Source: Space

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Context

• The Eta Aquariids will peak on May 5 and 6.
• Countries in the Southern Hemisphere, such as Indonesia and Australia, offer the best views due to their favorable position.

Details

About the meteor

• The Eta Aquariid meteor shower is an annual celestial event known for its dazzling display of shooting stars.
• Eta Aquariid meteors move at speeds of around 66 km per second and are composed of burning space debris.
• The shower appears to originate from the Aquarius constellation, hence the name "Eta Aquariids."
• In the Northern Hemisphere, the radiant is lower, leading to Earthgrazer meteors, while in the Southern Hemisphere, they are higher in the sky.
• In the Southern Hemisphere, observers may see around 30 to 40 meteors per hour during the peak, while in the Northern Hemisphere, the rate may decrease to about 10 meteors per hour.

Formation and Origin:

• Halley's Comet: Halley's Comet, a famous periodic comet, swings by Earth approximately every 76 years. As it travels through space, it leaves behind a trail of dust and debris.
• Debris Trail: When Earth passes through this debris trail, the particles collide with our atmosphere, creating the spectacular light show known as meteor showers.

Halley's Comet

• Periodic Comet.
• Edmond Halley, in 1705, used Newton's laws of motion to predict the return of the comet, which later came to be named after him.
• Recorded observations date back to at least 240 BCE, making it one of the most well-documented comets in history.
• Orbital Period: Approximately 75-76 years.
• Next Perihelion Passage: The last perihelion passage occurred in 1986. The next one is projected around 2061.
• Halley's Comet nucleus is estimated to be about 15 kilometers long and 8 kilometers wide.
• Composed of rock, dust, ice, and various gases, including water vapor, carbon dioxide, and carbon monoxide.
• The comet's tail is formed as solar radiation heats up its nucleus, causing gas and dust to stream away from it. The tail can extend for millions of kilometers.
• Travels through space at speeds of up to 70,000 kilometers per hour.
• Halley's Comet follows an elliptical orbit around the Sun, with its aphelion (farthest point from the Sun) beyond the orbit of Neptune and its perihelion (closest point to the Sun) between the orbits of Venus and Mercury.

Scientific Exploration:

• Giotto Mission: In 1986, the European Space Agency's Giotto spacecraft provided close-up images of the comet's nucleus during its flyby.
• Other Missions: Several other spacecraft, including NASA's Stardust and Deep Impact missions, have studied Halley's Comet and collected valuable data about its composition and behavior.

Comets

• Comets are small celestial bodies composed of dust, rock, water ice, and frozen gases, often referred to as "dirty snowballs" or "icy dirtballs."
• Comets orbit the Sun in highly elliptical orbits, with periods ranging from a few years to several thousand years.
• Comets typically consist of a nucleus, coma, hydrogen envelope, dust tail, and ion tail.
• The composition of comets includes water ice, carbon dioxide, methane, ammonia, silicate dust, and organic compounds.
• Several spacecraft have been sent to study comets up close, including NASA's Stardust, Deep Impact, and Rosetta missions, as well as the European Space Agency's Giotto mission.

Structure:

• Nucleus:
  • The solid central part of a comet, typically a few kilometers in diameter.
  • Composed of rock, dust, water ice, and various frozen gases.
  • Nuclei are thought to be among the most primitive objects in the solar system, containing clues about its early formation.
• Coma:
  • A cloud of gas and dust that surrounds the comet's nucleus.
  • Formed as sunlight heats up the nucleus, causing volatile substances to sublimate and release dust and gas.
  • Coma can extend for thousands to millions of kilometers in diameter.
• Hydrogen Envelope:
  • A region of hydrogen gas that surrounds the coma and extends outward from the nucleus.
  • Produced by the dissociation of water molecules in the comet's coma by solar ultraviolet radiation.
• Dust Tail:
  • Composed of tiny dust particles released from the comet's nucleus.
  • Pointed away from the Sun due to radiation pressure and solar wind.
  • Dust tails can appear yellowish or reddish and may stretch for millions of kilometers.
• Ion Tail:
  • Composed of ionized gas molecules, primarily composed of water vapor, carbon monoxide, and carbon dioxide.
  • Affected by the solar wind and electromagnetic forces, causing it to point directly away from the Sun.
  • Ion tails can appear bluish and may extend for millions of kilometers.

Types of Comets:

• Short-Period Comets: These comets have orbits that take less than 200 years to complete, typically originating from the Kuiper Belt or the scattered disc beyond Neptune.
• Long-Period Comets: These comets have orbits that take more than 200 years to complete and may originate from the Oort Cloud, a region of icy bodies far beyond the orbit of Pluto.
• Sungrazing Comets: Comets that pass extremely close to the Sun, often disintegrating due to intense solar heat and gravitational forces.

