Yesterday, Earth's 'second moon' officially appeared

NASA scientists say Earth will get a "second moon" on Sunday, but it won't last long.

The "second moon" is asteroid 2024 PT5 , which orbits the Sun as part of the small asteroid belt that follows Earth. This is the result of a new study published in the journal Research Notes of the AAS by two experts Carlos de la Fuente Marcos and Raúl de la Fuente Marcos from the Complutense University of Madrid, Spain.

The positions of Earth, the Sun and Mercury on Sunday (September 29) when Earth has a "second moon". (Image: NASA/JPL).

The latest data from NASA's Jet Propulsion Laboratory's Horizons system shows the second Moon's appearance will begin at 3:54 p.m. EDT (12 p.m. Hanoi time, September 29) and end at 12 a.m. on November 25.

After orbiting Earth for a short time, asteroid 2024 PT5 will continue to orbit the Sun as part of the Arjuna asteroid family.

2024 PT5 is not the first asteroid to be captured by Earth's gravity and become a mini-moon. Scientists have recorded two previous captures, each lasting about a week and estimated to occur several times per decade. Rarer, longer captures can last years rather than weeks, resulting in the captured asteroid completing one or more full orbits around Earth.

The fact that asteroid 2024 PT5 will only last a few weeks instead of billions of years isn't the only major difference between this "mini-moon" and the real Moon.

Although this second moon will appear in Earth's night sky for at least half a month, 2024 PT5 will not be visible to casual skywatchers. However, professional astronomers will likely be able to capture some images of this temporary appearance.

This is largely due to the huge difference in size between the two bodies. While the Moon is estimated to be 2,159 miles (3,475 kilometers) in diameter, 2024 PT5 is thought to be just over 30 feet (10 meters) wide. That means the Moon is 308,108 times larger than the pseudo-moon asteroid 2024 PT5.

" This object is too small and faint for ordinary amateur telescopes and binoculars. However, it is within the brightness range of conventional telescopes used by professional astronomers ," concluded Professor Raúl de la Fuente Marcos. He recommends that users use a telescope of at least 30 inches in diameter plus a CCD or CMOS detector for observation. "A 30-inch telescope and the naked eye will not be enough ," he said.