A couple of years ago, a team of researchers dedicated to finding killer asteroids before they kill us came up with a clever trick.
Instead of scanning the skies with telescopes for asteroids, scientists wrote an algorithm that examines old images of the night sky and discovers about 100 asteroids that had gone unnoticed in those images.
On Tuesday, those scientists, from the Asteroid Institute and the University of Washington, revealed an even bigger bounty: 27,500 newly identified solar system bodies.
This is more than all the world's telescopes discovered last year.
“This is a sea change” in the way astronomical research will be conducted, said Ed Lu, executive director of the institute, which is part of the B612 Foundation, a nonprofit group that Dr. Lu helped establish. found.
The findings include about 100 near-Earth asteroids, the space rocks that pass within Earth's orbit. None of the 100 appear to be on track to collide with Earth anytime soon. But the algorithm could prove a key tool in detecting potentially dangerous asteroids, and the research helps “planetary defense” efforts undertaken by NASA and other organizations around the world.
Most of the space rocks identified by the institute are found in the main asteroid belt, between the orbits of Mars and Jupiter. Others, known as Trojans, are trapped in Jupiter's orbit. The search also found some much more distant small worlds, known as Kuiper Belt objects, beyond the orbit of Neptune.
“There is a lot of excellent science here,” said Dr. Lu, a former NASA astronaut who noted that in the future the key to astronomical discovery may not be more observing time at telescopes but rather more powerful computers to process vast treasures of observations that already exist. gathered.
Historically, astronomers detected new planets, asteroids, comets, and Kuiper Belt objects by photographing the same stretch of sky several times during a night. The pattern of distant stars and galaxies remains unchanged. But objects that are much closer, within the solar system, move noticeably within a few hours.
Multiple observations of a moving object, called a “tracklet,” map out its trajectory, providing enough information to give astronomers a good idea of where to look another night and pinpoint its orbit.
Other astronomical observations inevitably include asteroids, but only at a single time and place, not in the multiple observations needed to assemble a tracklet.
The 412,000 images in the digital archives of the National Optical-Infrared Astronomy Research Laboratory (NOIRLab) contain about 1.7 billion points of light that appear in a single image.
The algorithm used in the current research, known as Tracklet-less Heliocentric Orbit Recovery, or THOR, is capable of connecting a point of light seen in one image with a different point of light in a different image taken on a different night, sometimes through a different telescope, and discover that these two points are actually the same object, usually an asteroid that has changed position as it orbits the sun.
THOR's identification of asteroid candidates across disparate images is a daunting computational task, one that would have been impossible not long ago. But Google Cloud, a distributed computing system, was able to perform the calculations in about five weeks.
“This is an example of what is possible,” said Massimo Mascaro, technical director of Google Cloud's office of the chief technology officer. “I can't even quantify how many opportunities there are in terms of data that is already collected and, if analyzed with the right calculation, could lead to even more results.”
Dr. Lu said improved software tools have made it easier to harness computing power. When scientists no longer need a giant software engineering team to search for their data, “that's when really interesting things can happen,” he said.
The THOR algorithm could also transform the operations of the new Vera C. Rubin Observatory in Chile, which is expected to begin operations next year. The 8.4-meter telescope, funded by the National Science Foundation and the Department of Energy, will repeatedly scan most of the night sky to track changes over time.
Currently, the Rubin telescope will scan the same part of the sky twice a night, a cadence designed to detect asteroids. With THOR, the telescope may not need a second pass, which could allow it to cover twice the area.
“Most science programs would be happy to go from a baseline cadence with two observations to just one observation per night,” said Zeljko Ivezic, a professor of astronomy at the University of Washington who serves as director of Rubin Construction.
The algorithm could increase the number of asteroids Rubin can find, perhaps enough to meet a mandate passed by Congress in 2005 to locate 90 percent of near-Earth asteroids that are 460 feet in diameter or larger. .
“Our latest estimates say about 80 percent,” Dr. Ivezic said. “With THOR, maybe we can take it to 90 percent.”
