Astronomers still have their eyes on that asteroid NASA whacked
NASAのハッブル宇宙望遠鏡からのこの画像は、NASAのダーツ宇宙船が小惑星の表面に砕けた285時間後に二型の表面から爆破された破片を示しています。(English) This image from NASA's Hubble Space Telescope shows the debris blasted from the surface of Dimorphos 285 hours after NASA's DART spacecraft smashed into the asteroid's surface.
Astronomers still have their eyes on that asteroid NASA whacked
//Summary - Level-B2//
NASA's Double Asteroid Redirection Test (DART) mission sent a spacecraft crashing into an asteroid called Dimorphos in September, resulting in the first-ever test of whether an asteroid could be deliberately pushed off-course. Scientists have hailed it as a huge success and a powerful demonstration that an asteroid's trajectory can be altered. Moreover, the experiment has boosted scientists' confidence that this deflection technique could protect the planet if Earth ever got menaced by a dangerous incoming space rock.
//Summary - Level-C1//
NASA's Double Asteroid Redirection Test (DART) mission, which involved sending a spacecraft crashing into an asteroid, has been an enormous success. The collision altered the asteroid's path through space, and scientists say it has boosted their confidence in the effectiveness of deflection techniques to protect the Earth from incoming space rocks. The experiment also shows that impacts can generate a tail on an asteroid. While no large space rocks are currently known to threaten Earth, astronomers say it's good to be prepared.
//Summary - Level-C2//
NASA's Double Asteroid Redirection Test (DART) mission successfully hit Dimorphos, altering its path through space, in a first-ever test of asteroid deflection. The experiment boosted scientists' confidence that this deflection technique could protect the planet if a dangerous incoming space rock ever threatened Earth. However, the collision kicked up considerable dust and rocky debris, creating a comet-like tail, and telescopes continued to observe it. The European Space Agency will send out a mission next year to reveal the size of any crater left behind and determine the asteroid's mass.
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Astronomers are still watching that asteroid that NASA whacked with a spacecraft in September in the first-ever test of whether an asteroid could be deliberately pushed off-course.
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Almost immediately after NASA's Double Asteroid Redirection Test (DART) mission sent a golf cart-sized spacecraft crashing into an asteroid called Dimorphos, scientists hailed it as a huge success – and a powerful demonstration that an asteroid's trajectory can be altered.
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"We know this process is very effective – even more effective than many people had originally expected," says Andy Cheng with the Johns Hopkins University Applied Physics Laboratory.
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The experiment has boosted scientists' confidence, he says, that this kind of deflection technique could work to protect the planet if Earth ever got menaced by a dangerous incoming space rock.
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The collision altered the path of Dimorphos through space, shortening the time it takes to orbit another giant asteroid by 33 minutes, according to a new analysis in the journal Nature. The journal published a study detailing the results this week, alongside four additional scientific reports on this unprecedented asteroid deflection experiment.
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Dimorphos is millions of miles away and about the size of the Great Pyramid of Giza in Egypt. Astronomers got their first good look at it in the mission's final moments, as the DART spacecraft drew ever closer, sending back images of a grey, egg-shaped asteroid strewn with rubble.
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Once the spacecraft hit the surface, it was obliterated, and its stream of pictures stopped. But telescopes watching the pair of asteroids saw that the impact kicked up a considerable amount of dust and rocky debris, brightening the scene.
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"It's just a bright cloud. A lot of dust came off. And we were just amazed. We knew right then we could do some good science with this," says Ariel Graykowski with the SETI Institute.
All the material ejected out of the asteroid by the impact gave the asteroid an extra kick, says Cheng, in the same way, that shooting a bullet out of a gun makes the gun kick back.
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"That's the recoil force, an extra force that's pushing against the asteroid," says Cheng, adding that this extra force was a lot bigger than the push the spacecraft delivered by hitting the asteroid embedding itself inside.
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The orbiting Hubble Space Telescope was on the wrong side of Earth when the collision happened so it couldn't watch the event, but it gazed at the asteroid soon after and watched the debris cloud change over time.
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He says it looked remarkably like tails occasionally seen on other asteroids. However, it had never been clear what created those so-called 'active' asteroids, although some astronomers suspected impacts played a role.
"DART is the first experiment that demonstrated that impact can generate a tail," he says.
Telescopes can still detect the tail streaming off of Dimorphos. "We are still observing," says Cristina Thomas with Northern Arizona University, who says observations should wrap up this month.
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Next year, the European Space Agency will send out a mission called Hera that should take close-up images of the asteroid, revealing the size of any crater left behind. It should also be able to determine the asteroid's mass. All of this should help astronomers understand how to push asteroids around.
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While astronomers say no large space rocks are currently known to threaten Earth, many small-but-still-dangerous asteroids have not yet been tracked, and planetary defenders say it's good to be prepared, just in case.
"We've shown now that we have a method to move an asteroid," says Graykowski. "Seeing that it worked so well makes me feel much better."
Astronomers still have their eyes on that asteroid NASA whacked
Time-Lapse Video of Didymos-Dimorphos System
https://www.youtube.com/watch?v=SYvxLedAcoE
This movie captured the breakup of the asteroid Dimorphos when it was deliberately hit by NASA's 1,200-pound Double Asteroid Redirection Test (DART) mission spacecraft on September 26, 2022. The Hubble Space Telescope had a ringside view of the space demolition derby.
The Hubble movie starts 1.3 hours before impact. The first post-impact snapshot is 2 hours after the event. Debris flies away from the asteroid in straight lines, moving faster than four miles per hour (fast enough to escape its gravitation pull so it does not fall back onto it). The ejecta forms an essentially hollow cone with long, stringy filaments.
About 17 hours after the impact, the debris pattern entered a second stage. The dynamic interaction within the binary system started to distort the cone shape of the ejecta pattern. The most prominent structures are rotating, pinwheel-shaped features. The pinwheel is tied to the gravitational pull of the companion asteroid, Didymos.
Hubble next captures the debris being swept back into a comet-like tail by the pressure of sunlight on the tiny dust particles. This stretches into a debris train, where the lightest particles travel the fastest and farthest from the asteroid. The mystery is compounded later when Hubble records the tail splitting in two for a few days.