The horizontal velocity that has to be imparted to a satellite at the determined height, so that it makes a circular orbit around the planet is called orbital velocity.

The Sun and celestial bodies which revolve around it form the solar system.

Kepler's three laws of planetary motion.
First Law: The Law of Ellipses
The path of the planets about the Sun is elliptical in shape, with the center of the Sun being located at one of the foci.
Second Law: The Law of Equal areas.
An imaginary line drawn from the center of the Sun to the center of the planet will sweep out equal areas in equal intervals of time.
Third Law: The Law of Harmonies
The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their semi major axis from the Sun.

Supporting Water - Purification Efforts:
1. Using the technology developed for the ISS, areas having water scarcity can gain access to advanced water filtration and purification systems.
2. This could very well be a life - saving difference for the people in such hazardous locations.
3. The water recovery system (WRS) and the oxygen generation system (OGS) developed for the ISS have saved a village in Iraq from being deserted due to lack of clean water.
Eye tracking technology:
1. The Eye tracking device, built for a microgravity experiment has proved ideal to be used in many laser surgeries.
2. This device tracks the eyes position very accurately without interfering with the surgeon's work.
3. Eye tracking technology is helping disabled people with limited movement and speech.
Robotic arms and Surgeries:
1. Robotic arms developed for research in ISS are providing significant help to the surgeons in removing inoperable tumours and taking biopsies with great accuracies.
2. Robotic arms do heavy lifting in Cancer treatment in the form of surgical robots.
3. ISS technology are useful in the development of improved vaccines, breast cancer detection and treatment, ultrasound machines for remote regions etc.

We saw that there are natural satellites moving around the planets. There will be gravitational force between the planet and satellites. Satellite moves around the planets due to gravity and the centripetal force.

Stars appear to be in different colours depending on their temperature. Hot stars are white or blue, whereas cooler stars are orange or red in colour.