After six months of fine-tuning, the Pan-STARRS 1 telescope atop Haleakala, using the world's largest digital camera, has spotted its first potentially hazardous asteroid.
It is zooming toward Earth and will miss us in mid-October, but now that astronomers know it is there, they can start worrying about whether it might crash into Earth when it returns in 2098.
Already another half-dozen PHOs (potentially hazardous objects) have been detected.
The Pan-STARRS 1 telescope atop Haleakala has located a potentially hazardous asteroid, about 150 feet in diameter, which is expected to pass the Earth in mid-October about 4 million miles away or about 16 times the distance to the moon.
ROB RATKOWSKI photo
On Monday, University of Hawaii Institute for Astronomy researcher Robert Jedicke said: "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."
The first PHO, labeled 2010 ST 3, is just about 150 feet in diameter and was spotted at a distance of 20 million miles on Sept. 16. It will pass about 4 million miles away. That is about 16 times the distance to the moon.
Asteroids that small usually, but not always, break up and burn up when they crash into Earth's atmosphere, but Jedicke said they are unpredictable.
Up to a size of about 100 to 150 yards across, asteroids are expected to break up harmlessly, but the metallic rock that created Meteor Crater in Arizona was estimated at only 60 to 70 yards across, Jedicke said, and it created a hole three-quarters of a mile across.
About three or four institutions around the world are cataloguing space rocks, Jedicke said, and about 90 percent of the big ones have been detected. Those are the ones that could cause worldwide destruction, and their orbits have been registered over the past few years.
Jedicke is confident that the missing 10 percent will be picked up within the next 10 years.
That will give rocket scientists time to start dealing with the next one that is on a real collision course.
Pan-STARRS 1 has now been shown to be capable of picking up asteroids down to about 300 yards in diameter - and sometimes, as 2010 ST 3 shows, even smaller.
Notice that that is not the danger threshold, which goes down to considerably smaller rocks. There is no doubt there is a need to do more, said Jedicke, who is a member of the PS1 Scientific Consortium working on the asteroid data.
Pan-STARRS is capable of researching hundreds of astronomical questions, such as detecting supernovas at extreme distances, and it will be used to create a map of the galaxy in unprecedented detail. PS1 is a prototype, with a 60-inch mirror. The full Pan-STARRS, with four larger telescopes and an even bigger camera, is intended for Mauna Kea.
Money is hard to find, but now that the telescope has proven its capacity, Jedicke said he is sure the asteroid-mapping function will attract more interest.
The camera, designed and built at the IfA, has been in operation for about six months, but it is so sensitive that even stray electrons can create false positives. Only within the past few weeks did the researchers figure out how to screen the false detections.
The camera, actually a charge-coupled device that presents a grid that captures individual photons, has a capacity of a billion pixels - 100 times bigger than the 10 million or so in a commercial digital camera. And each pixel is far more sensitive than the commercial pixel.
The camera "film" is the size of a chessboard and the whole camera is "about the size of a small washing machine."
The tiny 2010 ST 3 showed up as a dot against a background of other dots. Two images taken about 15 minutes apart revealed that the dot had moved against the background stars.
An animated graphic showing the almost imperceptible difference in the two pictures is online at www.ifa.hawaii.edu/info/press-releases/PHO/.
Timothy Spahr, director of the Minor Planet Center, 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 center, located in Cambridge, Mass., was established by the International Astronomical Union in 1947 to collect and disseminate positional measurements for asteroids and comets.
Pan-STARRS expects to discover tens of thousands of 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."
The PS1 Science Consortium (www.ps1sc.org) includes the IfA; the Pan-STARRS Project Office; the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching; the Johns Hopkins University; Durham University; the University of Edinburgh; the Queen's University Belfast; the Harvard-Smithsonian Center for Astrophysics; Las Cumbres Observatory Global Telescope Network Inc.; and the National Central University of Taiwan.
Construction funding for Pan-STARRS (short for Panoramic Survey Telescope & Rapid Response System) has been provided by the Air Force Research Laboratory.
* Harry Eagar can be reached at firstname.lastname@example.org.