Two weeks ago, the asteroid Dimorphos was quietly circling around its partner Didymos, when NASA's DART spaceship swooped in to destroy it.
Should humankind ever need to defend the planet from an oncoming space rock, the space agency and its partners planned that collision to see if it could alter an asteroid or comet's trajectory. One lap every 11 hours and 55 minutes was how long Dimorphos circled its neighbor before it crashed. The proof would be a change in the asteroid's trajectory if the DART test was a success.
Even better than expected, it worked for the DART team. The team would have considered a 10-minute difference a success, said NASA chief Bill Nelson. The asteroid was shortened by 32 minutes. He said that Dimorphos can now circle its partner in about 11 hours and 23 minutes. He said that NASA is serious about protecting the planet.
The DART collision was observed by many scientists. The oncoming space rock was first glimpsed by the probe with its onboard optical camera. Astronomers didn't know if Dimorphos was a solid sphere or a loose dustball until they looked at it for the first time.
The camera was destroyed on impact. The Italian Space Agency's LICIACube, which detached from DART 15 days before the crash, was following them.
The Southern Astrophysical Research Telescope in Chile was one of the telescopes used to observe the collision. The telescopes captured what looked like a comet-like tail extending from the asteroid.
The DART team carefully tracked how the light from the asteroid changed over the course of a year. When Dimorphos eclipses Didymos or passes behind it, the asteroid pair's brightness goes down by about 10 percent. Measuring how exoplanets transit in front of distant stars is the same thing.
The more time we have, the better off we are. When a small change in trajectory can lead to a big change in the asteroid's trajectory, NASA would like to have it bumped. It may be difficult for asteroids that are hard to see to be found.