Context
Astronomers recently confirmed dark comets fall into two main categories: smaller objects that reside in our inner Solar System, and larger objects (100 metres or more) that remain beyond the orbit of Jupiter.
About Dark Comets
- Celestial objects without bright tails, resembling asteroids but following elliptical orbits.
- Comparison with Regular Comets:
- Regular Comets: Known as “dirty snowballs,” made of rock, dust, and ice.
- Dark Comets: Lack glowing tails and resemble asteroids, appearing as faint points of light.
- Orbital Characteristics:
- Elliptical paths, similar to bright comets.
- Can travel beyond Pluto and reach the Oort Cloud.
- Key Features Making Them ‘Dark’:
- Size: Typically small, a few meters to a few hundred meters wide, with limited material to form visible tails.
- Spin: Rapid rotation disperses gas and dust uniformly, reducing visibility.
- Composition and Age: Older comets with depleted volatile materials that produce tails.
Importance of Dark Comets
- Related to bright comets and significant for understanding the Solar System’s dynamics and formation.
- Provide insights into the early Solar System and hidden celestial phenomena.
- Detection of Dark Comets
- Challenges: Lack of visible tails makes them difficult to identify.
- Current Detection Methods:
- Observed via light reflected from the Sun.
- Dark Energy Camera (DECam): Instrument in Chile used for recent discoveries.
- Studies pieced together images to identify dark comets among hidden Solar System objects.
Discovery of Interstellar Objects
- Oumuamua: First interstellar object discovered entering our Solar System, named from the Hawaiian word for “scout.”
- Nature:
- Speed and path deviate from typical asteroids.
- Lacks a bright tail or nucleus, unlike normal comets.
- Exhibits erratic motions consistent with gas escaping its surface, termed a “dark comet.”
- New Discoveries: Ten additional interstellar objects identified recently, categorized as:
- Smaller objects within the inner Solar System.
- Larger objects (100m+) beyond Jupiter’s orbit.
- Notable Example: 3200 Phaethon, the parent body of the Geminid meteor shower, may be a dark comet.
Source: TH
Previous Year Question
Consider the following pairs:
Objects in space: Description
1. Cepheids: Giant clouds of dust and gas in space
2. Nebulae: Stars which brighten and dim periodically
3. Pulsars: Neutron stars that are formed when massive stars run out of fuel and collapse
How many of the above pairs are correctly matched?
[UPSC Civil Services Exam – 2023 Prelims]
(a) Only one
(b) Only two
(c) All three
(d) None
Answer: (a)