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Flashcards in Astronomy Deck (17):

What is the equation of weight?

weight (Newtons) = mass (kg) x gravitational field strength


Where is out solar system?

In the milky way


What is a galaxy?

A large collection of billions of stars


What is the universe?

A large collection of billions of galaxies


What is the gravitational field strength on other planets?

Earth - 10N/Kg
Moon - 1.6N/Kg
Mars - 4N/Kg
-g is different on other planets and the moon from that on Earth


What are moons?

Non luminous objects, we see them because they reflect light from the sun


Does the Earth have a moon?

It has one that orbits the earth in 29.5 days (1 lunar month)
Mars - 2 moons
Jupiter - over 60 moons
Uranus - 27 moons


What are planets?

Non luminous objects, we see them because they reflect light from the sun
The orbits of planets are elliptical with the sun close to the centre.
They are held in orbit by the gravitational pull of the sun. (GF also cause moons (earth), comets (sun) and artificial satellites (earth) to orbit their things) Gravity decreases quickly as you get further away


What are comets?

-Comets orbit the sun, with a very elliptical orbit.
-They are made of dust and ice ('icy mud balls')
-Comets speed up nearer the sun as the gravitational forces increase nearer the sun
-Comets move slower further away from the sun as the gravitational forces are smaller.
-Close to the sun some of the comets frozen gases evaporate forming a long tail that shines in the sunlight
-The tail always points away from the sun


What is an asteroid?

Are minor planets or rocks that orbit the sun
Asteroid belt between the orbits of Mars and Jupiter


What is a satellite?

Satellites are objects that orbit a planet
Moons are natural satellites
Manufactured objects are artificial satellites


What is the equation for orbital speed?

(2x🍰x orbital radius) / time period


How do you calculate the speed of a satellite?

speed = distance / time
distance travelled = 2 x pie x radius of orbit


What does gravitational force do?

1. Causes moons to orbit planets
2. Causes the planets to orbit the sun
3. Causes artificial satellites to orbit the Earth
4. Causes comets to orbit the sun


Where do you draw the weight arrow on a diagram from?

The weight of a body acts through its centre of gravity (draw from centre of body)


What is the orbits of comets like?



What is the orbits of moons and planets like?

-Usually slightly elliptical
1. With very large masses like stars and planets, gravity is very big and acts a long way out
2. The closer you get to a star or planet, the stronger the force of attraction
3. Because of this stronger force, planets nearer the Sun move faster and cover their orbit quicker
4. Moons and artificial satellites are also held in orbit by gravity
5. The further out from Earth they orbit, the slower they move