Meteors

• Meteors, also known as shooting stars or falling stars, are small rocky or metallic bodies that enter Earth's atmosphere and produce a bright streak of light as they burn up due to friction with the air.
• Meteors originate from comets, asteroids, or meteoroids. They are typically debris left behind by comets or fragments from collisions between asteroids.
• Meteors appear as bright streaks of light in the sky, often lasting only a few seconds before disappearing.

Characteristics:

• Meteoroids:
  • Small rocky or metallic bodies ranging from the size of a grain of sand to several meters in diameter.
  • Originating from comets or asteroids, meteoroids travel through space at high speeds.
• Meteor:
  • When a meteoroid enters Earth's atmosphere, it undergoes rapid heating due to air friction, causing it to glow brightly.
  • The intense heat causes the meteoroid to vaporize and disintegrate, creating a visible streak of light.
  • Meteors typically burn up at altitudes between 80 and 120 kilometers (50-75 miles) above the Earth's surface.
• Meteorite:
  • If a portion of the meteoroid survives its passage through the atmosphere and lands on Earth's surface, it is called a meteorite.
  • Meteorites can vary in size from small pebbles to large boulders and can provide valuable scientific information about the composition of asteroids and other celestial bodies.

Types of Meteors:

• Sporadic Meteors:
  • These are random meteors not associated with any specific meteor shower. They occur randomly throughout the year and are often caused by small, isolated meteoroids entering Earth's atmosphere.
• Meteor Showers:
  • Meteor showers occur when Earth passes through the debris trail left behind by a comet or asteroid.
  • During a meteor shower, the rate of meteors visible in the sky can increase dramatically, sometimes reaching dozens or even hundreds of meteors per hour.

Notable Meteor Showers:

• Perseids: Active from late July to mid-August, the Perseids are one of the most popular annual meteor showers, known for their bright and frequent meteors.
• Leonids: The Leonids, active in mid-November, are famous for producing periodic meteor storms with hundreds or even thousands of meteors per hour.
• Geminids: Occurring in mid-December, the Geminids are notable for their slow-moving and colorful meteors, often considered one of the best meteor showers of the year.

Asteroids

• Asteroids are small rocky or metallic bodies that orbit the Sun, primarily found in the asteroid belt between the orbits of Mars and Jupiter, as well as in other regions of the solar system.
• Asteroids range in size from a few meters to several hundred kilometers in diameter.
• They are composed primarily of rock and metal, with some containing water ice and organic compounds.
• Several spacecraft have been sent to study asteroids up close, including NASA's NEAR Shoemaker, Dawn, OSIRIS-REx, and the Japanese Hayabusa missions.

Characteristics:

• Asteroids are believed to be remnants from the early solar system, leftover material that did not form into planets.
• They may have originated from collisions between protoplanets or the disruption of larger bodies.
• Asteroids can have irregular shapes, ranging from roughly spherical to highly elongated or irregular.
• Some asteroids have moons (natural satellites) orbiting them, indicating past collisions or gravitational capture events.

Classification:

• Based on Location:
  • Main Belt Asteroids: Located in the asteroid belt between Mars and Jupiter, these are the most numerous and well-known asteroids.
  • Near-Earth Asteroids (NEAs): Asteroids whose orbits bring them close to Earth's orbit. Some NEAs pose a potential impact hazard and are closely monitored.
• Based on Composition:
  • C-Type Asteroids: Carbon-rich asteroids, the most common type in the outer asteroid belt.
  • S-Type Asteroids: Silicate-rich asteroids, common in the inner asteroid belt.
  • M-Type Asteroids: Metallic asteroids, primarily composed of nickel and iron, often found in the middle region of the asteroid belt.

Notable Asteroids:

• Ceres: The largest asteroid in the asteroid belt, Ceres is also classified as a dwarf planet and was visited by the NASA Dawn spacecraft.
• Vesta: The second-largest asteroid, Vesta is known for its large impact crater and was also visited by the Dawn spacecraft.
• Bennu: A near-Earth asteroid studied by the NASA OSIRIS-REx mission, which returned a sample of its surface material to Earth.

Sources:

IndianExpress

PRACTICE QUESTION Q.  Discuss the differences between meteors, comets, and asteroids, and explain their significance in the study of astronomy. How do these celestial bodies impact Earth and what measures can be taken to mitigate potential threats they pose?  (250 words)