IAS Gyan

Daily News Analysis


7th September, 2023 Science and Technology

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  • Comet Nishimura could become visible this week
  • Comet Nishimura, officially known as C/2023 P1 Nishimura, was discovered in mid-August by amateur astronomer Hideo Nishimura.
  • It has been increasing in brightness as it travels along its path in the inner solar system.


Discovery and Characteristics

Orbital Characteristics

  • NASA's Jet Propulsion Laboratory (JPL) has calculated that this comet completes an orbit around the Sun approximately once every 435 years.
  • On September 12, the comet is expected to make a close approach to Earth, possibly coming as close as 125 million kilometers away.

Visibility and Location

  • Currently, the comet is situated in the constellation Leo.
  • Given its angular proximity to the Sun, it will likely only be visible shortly before sunrise or after sunset.
  • EarthSky suggests that September 8 may be a good date for observers to attempt to spot the comet with the unaided eye, particularly before dawn.
  • On September 8, the comet could be located near the crescent moon in the eastern sky, with Venus nearby, and it may be found near the star Adhafera in Leo's Sickle.



Definition of Comets

  • Comets are celestial objects primarily composed of ice, dust, and rocky material.
  • They are often described as "dirty snowballs" or "icy dirtballs" due to their mixture of volatile and non-volatile components.
  • Comets typically have highly elliptical orbits that take them from the distant regions of the solar system into the inner solar system, where they become visible to observers on Earth.

Structure and Composition

  • Nucleus: The core of a comet is called the nucleus. It is the solid, central part of the comet and can range in size from a few meters to several kilometers in diameter. The nucleus is composed of water ice, frozen gases (such as carbon dioxide and methane), dust, and rocky material.
  • Coma: As a comet approaches the Sun, solar radiation causes the nucleus to heat up and release gas and dust into space. This forms a glowing, cloud-like envelope around the nucleus called the coma.
  • Tail: The interaction of solar wind and radiation pressure pushes the released gas and dust away from the Sun, forming a visible tail. Comets can have two types of tails: a dust tail, which is bright and curved, and an ion tail, which is fainter and points directly away from the Sun.

Orbital Characteristics

  • Comets have highly eccentric (elongated) orbits, which can take them from the outer reaches of the solar system (Kuiper Belt or Oort Cloud) to close approaches to the Sun.
  • When comets approach the Sun, they become more active, developing a coma and tails, making them visible from Earth.
  • The period of a comet's return to the inner solar system can vary widely, from a few years to thousands of years.

Role in the Solar System

Comets play several important roles in our solar system:

  • Remnants from the Early Solar System: Comets are thought to be remnants from the early solar system, preserving material from its formation. They offer valuable clues about the conditions and composition of the early solar nebula.
  • Delivery of Volatiles: Comets contain volatile ices, which can include water, carbon dioxide, and more. When comets impact planets or release their volatiles into space, they can influence planetary atmospheres and provide a source of water for Earth and other celestial bodies.
  • Study of Celestial Mechanics: The study of comets and their orbits contributes to our understanding of celestial mechanics and the gravitational interactions within the solar system.

Famous Comets

  • Halley's Comet: Perhaps the most famous comet, Halley's Comet is visible from Earth approximately once every 76 years. Its last appearance was in 1986, and it is expected to return in 2061.
  • Comet Hale-Bopp: This comet, which made a bright appearance in 1997, was one of the most widely observed comets in history. It had a strikingly long and well-defined tail.
  • Comet NEOWISE (C/2020 F3): Discovered in 2020 by NASA's NEOWISE spacecraft, this comet became visible to the naked eye and delighted skywatchers around the world.

Missions to Study Comets

  • Several spacecraft have been sent to study comets up close, including NASA's Stardust, Deep Impact, and ESA's Rosetta mission, which successfully landed a probe, Philae, on the comet 67P/Churyumov-Gerasimenko.



  • Asteroids are rocky or metallic objects that orbit the Sun, primarily found in the asteroid belt, a region located between the orbits of Mars and Jupiter.


  • Asteroids vary in size, from a few meters to hundreds of kilometers in diameter.
  • They are primarily composed of rock and metal, with some containing water ice and organic materials.
  • Asteroids have a wide range of shapes and compositions.


  • Asteroids are considered remnants from the early solar system and can provide information about its formation and evolution.
  • Some asteroids are of interest for potential resource extraction in the future.



  • Meteors are the streaks of light produced when small objects from space, called meteoroids, enter Earth's atmosphere and vaporize due to friction with the air. They are often colloquially referred to as "shooting stars."


  • Meteors can vary in brightness, from faint streaks to bright fireballs.
  • They typically travel at high speeds, with velocities ranging from 11 to 72 kilometers per second.


  • Meteors provide a visual spectacle when they produce bright trails across the night sky.
  • Meteor showers occur when the Earth passes through the debris left by a comet, resulting in an increased number of meteors.



  • Meteorites are fragments of meteoroids that survive their journey through Earth's atmosphere and land on the surface. They are solid remnants of space objects.


  • Meteorites come in three main types: stony meteorites (silicate-rich), iron meteorites (mostly metallic iron-nickel), and stony-iron meteorites (a combination of both).
  • They can vary in size from tiny pebbles to large masses weighing several tons.


  • Meteorites provide valuable information about the composition of asteroids and the early solar system.
  • They can help scientists understand the geological and chemical processes occurring on other celestial bodies.



  • Meteoroids are small, solid objects in space that range in size from a grain of sand to a few meters in diameter. They are the precursors to meteors when they enter Earth's atmosphere.


  • Meteoroids can be composed of rock, metal, or a combination of materials.
  • They can travel at high speeds through space.


  • Meteoroids are a component of the broader population of small objects in the solar system and play a role in the formation and evolution of celestial bodies.


In summary, comets, asteroids, meteors, meteorites, and meteoroids are distinct but interconnected celestial objects, each contributing to our understanding of the solar system's history, composition, and dynamics. They have captivated human interest for centuries and continue to be important subjects of scientific study and exploration.


Q. Which of the following statements about comets is correct?

  1. Comets are primarily composed of rock and metal.
  2. They have highly circular orbits within the solar system.
  3. Comets develop a coma and tails when they approach the Sun.


A. Only Statement 1

B. Only Statement 2

C. Only Statement 3

D. Statements 1 and 3

Correct Answer: C)