ASTEROID 2011 UL21 (Syllabus: GS Paper 3 – Sci and Tech)

Context: Mountain-sized asteroid, 2011 UL21 made a close approach to Earth recently.

Asteroid 2011 UL21

• About: It is a giant space rock, was first discovered in 2011 and completes an orbit around the sun every 3 years.
• Size and Classification: It is larger than 99% of known near-Earth asteroids, estimated to have a diameter of 2.5 kilometers, and is nicknamed the Planet Killer due to its size.
• Characteristics: This asteroid is exceptionally bright with an absolute magnitude of 15.8, making it one of the brightest near-Earth asteroids observed.
• Earth Approach and Safety: Despite its nickname, Asteroid 2011 UL21 poses no current threat to Earth and is not projected to collide with our planet.

Near Earth Objects (NEO)

• About: It is an asteroid or comet which passes close to the Earth's orbit.
• Orbital Mechanics: NEOs are influenced by gravitational interactions with nearby planets, which can alter their orbits over time.
• Proximity to Earth: A NEO is defined as any object whose orbit brings it within 1.3 astronomical units (AU) of the sun, placing it within about 45 million kilometers of Earth's orbit.
• Classification: NEOs that intersect Earth's orbit are categorized into Atens (with orbits smaller than Earth's) and Apollos (with orbits larger than Earth's).
• Impact: Even small NEOs, starting from about 20 meters in diameter, can cause significant damage upon impact with Earth's surface.
• Potentially Hazardous Objects (PHOs): NEOs larger than 140 meters in diameter that intersect Earth's orbit are classified as potentially hazardous objects due to their potential impact threat.