Astronomers still have their eyes on NASA’s whacked asteroids

This image from NASA’s Hubble Space Telescope shows debris from the surface of Dimorphos 285 hours after NASA’s DART spacecraft blasted off the asteroid’s surface.

NASA/ESA/STScI/Hubble

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NASA/ESA/STScI/Hubble

This image from NASA’s Hubble Space Telescope shows debris from the surface of Dimorphos 285 hours after NASA’s DART spacecraft blasted off the asteroid’s surface.

NASA/ESA/STScI/Hubble

Astronomers are still watching the asteroid that NASA’s spacecraft shot down in September, in the first-ever test of whether asteroids could be pushed back on a deliberate course.

Almost immediately after NASA’s Double Asteroid Redirection Test (DART) mission sent a medium-sized spacecraft crashing into an asteroid named Dimorphos, scientists hailed it as a huge success — and a powerful demonstration that an asteroid’s trajectory can be changed.

“We know that this process is really efficient – even more efficient than a lot of people previously expected,” says Andy Cheng with the Johns Hopkins University Physics Laboratory.

The experiment boosted the scientists’ confidence, he says, that this type of deflection technology could really work to protect the planet if Earth were ever threatened by a dangerous incoming space rock.

The collision changed Dimorphos’ path through space, shortening the time it orbited another, larger asteroid by 33 minutes, according to a new analysis in the journal. nature. The Journal published a study explaining the results this week, along with four additional scientific reports on this unprecedented asteroid deflection experiment.

It is a million miles long and about the size of the Great Pyramid of Giza in Egypt. Astronomers are getting their first good look in the final moments of the mission, as the space jet gets closer and closer, sending back images of a gray, egg-shaped layer of asteroid debris.

After they hit the surface of space, it was obliterated, and the stream of images was stopped. But telescopes looking at the pair of asteroids saw a huge impact kick of dust and rock debris to light up the scene.

“It’s just a bright cloud. A lot of dust left. And we were just amazed. Then we knew we were doing good science with this,” says Ariel Graykowski with the SETI Institute, who works with the global network. telescope fanatic.

All the material ejected from the asteroid by the impact gave the asteroid an extra kick, says Cheng, in the same way that a bullet fired from a gun causes the gun to kick back.

“That is the force of exile, the extra force that pushes against the asteroid,” says Cheng, adding that this extra force is much greater than the impact that the space asteroid delivered by hitting and restraining itself inside.

The orbiting Hubble Space Telescope happened to be on the wrong side of Earth when the collision occurred, so it couldn’t watch the event, but it looked just after the asteroid and watched the debris cloud change over time.

“That’s something really exciting to see,” says Jian-Yang Li, with the Institute of Planetary Science, who says eventually, the tail formed like a comet and got longer and longer.

It looked remarkably like the tails that are sometimes seen on other asteroids, he says. It is never clear what created the so-called “active” asteroids, although some astronomers suspect impacts played a role.

“It’s believed to be the first experiment that actually demonstrates that a stroke can actually generate a tail,” he says.

The tail of Dimorphos can still be detected by telescopes. “We’re still observing,” says Cristina Thomas with Northern Arizona University, who should wrap up observations this month.

Next year, the European Space Agency will launch a mission called Hera that should take close-up pictures of asteroids, showing the size of any craters left behind. It will also be able to determine the mass of the asteroid. All of this should help astronomers understand more about asteroids.

While astronomers say no large space rocks are currently known to threaten Earth, many small but still dangerous asteroids have yet to be explored, and planetary defenders say it’s good to be prepared, just in case.

“We’ve now shown that we have a way to move an asteroid,” says Graykowski. “It makes me a lot better to see that it worked, and it worked well.”