topic 8 - Astrophysics Flashcards
1
Q
what is a universe
A
a large collection of billions of galaxies
2
Q
what is a galaxy
A
a large collection of billions of stars
3
Q
what is our solar system
A
the Milky Way
4
Q
why does gravitational field strength vary
A
- An object’s gravitational field strength depends on its MASS.
- The Moon has less mass than the Earth, so its gravitational field is much weaker.
5
Q
how does gravitational force cause things to orbit
A
- there is an attractive gravitational force between any two objects– pulling them together. E.g. the planets and comets experience an attractive force towards the Sun.
- This gravitational force keeps them moving in curved paths called orbits. The Moon does not crash into the Earth, and the planets do not crash into the Sun because they are moving.
6
Q
how do comets orbit
A
Comets have highly elliptical orbits, with the Sun at one focus. When they come in close to the Sun they speed up, due to the larger gravitational force on them.
7
Q
how do moons orbit
A
Moons have circular orbits
8
Q
how do planets orbit
A
in slightly squashed circles, called ellipses.
9
Q
how to calculate orbital speed
A
(2 x π x orbital radius)/time period
v = 2πr/T