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Flashcards in ⭐️topic SP7 - Astronomy Deck (61)
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What is the geocentric model?

The idea that the sun and all the planets are orbiting the Earth; the earth is the Center of everything


Who came up with the geocentric model?

The greeek astronomer ptolemy


What is the heliocentric model?

The idea that the sun is in the centre of the solar system


Who came up with the heliocentric model?

The polish astronomer nicolaus Copernicus


What did the invention of the telescope allow?

Scientists to see objects in space in much more detail and to find new objects


What did Galileo Galilei achieve?

The discovery of four of Jupiter’s moons and by plotting their movements he proved not everything orbited the earth and lead him to support coppernicus’s idea


What other discoveries were made with the improvements of telescopes?

Uranus, Neptune, the dwarf planet Pluto, asteroids and many comets


What is the difference between a comet and an asteroid?

Comets are mostly made of ice, asteroids are rocky bodies


What shape do all the planets move around the sun?

In an elliptical orbit


What are natural satellites?



What has the invention of photography allowed astronomers to do?

Make detailed observations and measurements.


How have computers affected modern astronomy?

Increased the speed and detail in which info from telescopes can be analysed.


Why are some telescopes in orbit around the earth?

-They give much clearer images as clouds and dust aren’t in the way.
-if the telescope is designed to detect radio waves and infrared emitted by space objects, they must be placed in orbit as the atmosphere absorbs some of that radiation


What is weight?

Mass x gravitational field strength


What is gravitational field strength in earth?



What does gravitational field strength on a body depend on?

The mass of the body and the distance from its centre to the surface (radius)


The greater the mass of a body...

...the smaller it’s radius and the greater it’s surface gravity


What are artificial satellites used for?

Communication and to observe earth and space


Describe satellites in highly elliptical orbits

The are used for communication in parts of the earth near the poles


Describe a satellite in a polar orbit

Will eventually pass over all parts of the earth


Describe satellites in circular geostationary orbits

They remain over 1 point on the Earth and are used for broadcasting. They move at 3070 m/s


Describe satellites in low earth orbits

Need the least fuel for launching and they move around 7500 m/s


Why does the force change its direction but not it’s speed on an orbiting body?

As the gravitational force between the earth and the satellite is at right angles to the direction of movement


The gravitational force of a satellite in low orbit is...

...greater than that on a satellite in higher orbit


There are two satellites. A is in a higher orbit than B, which one has to be moving faster to stay in orbit

B as if it slows down, it will fall towards the earth.


What happens when an object falls out of orbit?

It gains speed as it falls until its moving fast enough to stay in a new lower orbit, if it falls into contact with the atmosphere, then the air will slow it down and it’ll eventually fall to earth


How does a star start off?

A nebula - cloud of gas and dust


If the hydrogen in a nebula has a large enough mass?

Gravity will cause it to pull into itself to form a ball being a protostar


How is fusion triggered in starts?

When as the hydrogen atoms accelerate increasing kinetic energy and temperature allowing them to collide due to the increase in pressure


What happens to a protostars once fusion is triggered?

It becomes a main sequence star upon entering the stable phase