Origins
A key factor leading to the creation of the project was the problem of what has been referred to as data deluge, where research produces vast sets of information to the extent that research teams are not able to analyse and process much of it. Kevin Schawinski, previously 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 more than 900,000 galaxies by eye that had been imaged by the Sloan Digital Sky Survey at the Apache Point Observatory in New Mexico, USA. "I classified 50,000 galaxies myself in a week, it was mind-numbing." Chris Lintott, a co-founder of the project and a professor of astrophysics at the University of Oxford, stated: "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 Galaxy Zoo concept was inspired by others such as 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 (also known as distributed or volunteer computing), Stardust@home involved the active participation of human volunteers to complete the research task. In August 2014, the Stardust team reported the discovery of first potential interstellar space particles after citizen scientists had looked through more than a million images.
In 2007, when Galaxy Zoo first started, the science team hoped that 20–30,000 people would take part in classifying the 900,000 galaxies that made up the sample. It had been estimated that a perfect graduate student working 24 hours a day 7 days a week would take 3–5 years to classify all the galaxies in the sample once. However, in the first Galaxy Zoo, more than 40 million classifications were made in approximately 175 days by more than 100,000 volunteers, providing an average of 38 classifications per galaxy.
ARCSAT and SDSS telescope buildings at the Apache Point Observatory
Rotation of galaxies
One of the original aims for Galaxy Zoo was to explore which way galaxies rotated. Cosmologist Kate Land stated: "Some people have argued that galaxies are rotating all in agreement with each other, not randomly as we'd expect. We want people to classify the galaxies according to which way they're rotating and I'll be able to go and see if there's anything bizarre going on. If there are any patterns that we're not expecting, it could really turn up some surprises." In Galaxy Zoo 1, volunteers were asked to judge from the SDSS images whether the galaxies were elliptical or spiral and, if spiral, whether they were rotating in a clockwise (Z-wise) or anti-clockwise (S-wise) direction. The rotation, also called the chirality, of galaxies has been examined in several Galaxy Zoo related papers.
This HST image of Messier 101, the Pinwheel galaxy has it in its normal S-wise orientation and then reversed.
Among the results a psychological bias was demonstrated. Galaxy Zoo scientists wanted to determine whether spiral galaxies were evenly distributed, or whether an intrinsic property of the universe caused them to rotate one way or the other. When the Science team came to analyse the results, they found an excess of anticlockwise-spinning spiral galaxies. But when the team asked volunteers to classify the same images which had then been reversed, there was still an excess of anticlockwise classifications, delegating that the human brain has real difficulty discerning between something rotating clockwise or anticlockwise. Having measured this effect, the team could adjust for it, and established that spirals near each other tended to rotate in the same direction.
Examples
Examples of crowdsourced astronomy projects include:
- Galaxy Zoo: morphologies derived from visual inspection of galaxies from the Sloan Digital Sky Survey.
- Galaxy Zoo 1: data release of morphological classifications for nearly 900,000 galaxies.
- Galaxy Zoo 2: detailed morphological classifications for 304,122 galaxies from the Sloan Digital Sky Survey.
- Galaxy Zoo: the dependence of morphology and colour on environment.
