Chapter 1: Introduction to Cruithne

Cruithne, often dubbed as Earth's second moon, is an intriguing celestial body that shares our solar system. This asteroid orbits the Sun, providing Earth with a cosmic companion along its journey.

While technically classified as an asteroid, Cruithne's orbit intriguingly intersects with Earth’s, creating the illusion that it orbits our planet. This fascinating orbital relationship is known as a co-orbital configuration, where two bodies (Earth and Cruithne) revolve around a third body (the Sun) together.

1.1 Understanding the Horseshoe Orbit

From our vantage point on Earth, Cruithne appears to follow a “horseshoe” path; however, its true orbit resembles a more complex bean shape. It completes a revolution around the Sun approximately once a year. Due to the gravitational pull from Earth, Cruithne can accelerate as it approaches and decelerate as it moves away, resulting in varying orbital times.

1.2 Why Isn’t Cruithne a Moon?

Despite its close association with Earth, Cruithne is not classified as a moon. It takes about 800 years for the asteroid to orbit our planet compared to the one Earth year it takes to complete a solar orbit. This indicates that Cruithne is primarily influenced by the Sun's gravity rather than Earth's. In contrast, our Moon orbits Earth every 27 days and shares the same solar orbit duration as our planet.

The blue dot represents Earth, while the red represents Cruithne, illustrating its unique orbital path. Credit: Business Insider

1.3 The History and Future of Cruithne

Discovered in 1986, Cruithne is categorized as an Aten asteroid, residing in the inner solar system between the Earth and the Sun. It took scientists over a decade to unravel the complexities of its orbit. However, this orbit is not stable; predictions suggest that in about 5000 years, Cruithne may drift into Earth's orbit, potentially becoming a “mini-moon.” Yet, in another 3,000 years, it would revert to its solar orbit.

1.4 Other Mini-Moons in Our Solar System

Numerous planets host mini moons, and Earth had its own temporary mini-moon, 2006 RH120, which orbited us from September 2006 to June 2007. Mars boasts four mini moons, while Jupiter has identified 7040 Trojans as of 2018.

1.5 The Question of Collision

With Cruithne's close proximity, one might wonder if a collision is possible. Given its size of 5 kilometers, a collision would be catastrophic, akin to the asteroid that led to the extinction of the dinosaurs. Fortunately, the closest Cruithne approaches Earth is about 15 million kilometers, a distance that won't change for centuries. When considering a three-dimensional perspective, Cruithne's orbit is slightly angled, making a collision highly improbable.

1.6 The Significance of Studying Cruithne

Researching Cruithne goes beyond mere curiosity; it offers insights into the solar system's history and the dynamics of asteroid orbits. Investigating this asteroid could lead to groundbreaking discoveries and reveal potential natural resources, possibly serving as a refueling stop for future space missions. The possibilities for exploration and discovery are endless!

The first video titled "Cruithne, the Asteroid With a Horseshoe Orbit" delves into the unique characteristics of Cruithne and its fascinating path through space.

The second video, "Earth's Second Moon: Meet 3753 Cruithne," explores the relationship between Cruithne and Earth, highlighting its significance in our solar system.