Ed Lu wants to save the earth from killer asteroids.
Or at least, if there’s a big space rock streaking our way, Dr. Lu, a former NASA astronaut with a doctorate in applied physics, wants to find it before it hits us – hopefully with years of advance warning and a chance to deflect humanity.
On Tuesday, the B612 Foundation, a nonprofit group that Dr. Lu helped found, announced the discovery of more than 100 asteroids. (The foundation’s name is a nod to Antoine de Saint-Exupéry’s children’s book, “The Little Prince”; B612 is the home asteroid of the main character.)
That by itself is unremarkable. New asteroids are reported all the time by skywatchers around the world. That includes amateurs with backyard telescopes and robotic surveys systematically scanning the night skies.
What is remarkable is that the B612 did not build a new telescope or even make new observations with existing telescopes. Instead, researchers financed by B612 applied cutting-edge computational might to years-old images – 412,000 of them in digital archives at the National Optical-Infrared Astronomy Research Laboratory, or NOIRLab – to sift asteroids out of the 68 billion dots of cosmic light. captured in the images.
“This is the modern way of doing astronomy” Dr. Lu said.
The research adds to the “planetary defense” efforts undertaken by NASA and other organizations around the world.
Today, of the estimated 25,000 near-Earth asteroids at least 460 feet in diameter, only about 40 percent of them have been found. The other 60 percent – about 15,000 space rocks, each with the potential for unleashing energy versus hundreds of millions of tons of TNT in a collision with Earth – remain undetected.
B612 is supported by Joachim Moeyens, a graduate student at the University of Washington, and his doctoral adviser, Mario Juric, is a professor of astronomy. They and colleagues at the University’s Institute for Data Intensive Research in Astrophysics and Cosmology developed an algorithm that not only examined astronomical imagery to identify those points that might be asteroids, but also figure out which dots of light in images taken. Different nights are actually the same asteroid.
In essence, researchers are developing a way to discover what has already been seen but not noticed.
Typically, asteroids are discovered when the same part of the sky is photographed multiple times during the course of one night. A swath of the night sky contains a multitude of points of light. Distant stars and galaxies remain in the same arrangement. But objects that are much closer, within the solar system, move faster, and shift their positions over the course of the night.
Astronomers call a series of observations of a single moving object during a single night on a “tracklet.” A tracklet provides an indication of the object’s motion, pointing to astronomers where they might look for it on another night. They can also search for older images for the same object.
Many astronomical observations that are not part of systematic asteroid searches inevitably record asteroids, but only at a single time and place, multiple observations are not required to put together tracklets.
The NOIRLab images, for example, were taken by the Victor M. Blanco 4-Meter Telescope in Chile as part of a survey of nearly one-eighth of the sky’s distribution of galaxies in the universe.
The additional specks of light were ignored, as they were not what the astronomers were studying. “They’re just random data in the sky,” said Dr. Lu said.
But for Mr. Moeyens and Dr. Juric, a single point of light that is not a star or a galaxy is a starting point for their algorithm, which they named Tracklet-less Heliocentric Orbit Recovery, or THOR.
The motion of an asteroid is precisely determined by the law of gravity. THOR constructs a test orbit that corresponds to the observed point of light, assuming a certain distance and velocity. It then calculates where the asteroid would be on subsequent and previous nights. If a point of light shows up in the data, that could be the same asteroid. If the algorithm can link together five or six observations across a few weeks, that is a promising candidate for an asteroid discovery.
In principle, there is an infinite number of possible test orbits to examine, but that would require an impractical eternity to calculate. In practice, because asteroids are clustered around certain orbits, the algorithm needs to consider only a few thousand carefully chosen possibilities.
Still, calculating thousands of test orbits for thousands of potential asteroids is a humongous number-crunching task. But the advent of cloud computing – huge computational power and data storage distributed across the internet – makes that feasible. Google partners with Google on its Google Cloud platform.
“It’s one of the coolest applications I’ve seen,” said Scott Penberthy, director of applied artificial intelligence at Google.
So far, the scientists have sifted through about one-eighth of the data of a single month, September 2013, from the NOIRLab archives. THOR churned out 1,354 possible asteroids. Many of them are already in the catalog of asteroids maintained by the International Astronomical Union’s Minor Planet Center. Some of them had been observed annually, but only during one night and the tracklet was not sufficiently confident to determine an orbit.
