Earth’s moon will soon have some temporary company in the form of a “mini moon” — an asteroid approximately the size of a school bus, measuring about 33 feet (10 meters). On Sunday, the asteroid, named 2024 PT5, will pass by Earth and become briefly trapped by the planet’s gravity, orbiting it for around two months.
Discovered in August by astronomers at Complutense University of Madrid using a telescope in Sutherland, South Africa, this mini moon is one of several small space rocks that occasionally get caught in Earth’s gravity. According to Richard Binzel, an astronomer at MIT, such occurrences happen fairly frequently, but because these mini moons are small and difficult to detect, they often go unnoticed. It was last seen happening in 2020.
Carlos and Raúl de la Fuente Marcos, who identified 2024 PT5, published their findings with the American Astronomical Society. While it won’t be visible to the naked eye or through amateur telescopes, the asteroid can be observed using large, research-grade equipment, according to Carlos de la Fuente Marcos.
Though it remains unclear whether this object is a true asteroid or a fragment of the moon, Binzel speculated it might have originated as a lunar chunk that was blasted into space. The mini moon will orbit Earth for nearly 57 days, without completing a full orbit, before continuing its journey through space on November 25. It is expected to pass by again in 2055.
In other space news, time behaves a little differently on the moon, where it moves slightly faster due to the moon’s lower gravity. To address this, an international group of astronomers has called for a dedicated lunar timekeeping system. The International Astronomical Union recently voted to encourage global collaboration on establishing a unified lunar clock, with U.S. Naval Observatory’s Susan Stewart spearheading the resolution.
The moon’s time is unique due to its gravity, which causes time to pass about 58.7 microseconds faster each day than on Earth. As more nations and private companies plan lunar missions, astronomers want to ensure these missions operate on a synchronized time system. While lunar missions currently follow the time of the country operating the spacecraft, the European Space Agency has been advocating for a lunar clock since last year. The White House has also directed NASA and other agencies to create an initial concept by the end of the year, with a finalized plan expected by 2026.