PMF IAS Current Affairs
PMF IAS Current Affairs

Components of the Solar System, Planets and Their Major Moons

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  • Our solar system consists of the sun, eight planets, dwarf planets (Pluto, Ceres, Eris), satellites & countless minor planets, asteroids, meteors, comets, etc.

  • Nicolaus Copernicus was the first to develop a mathematically predictive heliocentric solar system — an astronomical model in which the Earth and planets revolve around the Sun.
  • Most large objects in orbit around the Sun lie near the plane of Earth’s orbit, known as the ecliptic. The planets are very close to the ecliptic, whereas comets and Kuiper belt objects (like Pluto) are frequently at greater angles to it.
  • The orbits of the planets around the sun are nearly circular, but many comets, asteroids, and Kuiper belt objects follow highly elliptical orbits.

[UPSC Prelims 2001] Who amongst the following was the first to state that the earth was spherical?

  1. Aristotle
  2. Copernicus
  3. Ptolemy
  4. Strabo
Explanation:
  • The idea of a spherical Earth was floated by Pythagoras around 500 BC & later validated by Aristotle in 340 BC.
  • Ptolemy placed the Earth at the centre of his geocentric model of the solar system. Nicolaus Copernicus refuted the geocentric model with his heliocentric model.
  • Strabo is best known for his work Geographica (“Geography”), which presented a descriptive history of people and places from different regions of the world know during his lifetime.

Kepler’s Laws of Planetary Motion

  1. The orbit of a planet is an ellipse with the Sun at one of the two foci.
  2. A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.
  3. The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit.

Planet

Surface Temp in ֯C

Period of Rotation

Period of Revolution

Distance in AU

Diameter (km)

Size

Rank

Moons

Density (gm/cm3)

Specific gravity (m/s2)

1. Mercury +427

58 days

87 days

0.4

4,878

0.38

8

0 5.4 3.7 0.38
2. Venus

+480

243 days

224 days

0.7

12,104

0.95

6 0 5.2 8.9 0.9
3. Earth +22

23:56 hrs

365 days

1

12,756

1.00

5

1

5.5

9.8

1
4. Mars -23

1.025 days

687 days

1.5

6,787

0.53

7 2 3.9 3.7 0.38
5. Jupiter -150

9.9 hrs

11.9 years

5.2

1,40,000

11.19

1

79 1.3

24.9

2.53

6. Saturn -180

10.7 hrs

29 years

9.6

1,16,000

9.46

2

82

0.7

10.4 1.06
7. Uranus -214

17 hrs

84 years

19.2

51,000

4.11

3 27 1.3 8.8 0.9
8. Neptune -220

16 hrs

164 years

30.0

48,000

3.88

4 14 1.6 11.1 1.13

Pluto (dwarf)

-223

6.39 days

248 years

39.5

2,377

0.18

9 5 1.9 0.6 0.06

Some of the values given in the table are rounded off.

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