The Minor Planet Center has confirmed 104 objects as new discoveries so far. The NOIRLab archive contains seven years of data, suggesting that there are thousands of asteroids waiting to be found.
“I think it’s awesome,“Said Matthew Payne, director of the Minor Planet Center, who was not affiliated with THOR. “I think it’s hugely interesting and it also allows us to make good use of the archival data that already exists. “
The algorithm is currently configured to find only main belt asteroids, those with orbits between Mars and Jupiter, and not near-Earth asteroids, the ones that could collide with our planet. Identifying near-earth asteroids is more difficult because they move faster. Different observations of the same asteroid can separate farther in time and distance, and the algorithm needs to perform more number crunching to make connections.
“It’ll definitely work,” Mr. Moeyens said. “There is no reason why it can’t. I just really didn’t have a chance to try it. “
THOR not only has the ability to discover new asteroids in old data, but it can also transform future observations as well. Take, for example, the Vera C. Rubin Observatory, formerly known as the Large Synoptic Survey Telescope, currently under construction in Chile.
Financed by the National Science Foundation, the Rubin Observatory is an 8.4-meter telescope that will repeatedly scan the night sky to track what changes over time.
Part of the observatory’s mission is to study the large-scale structure of the universe and spot distant exploding stars, also known as supernovas. Closer to home, it will also spot a multitude of smaller-than-a-planet bodies whizzing around the solar system.
Several years ago, some scientists suggested that the Rubin telescope’s observing patterns could be adjusted so that it could identify more asteroid tracklets and thus locate more dangerous, as-yet-undiscovered asteroids more quickly. But that change would have slowed down other astronomical research.
If the THOR algorithm proves to work well with the Rubin data, then the telescope would not need to scan the same part of the sky twice a night, allowing it to cover twice as much area instead.
“That in principle could be revolutionary, or at least very important,” said Zeljko Ivezic, director of the telescope and an author on a scientific paper that described THOR and tested it against observations.
If the telescope could return to the same spot in the sky every two nights instead of every four, that could benefit other research, including the search for supernovas.
“That would be another effect of the algorithm that doesn’t even have to do with asteroids,” said Dr. Ivezic said. “This is showing nicely how the landscape is changing. The science of ecosystem is changing because software can now do things that 20, 30 years ago you wouldn’t even dream about, you wouldn’t even think about. “
For Dr. Lu, THOR offers a different way to accomplish the same goals he had a decade ago.
Back then, the B612 had an ambitious and far more expensive project on its sights. The nonprofit was going to build, launch and operate its own space telescope called Sentinel.
At the time, Dr. Lu and the other leaders of the B612 were frustrated by the slow space rocks for dangerous space rocks. In 2005, Congress passed a mandate for NASA to locate and track 90 percent of near-Earth asteroids with diameters of 460 feet or more by 2020. But lawmakers never provided money to NASA’s task, and the deadline passed less than. Half of those asteroids were found.
Raising $ 450 million from private donors to underwrite Sentinel was difficult for B612, especially because NASA had an asteroid-finding space telescope of its own.
When the National Science Foundation gave the go-ahead to construct the Rubin Observatory, B612 re-evaluated its plans. “We could quickly pivot and say, ‘What is a different approach to solve a problem that we exist to solve?'” Lu said.
The Rubin Observatory is about to make its first test observations in about a year and has been operational for about two years. Ten years of Rubin observations, together with other asteroid searches could finally meet Congress’s 90 percent goal, Dr. Ivezic said.
NASA is accelerating its planetary defense efforts as well. Its asteroid telescope, named NEO Surveyor, is in the preliminary design stage, aiming for launch in 2026.
And later this year, its Double Asteroid Redirection Test mission will include a projectile into a small asteroid and measure how much that changes the asteroid’s trajectory. China’s national space agency is working on a similar mission.
For B612, instead of wrangling a telescope project costing almost half a billion dollars, it could contribute to less expensive research endeavors like THOR. Last week, it announced that it had received $ 1.3 million of gifts to finance further work on cloud-based computational tools for asteroid science. The foundation also received a grant from Tito’s Handmade Vodka that will match up to $ 1 million from other donors.
B612 and Dr. Lu is not just trying to save the world. “We’re the answer to a trivia question of how vodka is related to asteroids.” he said.