Which is the nearest star to the earth after the Sun?
- A.Sirius
- B.Proxima Centauri
- C.Polaris
- D.Betelgeuse
Correct answer
Explanation
The correct answer is B, Proxima Centauri, a faint red dwarf about 4.24 light years from the earth and a member of the Alpha Centauri system in the southern sky. Being a red dwarf it cannot be seen with the naked eye, although it is the closest star to us after the Sun. Option A, Sirius, in the constellation Canis Major, is the brightest star of the night sky and lies about 8.6 light years away, so candidates who confuse brightest with nearest choose it. Option C, Polaris, the Pole Star, is important because it stands almost above the north pole of the earth and therefore appears fixed in the sky, but it is hundreds of light years away. Option D, Betelgeuse, is a red supergiant in Orion and is one of the stars expected to end in a supernova. The distinction to keep clear is nearest, which is Proxima Centauri, against brightest, which is Sirius.
Read the full article: Space Science: Stars, Galaxies and Satellites Notes
Practice Questions
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- A.Fusion of heavy nuclei
- B.Fusion of lighter nuclei
- C.Fission of light nuclei
- D.Fission of heavy nuclei
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- A.Scattering of light by dust particles
- B.Internal reflection of light by clouds
- C.Atmospheric refraction of star light
- D.Dispersion of light by water droplets
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A star is so far away that it is a point source of light.
Read the full explanation →Once a satellite has been launched into orbit, the only force governing its motion is the force of ______.
- A.gravity
- B.elasticity
- C.friction
- D.fuel driven
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A satellite is given the required height and speed by its launch vehicle, and after that no engine is needed: the gravitational pull of the earth alone acts on it and provides the centripetal force that keeps it in a curved path, so the satellite keeps falling towards the earth…
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- A.Time
- B.Distance
- C.Brightness
- D.Mass
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A light year is the distance travelled by light in vacuum in one year, which is about 9.46 times ten to the power twelve kilometres, or roughly nine and a half trillion kilometres.
Read the full explanation →A geostationary satellite completes one revolution around the earth in
- A.90 minutes
- B.12 hours
- C.24 hours
- D.365 days
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A geostationary satellite is placed in a circular orbit about 35,786 kilometres above the equator, where its period of revolution equals the period of rotation of the earth about its axis, and it moves from west to east like the earth, so it appears to stay over the same point…
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