A spacecraft zooming quietly through the solar system has caught its first glimpses of the asteroids it was sent to study ffrom a distance of hundreds of thousands of kilometers.
Launched in October 2021NASA’s Lucy probe is leading the first-ever mission to study the asteroids that accompany it Jupiter. Of the 11 objects it is scheduled to visit, the probe has already imaged four, giving us time-lapses of the asteroids Eurybates, Polymele, Leucus and Orus.
The Trojan asteroids are a group of space rocks that share Jupiter’s orbit. They are divided into two populations that precede and follow the giant planet on its journey around the sun.
Asteroids tend to cluster at these two positions in Jupiter’s orbit in what are known as Lagrange points. These are pockets of gravitational stability created by an interaction between two bodies in an orbital system. In these pockets, the gravitational pulls of the two bodies—in this case, Jupiter and the Sun—balance perfectly with an object’s centripetal force within the Lagrangian to hold it in place.
Every two-body system has five Lagrangians; The two where the trojans gather are L4 and L5. Although the asteroids are all collectively known as Trojans, the group that resides in L4 is classified as Greeks, while the L5 asteroids are Trojans. You can see them moving with Jupiter in the animation below.
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There are thousands of asteroids in the Trojan swarms, and they are believed to be composed of pristine material from which the planets formed in the early days of the solar system. Lucy’s mission is to fly past nine of them and examine them closely, from both the Greek and Trojan camps, as well as two asteroids in the main belt, located between Jupiter and Marsduring his 12-year mission.
Human evolution fans may recall that the name Lucy also belongs to a certain Fossil of a ancestral species called Australopithecus afarensis. Just like the hominid Lucy taught us about the origins of homo sapiensscientists hope the Lucy mission will tell us more about the formation of the solar system.
Eurybates, Polymele, Leucus and Orus all belong to the Greek swarm, and Lucy will visit them in 2027 and 2028 and send the data back to Earth. When these images were taken between March 25 and 27, the spacecraft was over 530 million kilometers (330 million miles) from some of its satellites asteroid Goals. That’s more than three times the distance between the earth and the sun.
Each objective was viewed over a specific time period: 6.5 hours for Eurybates, 2.5 hours for Polymele, 2 hours for Leucus, and 10 hours for Orus. The resulting data will be combined with ongoing observations as Lucy approaches to study how these objects reflect sunlight in ways we can’t see from here on Earth.
Lucy’s first asteroid encounter is to be held in November of this year when passing the main belt asteroid Dinkinesh (the Ethiopian name for Lucy) before flying back to Earth for a gravity-assist maneuver that will give it a boost back toward Jupiter’s orbit.
It will fly past another main belt asteroid, Donaldjohanson (named after the Paleoanthropologist who discovered Lucy), in April 2025 on the way to the Greeks, before finally having his historical encounter with Eurybates in August 2027.
