“We never suspected anything so strange!”

NASA’s Lucy’s surprising observation of the first asteroid ever orbiting a connected binary

It turns out there’s more to the “magnificent” Dinkenish asteroid and its newly discovered satellite than meets the eye. like NASADinkinesh’s Lucy spacecraft continued to return data of the first asteroid encounter on November 1, 2023, and the team was surprised to discover that Dinkinesh’s unexpected satellite is itself a contact binary — that is, it is made of two smaller objects touching each other. .

Initial notes and surprises

In the first downlink images of Dinkinesh and its satellite, taken from the closest point, the binary’s communication lobes happen to be located one behind the other from Lucy’s point of view. It was only when the team linked additional images, taken in the minutes following the encounter, that the true nature of the object was revealed.

A diagram showing the path of NASA’s Lucy spacecraft (red) as it flies by the Dinkenish asteroid and its satellite (gray). The letter “A” indicates the spacecraft’s position at 12:55 PM EDT (1655 UTC) on November 1, 2023, and the inset shows the L’LORRI image taken at that time. The letter “B” indicates the spacecraft’s position a few minutes later at 1 p.m. EDT (1700 UTC), and the inset shows the corresponding L’LORRI view at that time. Source: Panoramic drawing, NASA/Goddard/SwRI; Attached image “A” NASA/Goddard/SwRI/Johns Hopkins APL/NOIRLab; Attached image “B”, NASA/Goddard/SwRI/Johns Hopkins APL

“Connecting binaries appear to be fairly common in the solar system,” said Lucy deputy project scientist John Spencer, of the Boulder, Colorado, branch of the San Antonio-based Southwest Research Institute. “We haven’t seen many of them up close, and we’ve never seen one orbiting another asteroid. We were puzzled by the strange variations in Dinkenish’s brightness that we saw on approach, which gave us a hint that Dinkenish might have a moon of some sort, but we didn’t We never suspect anything too strange!

Mission objectives and unexpected outcomes

Lucy’s primary goal is to survey Jupiter-Trojan asteroids that have never been visited before. This first encounter with a small asteroid in the main belt was added to the mission only in 2013 January 2023, primarily to serve as an in-flight test of the system that allows the spacecraft to continuously track and image asteroid targets as they fly by at high speed. The excellent performance of this system at Dinkinesh allowed the team to capture multiple views of the system, enabling the team to better understand the shapes of asteroids and make this unexpected discovery.

NASA’s Lucy mission, which launched on October 16, 2021, is the first to survey the Trojans, a group of primitive asteroids that orbit alongside Jupiter. In this artist’s concept (not analogy), the Lucy spacecraft flies close to Eurybates, one of six diverse and scientifically important Trojans that will be studied. Credit: Southwest Research Institute

“It’s puzzling, to say the least,” said Hal Levison, Lucy’s principal investigator, also of the Southwest Research Institute. “I never expected a system to look like this. In particular, I don’t understand why the two components of the satellite are so similar in size. It would be interesting for the scientific community to discover.”

This second image was taken about 6 minutes after closest approach from a distance of about 1,010 mi (1,630 km). The spacecraft traveled about 960 miles (1,500 km) between the two images released.

Continue the journey through space

“It’s really wonderful that nature can surprise us with a new mystery,” said Tom Statler, Lucy program scientist from NASA Headquarters in Washington. “Great science pushes us to ask questions we didn’t know we needed to ask.”

The team continues the downlink process and processes the rest of the encounter data from the spacecraft. Dinkinesh and its satellite are the first two of 11 asteroids that Lucy plans to explore during her 12-year journey. After scraping the inner edge of the main asteroid belt, Lucy will now head towards Earth for gravitational assistance in December 2024. This close flyby will push the spacecraft back through the main asteroid belt, where it will observe asteroid Donald Johansson in 2025. Then to the Trojans in 2027.

NASA’s Lucy mission

Principal Investigator Lucy is based in Boulder, Colorado, and the Southwest Research Institute (SwRI) affiliate is based in San Antonio. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides comprehensive mission management, systems engineering, safety, and mission assurance. Lockheed Martin Space in Littleton, Colorado, built and operates the spacecraft. Lucy is the thirteenth mission in NASA’s exploration program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Discovery Program for the Science Mission Directorate at NASA Headquarters in Washington.