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The Universe

📆 October 21, 2024

Total Questions: 51

21. The theory of continental drift was developed by- [67th B.P.S.C. (Pre) 2022]

Correct Answer: (b) A. Wegener
Solution:Continental Drift Theory was introduced by Alfred Wegener, who is credited with the formal development of the Continental Drift Theory (also known as Wegener's hypothesis), which he first presented in 1912. Wegener proposed that the continents were once part of a single supercontinent called Pangaea, which began to break apart about 200 million years ago.
  • Continental Drift Concept: He suggested that the continents drifted through the oceanic crust, forming the present-day configuration of continents.
  • Evidence Supporting Theory: Wegener's theory was based on various forms of evidence, including the fit of the continents, similarities in rock formations and fossil records across different continents, and paleoclimatic data.
  • Lack of Immediate Acceptance: Despite the compelling nature of his evidence, Wegener's theory was not widely accepted during his lifetime due to a lack of a plausible mechanism for how continents could move.

22. The milky way is classified as - [U.P.P.C.S. (Pre) 2001]

Correct Answer: (a) Spiral Galaxy
Solution:According to the theory propounded by Georges Lemaitre, 13.7 or 13.8 billion years ago the total cosmic substance was in the form of dense mass which spread to form a number of galaxies. An Infinite group of these swirling galaxies are visible to us collectively in the form of Universe. Every Galaxy is estimated to contain around 100 billion stars. The galaxy in which our solar system is situated is known as 'Milky Way'. There are various shapes of galaxies, for example elliptical, spiral, irregular etc. Spitzer space telescope in 2005, produced clear proof against the preconception about the shape of Milky Way and made it clear that the shape of our Milky Way is Barred spiral.

23. Time taken by the Sun to revolve around the centre of our galaxy is - [40th B.P.S.C. (Pre) 1995]

Correct Answer: (c) 25 crores years
Solution:Sun is one of the star of our galaxy (Milky Way). Every star of the galaxy revolves around the galactic centre and the time taken by a star in revolving around this centre depends upon the distance between the galactic centre and the star. Sun is relatively far from the centre, so it takes more time to revolve around. Sun is at a 7.94 KPC or 25.896 thousand light years away from the centre and with a speed of 720 thousand km/hour, it takes 22.5 to 25 crore years, to revolve around the centre of the Milky Way galaxy. This period is called 'Cosmic Year or Galactic Year'.

24. The colour of the star indicates its - [I.A.S. (Pre) 1994]

Correct Answer: (d) Temperature
Solution:The colour of a star indicates it's temperature. The temperature of stars of different colors is as follows -
ColourTemperature Range
Blue50,000 - 28,000 K
Blue-white28,000 - 10,000 K
White10,000 - 7,500 K
White Yellow7,500 - 6,000 K
Yellow6,000 - 4,900 K
Orange4,900 - 3,500 K
Red3,500 - 2,000 K

25. The limit beyond which stars suffer internal collapse is called: [U.P.P.C.S. (Pre) 1997]

Correct Answer: (a) Chandrashekhar limit
Solution:Subrahmanyan Chandrashekhar was an Indo-American physicist who described the "Chandrashekhar Limit". This limit describes the maximum mass of a White Dwarf star or the mass limit above which a star will ultimately collapse into a Neutron star or a Black hole. He revealed that this mass was approximately 1.44 times of the solar mass. In 1983 Chandrashekhar was awarded the Nobel Prize in Physics for his work on the evolution of stars.

26. Black-hole is: [U.P.P.C.S. (Pre) 2019]

Correct Answer: (d) a collapsed star
Solution:Black holes are formed after the supernova explosion when the core of a massive dying star more than 2.5 times the mass of the Sun collapses until an infinite density where gravity is so high that even light cannot escape. Predicted by Einstein, through his general relativity theory which says that a sufficiently compact mass can bend spacetime and create a black hole, its theoretical structure was prepared independently by Tolman, Oppenheimer, Volkoff and S. Chandrasekhar. Black holes, with their extreme gravitational pull and unique properties, play a significant role in various aspects of astrophysics and cosmology. They are of different types, primarily based on their mass and the process of their formation.

