NASA's team working on the Lucy mission may have detected a previously undiscovered mini-moon in the outer Solar System. Science Alert reported that it was a small rocky object orbiting an asteroid near Jupiter.
The mini-moon is estimated to be just a little over the width of Manhattan and is confirmed to be a moon, a term used to describe a celestial body that orbits a planet, an asteroid, or something else is not a star. The team said its small size makes it one of the smallest moons ever found.
Mysterious 3-Mile Mini-Moon
NASA's Lucy mission has been visiting asteroids since it was launched on 16 October 2021 and is expected to reach the Trojan asteroids in 2027. Researchers said that the long observation campaign can now add one new asteroid to the list.
On March 27 this year, the Lucy mission team discovered the smallest of the Trojan asteroid targets, known as Polymele. The asteroid was passing in front of a star that day, allowing the scientists to observe and study it.
Polymele briefly blocked or occulted the star, and about 26 teams of professional and amateur astronomers studied the path where the occultation would be visible to measure its location, size, and shape. These occultation campaigns have been successful before and provided scientists with valuable information about the Lucy mission about its target asteroids.
But as Lucy's mission teams analyzed the data, they saw that two of the observations were not the same as the others, says Lucy occultation science lead Marc Buie from the Southwest Research Institute in a statement. He noted that two observers detected a satellite about 124 miles (200 kilometers) away from Polymele, which is likely its natural satellite.
They assessed the said satellite and found that it was a mini-moon roughly 3 miles (5 kilometers) in diameter that orbits Polymele. This P-type Jupiter L4 trojan asteroid measures 17 miles (27 kilometers) at its widest axis. For now, it has no official name until the team can determine its orbit.
Furthermore, the moon was so close to the asteroid that it could not be seen by telescopes here on Earth. The only option for astronomers to study it is by waiting for another occultation or waiting for the Lucy mission to arrive on the asteroid in 2027.
Lucy's 12-Year Mission to Visit Trojan Asteroids
NASA's Lucy mission is the first spacecraft launched to explore the Trojan asteroids, a group of asteroids that share Jupiter's orbit around the Sun. The mission is named after the first fossilized human ancestor discovered, providing a unique insight into human evolution.
NASA researcher and Lucy team member Dr. Tom Statler said the mission's original tagline was "12 years, seven asteroids, one spacecraft." Cosmos magazine reported that they have been changing it because of its recent discoveries, a problem that is good to have.
The Lucy mission was initially designed to complete a 12-year mission that would visit seven asteroids, wherein six were within the Trojan group. Although there were some problems with the rocket when two solar arrays were only partially unfurled, the space agency is confident that its powers will be enough to keep it healthy and functioning to finish the mission.
Lucy has been exceeding expectations as it will now visit two more asteroids, making it a total of nine asteroids. Visiting these rocky worlds will help scientists determine the history and formation of the Solar System that may even hold the keys to the origins of life.
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