No, there will not be a second moon in the night sky

MEMPHIS, Tenn. — You may have seen on social media that the Earth is gaining a second moon this month. Articles all over the internet are titled to claim that our own Moon might be gaining a neighbor this month. While there will be a close encounter, there is more to this than it may seem.

THE QUESTION

Will there be a second moon in our night sky?

THE SOURCES

• The International Astronomical Union
• The University of Sydney
• The Journal Research Notes of the American Astronomical Society

THE ANSWER

No, we will not have a second moon later this month, but we will have what is called a mini-moon event with this asteroid over the next 2 months.

Earlier this month, research out of Madrid Spain was published showing that 24 foot wide asteroid 2024 PT5 would be captured in the Earth’s gravity and appears to orbit the Earth from September 29th through November 25th. 

This event is titled as a mini-moon event. This is where objects such as asteroids slow down and are temporarily captured by a planet’s gravity.  According to the University of Sydney: 

A mini-moon is a “temporarily captured orbiter” if it completes at least one full orbit of the Earth before returning to its usual orbit around the Sun.

If a mini-moon is captured by Earth’s gravity but doesn’t make it around for a full orbit, it’s a “temporarily captured flyby” instead.

Two of Earth’s mini-moons were “temporarily captured orbiters”, while the other three (including 2024 PT₅) fall into the “temporarily captured flybys” category.

Asteroids tend to be rather dark which makes this only visible to scientists with advanced telescopes during this window.

It turns out there is no hard definition for what is and isn’t a moon. But the commonly used definition from the International Astronomical Union states a moon is  “A natural satellite, a solid object in orbit around a planet”

Considering Asteroid 2024 PT5 will only temporarily orbit around the Earth before it is ejected back out into space it will not be in a stable orbit it will not be considered a moon but will be involved in a mini-moon event.