Stellar Black Holes: These are often identified by observing the high-energy phenomena that occur as they interact with other stars or accrete matter from their surroundings.

Supermassive Black Holes: They play a crucial role in the formation and evolution of galaxies, influencing star formation and galaxy dynamics.

Intermediate Black Holes: They are of great interest to astronomers as they could provide a missing link in our understanding of black hole evolution.

Primordial Black Holes: They could offer insights into the conditions of the early universe and the nature of dark matter.

27. Which is a celestial phenomenon occurring due to stars? [U.P.P.C.S. (Pre) 1997]

Correct Answer: (b) Black Hole
Solution:Black holes are formed after the supernova explosion when the core of a massive dying star more than 2.5 times the mass of the Sun collapses until an infinite density where gravity is so high that even light cannot escape. Predicted by Einstein, through his general relativity theory which says that a sufficiently compact mass can bend spacetime and create a black hole, its theoretical structure was prepared independently by Tolman, Oppenheimer, Volkoff and S. Chandrasekhar. Black holes, with their extreme gravitational pull and unique properties, play a significant role in various aspects of astrophysics and cosmology. They are of different types, primarily based on their mass and the process of their formation.

Stellar Black Holes: These are often identified by observing the high-energy phenomena that occur as they interact with other stars or accrete matter from their surroundings.

Supermassive Black Holes: They play a crucial role in the formation and evolution of galaxies, influencing star formation and galaxy dynamics.

Intermediate Black Holes: They are of great interest to astronomers as they could provide a missing link in our understanding of black hole evolution.

Primordial Black Holes: They could offer insights into the conditions of the early universe and the nature of dark matter.

28. The "Black Hole Theory" was propounded by : [U.P.P.C.S. (Pre) 1996]

Correct Answer: (c) S.Chandrashekhar
Solution:Black holes are formed after the supernova explosion when the core of a massive dying star more than 2.5 times the mass of the Sun collapses until an infinite density where gravity is so high that even light cannot escape. Predicted by Einstein, through his general relativity theory which says that a sufficiently compact mass can bend spacetime and create a black hole, its theoretical structure was prepared independently by Tolman, Oppenheimer, Volkoff and S. Chandrasekhar. Black holes, with their extreme gravitational pull and unique properties, play a significant role in various aspects of astrophysics and cosmology. They are of different types, primarily based on their mass and the process of their formation.

Stellar Black Holes: These are often identified by observing the high-energy phenomena that occur as they interact with other stars or accrete matter from their surroundings.

Supermassive Black Holes: They play a crucial role in the formation and evolution of galaxies, influencing star formation and galaxy dynamics.

Intermediate Black Holes: They are of great interest to astronomers as they could provide a missing link in our understanding of black hole evolution.

Primordial Black Holes: They could offer insights into the conditions of the early universe and the nature of dark matter.

29. Which of the following does not belong to the solar system? [53rd to 55th B.P.S.C. (Pre) 2011]

Correct Answer: (d) Nebula
Solution:The solar system was formed around 4.6 billion years ago. The solar system consists sun (star), cosmic dust or masses attached with each other by gravitational force, planets, dwarf Planets, natural planetoid, asteroids, comets, meteoroid and cosmic dust while Nebulae is not a part of Solar System.

30. Who first propounded that the Sun is the centre of our Solar system and the earth revolves around it? [M.P.P.C.S. (Pre) 1995]

Correct Answer: (d) Copernicus
Solution:Nicolaus Copernicus was an astronomer, mathematician of Poland. In 1514, Copernicus propounded the Heliocentric Theory of the solar system in his Essay 'Commentariolus' (Little commentary). Notably, Indian astronomers Varahamihira propounded the same theory around a thousand years before Copernicus in the sixth century. He mentioned that the moon revolves around the earth and the earth revolves around the sun.
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