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Solar System GK ?Questions and Answers

1. What is a circumpolar star?

Ans: Due to the earth?s rotation, stars generally appear to rise in the east and set in the west. If you go to the poles, you will find that stars revolve around the earth but don?t go under or come above the horizon. They are visible for the entire night on every day of the year. Hence, a circumpolar star is one that never sets as seen from a given latitude. At either of the earth?s pole, all stars are circumpolar, whereas exactly at the equator there are none. A star will be circumpolar at a given latitude if its declination (equivalent of latitude measured in degrees from the celestial equator (0 to 90) is greater than 90 degrees minus the observer?s latitude.

2. What is the name of the tenth planet?

Ans: The tenth planet in the outer solar system was discovered recently. Right now, it?s about 97 times further from the sun than the Earth and it?s the farthest-known object in the solar system. Mike Brown (California Institute of Technology) along with colleagues Chad Trujillo (Gemini Observatory, Hawaii) and David Rabinowitz (Yale University) discovered it. It goes under the temporary name of 2003UB313; a new name has been proposed to the International Astronomical Union.

3. What is the Chandrasekhar Limit?

Ans: In the 1930s, Subramanya Chandrasekhar, now recognised as the founder of relativistic astrophysics, address the important question: What happens to a star once it has burnt all its nuclear fuel? Chadrasekhar?s answer was that it depends on the mass of the burnt core left behind. If the mass of this core (mind you, not the mass of the shining star) is less than 1.4 times the mass of the sun, the core will retire as a white dwarf star. Immediately above this limit, say up to three times the solar mass, the core will become a neutron star. If the mass of the core is still higher, a black hole will be formed. In an ordinary shining star, the force of gravitation is balanced by nuclear reactions. In white dwarf and neutron stars, by complex quantum forces. In a black hole, gravitation dominates. For this pioneering work Chandrasekhar belatedly received the Nobel Prize for Physics in 1983.

4. What is a brown dwarf?

Ans: The small particles of dust, left over after the formation of the star, collide and sometimes stick together forming larger clumps. These collide to form larger clumps, the process continuing until most of the dust is used up. The result is a relatively cold body which is not sufficiently hot or heavy to produce its own light. If, for some reason, insufficient gas is available to form a star, then the body will not be able to increase its mass and temperature sufficiently to be able to sustain hydrogen fusion. The resulting object is a brown dwarf.

5. What is the Chandrashekar Limit?

Ans: The maximum limit of 1.44 times the solar mass (or sun’s mass) of a star, to end its life as a white dwarf star, is known as the Chandrashekar Limit. This is the basic principle to determine the future of a star after the red giant phase. The stars with a mass more than 1.44 times the solar mass go through supernova explosions and end their lives as neutron stars or black holes. This limit was discovered by Indian astrophysicist S Chandrashekar and hence it has been named after him.

6. What is solar wind?

Ans: It?s the flux of particles, chiefly protons and electrons together with nuclei of heavier elements in smaller numbers, that are accelerated by the high temperatures of the solar corona, or outer region of the Sun, to velocities large enough to allow them to escape from the Sun?s gravitational field. The solar wind is responsible for deflecting both the tail of the Earth?s magnetosphere and the tails of comets away from the Sun.

7. What are the orbits of Staurn?s moons called?

Ans: Saturn has at least 47 known moons. However, the moons have two orbits ? Janus and Epimethus. Saturn has been in the news ever since a new ring was discovered, possibly caused by a meteorite?s impact on one of its moons. Saturn is said to have at least seven rings.

8. What is the new name for Pluto?

Ans: After Pluto was deemed not to be a planet but a dwarf planet, it?s also known by another name now. Or rather a number. In all scientific references, it?ll be known by the asteroid number 134340. This has decided by the Minor Planet Centre, the organisation responsible for data collection about objects in the solar system.

9. What?s unique about space vehicle Orion?

Ans: Orion is the new moonship that NASA plans to develop. This was revealed when US astronaut Jeff Williams inadvertently mentioned the name of the vehicle while taping a message for a space agency when floating 354 kms above the earth in the International Space Station. It was transmitted by accident over space-to-ground radio.

10. What is the Kuiper Belt?

Ans: The Kuiper Belt is disk-shaped belt of billions of small, icy bodies orbiting the Sun beyond the orbit of Neptune, mostly at distances 30-50 times the Earth?s distance from the Sun. Modern computer simulations show the Kuiper Belt to have been strongly influenced by Jupiter and Neptune.