Didymos, Brace for Impact!

Liz Phillips
Las Cumbres Observatory


The binary asteroid system of Didymos and Dimorphos lies in the center of this telescope photo. In 2022, NASA's Double Asteroid Redirection Test (DART) spacecraft intentionally crashed into Dimorphos to test how much momentum could be transferred to it. This image was taken prior to DART's impact. 

The Double Asteroid Redirection Test (DART) is a planetary defense mission led by NASA and Johns Hopkins APL to test how effective our current technology is at redirecting asteroids that may pose a threat to Earth. This was done by intentionally crashing a spacecraft into an asteroid! The binary asteroid system of Didymos and Dimorphos was selected as the target for this test, pictured front and center in this astronomical image. While Dimorphos is too small to see from Earth, we can measure how fast it orbits using the varying brightness of Didymos, the larger asteroid. By measuring this period before and after the impact, we can get a good idea of how much momentum was transferred.

This image is one of many that I captured in the months before the impact in 2022, in order to get a "before" measurement. The background contains lots of stars and galaxies that actually get in the way of a good brightness measurement, so I had to remove them for data-taking. But I kept the original images, to remind me of just how small we are in this universe! One day, Earth will have to defend against a real asteroid threat, and the data from the DART mission will help pave the way to better defenses.