Astrophysics

Question 1

Why does you weight vary across planets?

Answer 1

-Your weight is dependant of gravitational fiel strength (w=mxg)
-The g of the planet varies depending on the radius and mass of a planet

Question 2

What does our solar system consist of

Answer 2

-The Sun
-8 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune)
-The planet’s natural planets
-Dwarf planets
-Comets and asteroids

Question 3

Describe the orbits of moons, planets, comets and artificial satellites.

Answer 3

-Planets follow an approximately circular orbits around the sun
-Satellites including moons follow an approximately circular orbit around planets
-Comets follow elliptical orbits around the sun

Question 4

Which force makes astronomical objects follow orbits?

Answer 4

Gravitational force pulls the objects causing them to follow orbits around massive objects.

Question 5

What is a galaxy?

Answer 5

An astronomical object forms formed from the collection of billions of stars

Question 6

What is the name of our galaxy?

Answer 6

The Milky way

Question 7

What is the large collection of billions of galaxies called?

Answer 7

The Universe

Question 8

State an equation linking orbital speed, orbital radius and time period

Answer 8

Orbital speed= 2xπxradius/time period
v=2xπxr/T

Question 9

Stars can be classified according to colour. Order the colour of stars from coldest to hottest

Answer 9

Red→Orange→Yello→White→Blue

Question 10

Name each stage the sun has gone/will go through in its lifetime in order

Answer 10

1.Nebula
2.Main sequence star
3.Red giant
4.White dwarf

Question 11

What stage is the sun currently in?

Answer 11

Main sequence

Question 12

What is a nebula?

Answer 12

A cloud of gas and dust

Question 13

Describe the transition of the star from the nebula stage to the main sequence

Answer 13

-Nebula increases in size until it is pulled in due to its gravity, causing GPE to turn to KE of molecules
-As it gets smaller, particles move faster and collide harder so temperature increases
-Eventually the nebula will become dense and hot enough to begin fusion

Question 14

What occurs in the stage when a star is a main sequence star?

Answer 14

-Fusion in the star releases energy
-During fusion, main sequence stars mostly turn hydrogen into helium
-Thermal energy released from fusion causes an outward pressure which balances the inward pressure caused by gravity
-The star is in equilibrium so will not collapse due to gravity or expand due to fusion. It is stable

Question 15

What happens when a star transitions to the red giant stage?

Answer 15

-Once all of the hydrogen fuel has been used up, the star begins to fuse helium and other larger nuclei
-This causes the star to expand and become a red giant

Question 16

How does a star become a white dwarf from a red giant?

Answer 16

-Once all reactions have taken place, the star’s gravity pulls in all of its mass, making a small, dense white dwarf
-This will cool down to form a black dwarf

Question 17

What stages occur for the evolution of stars that have a larger mass than the sun?

Answer 17

-Nebula
-Main sequence star
-Red supergiant star
-supernova
-Black hole/Neutron star

Question 18

What is a supernova?

Answer 18

After the red supergiant stage the star will expand and get hotter, eventually it will explode as a supernova. What is left turns into a neutron star of a black hole if it’s very large.

Question 19

What absolute magnitude

Answer 19

scale that measures brightness of a star for a fixed distance so it becomes independent of distance

Question 20

Stars can be classified in HR diagram. What do the axes of the HR diagrams represent?

Answer 20

X axis: decreasing temp
Y axis: Absolute magnitude/luminosity

Question 21

Star A has absolute magnitude of -3, star B has 1. Which star has the highest luminosity

Answer 21

Star A. Absolute magnitude has an inverted scale

Question 22

Summarise the Big Bang Theory

Answer 22

According to the Big Bang theory, the universe expanded from a very small dense point about 14 billion year ago

Question 23

Give 2 pieces of evidence that support the big bang theory

Answer 23

-Cosmic Microwave Background Radiation (CMB):comes from all directions of space. It is the leftover thermal energy from big bang
-Redshift of distant galaxies:The further the galaxy is the greater is its red shift, hence the faster it’s moving away. This shows that the universe and space itself is expanding

Question 24

Explain what is meant by redshift

Answer 24

When a galaxy (or star), is travelling away from the Earth, wavelength of the light emitted by the object increases therefore it shifts towards the red end of the visible light spectrum

Question 25

Explain what is meant by redshift

Answer 25

When an object is travelling towards the Earth, wavelength of the light emitted by the object decreases therefore it shifts towards the blue end of the visible light spectrum

Question 26

How is observed frequency and observed wavelength affected by A. Redshift? B. Blueshift?

Answer 26

-In redshift, observed wavelength increases and observed frequency decreases
-In blueshift, observed wavelength decreases asn observed frequency increases
-This is due to wave speed being constant (V=λxf)

Question 27

State the equation linking the change in wavelength, reference wavelength, recessional speed of galaxy and speed of light

Answer 27

Change in wavelength/reference wavelength=velocity of galaxy/speed of light

Question 28

Explain how redshift observation from distant galaxies supports the big bang theory

Answer 28

Observation show distant galaxies show greater redshift. This means that distant galaxies are moving away faster. So all galaxies are moving away from each other therefore the universe and space is expanding