universe & solar system section 5 Practice Questions Answers Test with Solutions & More Shortcuts

Answer: (c)

The sidereal day is the time it takes for the Earth to complete one rotation about its axis with respect to the ‘fixed’ stars.

By fixed, we mean that we treat the stars as if they were attached to an imaginary celestial sphere at a very large distance from the Earth. A measurement of the sidereal day is made by noting the time at which a particular star passes the celestial meridian (i.e. directly overhead) on two successive nights.

On Earth, a sidereal day lasts for 23 hours 56 minutes 4.091 seconds, which is slightly shorter than the solar day measured from noon to noon. At the same time that the Earth spins on its axis, it also orbits or revolves around the Sun. This movement is called revolution.

Answer: (c)

The group of stars arranged in a definite pattern is called a constellation. In modern astronomy, a constellation is an internationally defined area of the celestial sphere.

These areas are grouped around asterisms, which are patterns formed by prominent stars within apparent proximity to one another on Earth’s night sky.

Answer: (b)

On the equator, the day and night stay approximately the same length all year round, the earth’s rotational velocity is maximum at the Equator.

The coriolis force is greatest at the poles and 0 at the equator.

Answer: (b)

The twinkling of a star is due to the atmospheric refraction of starlight. The scientific name for the twinkling of stars is stellar scintillation (or astronomical scintillation).

Stars twinkle when we see them from the Earth’s surface because we are viewing them through thick layers of turbulent (moving) air in the Earth’s atmosphere.

Answer: (a)