Earth is about to gain a temporary second moon, as the small asteroid 2024 PT5 will be gravitationally captured by our planet this month. However, unlike our permanent lunar companion, this "mini-moon" will only stick around for about two months before returning to its usual orbit within the Arjuna asteroid belt.
A Window Shopper, Not a Customer
A team of scientists specialising in "mini-moon events" discovered the impending capture while monitoring newly discovered objects for interesting behaviour.
"The object that is going to pay us a visit belongs to the Arjuna asteroid belt, a secondary asteroid belt made of space rocks that follow orbits very similar to that of Earth at an average distance to the sun of about 93 million miles (150 million kilometres)," Carlos de la Fuente Marcos, research lead author and professor at Universidad Complutense de Madrid, told Space.com. "Objects in the Arjuna asteroid belt are part of the near-Earth object population of asteroids and comets."
Marcos explained that 2024 PT5 will not complete a full orbit around Earth. "You may say that if a true satellite is like a customer buying goods inside a store, objects like 2024 PT5 are window shoppers," he said.
Short Capture, Frequent Occurrence
Mini-moon events can be classified into two types: long captures, lasting a year or more, and short captures, lasting days, weeks, or months. While long captures are rare, occurring every 10-20 years, short captures like the one involving 2024 PT5 are more frequent, happening several times per decade.
The gravitational influence of the sun ultimately causes these objects to be ejected from Earth's orbit, returning them to their sun-centred paths.
Invisible to Most Skywatchers
Unfortunately, the 2024 PT5 will be too faint to be observed with amateur telescopes or binoculars. However, professional astronomers will be able to study the mini-moon using larger telescopes and specialised equipment.
"The object is too small and dim for typical amateur telescopes and binoculars," said Marcos. "However, the object is well within the brightness range of typical telescopes used by professional astronomers. A telescope with a diameter of at least 30 inches plus a CCD or CMOS detector is needed to observe this object, a 30-inch telescope and a human eye behind it will not be enough."
Further Study and Research
Marcos and his team plan to conduct spectroscopic and photometric observations of 2024 PT5 to gain a better understanding of its composition and properties.
This temporary lunar visitor provides a unique opportunity for scientists to study a near-Earth object up close and learn more about the dynamics of our solar system.