Astrophysics

Question 1

Why does your weight vary across planets?

Answer 1

● Your weight is dependant on g, since weight = mass x g
● The gravitational field strength (g) of a planet varies depending on the radius and mass of the planet
● This means that your weight will also vary

Question 2

What does our solar system consist of?

Answer 2

● The sun (our star)
● 8 Planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune)
● The planet’s natural satellites (ie. the moon)
● Dwarf planets
● Comets and asteroids

Question 3

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

Answer 3

·Planets follow a (approximately) circular orbit around the Sun.
·Satellites including moons follow a (approximately) circular orbit around planets.
·Comets follow elliptical orbits around the Sun.

Question 4

Which force is makes astronomical objects follow orbits?

Answer 4

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

Question 5

Which astronomical object forms from the collection of billions of stars?

Answer 5

A Galaxy

Question 6

What is the name of the galaxy that contains our solar system?

Answer 6

Milky Way galaxy

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

Question 9

Stars can be classified according to colour. Order the given colours of stars from coldest to hottest
● Yellow
● Blue
● Red
● White
● Orange

Answer 9

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

Which 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

● The nebula increases in size until it is pulled in due to its gravity,causing GPE to turn into 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

● The 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 mass which is larger
than the sun?

Answer 17

• Nebula
• Main sequence star
• Red supergiant star
• Supernova
• Black hole/ neutron star

Question 18

What is 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 (or a black hole if it is very large).

Question 19

Define Cosmic background radiation

Answer 19

Cosmic background radiation is a form of electromagnetic radiation that fills the universe and is believed to be the residual energy left over from the Big Bang.

Question 20

Define Redshift

Answer 20

Redshift refers to the displacement of spectral lines in the light from distant celestial objects towards longer (red) wavelengths, indicating that the object is moving away from the observer, and is a key piece of evidence for the expansion of the universe.