Chapter 19: Stars

Question 1

Planets

Answer 1

A planet is an object in orbit around a star with three important characteristics:

• it has made large enough for it’s own gravity to give it a round shape
• it has no fusion reactions
• it has created it’s orbit of most other objects

Question 2

Planetary satellites

Answer 2

A planetary satellite is a body in orbit around a planet

including moon and man-made satellites

Question 3

comets

Answer 3

Comets range for few hundred metres to tens of kilometres across. they are small irregular bodies made up of ice, dust and small pieces of rock.
All comets orbit the Sun, many in highly eccentric elliptical orbits.
As they approach the Sun, some comets develop tails ( ice melting due to heat from sun)

Question 4

Solar system

Answer 4

A planetary system consisting of a star and at least one planet in orbit around it.
e.g. our solar system ( Sun and planets)

Question 5

Galaxies

Answer 5

A collection of stars, and interstellar dust and gas. on average A galaxy will contain 100 billion stars, a significant proportion of which have their own solar systems.
our galaxy is the milky way

Question 6

the universe

Answer 6

it is everything.
it is all em radiation, energy and matter, all space-time and everything that exists within it.
This includes all galaxies and all the contents of Intergalactic space.