Gravitational lenses, which are massive galaxies or galaxy clusters that act as a magnifying glass by bending light passing them, are one of the Universe's golden gifts to astronomers. To help unlock the mysteries that might lie behind these untapped celestial resources, Zooniverse, a program of the Citizens Science Alliance, has begun the Space Warps project. It allows citizen scientists to put their skills at pattern/image recognition to use, toward finding these fugitive gravitational lenses.

Gravitational lenses have become a serious tool for studying the Universe, as they can gather extra light for our telescopes, and let us see farther into the distant past. Although about 400 such lenses are known, astronomers estimate that at least 10 times more have been captured, but not yet recognized, in photographic sky surveys such as the Sloan Digital Sky Survey.

The current candidate for most distant galaxy in the Universe, MACS0647-JD, is 13.3 billion light years distant. We see it as it was about 420 million years after the Big Bang. A very significant factor in its discovery is that it is being significantly enhanced by intervening galaxy MACSJ0647+7015 at a distance of about five billion light years.

MACS0647-JD is a candidate for the most distant galaxy in the Universe – it can only be seen here due to the influence of a gravitational lens formed by an intervening galaxy cluster

Another example is the discovery of the supernova PS1-10afx. It occurred in a galaxy about nine billion light years distant, making it one of the most distant Type 1a supernovae ever found. The distance should also have made it too dim for the Pan-STARRS survey that found it – it was about 30 times brighter than expected for that distance. A gravitational lens is responsible, that collected and focused light from the supernova so that it appeared far brighter than it would without the gravitational lens.

The Space Warps project is aimed at identifying many of the undiscovered gravitational lenses recorded on the Sloan Digital Sky Survey (SDSS). The SDSS is carried out using a 2.5-meter (100-inch) telescope dedicated solely to the purpose of taking a deep look at what is in the heavens. SDSS has mapped over a third of the total sky with a sensitivity that allows most of the Universe to be studied.

How does Space Warps work? You sign up for access, and go through a brief training session which concentrates on what common forms of gravitational lensing look like. You are then presented with a series of SDSS images mixed with images on which simulated gravitational lenses are inserted, or on which no gravitational lenses are to be found. Evidence for gravitational lenses is entered on the images as and if you find it. If you miss a simulated gravitational lens, or find evidence for a gravitational lens in a cleared image, you get immediate feedback. Feedback also is returned for correct results. There are no time or effort requirements – you simply check images as long and as often as you desire.

Like most citizen scientist programs, the return to science is profound. This is a job that computers cannot accomplish, and for which astronomers (and their graduate students) don't have enough time. Besides that, the work is important. Past projects of similar subject and scope have resulted in the Citizens Science Alliance projects co-authoring scientific papers. As I scrutinized image after image, I came to a better appreciation of just how enormous the Universe is – nearly empty, yet full of wonder. And yes, I will go back and do some more searching for gravitational lenses!

Source: Space Warps

All images courtesy of NASA.

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