LEARNATHON
III

Competition for grade 6 to 10 students! Learn, solve tests and earn prizes!

### Theory:

Members of the solar system:
Apart from planets, there are some other celestial bodies that revolve around the Sun. They are:

1. Asteroids:
Asteroids are rocky celestial objects that orbit in space and revolve around the Sun in a particular path. The asteroids form a belt-like structure between Mars and Jupiter known as the asteroid belt. It looks like a dividing line between the inner rocky planets and the outer gaseous giants in the solar system.

2. Comet:
Comets are lumps of gas and dust which revolve around the Sun in highly elliptical orbits. A comet's tail is always directed opposite to the direction of the sun. Halley’s comet is a periodical comet, which appears after every $$76\ years$$.

3. Meteoroids:
Meteoroids are rocky celestial bodies smaller than asteroids.

4. Meteors:
Meteoroids break away from the Sun's orbit and fall towards the Earth, becoming meteor. Meteors are tiny rocks in the solar system.

5. Meteorites:
Sometimes, the large meteors cannot be burnt completely, and they fall on the Earth's surface as meteorites.

Satellite:
A satellite is a body revolving around a planet in orbit due to the planet's gravity and the centripetal force. There are two types of satellites. They are

Natural satellite: Moon is the only natural satellite of the Earth.
Artificial satellites: They are man-made satellites that revolve around the Earth.

Orbital velocity:
The horizontal velocity imparted to a satellite at the determined height to make a circular orbit around the planet is called orbital velocity.

The formula of orbital velocity:

$v\phantom{\rule{0.147em}{0ex}}=\phantom{\rule{0.147em}{0ex}}\sqrt{\frac{\mathit{GM}}{\left(R+h\right)}}$

The time taken by a satellite to complete one revolution around the Earth is called the time period ($$T$$).

$\begin{array}{l}T=\frac{2\mathrm{\pi }r}{v}\\ \\ T\phantom{\rule{0.147em}{0ex}}=\phantom{\rule{0.147em}{0ex}}\frac{2\mathrm{\pi }\left(R+h\right)}{\sqrt{\frac{\mathit{GM}}{\left(R+h\right)}}}\end{array}$

Kepler's  Laws of planetary motion:

1. First law or the law of ellipses:
All planets revolve around the Sun in elliptical orbits, with Sun at one of their foci.
2. Second law or the law of equal areas:
The line connecting the planet and the Sun covers equal areas in equal intervals of time.
3. Third law or the law of harmonies:
The square of the time period of revolution of a planet around the Sun is directly proportional to the cube of the distance between the sun and the planets.
International Space Station:
The International Space Station (ISS) is a huge spacecraft capable of accommodating astronauts. ISS orbits the Earth at a distance of about $$400\ kilometres$$, serving as a science laboratory and observatory in space.

The ISS is built, maintained, and operated by an international collaboration of five distinct space organisations from $$16$$ countries.

The five space organisations are NASA (USA), Roskosmos (Russia), ESA (Europe), JAXA (Japan), and CSA (Canada).

The above consortium or group of space organisations includes several countries such as Belgium, Brazil, Denmark, France, Germany, Italy, Holland, Norway, Spain, Sweden, Switzerland, and United Kingdom.