Astronomy (11) Flashcards
Our Solar System is in the _________ _______ galaxy
Milky way
What is a galaxy
A collection of stars
Our Sun is just one of many billions of ________ which form the Milky Way galaxy
Stars
The distance between neighbouring stars in the galaxy is often millions of times __________ than the distance between planets in our solar system
Greater
The force which keeps the stars together in a galaxy is called ____________
Gravity
Like most things in the universe, galaxies ___________
Rotate
What is a universe
A large collection of billions of galaxies
Galaxies themselves are often millions of times ____________ ___________ than the stars are within a galaxy
Further apart
The universe is mostly ____________ __________ and is really really _____
Empty space
Big
Gravity provides the force which causes _____________
Orbits
If an object is travelling in a circle it is constantly changing direction, which means there must be a _________ acting on it
Force
What is an orbit
A balance between the forward motion of the object and a force pulling it inwards
The planets move around the sun in almost ____________ orbits. The forces that make this happen are provided by the _____________ between each planet and the ______
Circular
Gravity
Sun
The _________ orbits the earth. Confusingly, other planets also have ‘________’ orbiting them. These __________ have their own names, but we just call the earth’s _______ -‘_______’
Moon Moon Moon Moon Moon
Artificial satellites that are made by man and put into space by rockets also ________ the Earth
Orbit
Gravity ____________ quickly as you get further away
Decreases
The closer you get to a star or planet, the ____________ the force of attraction. Because of this stronger force, planets nearer the sun move ____________ and cover their orbit _____________
Stronger
Faster
Quicker
Moons and artificial satellites are also held in orbit by gravity. The further out from earth they orbit, the ___________ they move
Slower
The orbits of moons and planets are usually slightly _____________
Elliptical
Comets orbit the sun but have very ____________ orbits with the Sun at one focus (near one end of the orbit)
Elliptical
Comets have orbital periods much ___________ than the earth, as they travel from the outer edges of the Solar System
Longer
A comet travels much ____________ when it’s nearer the sun than it does in more distant parts of its orbit. Why?
Faster
Because the increased pull of gravity makes it speed up the closer it gets to the sun
Some artificial earth satellites have an orbital speed of exactly one day. They’re called __________________ satellites, and are useful in communications because they’re always over the same part of the planet
Geostationary
You can calculate the speed of an orbit using which formula?
Speed = Distance / Time
For a circular object, the distance travelled is the ________________ of the orbit which is given by the formula
Circumference
2 x π x radius of orbit
What is the formula for the speed of an orbit
2 x π x radius of orbit / Time period
Symbol formula for the speed of an orbit
V = 2 π r / T
