SP7 Astronomy

Question 1

Define weight

Answer 1

The force acting on an object due to gravitational attraction

Question 2

What is the equation used to calculate weight?

Answer 2

weight = mass x gravitational field strength

Question 3

How does the mass of a planet affect the weight of something on said planet?

Answer 3

The greater the mass of a planet = the greater its gravitational strength

Question 4

The greater the mass of a planet = the greater its gravitational strength
Why is this true?

Answer 4

The more mass a planet has = a greater gravitational pull = higher the value of gravitational acceleration = greater value of g

Question 5

What does the solar system consist of?

Answer 5

• the sun
• eight planets
• dwarf planets
• natural and artificial satellites
• asteroids and comets

Question 6

What are the four gas giants?

Answer 6

Jupiter, Saturn, Uranus , Neptune

Question 6

What are the four rocky planets?

Answer 6

Mercury, Venus, Earth, Mars

Question 7

Why do larger planets have rings?

Answer 7

Their gravitational pull is so strong that it attracts debris

Question 8

How long does light from the sun need to reach us here on Earth?

Answer 8

8 minutes

Question 9

What was the geocentric model?

Answer 9

• model that put earth in the centre
• and the other planets + sun orbited earth
• everything orbited in perfect circles
• with a fixed background of stars

Question 10

What is the heliocentric model?

Answer 10

Sun was at the centre of planets’ orbit, instead of the Earth

Question 11

What was the evidence for the heliocentric model?

Answer 11

• mars being in retrograde
• Galileo observing Jupiters’s moons orbiting it
• Kepler showed that planets orbited in elipses instead of perfect circles

Question 12

When a planet is orbiting the sun, its velocity is always changing. How is this possible?

Answer 12

• gravitational force causes planet to change direction constantly
• but speed of planet is constant
• velocity is always changing = accelerating without increasing its speed
• same goes for satellites around a planet

Question 13

Why is it that closer planets have a faster orbital speed than gas giants?

Answer 13

• closer the planet = stronger the sun’s gravitational strength
• force increases
• therefore acceleration increases
• causing an increase in velocity
• therefore orbital speed is faster

Question 14

Describe the orbits of all planets around the sun

Answer 14

• slightly elliptical
• orbit in the same plane
• travel the same direction around the sun

Question 15

Describe the orbit of comets

Answer 15

• highly elliptical
• causes speed of comet to change
• not all comets orbit in the same field as planets + may not even be in the same direction

Question 16

What are the two forces that stars are held together by?

Answer 16

Gravitational pressure and pressure caused by thermal expansion

Question 17

What happens when the temperature of a star increases?

Answer 17

The star begins to expand because outward pressure will increase

Question 18

What happens when the temperature of a star decreases?

Answer 18

Outward pressure decreases, star begins to shrink

Question 19

Name the life cycle of solar mass stars

Answer 19

1. nebulae
2. protostar
3. main sequence star
4. red giant
5. white dwarf

Question 20

What is a nebula?

Answer 20

All stars form in giant clouds of hydrogen gas and dust called a nebula

Question 21

Define protostar

Answer 21

• The force of gravity within a nebula pulls the particles closer together until it forms a hot ball of gas
• As the particles are pulled closer together the density of the protostar will increase
• This will result in more frequent collisions between the particles which causes the temperature to increase

Question 22

Define main sequence star

Answer 22

• temperature and pressure of protostar increases as particles get pushed so close
• eventually, temperature and pressure gets so great that particles are able to fuse together
• fusion releases a large amount of energy that opposes the collapsing of the cloud due to gravity
• forming an equillibrium

Question 23

Define red giant

Answer 23

• eventually, star runs out of gas to fuse, causing it to collapse
• collapse increases the pressure and temperature of the core allowing heavier elements to fuse
• as core shrinks, outer layer of star will expand and start to cool

Question 24

Define **white dwarf**

Answer 24

- star will eventually become unstable + eject outer layer as a planetary nebulae - core that remains will collapse entirely and begin cooling as a white dwarf

Question 25

Describe the life cycle of stars with a mass higher than the solar mass

Answer 25

1. nebulae 2. protostar 3. main sequence 4. red supergiant 5. supernova 6. neutron star or black hole

Question 26

Define **red supergiant**

Answer 26

Larger version of a red giant

Question 27

Define **supernova**

Answer 27

- once reactions in the red supergiant finish completely, core will collapse suddenly - causing a huge explosion - outer remanents of star ejected into space

Question 28

Define **neutron star**

Answer 28

- star made up entirely of neutrons - spins rapidly

Question 29

Define **black hole**

Answer 29

Point in space from which even light cannot escape

Question 30

Describe the **big bang theory**

Answer 30

- universe began from a small region that was incredibly hot and dense - there was a giant explosion (called big bang) - caused universe to expand from a single point and continue to expand till today

Question 31

Describe the **steady state theory**

Answer 31

- universe always existed - as universe expands, matter is constantly being made so there is a constant density of matter in the universe

Question 32

What is cosmic microwave backrgound radiation?

Answer 32

Thought to be the remains of the thermal radiation from the original big bang

Question 33

What is red shift?

Answer 33

The increase in wavelength due to the distance between the observer and the celestial body increasing

Question 34

What is the evidence for the big bang theory?

Answer 34

- red shift - cmbr

Question 35

Telescopes for what part of the EM spectrum need to be located outside the atmosphere?

Answer 35

X rays, gamma rays, UV rays

Question 36

Why do some telescopes need to be located outside the atmosphere?

Answer 36

Atmosphere blocks these wavelengths out majorly