Test: Astronomy - 2 - ACT MCQ

On 21st June, the summer solstice in the Northern Hemisphere, the Sun does not set below the horizon at the Arctic Circle. This phenomenon is known as the "midnight sun," where areas north of the Arctic Circle experience continuous daylight for 24 hours. Conversely, during the same period, the Antarctic Circle experiences the polar night, with the Sun not rising above the horizon. This occurrence marks the tilt of the Earth's axis towards the Sun, resulting in longer daylight hours in the Northern Hemisphere and shorter daylight hours in the Southern Hemisphere.

Saturn has the largest number of natural satellites or moons among the listed planets. It boasts an impressive count of over 80 confirmed moons, with more discoveries ongoing. These moons vary in size and characteristics, with some as large as planets themselves, like Titan, the second-largest moon in the solar system. The abundance of moons around Saturn makes it a fascinating celestial object for study, offering insights into planetary formation and the dynamics of moon systems.

The average distance between the Sun and the Earth is approximately 150 x 10⁶ kilometers, often referred to as one astronomical unit (AU). This distance serves as a fundamental unit for measuring distances within the solar system. Understanding this distance is crucial for studying celestial mechanics, planetary orbits, and astronomical phenomena. It's the baseline for calculating distances to other planets, asteroids, and celestial bodies, forming a key reference point in astronomical observations and calculations.

The assertion (A) is true because the same face of the Moon is indeed always presented to the Earth due to synchronous rotation.

However, the reason (R) is false. The Moon's rotation period is approximately 27.3 days, which is roughly the same as its orbital period around the Earth, not 23.5 days as stated. The synchronization of rotation and orbit is the reason behind the phenomenon, but the incorrect value provided in the reason makes it false. Therefore, option (c) is the correct choice. Thank you for bringing this to my attention.

The Earth is the densest planet in our solar system, primarily due to its composition, which includes heavy elements like iron and nickel in its core. This density contributes to its strong gravitational pull compared to other planets. Therefore, option (a) is the correct choice. Thank you for your patience.

A black hole's property of not allowing any radiation to come out is due to its extremely high density. The gravitational pull of a black hole is so strong that not even light can escape from it, resulting in its characteristic feature of being "black" or devoid of any observable radiation. Therefore, option (c) is the correct choice.

In the Northern Hemisphere, the polestar, also known as Polaris, appears nearly fixed in the sky towards the north. As the person is standing in a desert and wants to reach a location 5 km east of his current position, he should keep the polestar to his left as he walks. This would ensure that he is heading roughly in an easterly direction, towards his village. Therefore, option (c) is the correct choice.

Otto Schmidt, a Soviet scientist, was one of the scholars who suggested that the Earth's origin could be attributed to gases and dust particles. Schmidt proposed this theory as part of his research on the formation of celestial bodies, including planets like Earth. Therefore, option (d) is the correct choice.

1. Asteroids are indeed rocky debris of varying sizes orbiting the Sun.
2. Most asteroids are small, but some can have diameters as large as 1000 km.

Statement 3 is incorrect. The majority of asteroids have orbits lying between the orbits of Mars and Jupiter, forming the asteroid belt. Therefore, the correct option is (c) 1 and 2 are correct.

Saturn's density is less than that of water. Its average density is approximately 0.69 times the density of water, making it less dense than water. Therefore, if Saturn were placed in a body of water large enough to contain it, it would indeed float.