Ed Lu wants to save Earth from a killer asteroid.
Or at least, if a giant space rock streaks in front of us, Dr. Lu, a former NASA astronaut with a Ph.D. in applied physics, hopes to find it before it hits us—hopefully with years of warning and human chance to deflect it.
On Tuesday, the B612 Foundation, a nonprofit that Dr. Lu helped found, announced the discovery of more than 100 asteroids. (The foundation’s name is a tribute to Antoine de Saint-Exupéry’s children’s book The Little Prince; B612 is the main character’s home asteroid.)
This in itself is not noticeable. Astronomers around the world are reporting new asteroids all the time. This includes hobbyists with backyard telescopes and robotic surveys to systematically scan the night sky.
Notably, no new telescopes were built for B612, or even new observations were made with existing ones. Instead, B612-funded researchers applied cutting-edge computing power to images from many years ago — 412,000 of which are in the National Optical Infrared Astronomy Research Laboratory, or NOIRLab’s digital archives — from 68 billion cosmic light spots. Filter out asteroids captured in the image.
“This is the modern way of doing astronomy,” Dr. Lu said.
The research adds to “planetary defense” work being carried out 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 have been discovered. The remaining 60 percent — about 15,000 space rocks, each with the potential to release the equivalent of hundreds of millions of tons of TNT on collision with Earth — remain undiscovered.
B612 is in collaboration with UW graduate student Joachim Moeyens and his doctoral advisor, astronomy professor Mario Juric. They and colleagues at the University’s Data-Intensive Institute for Astrophysics and Cosmology have developed an algorithm that is able to examine astronomical images not only to identify those blips that might be asteroids, but also to find out which spots in the captured images Nights with different points of light are actually the same asteroid.
Essentially, researchers have developed a way to discover what has been seen but not noticed.
Typically, asteroids are discovered when the same part of the sky is photographed multiple times in a single night. A night sky contains many points of light. Distant stars and galaxies remain in the same alignment. But objects that are closer within the solar system move quickly, and their positions change during the night.
Astronomers refer to a series of observations of a single moving object overnight as a “trajectory.” The small trail provides an indication of the object’s motion, pointing astronomers to where they might be looking for it another night. They can also search for the same objects in old images.
Many astronomical observations that are not part of the systematic asteroid search inevitably record asteroids, but only at one time and place, rather than the multiple observations required to combine trajectories.
For example, NOIRLab images were captured primarily by the Victor M. Blanco 4-meter telescope in Chile as part of a survey of nearly one-eighth of the night sky to map the distribution of galaxies in the universe.
The extra points of light were ignored because they weren’t what astronomers were studying. “They’re just random data in a random image of the sky,” Dr Lu said.
But for Mr Moeyens and Dr Juric, a point of light that is not a star or galaxy is the starting point for their algorithm, which they have named Trajectoryless Heliocentric Orbit Recovery, or THOR.
The motion of asteroids is determined by the law of universal gravitation. Assuming a certain distance and speed, THOR builds a test track corresponding to the observed blip. It then calculates the position of the asteroid on the following and previous nights. If a blip appears in the data, it’s probably the same asteroid. If the algorithm can tie together five or six observations in a matter of weeks, that would be a promising candidate for asteroid discovery.
In principle, there are an infinite number of possible test tracks to examine, but this would take an unrealistic eternity to calculate. In practice, since asteroids cluster around certain orbits, the algorithm only needs to consider a few thousand carefully chosen possibilities.
Still, computing thousands of test orbits for thousands of potential asteroids is a daunting number-crunching task. But the advent of cloud computing—giant computing power and data storage distributed across the Internet—made this possible. Google contributes time to this work on its Google Cloud Platform.
“It’s one of the coolest apps I’ve ever seen,” said Scott Penberthy, Google’s director of applied artificial intelligence.
So far, scientists have sifted through one-eighth of the September 2013 single-month data from NOIRLab archives. THOR produced 1,354 possible asteroids. Many of these are already in the catalog of asteroids maintained by the International Astronomical Union Minor Planet Center. Some of these had been observed before, but only on one night, and the trajectory wasn’t enough to determine the orbit with confidence.
