Unit 6 - Space physics

Question 1

Heliocentric

Answer 1

The idea that the Earth orbits around the Sun

Question 2

Earth’s rotation

Answer 2

• 24 hours is a day/one full rotation on its axis
• 365 days is a year/ one full orbit of the Sun
• Four seasons in the year - winter, spring, summer & autumn - due to axis tilt

Question 3

Phases of the moon

Answer 3

• New moon
• Waxing crescent
• First quarter
• Waxing gibbous
• Full moon
• Waning gibbous
• Third quarter
• Waning crescent

Question 4

Moon’s orbit

Answer 4

• Takes around a month for the moon to orbit the earth

Question 5

Eight planets of the solar system in order from the sun

Answer 5

• Mercury
• Venus
• Earth
• Mars
• Jupiter
• Saturn
• Uranus
• Neptune

Question 6

Other bodies in the solar system

Answer 6

• Moons - Mercury and Venus do not have moons
• Minor plants - dwarf planets
• Asteroids in asteroid belt - between Mars and Jupiter
• Comets
• Natural satellites e.g. moons

Question 7

Comets

Answer 7

Balls of ice that orbit the Sun in elliptical orbits - when close to the sun they heat up and some ice evaporates becoming a visible tail

Question 8

Big-bang theory explained

Answer 8

• Almost every object was formed from interstellar clouds of dust
• Over billions of years they gradually clumped together because of its own gravity and began to spin as a disc and eventually most ignited and became the sun
• The particles in the remaining disc began to clump and combine growing into larger chunks pulled together by gravity - accretion model
• Accretion disc was made of all different elements, but mostly hydrogen and helium
• Material like hydrogen and helium could not solidify into planets close to the sun due to low boiling points, and heavier elements like iron could so planets closest to the sun are rocky and further away are hydrogen and helium based

Question 9

Correlation with mass and gravitational field strength

Answer 9

The more mass an object has, the greater the gravitational field strength at its surface

Question 10

Sun’s mass

Answer 10

• Sun accounts for 99.8% of our solar system’s mass

Question 11

Speed of light

Answer 11

3x10^8m/s

Question 12

Time it takes light from the sun to reach earth

Answer 12

8 minutes

Question 13

Factors of gravitational force

Answer 13

• Mass of object
• Distance from the object

Question 14

Reason for why planets travel faster closer to the sun

Answer 14

• Gravitational potential energy is converted into kinetic energy

Question 15

Shape of a planet’s orbit

Answer 15

Elliptical

Question 16

Star

Answer 16

A ball of gas which radiated energy in the form of electromagnetic waves

Question 17

Main elements in stars (unless they are dying)

Answer 17

• Hydrogen & Helium

Question 18

Nuclear fusion in stars

Answer 18

In stable stars, hydrogen atoms join together with enough force to make helium atoms, producing energy which is released in electromagnetic waves

Question 19

Galaxies

Answer 19

Collections of billions of stars, all orbiting around a galactic center which is usually a black hole e.g. the Milky Way

Question 20

Distance of one light year

Answer 20

9.5 trillion km / 9.5x10^15

Question 21

Stages of an average star’s life

Answer 21

• Stellar nebula - cloud of hydrogen and dust before a star is born
• Protostar - stellar nebula gradually collapses under its own gravity, temperature increases and light starts to be emitted
• Average star - relatively low mass and average size, force of gravity is balanced by outward force due to high temperature in the center
• Red giant - outer layer expands when hydrogen runs out becoming a red giant
• Planetary nebula - when the red giant runs out of fuel, the outer layers will spread out further while cooling down eventually becoming a loose cloud of gas and dust
• White dwarf - the core of the star remains but no fusion, temperature is high and glows white

Question 22

Stages of a massive star’s life

Answer 22

• Stellar nebula - cloud of hydrogen and dust before a star is born
• Protostar - stellar nebula gradually collapses under its own gravity, temperature increases and light starts to be emitted
• Massive star - relatively high miss, force of gravity is balanced by outward force due to high temperature in center
• Red supergiant - runs out of hydrogen and outer layers expand
• Supernova - after red supergiant runs out of fuel, gravity pulls all the matter back into the center causing a huge amount of pressure that causes the star to violently explode supernova - can create a stellar nebula and form new stars and planets
• Neutron star - core is left after supernova but there is so much mass and gravity that atoms cannot exist and are crushed together to form a block of neutrons
• Black hole - If the core is massive enough even neutrons cannot exist because gravity is crushing them together, all matter is crushed together to a single point creating the most dense object in the Universe

Question 23

Size of the Milky Way

Answer 23

100,000 light years in diameter

Question 24

Redshift

Answer 24

If a source of light moves away from an observer, the observed wavelength increases hence the wavelength of light shifts towards the red end of the spectrum

Question 25

Cosmic microwave background radiation (CMBR)

Answer 25

The microwave radiation left over from he Big Bang which is observed everywhere in the Universe

Question 26

Hubble constant

Answer 26

• For every galaxy in the sky, the ratio between the receding speed (v) and the distance to that galaxy (d) was constant, H0
• H0 = v/d = 2.2x10^-18 per second

Question 27

Equation for the time the galaxy started moving / time since the Big Bang

Answer 27

• Reciprocal of the Hubble constant equation
• 1/H0 = d/v