AQA A Level Physics Paper 3 Section B: Astrophysics June 2024 question paper 7408/3BA

A student uses a refracting telescope in normal adjustment to make observations of Jupiter. The telescope has an angular magnification of 75

The eyepiece has a focal length of 22 mm.

Determine the distance between the eyepiece and the objective lens.

When viewed through the telescope, the image of Jupiter subtends an angle

Calculate, in km, the distance between the Earth and Jupiter.

mean radius of Jupiter = 7.0 × 10⁴ km

The student places a cap over one end of the telescope. The cap has a circular hole in its centre. Figure 1 shows the end of the telescope, the objective lens and the cap.

State and explain the effect that the addition of the cap has on the chromatic aberration caused by the lens.

Explain two other effects that the addition of the cap has on the image of Jupiter.

The apparent change in position of a nearby star relative to distant stars is due to an effect known as parallax.

Figure 2 shows how parallax arises. As the Earth moves from point P to point Q, an observer on the Earth sees the position of a nearby star S change in relation to distant stars.

Angle A is the parallax angle. This angle can be used to determine the distance to a nearby star, provided that the relative motion between the star and the Sun is negligible between observations.

The distance from the Sun to S is 79 ly. The Earth takes 6 months to move from point P to point Q.

Calculate, in degrees, angle A.

Parallax is used to determine the distance to a different star. Observations of the star produce the following data:

distance determined using parallax = 0.40 pc apparent magnitude = 13.5 absolute magnitude = 16.7

An astronomer suggests that the star moved significantly relative to the Sun between the two parallax observations.

Discuss whether this suggestion is valid.

Figure 3 shows the variation of intensity with wavelength for a star.

Show that Figure 3 is consistent with a black-body temperature of about 6.0 × 10³ K.

The radius of the star is 9.6 × 10⁶ m.

Calculate the power output of the star.

Which row gives the type and spectral class of the star?

The light from the star passes through an interstellar dust cloud before reaching Earth. The reduction in intensity when light passes through a dust cloud is assumed to be inversely proportional to the wavelength of the light.

An astronomer on the Earth estimates the black-body temperature of the star.

Discuss the effect that the dust cloud has on this estimate.

The Earth is in the galaxy known as the Milky Way. The Andromeda Galaxy is one of the closest galaxies to the Milky Way.

The Andromeda Galaxy approaches the Milky Way at a speed of 110 km s⁻¹. The distance between the galaxies is 770 kpc.

Discuss whether these data can be used to estimate an age for the Universe.

There is a supermassive black hole at the centre of the Andromeda Galaxy. The mass of this black hole is 1.60 × 10⁸ solar masses.

Calculate the radius of the event horizon of this black hole. State an appropriate unit for your answer.

Scientists predict that a quasar will be produced as the Milky Way and the Andromeda Galaxy merge.

Explain what is meant by a quasar. Go on to suggest why a quasar may be produced as galaxies merge.

In your answer you should:

• describe the typical properties of a quasar

• explain how observations of quasars provide evidence for these properties

• suggest the process of quasar formation that is likely when two galaxies merge.