What is Asteroid YR4?
- YR4 is a Near-Earth Asteroid (NEA) discovered in December 2024 using the ATLAS telescope in Chile.
- Its orbit brings it within 1.3 times the Earth-Sun distance, making it a Near-Earth Object (NEO).
- Initially, YR4 triggered the highest-ever NASA asteroid impact alert in February 2025.
- New infrared data from the James Webb Space Telescope estimates its size at ~65 metres, comparable to a 10-storey building, which is below the 140-meter threshold for classification as a "Potentially Hazardous Asteroid".
- Earlier, YR4 had a 1% chance of hitting Earth, but the latest trajectory analysis shows a negligible risk to Earth.
What are Asteroids?
- Asteroids, also known as minor planets, are rocky remnants from the early solar system, dating back 6 billion years.
- They exhibit irregular shapes, though a few are nearly spherical, and some host small companion moons or even exist as binary or triple systems.
Classification of Asteroids
- Main Asteroid Belt: Located between Mars and Jupiter, this is where the majority of known asteroids are found.
- Trojans: These share an orbit with a planet and remain stable due to the Lagrange Points (L4 and L5), where gravitational forces from the Sun and the planet balance.
- Near-Earth Asteroids (NEAs): These are asteroids whose orbits pass close to Earth’s orbit. Those that cross Earth’s orbital path are known as Earth-crossers.
