Astronomers have discovered Earth’s newest quasi-satellite

The land has It has just added its seventh confirmed semilunar moon. It’s 2025 PN7, a small Apollo-type asteroid that was discovered in August by its brightness alone, thanks to Hawaii’s Pan-STARRS 1 telescope.

After analyzing its path, scientists concluded that the object maintains a 1:1 resonance with the Earth. In other words, it orbits the Sun at the same time as our planet. From a distant perspective, this conjunction makes it look as if Earth is accompanied by a small asteroid, and as if it has an extra moon.

Unlike the Moon, semilunar moons are not bound by Earth’s gravity. They are ephemeral companions, cosmically speaking, following their own path around the sun. Only at certain times do they get close enough to seem restricted. In the case of 2025 PN7, its minimum distance is 299 thousand kilometers, while at the farthest point it can reach 17 million kilometers. For comparison, the moon remains at an average distance of 384 thousand kilometers from Earth.

According to the article published in AAS Research Notes, The asteroid has been passing through a semi-lunar phase since 1965, and is expected to remain so for 128 years. Some researchers estimate that 2025 PN7 will finally move away in 2083.

Why does Earth have semi-moons?

So far, seven bodies have been confirmed that appear to accompany the planet in its orbit. Astronomers believe that more can be discovered in the future. Earth is a natural repository of quasars because Earth’s orbit is similar to the orbit of some nearby objects inhabiting the so-called Arjuna group of asteroids, a group that has only recently begun to be studied in more detail.

The Arjuna group does not form a ring like the asteroid belt between Mars and Jupiter, but it includes a large group of rocks near Earth that orbit the sun on a similar path to our planet. Occasionally, some of these asteroids coincide with our path and, depending on their orbital dynamics, are classified as semi-moons or mini-moons.

The sublunar 2025 PN7 is located in the Arjuna asteroid group near Earth.Illustration: Wired