How many moons does Earth have? The answer seems obvious: Earth has only one moon. It’s even in the name: the moon. In the beginning, the Earth The moon needs no other name, because for thousands of years, we did not know that there was any other natural satellite. But over centuries of astronomy and space exploration, we’ve found out Hundreds of moons in the solar systemAnd there may be more to our planet than you think.
“the moonIt bears the title of the only fixed and permanent moon of the Earth Gabor Horvat (Opens in a new tab), an astronomer at Eötvös Loránd University in Hungary. But it’s not the only object being pulled into Earth’s orbit; A group of near-Earth objects and dust clouds are also caught in Earth’s gravity. These often temporary satellites technically qualify as mini-satellites, quasi-satellites, or ghost satellites.
So the question of how many moons Earth has is more complicated than you might think. The number has changed over time — from zero, to one, to sometimes several moons.
Back in the early days of Earth, about 4.5 billion years ago, our planet was moonless. then, About 4.4 billion years ago, a Mars-sized protoplanet called Theia struck Earth. Large pieces of the Earth’s crust were hurled into space. Rocky debris came together — perhaps within a few hours — to form the moon, according to 2022 research published in Astrophysical Journal Letters (Opens in a new tab).
Other “moons” are only a few feet across It was much more temporary, captured by Earth’s gravity for short periods before escaping back into space. In 2006, there was Asteroid up to 20 feet (6 meters) wide 2006 RH120 (Opens in a new tab)Space Rock ran for 18 months and was Long-range capture was first observed (Opens in a new tab) an asteroid in Earth’s orbit. And 2020 CD3, a space rock measuring 11.5 feet (3.5 m) wideIt left Earth’s orbit in March 2020 after spending three years as a small second moon. In 2020, scientists also spotted SO 2020, a small moon that returned to space in early 2021. However, SO 2020 turned out not to be a natural satellite; was the Remnants of the rocket booster From the sixties.
Related: Why can we sometimes see the moon during the day?
For 13 hours in 2015, scientists thought they had found a new temporary moon orbiting Earth. But they quickly realized their mistake when it was revealed that the “moon” was just the European Space Agency’s Gaia space telescope, prompting the International Astronomical Union’s Minor Planet Center to Rollback version (Opens in a new tab).
In addition to the moons that come and go from Earth’s orbit, there are space objects that NASA calls quasi-satellites, such as the asteroid 3753 Cruithne. These space rocks orbit the sun so similar to Earth that they stick around our planet for its entire 365-day orbit. Semi-moon Kamo’oalewa – It is suspected to be an actual moon artifact It is mainly driven by the sun’s gravity but appears to revolve around the Earth in a corkscrew-like path.
Some space objects, such as asteroid 2010 TK7, earn the nickname “the Moon” because they get caught in the unique gravity of the Sun-Earth or Earth-Moon systems. The attraction of the two large objects creates regions of gravitational force, called Lagrangian points, which keep smaller objects in place at fixed gravitational points in space, according to NASA (Opens in a new tab). The two Lagrangian points, L4 and L5, form an equilateral triangle with the Earth. Effectively, the objects captured at these Lagrangian points, called Trojan horses, align with the Earth and join in its orbit around the sun.
In parallel with the formation of the solid Moon and the stability of its orbit around the Earth, Lagrangian points L4 and L5 also arose and began to gather. [and] “The interplanetary dust particles were trapped,” Horvath told Live Science in an email. Some astronomers call these particle clouds “ghost moons.” They are also called Kordylewski clouds, after the Polish astronomer who first reported them in the 1960s. At first, many scientists weren’t convinced, but since then, astronomers like Horvath have Certain (Opens in a new tab) Clouds of dust are accumulating at these Lagrangian points.
However, these ghost moons will never form a more solid moon, because dust can’t bind, stick together, or stick together, Horvath said. And while the Lagrangian points remain static, the matter in them is dynamic, constantly entering and exiting the dust cloud.