To date, the Minor Planet Center has confirmed 104 new objects. The NOIRLab archive contains seven years of data showing that there are tens of thousands of asteroids waiting to be discovered.
“I think it’s great,said Matthew Payne, director of the Minor Planet Center, who was not involved in developing THOR. “I think it’s very interesting, and it also allows us to take advantage of the archival data that already exists.”. “
The algorithm is currently configured to only look for main-belt asteroids, those orbiting between Mars and Jupiter, and not near-Earth asteroids, those that could collide with our planet. Identifying near-Earth asteroids is more difficult because they move faster. Different observations of the same asteroid can be farther apart in time and distance, and algorithms need to perform more number crunching to make connections.
“It’s definitely going to work,” Mr Moeyens said. “There’s no reason it couldn’t. I really didn’t get a chance to try it.”
THOR not only has the ability to find new asteroids in old data, but it can also transform future observations. Take the Vera C. Rubin Observatory, currently under construction in Chile, formerly the Large Synoptic Observatory.
The Rubin Observatory, funded by the National Science Foundation, is an 8.4-meter telescope that will repeatedly scan the night sky to track changes over time.
Part of the observatory’s mission is to study the large-scale structure of the universe and discover distant exploding stars, also known as supernovae. Closer to home, it will also find many objects smaller than planets whizzing around the solar system.
A few years ago, some scientists suggested that the Rubin telescope’s observation mode could be adjusted so that it could identify more asteroid trajectories and thus locate more dangerous, yet-to-be-discovered asteroids more quickly. But the change would slow other astronomical research.
If the THOR algorithm proves to work well with Rubin data, instead of scanning the same part of the sky twice a night, the telescope could cover twice the area.
“This could be revolutionary in principle, or at least very important,” said Zeljko Ivezic, head of the telescope and author of a scientific paper describing THOR and testing it based on observations.
If the telescope could return to the same spot in the sky every two nights instead of every four, it would benefit other research, including the search for supernovae.
“This will be another effect of the algorithm, which is not even relevant for asteroids,” Dr Ivezic said. “It’s a great demonstration of how the landscape is changing. The ecosystem of science is changing because software can now do things that you wouldn’t even dream of or even imagine 20, 30 years ago. “
For Dr. Lu, THOR offers a different way to achieve the same goals he had a decade ago.
At the time, the B612 set its sights on an ambitious and more expensive project. The nonprofit will build, launch and operate its own space telescope called Sentinel.
At the time, Dr Lu and the other leaders of B612 were frustrated by the slow pace of the hunt for dangerous space rocks. In 2005, Congress passed a mandate requiring NASA to locate and track 90 percent of near-Earth asteroids 460 feet or larger in diameter by 2020. But lawmakers never gave NASA the funding it needed to complete the mission, and less than half of the asteroids were discovered before the deadline.
Raising $450 million from private donors to fund Sentinel will be difficult for B612, especially since NASA is considering using its own space telescope for asteroid detection.
When the National Science Foundation approved the construction of the Rubin Observatory, B612 re-evaluated its plans. “We can quickly pivot and say, ‘What different approaches are there to the problem we’re trying to solve?'” Dr. Lu said.
The Rubin Observatory will make its first test observations in about a year and be operational in about two years. Dr. Ivezic said a decade of Rubin observations, along with other asteroid searches, could eventually reach 90 percent of Congress’s goals.
NASA is also accelerating its planetary defense efforts. Its asteroid telescope, called the NEO Surveyor, is in the preliminary design stages and is targeted for launch in 2026.
Later this year, its Double Asteroid Redirection Test mission will slam a projectile into an asteroid and measure how much the pair’s trajectory has changed. The China National Space Administration is working on a similar mission.
For B612, instead of competing for a nearly $5 billion telescope project, it could contribute to lower-cost research efforts like THOR. Last week, it announced that it had received a $1.3 million gift to fund further research into cloud-based computing tools for asteroid science. The foundation has also received a grant from Tito’s Handmade Vodka, which will be matched with $1 million from other donors.
B612 and Dr. Lu are now not just about saving the world. “We answered the trivial question of the relationship between vodka and asteroids,” he said.