Notes
The Sun
- accounts for 99.85% of the mass of the Solar System
- is 150 million km from the Earth
- has a diameter of 1.4 million km
- is 5 billion years old
- is expected to die in another 5 billion years
- temperature at the core: 15 million K
- temperature at the surface: 5700 K
- chemical composition: Hydrogen 82%, He lium18%, Oxygen 0.03%
Cosmic year is the time taken by the Sun to complete one revolution around the center of the galaxy. It is taken to be 250 million years.
Red Giant is a star that has completely burnt out its resources of Hydrogen. The star then loses its luminous intensity and turn red in colour. The Sun is expected to become a Red Giant in about 5 billion years.
Sunspots are regions on the surface of the Sun that are cooler (1500 C) relative to the normal temperature (6000 C). Sunspots cause magnetic interference on the Earth, thereby resulting in interruptions to satellite and radio communication.
Questions
- One AU is the average distance between
- the Earth and the Sun
- the Earth and the Moon
- Jupiter and the Sun
- Pluto and the Sun
- Consider the following statements
- Asteroids are rock debris of varying size orbiting the Sun
- Most asteroids are small but some have diameters over 1000 km
- The orbit of asteroids lies between orbits of Jupiter and Saturn
Which of the above are correct?- a, b and c
- b and c
- a and b
- a and c
- Solar eclipse achieves totality only in limited geographical regions because
- the shadow of the Moon on the Earth is small compared to the cross section of the Earth
- the Earth is not a smooth flat surface, but instead has elevations and depressions
- the trajectory of the Moon around the Earth and the Earth around the Sun are not perfect circles
- the Sun’s rays reach most peripheral regions of the shadow of the Moon due to refraction
- The limit of mass beyond which stars suffer internal collapse is called the
- Chandrasekhar limit
- Eddington limit
- Hoyle limit
- Fowler limit
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