1. 1
   A student calculates the average orbital speed of the Earth around the Sun, given that the average orbital radius is 1.5 x 10^8 km and the orbital year is 365 days.

   (a)

   What is the orbital period of the Earth in seconds, to 3 significant figures, given that the year is 365 days?

   [1 mark]

   • A8.64 x 10^4 s
   • B3.15 x 10^7 s
   • C3.65 x 10^2 s
   • D3.15 x 10^8 s

   (b)

   Using r = 1.5 x 10^8 km and T = 3.15 x 10^7 s, which expression correctly calculates the Earth's average orbital speed?

   [1 mark]

   • A(2 x pi x 1.5x10^11) / (3.15x10^7)
   • B(2 x pi x 1.5x10^8) / (3.15x10^7)
   • C(1.5x10^11) / (2 x pi x 3.15x10^7)
   • D(2 x pi x 3.15x10^7) / (1.5x10^11)

   (c)

   Calculate the Earth's average orbital speed around the Sun, giving your answer in m/s to 3 significant figures.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An astronomy club compares data for Mercury and Neptune: Mercury has an average orbital radius of 5.8 x 10^7 km and an orbital period of 88 days, while Neptune has an average orbital radius of 4.5 x 10^9 km and an orbital period of about 165 years.

   (a)

   Which of these planets has the larger average orbital speed?

   [1 mark]

   • AMercury, because it is closer to the Sun and the Sun's gravitational field is stronger there
   • BNeptune, because it has a much longer orbital period
   • CMercury and Neptune have the same average orbital speed, since both orbit the Sun
   • DNeptune, because it has a much larger orbital radius

   (b)

   Which row correctly classifies Mercury and Neptune according to their composition and size?

   [1 mark]

   • AMercury: gaseous and large; Neptune: rocky and small
   • BBoth rocky and small
   • CBoth gaseous and large
   • DMercury: rocky and small; Neptune: gaseous and large

   (c)

   Explain, using the accretion model of Solar System formation, why the planets closer to the Sun, such as Mercury, are rocky and small, while planets further away, such as Neptune, are gaseous and large.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A textbook compares the Sun with a much more massive star that is nearing the end of its life, both stars being members of the Milky Way galaxy.

   (a)

   State the two elements that make up most of the Sun, describe how the Sun generates its energy, and name the regions of the electromagnetic spectrum in which the Sun radiates most of its energy.

   [3 marks]

   (b)

   The much more massive star described has used up most of the hydrogen in its core. Describe the changes that this star will undergo as its life continues, up to and including its eventual explosion.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A cosmologist explains that light from a distant galaxy is observed to have a longer wavelength than the same light emitted by a similar source on Earth, and that this galaxy is estimated to be 6.0 x 10^24 m away from the Earth, based on the brightness of a supernova observed within it.

   (a)

   Describe what is meant by redshift, explain what the observation described provides evidence for about the Universe, and describe the Big Bang Theory that this evidence supports.

   [6 marks]

   (b)

   The galaxy's distance from the Earth is estimated as 6.0 x 10^24 m using the brightness of a supernova within it. Given that the current estimate for the Hubble constant is 2.2 x 10^-18 per second, calculate the speed at which this galaxy is moving away from the Earth, and use the Hubble constant to estimate the age of the Universe in seconds.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A student calculates how long it takes light from the Sun to reach the Earth, given that the Earth orbits the Sun at an average orbital radius of 1.5 x 10^8 km, and that light travels at a speed of 3.0 x 10^8 m/s.

   (a)

   What is the Earth's average orbital radius in metres?

   [1 mark]

   • A1.5 x 10^5 m
   • B1.5 x 10^8 m
   • C1.5 x 10^11 m
   • D1.5 x 10^14 m

   (b)

   Which equation correctly calculates the time taken for light to travel from the Sun to the Earth, using the orbital radius r and the speed of light c?

   [1 mark]

   • Atime = r / c
   • Btime = c / r
   • Ctime = r x c
   • Dtime = c - r

   (c)

   Calculate the time taken for light from the Sun to reach the Earth, giving your answer in seconds to 2 significant figures.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A comet follows a highly elliptical orbit around the Sun, moving much faster when it is close to the Sun than when it is far away, at the opposite end of its orbit.

   (a)

   Which statement correctly describes the position of the Sun within the comet's elliptical orbit?

   [1 mark]

   • AThe Sun is always at the exact centre of the ellipse
   • BThe Sun is not at the centre of the elliptical orbit, except when the orbit is almost circular
   • CThe Sun is always located outside the orbit entirely
   • DThe comet orbits around the exact centre of the ellipse, not the Sun

   (b)

   Why does the comet move faster when it is close to the Sun than when it is far away?

   [1 mark]

   • AThe comet loses mass as it approaches the Sun, making it easier to accelerate
   • BConservation of energy: as the comet moves closer, gravitational potential energy decreases and kinetic energy increases, so speed increases
   • CThe comet's orbital period becomes shorter close to the Sun, which directly increases its speed
   • DThe Sun's magnetic field pushes the comet faster as it approaches

   (c)

   State how the strength of the Sun's gravitational field acting on the comet, and the comet's orbital speed, each change as the comet moves further away from the Sun.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   An astronomy magazine explains that the Sun radiates most of its energy in the infrared, visible and ultraviolet regions of the electromagnetic spectrum, and separately describes how a radio telescope detects cosmic microwave background radiation (CMBR) arriving with almost equal intensity from every direction in space.

   (a)

   Explain what powers the Sun, and state the two elements that make up most of its mass.

   [3 marks]

   (b)

   Explain what the cosmic microwave background radiation is, when in the history of the Universe it was produced, and why it is now observed in the microwave region of the spectrum rather than at a higher-energy wavelength.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A planetarium show describes the life cycle of a star with a similar mass to the Sun, and separately explains why the Earth experiences a cycle of seasons as it orbits the Sun.

   (a)

   Describe the life cycle of a star with a mass similar to the Sun, from its formation to its final remnant.

   [6 marks]

   (b)

   Explain why the Earth experiences a periodic cycle of seasons as it orbits the Sun, referring to the tilt of the Earth's axis and its orbital motion.

   [6 marks]

   Total for question 8: 12 marks

End of questions