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Catalina Sky Survey spawns Real-Time Transient Survey

Posted: August 25, 2009

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Primarily built for tracking down Near Earth Objects, the Catalina Sky Survey is set to expand into the Catalina Real-Time Transient Survey, the first and only fully public synoptic sky survey.

The Catalina Sky Survey (CSS) was originally funded by NASA to seek out potentially hazardous asteroids and comets that have Earth-crossing orbits, and in the last three and a half years, it has uncovered an impressive 70 percent of all known Near Earth Objects (NEOs).

Because the CSS telescopes span the whole sky each month, they have also picked up a whole host of other objects along the way, capturing more than 700 'optical transients' (objects that change brightness on time scales of minutes to years) and some 177 supernova in the last 17 months alone, more than dedicated supernova surveys have turned up in that time.

The arrow points to a supernova discovered by the CSS in a nearby pair of colliding galaxies called the Antennae Galaxies. Image: Robert Gendler.

Other finds have included the most energetic supernova ever seen, a stellar explosion in the Antennae galaxy that is helping astronomers to refine the cosmic distance scale, 185 cataclysmic variable stars, 32 blazars, 30 stellar flares and 100 other erratic light sources that include active galactic nuclei, high proper motion stars and some currently unknown sources, making the CSS one of the most successful cosmic bounty hunters to date.

Now, thanks to a $890,000 National Science Foundation grant, the CSS team can expand their resources into a spin-off project called the Catalina Real-Time Transient Survey (CRTS). A fully open synoptic sky survey, the initiative will centre around a website that will make some ten terabytes of data taken by the CSS over the last five years, and new data as it is collected, available to professional and amateur astronomers alike.

"The grant will allow our Caltech colleagues to expand our project to get real-time data from our two other telescopes – the 1.5 metre Mount Lemmon telescope and the Siding Spring telescope in Australia – and buy computers and storage equipment that will allow them to put all this data online for anybody in the world to use," says Steve Larson, a CSS investigator. CSS astronomers also use the 0.7-metre Schmidt telescope in the Santa Catalina Mountains north of Tucson, the Hale Telescope at Palomar Mountain, the Keck Telescope on Mauna Kea and the Gemini South Telescope in Chile.

This CRTS image shows how quickly astrophysical objects can disappear and reappear. The box highlights a so-called polar cataclysmic variable star that fades by 7,500 percent in about 10 minutes, then recovers completely 10 minutes later. Image: Catalina Real-Time Transient Survey.

This type of online data sharing is vital in a world where such a vast amount of data is collected in one night, often yielding more data than any one team of astronomers has time to follow up. "We just crank out the data so amateurs and professionals alike can figure out what they can do with it," says CSS director Ed Beshore.

Researchers will be able to compare real-time CSS images to any image in the five year CSS archive. "Fortunately, we decided to divide the sky into a grid and basically shoot and reshoot the same defined patches of sky within that grid," says Beshore. "That’s a big help when it comes to comparing what a specific patch of sky looked like earlier and what it looks like now."

The Catalina Sky Survey 60-inch telescope atop Mount Lemmon. Image: Lori Stiles.

The CRTS represents an important transition in astronomy research towards the quest to find objects that change on short timescales. For example, in one set of CRTS images, the team found a star that dims by 7,500 percent in about 10 minutes, recovering completely 10 minutes later. Deep sky images can also be created by co-adding images taken at specific locations, revealing objects down to 21st magnitude. The team's first catalogue of deep-sky images was created in this way.

The main focus of the CSS however, the search for NEOs, will still remain a top priority. Last year CSS astronomers made history by spotting the asteroid 2008 TC3 less than 24 hours before it entered the Earth's atmosphere above Sudan, then, by tracking the fireball's descent, meteorite hunters were able to pick up fragments from the asteroid afterwards. The transient object survey is set to be just as valuable to astronomers over the coming years.