blue stuff below?". Galaxy Zoo. Retrieved 21 July 2011.
- "What is Hanny's Voorwerp?". NASA. 25 June 2008. Retrieved 25 June 2008.
- Baldwin, Emily (26 November 2008). "Nature of ‘Hanny's Voorwerp’ revealed". Astronomy Now. Retrieved 21 July 2011.
- Baldwin, Emily (11 June 2009). "Galaxy Zoo puts new spin on galaxy rotation". Astronomy Now. Retrieved 21 July 2011.
- "Bars Kill Spiral Galaxies, Astronomers and Volunteers Discover". Science Daily. 9 November 2010. Retrieved 21 July 2011.
- 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
- How do you count the stars? – a BBC short newsfilm
- Discovery of Green-Pea Galaxies – Skymania News
- Discovery of Red Spirals – Skymania News
- Gray, Meghan (2009). "Hanny's Voorwerp". Sixty Symbols. Brady Haran for the University of Nottingham.