Astronomers in Hawaiʻi work every night to protect Earth from asteroids big and small
October 2, 2022, 6:30 AM HST
* Updated October 2, 7:01 AM
On Monday, the world watched as a spacecraft called Dart going almost 14,000 mph crashed with pinpoint accuracy into an asteroid a little bigger than the Rome Colosseum after traveling seven million miles from Earth.
NASA’s $325 million test is part of its work on a planetary defense system to save Earth from asteroid strikes like Chicxulub, which landed about 66 million years ago off the coast of today’s Yucatan, Mexico and led to the extinction of dinosaurs.
Unlike Hollywood’s version of saving the planet, with Bruce Willis and his crew blowing up an asteroid in the movie Armageddon, scientists simply wanted the impact of the vending machine-sized spacecraft to nudge the asteroid named Dimorphos into a slightly tighter orbit around a larger asteroid named Didymos.
NASA said there is no danger of either asteroid hitting Earth. But in the event there is a dangerous asteroid headed for our planet, a nudge could be all that is needed to divert the space rock off of its trajectory enough to avoid a collision.
Now astronomers all around the world are studying data and photos from many telescopes to determine the success of the Double Asteroid Redirection Test dubbed DART. They include University of Hawaiʻi astronomers and two sophomores from Maui High School, Wilson Chau and Holden Suzuki.
In the state, astronomers are using images and data from the Maui-based Faulkes North telescope on Haleakalā and the Big Island-based UH88 telescope on Maunakea. The Hawaiʻi observatories are part of the global Las Cumbres telescope network.
On Thursday, at the UH Institute for Astronomy’s building in Pukalani on Maui, Chau and Suzuki were analyzing images and data taken of Monday’s collision and from the previous night as part of the university’s HI-STAR astronomy research program for students and teachers.
Suzuki said they were analyzing the eclipse of when the larger Didymos goes if front of Dimorphos to see how much the light has been affected from the baseline recorded before the collision.
They are looking for the difference in the light curve, which is basically brightness versus time.
“If we can say it looks different than before, then we can say this is how much it got knocked off track,” Suzuki said. “And, if a partial eclipse became no eclipse at all we can say, ‘Oh my gosh, we really did something pretty massive to this’.
“We’re not sure how much it has changed course. That’s why we’re working on this.”
Before the collision, Dimorphos (about 520 feet across and 11 billion pounds) completed a lap around the much bigger Didymos (about 2,560 feet across and 116 billion pounds) every 11 hours and 55 minutes.
Scientists predicted that Dart, while weighing only 1,260 pounds, collided at such great speed into Dimorphous that it would push it slightly closer to Didymos, changing the speed by a fraction of one percent.
But NASA believes that is enough to alter the moonlet’s orbital period by about 10 minutes, which can be observed and measured by telescopes on Earth.
At that small percentage of change, a nudge would be required to be done years in advance to change the course enough to miss Earth. The time to travel millions of miles also must be part of the equation. It took Dart 10 months to reach the asteroid.
“And, it may require multiple impacts to deposit enough energy, depending on the size of the asteroid, to deflect it sufficiently,” said Doug Simon, director of the UH Institute for Astronomy. “To me, it’s just satisfying to see the technology convincingly demonstrate it. And we have the assets on the ground now to essentially identify all the asteroids of real concern probably within the next decade or so. It’s coming together.”
J.D. Armstrong, program director for HI STAR, said one of his former students, Luke Berrigan, who now attends Utah State University, was analyzing data sent to him and found that Dimorphos now appears to have a tail, like a comet.
“It looks a lot like the asteroid Gault,” said Orion Teagarden, a junior at Hawaiʻi Tech Academy in Kīhei. “I think in 2019 we saw it had a really big tail. It was pretty much my project to figure out what it was.”
Teagarden said his conclusion was the asteroid was spinning so fast that gravity couldn’t hold it together anymore and a piece of ice that was inside it got exposed.
“That could be the same reason there is a tail showing up on the asteroid that just got hit,” he said.
Armstrong explained that ice formed on the asteroid billions of years ago. Anytime an exposed block of ice gets closer to the sun than roughly the radius of Jupiter, it heats up enough to evaporate or sublime, which means going directly from a solid to a gas. Dimorphos is close enough to the sun to have exposed ice sublime.
“Our current hypothesis is the spacecraft’s collision exposed some of the ice,” Armstrong said. “That ice is subliming and driving dust off to form a tail.”
In the same building, Dr. Joanna Bulger from the United Kingdom, is looking for new asteroids using the University of Hawaiʻi’s two Pan-STARRS telescopes located on the summit of Haleakalā. Pan-STARRS stands for Panoramic Survey Telescope and Rapid Response System.
Already the team of four observers, who remotely operate both telescopes to sweep the sky nightly for new asteroids, has detected nearly 1,000 Near-Earth Objects candidates in 2022.
It’s the most of any program in the world this year, Armstrong said.
“Congress passed a mandate to try and find any asteroid bigger than 140 meters in size,” Bulger said. “That’s what we are looking for. These are the ones big enough to come through the atmosphere and cause relatively large amounts of devastation.”
There are the large-sized “dinosaur killers,” the one 66 million years ago that struck Mexico was about 6.2 miles in diameter.
“They are the ones that can wipe out the world or civilization for us,” she said. “But the smaller ones are still interesting.”
The NASA-funded ATLAS (Asteroid Terrestrial-Impact Last Alert System) program operated by UH’s Institute for Astronomy is looking for smaller asteroids. The program began with ATLAS telescopes on Haleakalā and Mauna Loa; and this year it has added two telescopes in the Southern Hemisphere, in Chile and South Africa, to enable complete coverage of the night sky.
“ATLAS is designed to detect in the last 24 to 48 hours objects that slip through the other deeper survey telescopes,” Simon said. “These happen every couple of years or so. They may be only a few meters across. So far the system has been demonstrated to work.”
Simon said there have been about four or five over the past five years. With the network of telescopes it is now possible to project where they are going to hit with “surprising accuracy.”
ATLAS will provide one day’s warning for a 30-kiloton “town killer,” a week for a 5-megaton “city killer” and three weeks for a 100-megaton “county killer,” according to the institute’s website.
“If we ever had an asteroid headed for a major populated area, I believe with quite a bit of confidence we could predict when and where it was going to strike,” Simon said. “It’s not a lot of time, 24 to 48 hours. But it’s better than nothing. Right. You can’t do anything about it in that amount of time. But the idea is like a hurricane, you clear everybody out before it actually strikes.”
Armstong said the Pan-STARRS observers are jokingly called the “Guardians of the Earth.” While Bulger said that Armstrong, who is nurturing the next generation of astronomers, is called “The Recruiter” for the guardians.
Armstrong’s students know they are lucky to live in Hawai’i, where the conditions are among the best in the world for viewing the sky and there are a variety of telescopes. They also say they are fortunate to be part of such an important project for the planet as DART.
“It’s a big leap for astronomy,” Chau said. “I’m excited to hop on for the ride.”