Universe

1. Which one of the following hypothesis/theory explains the origin of th

Which one of the following hypothesis/theory explains the origin of the universe ?

Nebular hypothesis
Binary theory
Big Bang theory
Planetesimal hypothesis
This question was previously asked in
UPSC NDA-2 – 2019
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The Big Bang theory is the most widely accepted cosmological model explaining the origin and evolution of the universe. It postulates that the universe originated from a singular point of extremely high density and temperature approximately 13.8 billion years ago and has been expanding ever since. The other hypotheses listed explain the formation of stars, planets, or solar systems, not the entire universe.
Cosmology studies the origin, evolution, and structure of the universe. The Big Bang theory is the standard model in cosmology.
Evidence supporting the Big Bang theory includes the cosmic microwave background radiation, the observed expansion of the universe (Hubble’s Law), and the abundance of light elements (hydrogen, helium, lithium). The nebular hypothesis and planetesimal hypothesis are related to the formation of stars and planetary systems within the universe, not the universe itself.

2. What is a constellation?

What is a constellation?

A particular pattern of equidistant stars from the earth in the sky
A particular pattern of stars that may not be equidistant from the earth in the sky
A particular pattern of planets of our solar system in the sky
A particular pattern of stars, planets and satellites in the sky due to their position in the space
This question was previously asked in
UPSC CDS-1 – 2019
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The correct answer is B. A constellation is defined as a group of stars that appear to form a pattern in the night sky as seen from Earth. The stars within a constellation are typically at vastly different distances from Earth and are not physically related to each other; their apparent pattern is merely a line-of-sight effect from our perspective.
A constellation is an apparent pattern of stars in the sky, where the constituent stars are generally not equidistant from Earth.
The International Astronomical Union (IAU) recognizes 88 official constellations covering the entire celestial sphere. Historically, constellations were used for navigation, timekeeping, and mythology. The stars in a constellation are connected by imaginary lines to form shapes that are often named after animals, mythological figures, or objects.

3. Which one among the following stars is nearest to the earth?

Which one among the following stars is nearest to the earth?

Sirius
Arcturus
Spica
Proxima Centauri
This question was previously asked in
UPSC CDS-1 – 2019
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The correct option is D.
Among the options provided, Proxima Centauri is the star nearest to the Earth (excluding the Sun). It is a red dwarf star located about 4.24 light-years away, part of the Alpha Centauri star system.
Sirius is the brightest star in the night sky, located about 8.6 light-years away. Arcturus is a bright giant star about 37 light-years away. Spica is a binary star system and one of the brightest stars, located about 250 light-years away.
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