Estimated reading time: 4 minutes
Table of contents
Why are Comets in News Recently?
In July 2025, an extraordinary celestial visitor, the interstellar comet 3I/ATLAS, was discovered by the ATLAS telescope in Chile. Classified as the third known object from outside our solar system, this originates beyond the Milky Way’s thick disk and is likely over 7 billion years old, possibly making it the oldest comet ever observed.
Unlike common comets dominated by water ice, 3I/ATLAS exhibits unusually high carbon dioxide content and complex organic compounds. It will pass closest to the Sun around October 30, 2025, just inside Mars’ orbit, and its nearest approach to Earth will be about 170 million miles away, posing no threat.
Scientists believe studying this comet helps in understanding primordial galactic material, planet formation processes, and even potential origins of life, making it a crucial subject for geography and science aspirants alike. Its hyperbolic path confirms it is an interstellar traveler and not bound by the Sun’s gravity.
What is a Comet?
A comet is a small icy body that orbits the Sun in elongated elliptical paths. When it approaches the Sun, the heat causes sublimation of ice, releasing gas and dust, which forms a bright glowing coma and a spectacular tail.
- Nucleus: Solid icy-rocky core.
- Coma: Cloud of gas and dust surrounding the nucleus.
- Tail: Extends millions of kilometers, always pointing away from the Sun due to solar wind.
Fact: The largest comet discovered so far is Bernardinelli-Bernstein (C/2014 UN271), nearly 150 km wide.
What are the Main Features of a Comet?
- They are mostly found in the Kuiper Belt and Oort Cloud.
- A comet’s brightness and size of its tail increase as it gets closer to the Sun.
- Their orbits are often highly elliptical.
- Comet tails can be millions of kilometers long but extremely thin.
Fact: In 1997, Comet Hale-Bopp’s tail stretched over 150 million km, making it visible for record 18 months.
How are Comets Classified?
Comets are classified based on the time they take to orbit the Sun:
- Short-period → complete orbit in less than 200 years (e.g., Halley).
- Long-period → take thousands or even millions of years (e.g.,Hale-Bopp).
- Single-apparition → pass once and may leave the Solar System forever.
Fact: There are around 400 known short-period comets that regularly return to the inner Solar System.
What is the Geographical Importance of Comets?
Though they are celestial, their geographical importance lies in:
- Studying the early Solar System formation.
- Carrying organic molecules and water, possibly contributing to Earth’s oceans.
- Impacting Earth’s history (e.g., the dinosaur extinction theory linked to cosmic impacts).
Fact: Isotopic studies suggest that up to 10% of Earth’s water might have come from cometary impacts.
What Recent Discoveries Have Been Made About Comets?
- Nishimura (2023): Visible to naked eyes in September 2023.
- Tsuchinshan-ATLAS (2024): Expected to brighten and may be seen without telescopes.
- Organic molecules detected on comet 67P, strengthening theories about life’s origin.
Fact: In 2021, astronomers confirmed that water vapor exists in comets beyond Jupiter, hinting at life-friendly conditions.
Quick Exam Facts
- Definition: Icy celestial body orbiting the Sun.
- Main parts: Nucleus, Coma, Tail.
- Famous Comet: Halley (76-year orbit).
- Origin regions: Kuiper Belt (short-period), Oort Cloud (long-period).
- Tail direction: Always away from Sun.
- Recent News: Comet Tsuchinshan-ATLAS (2024).
Fact: Astronomers have catalogued over 4,000 comets, but the Oort Cloud is estimated to contain trillions.
FAQs
Q1. What is a comet made of?
It is made of ice, rock, and dust, often called a “dirty snowball.”
Q2. Why does a comet have a tail?
The tail forms when solar radiation and solar wind push gas and dust away from the nucleus, always pointing opposite the Sun.
Q3. Which is the most famous comet?
Halley’s, visible every 76 years, is the most famous.
Q4. Where do they come from?
Most of them originate in the Kuiper Belt (short-period) and the Oort Cloud (long-period).
