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Pan-STARRS Discovers First Potentially Hazardous Asteroid

PS1 telescope

Pan-STARRS 1 Telescope atop Haleakala. With a 1.8-meter (71-inch) primary mirror, the PS1 telescope is modest in size, but it has an extraordinary field of view—six times the width of the full Moon. Its wide field of view requires both a much larger secondary mirror and much tighter tolerances than traditional telescopes. Photo by Rob Ratkowski © 2010 PS1SC.

The University of Hawai`i's Pan-STARRS PS-1 telescope on Haleakala has discovered an asteroid that will come within 4 million miles of Earth in mid-October. The object is about 150 feet in diameter and was discovered in images acquired on September 16, when it was about 20 million miles away.

2010 ST3
Two images of 2010 ST3 (circled in green) taken by PS1 about 15 minutes apart on the night of September 16 show the asteroid moving against the background field of stars and galaxies. Each image is about 100 arcseconds across. Credit: PS1SC.

It is the first "potentially hazardous object" (PHO) to be discovered by the Pan-STARRS survey and has been given the designation "2010 ST3."

"Although this particular object won't hit Earth in the immediate future, its discovery shows that Pan-STARRS is now the most sensitive system dedicated to discovering potentially dangerous asteroids," said Dr. Robert Jedicke, a University of Hawai`i member of the Pan-STARRS 1 Science Consortium who is working on the asteroid data from the telescope. "This object was discovered when it was too far away to be detected by other asteroid surveys," Jedicke noted.

Objects the size of 2010 ST3 usually break up in Earth's atmosphere, but the resulting blast wave on the surface can still devastate an area covering hundreds of square miles. "There is a very slight possibility that ST3 will hit Earth in 2098, so it is definitely worth watching," Jedicke said.

Most of the largest PHOs have already been catalogued, but scientists suspect that there are many more under a mile across that have not yet been discovered. These could cause devastation on a regional scale if they ever hit our planet. Such impacts are estimated to occur once every few thousand years.

Dr. Timothy Spahr, director of the Minor Planet Center (MPC), said, "I congratulate the Pan-STARRS project on this discovery. It is proof that the PS1 telescope, with its Gigapixel Camera and its sophisticated computerized system for detecting moving objects, is capable of finding potentially dangerous objects that no one else has found." The MPC, located in Cambridge, Mass., was established by the International Astronomical Union in 1947 to collect and disseminate positional measurements for asteroids and comets, to confirm their discoveries, and to give them preliminary designations.

Pan-STARRS expects to discover tens of thousands of new asteroids every year with sufficient precision to accurately calculate their orbits around the Sun. Any sizable object that looks like it may come close to Earth within the next 50 years or so will be labeled "potentially hazardous" and carefully monitored. NASA experts believe that given several years warning, it should be possible to organize a space mission to deflect any asteroid that is discovered to be on a collision course with Earth.

PS1 officially began its science mission on May 13. While scanning the skies nightly to search for asteroids that threaten Earth, it is mapping the Universe and investigating its biggest mysteries, dark matter and dark energy.

Pan-STARRS (short for Panoramic Survey Telescope and Rapid Response System) exploits the unique combination of superb observing sites and technical and scientific expertise available in Hawai`i. Conceived and designed at the IfA, the PS1 sits atop Maui's Haleakala but is operated remotely from the IfA's Advanced Technology Research Center in Pukalani, Maui.

"From inside the orbit of the Moon to the most distant quasars, PS1 is taking a census of the contents of our Universe," said PS1 Director Kenneth Chambers, head of the international PS1 Science Consortium that is funding the initial three-year PS1 science mission.