Killer asteroids lurk in plain sight. A new tool helps spot them.

Ed Lu wants to save the Earth from killer asteroids.

Or at least if there’s a big space rock heading our way, Dr. Lu, a former NASA astronaut with a PhD in applied physics, wants to find it before it hits us – hopefully. do it with years of forewarning and a chance for humanity to deflect it.

On Tuesday, the B612 Foundation, a nonprofit group 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 main character’s native asteroid.)

That in itself is not remarkable. New asteroids are reported all the time by skywatchers around the world. That includes amateurs with backyard telescopes and robotic surveys routinely scanning the night sky.

What is remarkable is that B612 did not build a new telescope or even make new observations with existing telescopes. Instead, B612-funded researchers applied cutting-edge computing power to years-old images — 412,000 of them in the digital archive of the National Optical-Infrared Astronomy Research Laboratory, or NOIRLab — to filter the asteroids of the 68 billion points of cosmic light captured in the images.

“It’s the modern way of doing astronomy“, said Dr. Lu.

The research is in addition to “planetary defense” efforts undertaken by NASA and other organizations around the world.

Today, of the approximately 25,000 near-Earth asteroids at least 460 feet in diameter, only 40% of them have been discovered. The remaining 60% – around 15,000 space rocks, each with the potential to release the energy equivalent to hundreds of millions of tons of TNT when colliding with Earth – remain undetected.

B612 collaborated with Joachim Moeyens, graduate student at the University of Washington, and his thesis supervisor, Mario Juric, professor of astronomy. They and their colleagues at the university’s Institute for Data Intensive Research in Astrophysics and Cosmology have developed an algorithm that can examine astronomical imagery not only to identify points of light that might be asteroids, but also to determine which points of light in images taken on different nights are actually the same asteroid.

Essentially, researchers have developed a way to find out what has already been seen but not noticed.

Typically, asteroids are discovered when the same part of the sky is photographed multiple times over the course of a night. A strip of the night sky contains a multitude of bright spots. Stars and distant galaxies remain in the same arrangement. But the objects that are much closer, in the solar system, move quickly and their positions change during the night.

Astronomers call a series of sightings of a single moving object over a single night a “tracklet.” A tracklet provides an indication of the object’s movement, telling astronomers where they might look for it 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, not the multiple observations needed to assemble tracklets.

Images from NOIRLab, for example, were taken 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. “It’s just random data in random images of the sky,” Dr Lu said.

But for Mr. Moeyens and Dr. Juric, a single point of light that isn’t a star or galaxy is a starting point for their algorithm, which they named Tracklet-less Heliocentric Orbit Recovery, or THOR.

The movement of an asteroid is precisely dictated by the law of gravity. THOR builds a test orbit that matches the observed light spot, assuming a certain distance and speed. It then calculates where the asteroid would be on subsequent and previous nights. If a bright spot appears in the data, it could be the same asteroid. If the algorithm can link five or six observations over a few weeks, it’s a promising candidate for an asteroid discovery.

In principle, there are an infinite number of possible test orbits to examine, but that would take an impractical eternity to calculate. In practice, because asteroids are clustered around certain orbits, the algorithm only needs to consider a few thousand carefully chosen possibilities.

Yet calculating thousands of test orbits for thousands of potential asteroids is a daunting task. But the advent of cloud computing – vast computing power and distributed data storage over the Internet – makes this possible. Google has dedicated time on its Google Cloud Platform to the effort.

“It’s one of the coolest apps I’ve seen,” said Scott Penberthy, director of applied artificial intelligence at Google.

So far, scientists have sifted through about an eighth of the data from just one month, September 2013, in NOIRLab’s archives. THOR produced 1,354 possible asteroids. Many of them were already listed in the catalog of asteroids maintained by the Center for Minor Planets of the International Astronomical Union. Some of them had already been observed, but only during one night and the tracklet was not sufficient to determine an orbit with certainty.

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 tens of thousands of asteroids waiting to be discovered.

“I think it’s great,“, said Matthew Payne, director of the Minor Planet Center, which was not involved in the development of THOR. “I think it’s extremely 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 whose orbits are 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 sightings of the same asteroid can be separated further in time and distance, and the algorithm must perform more numerical calculations to make the connections.

“It will definitely work,” Mr. Moeyens said. “There’s no reason why it shouldn’t. I really haven’t had a chance to try it.

THOR not only has the ability to discover new asteroids in old data, but it could also transform future observations. Take, for example, the Vera C. Rubin Observatory, formerly known as the Large Synoptic Survey Telescope, currently under construction in Chile.

Funded 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 supernovae. Closer to home, it will also spot a host of smaller-than-planet bodies orbiting 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 thereby locate more dangerous yet undiscovered asteroids more quickly. . But this change would have slowed down further astronomical research.

If the THOR algorithm proves to work well with the Rubin data, the telescope won’t need to scan the same part of the sky twice a night, allowing it to cover twice as much area.

“It could in principle be revolutionary, or at least very important,” said Zeljko Ivezic, director of the telescope and author of a scientific paper describing THOR and testing it against observations.

If the telescope could return to the same spot in the sky every two nights instead of every four, it could benefit other research, including the search for supernovae.

“That would be another algorithm impact that doesn’t even have to do with asteroids,” Dr. Ivezic said. “It shows how the landscape is changing. The ecosystem of science is changing because software can now do things that you wouldn’t even think of 20, 30 years ago, that you wouldn’t even think of.”

For Dr. Lu, THOR offers a different way to achieve the same goals as ten years ago.

At the time, B612 had an ambitious and much more expensive project in mind. The non-profit organization would build, launch, and operate its own space telescope called the Sentinel.

At the time, Dr. Lu and the other leaders of B612 were frustrated with the slow search for dangerous space rocks. In 2005, Congress gave NASA a mandate to locate and track 90 percent of near-Earth asteroids 460 feet in diameter or larger by 2020. But lawmakers never provided the money NASA needed. needed to complete the task, and the deadline has passed with less than half of those asteroids found.

Raising $450 million from private donors to guarantee Sentinel was difficult for B612, especially because NASA was considering its own asteroid-searching space telescope.

When the National Science Foundation gave the go-ahead for construction of the Rubin Observatory, B612 re-evaluated its plans. “We could quickly pivot and say, ‘What’s a different approach to solving the problem we’re here to solve?'” Dr Lu said.

The Rubin Observatory should make its first test observations in about a year and become operational in about two years. Ten years of Rubin’s observations, plus other asteroid searches could finally meet Congress’ 90% goal, Dr. Ivezic said.

NASA is also ramping up its planetary defense efforts. Its asteroid telescope, named NEO Surveyor, is in preliminary design, aiming for launch in 2026.

And later this year, its Double Asteroid Redirection Test mission will launch a projectile at a small asteroid and measure how much it changes the asteroid’s trajectory. China’s national space agency is working on a similar mission.

For B612, instead of fighting over a telescope project costing nearly half a billion dollars, it can contribute to less expensive research efforts like THOR. Last week, it announced it had received $1.3 million in donations to fund new 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 aren’t just trying to save the world anymore. “We are the answer to a trivial question about the link between vodka and asteroids.” he said.

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