The Galaxy Zoo is a public science project intended to solicit amateur astronomers and members of the public to assist scientists in classifying types of galaxies around the universe. Since 2009, a second project, Galaxy Zoo 2, has been following up on results from the first.
Galaxy Zoo originated in two observations. First, enlisting members of the public can be a highly useful and cost-effective way of completing scientific research tasks that are interesting but ultimately repetitive and highly labour-intensive. This was first proved by the [email protected] project, which since its inception over a decade ago has been a leading distributed computing project which processes deep space radio signals searching for potential alien transmissions using spare processing time on individuals' and businesses' computers (via a downloaded application). This sort of computing allows popular projects to achieve supercomputer-level processing capabilities at the minimal cost of a good public relations team and a central unit for coordinating tasks.
Second, however, it was also discovered that classifying galaxies is a pattern recognition task, which today's computers generally have great difficulty with. Robotic telescopes can (and do) generate very large numbers of pictures of deep space, and process them much more quickly than any number of humans sitting in observatories and manually operating the same telescopes. However, there are limits to what computers can reliably conclude about certain images.
The response was to throw open a large number of images of galaxies to the public and request that they identify certain basic properties used to classify these galaxies, namely whether they are spiral galaxies (with arms, like our own Milky Way Galaxy) or elliptical galaxies, and whether they are spinning clockwise or counter-clockwise. Multiple members of the public are asked to cast judgement on each image; those about which there seems to be disagreement can be flagged for further analysis, but for the most part the system is very reliable. Images were taken robotically by the Sloane Digital Sky Survey at Apache Point Observatory, New Mexico.
The effect is that the Galaxy Zoo project has been able to identify and classify a large number of galaxies in an unprecedentedly large amount of time. The first project has classified over sixty million galaxies since 2007 through individual inspection, a process which would take a funded research lab many more years. One quarter-million of the brightest galaxies identified in the first survey were then selected for Galaxy Zoo 2 in 2009, a similar survey which asks more detailed questions.
To university researchers, including coordinators at Oxford, Yale, and Berkeley, the Galaxy Zoo process offers the means of performing labour-intensive inspection tasks at low cost and great speed. In addition, members of the public, including amateur astronomers, have the attraction of getting a chance to look at deep-space images which no human has ever seen before. Since the original telescope images were taken robotically, volunteers in the Galaxy Zoo project can literally be identifying new galaxies never before classified by any other astronomer, professional or otherwise.
To researchers, the data also holds considerable interest in terms of the possibilities of statistical analysis of the evolution of galaxies and transition between spiral and elliptical galaxies. However, the survey is also known for producing a number of strange and poorly understood oddities not yet fully understood by modern astronomy. One of the most high-profile objects, Hanny's Object (usually known as Hanny's Voorwerp, because Hanny is Dutch) was discovered by a teacher in the Netherlands, Hanny van Arkel. Hanny's Voorwerp is a bright green-tinged blob about 700 million-light years from the Earth, which contains no stars but does have a 16,000-light-year-wide empty space in the centre. Hanny's Voorwerp does not correspond to any common celestial object. Currently, the best guess regarding its nature is that it is a large gas cloud being ionized by radiation emitted by the supermassive black hole in nearby galaxy IC2497.