Astronomers may have spotted an undiscovered “mini-moon” in the Solar System: a rocky object orbiting a small asteroid near Jupiter.
If the rocky satellite, which is slightly wider than the width of Manhattan, is confirmed to be a proper moon, it would be one of the smallest moons ever seen.
The tiny satellite was discovered by scientists working on NASA’s Lucy mission, which is sending a space probe to study some of the Trojan asteroids, two massive groups of space rocks that lie on either side of Jupiter in its orbit around the Sun.
The Lucy probe was launched on October 16, 2021 and will reach the Trojan asteroids in late 2027, after making a quick stop in the asteroid belt between Mars and Jupiter.
Until then, scientists on the Lucy mission are trying to learn more about some of these mysterious rocks to help identify where the probe can be most useful.
On March 27, the smallest of Lucy’s Trojan targets, known as Polymele, flew past a distant star, allowing mission scientists to precisely measure the size of the space rock by noting how much of starlight blocked the asteroid as it passed.
However, the team also observed a later, smaller, unexpected bump when a second asteroid followed after Polymele.
After reviewing the data, the team concluded that the second blip “had to be a satellite,” lead researcher Marc Buie, an astronomer at the Southwest Research Institute in Boulder, Colorado, said in a NASA statement .
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The newly discovered satellite has a diameter of about 3 miles (5 kilometers) and is separated from the 17-mile-wide (27 km) Polymele by a distance of about 201 km (125 miles). At the time of the observation, Polymele was about 480 million miles (772 million km) from Earth.
“These distances are roughly equivalent to finding a quarter on a Los Angeles sidewalk while trying to spot it from a Manhattan skyscraper,” NASA officials wrote in the statement.
A size comparison between Polymele and its unnamed satellite. (NASA Goddard Space Flight Center)
The term “Moon” can refer to any naturally occurring solid body orbiting a planet, dwarf planet, or asteroid. More than 200 moons have been recognized in the Solar System (not including asteroid moons), but the actual number is likely much higher, according to NASA.
Researchers could only make fleeting observations of Polymele’s satellite, so its orbital path is highly uncertain. As a result, the space rock cannot yet be officially designated as a moon or given a proper name.
But researchers are confident that when the Lucy probe reaches Polymele, the spacecraft will be able to collect enough data to designate it as a real moon.
This is not the first time that scientists on the Lucy mission have discovered a satellite tracking a Trojan asteroid.
In 2021, the team detected a 0.6-mile-wide (1 km) satellite orbiting Eurybates, which will be Lucy’s first Trojan target, after analyzing data collected by the Hubble Space Telescope in NASA, according to Live Science’s sister site Space.com. On this occasion, researchers determined the moon’s orbital path and officially named it Queta.
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This article was originally published by Live Science. Read the original article here.