universe & solar system section 8 MCQ Questions & Answers Detailed Explanation

Answer: (a)

A supernova is a stellar explosion that is more energetic than a nova. During this short interval, a supernova can radiate as much energy as the Sun is expected to emit over its entire life span.

The explosion expels much or all of a star's material at a velocity of up to 30,000 km/s (10% of the speed of light).

Answer: (a)

The Earth is closest to the Sun or at the perihelion on January 3, when it is winter in the Northern Hemisphere.

Answer: (a)

The atmosphere of Uranus is composed of 83% hydrogen, 15% helium, 2% methane and small amounts of acetylene and other hydrocarbons. Methane in the upper atmosphere absorbs red light, giving Uranus its blue-green colour.

Answer: (a)

The earth is nearest to the sun on about January 3rd. Earth is farthest from the sun on about 4th July.

Answer: (c)

Answer: (c)

The inexhaustible source of energy of the stars is due to the conversion of Hydrogen to Helium. In the interior of a star, the particles move rapidly in every direction because of the high temperatures present. Every so often a proton moves close enough to a nucleus to be captured, and a nuclear reaction takes place.

Only protons of extremely high energy (many times the average energy in a star such as the Sun) are capable of producing nuclear events of this kind. A minimum temperature required for fusion is roughly 10 million K. Since the energies of protons are proportional to temperature, the rate of energy production rises steeply as temperature increases.