Section 5 - Astronomy Flashcards
Order of planets?
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Example of a dwarf planet ?
Pluto
What are moons and how do they orbit earth ?
Moons are natural satellites and orbit earth in a circular orbit.
What’s a satellite?
A satellite is an object that orbits a second massive object.
What type of force is gravity?
Gravity is a centripetal force.
How does a satellite stay in orbit?
A satellite stays in orbit because Gravity it pulls it down but because they’re moving sideways they constantly fall around the earth because it’s a sphere
How is the moon accelerating and staying at the same speed at the same time ?
Because it’s changing direction and velocity takes into account direction
What’s an asteroid?
Where are they usually found ?
Asteroids are lumps of rocks and metals that orbit the sun.
Asteroids are usually found in asteroid belts.
What are comets?
What type of orbits do they have?
Comets are lumps of ice and dust that orbit the sun
They have highly eliptical orbits
What’s the geocentric model?
The earth is in the centre of our solar system
Why did the geocentric model become a thing?
Because people didn’t have telescopes and saw the moon and sun travelling across the sky every day.
Who created the geocentric model?
The Greeks
What was the heliocentric model?
What did it originally say?
Said the sun was at the centre of the solar system.
It originally said earth and all the planets orbited the sun in perfect circles
How did galieo prove the geocentric model wrong?
Whilst looking at Jupiter he noticed there was stars near it.
When he looked back, they never moved away
This proves not EVERYTHING orbits the earth and could only be explained by it orbiting the sun
What does the new heliocentric model change?
The planets orbits are eliptical not circular.
The planets orbit the sun
What force creates orbits ?
Gravity
Why is an object moving in a circular orbit constantly accelerating?
What force causes this?
In which direction does this force act?
-Because its velocity is changing.
-centripetal force
-towards the centre of a circle
If the object wasn’t moving, what would the centripetal force cause it to do?
It would towards whatever it was orbiting
What does gravitational field strength depend on?
Mass
Density
Where would an object weigh more on, the earth or the moon?
The earth
What happens to the gravitational field strength as you get closer to a planet?
It gets stronger
What’s needed to balance a strong force when someothing orbits something in a circular motion?
A larger instantaneous velocity
For an object in a stable orbit, if the speed changed what else must change?
The radius of its orbit must change if the speed its orbiting at changes
How do stars initially form?
From a cloud of dust and gas called a nebula
How’s a protostar formed?
What happens as the protostar gets denser?
Gravity pulls dust and gas together.
The temperature rises and hydrogen nuclei undergo nuclear fusion to form helium.
How’s a main sequence star formed?
What happens to a stars time on main sequence the heavier it is?
-The outward pressure by thermal expansion balances the force of gravity pulling everything inwards.
- the heavier a star is the shorter its time on main sequence is.
How’s a red giant or red supergiant formed?
Why does it turn red?
-The hydrogen in the core runs out, the core of the star is compressed till it’s dense and hot enough to expand the outer layers of the star.
- it turns red because it cools
How’s a white dwarf formed after being a red giant?
Ejects it outer layers and leaves behind a hot, dense, solid core
How’s a supernova formed after a red supergiant?
Big stars undergo more fusion. They expand and contract several times before exploding?
What two things can form after a supernova?
A neutron star
A black hole
How does a black hole form?
The exploding supernova throws it outer layers of dust and gas. This leaves behind a neutron star. If it’s big enough it will collapse into a black hole
Describe how evidence has changed our ideas of the universe (heliocentric and geocentric models)
-Telescopes support the heliocentric model
-gelileos observations of the moons orbiting Jupiter
-meaning not everything orbits the sun
- satellite observations
-computer modeling
-heliocentric model verified by voyager missions
