AQA A Level Physics Paper 3 Section B: Astrophysics June 2025 question paper 7408/3BA

HIP 56948 is a star with a black-body temperature of 5800 K. The star is at a distance of 210 ly from the Sun.

Sketch, on Figure 1, the black-body curve for HIP 56948. Label the wavelength axis with a suitable scale and unit.

The diameter of HIP 56948 is the same as the diameter of the Sun.

Suggest a value for the absolute magnitude of HIP 56948.

Astronomers study HIP 56948 in their search for Earth-like exoplanets because HIP 56948 is similar to the Sun.

Suggest one difficulty in detecting an Earth-like planet around HIP 56948.

Draw a ray diagram for an astronomical telescope in normal adjustment.

Include in your diagram:

three non-axial rays

labelled principal foci for the lenses.

An astronomer has two telescopes A and B.

The astronomer uses each telescope to make observations of Mars when Mars is 0.55 AU from the Earth.

Table 1 gives information about A and B.

angular resolution of the eye ≈ 3 × 10⁻⁴ rad

Compare the images formed by A and B.

In your answer, refer to:

the relative brightness of the images

the ability of each telescope to show features on Mars

the effect of any aberrations caused by each type of telescope.

One advantage of using a CCD with a telescope is that the data can be stored and processed on a computer.

Explain two other advantages of using a CCD rather than the eye when making an observation with a telescope.

The galaxy M87 is at a distance of 5.3 × 10⁷ ly from the Earth.

Determine, in m s⁻¹, the recessional velocity of M87 relative to the Earth.

Astronomers believe that M87 has an active supermassive black hole at its centre.

Suggest one observation that leads to this conclusion.

Which provides evidence for the existence of dark energy?

Tick (✓) one box.

Mintaka Aa1 and Mintaka Aa2 are two stars in a binary system. This means that they orbit their common centre of mass with the same period.

Table 2 gives information about the two stars.

Show that the data in Table 2 are consistent with the two stars being in a binary system.

State the most prominent absorption lines in the spectrum of Mintaka Aa2.

Explain which star in Table 2 has the greater temperature.

Figure 2 shows how the apparent magnitude of the binary system varies with time.

Explain the variation in apparent magnitude shown in Figure 2.

In your answer you should explain:

the changes in observed brightness at P and Q, as shown in Figure 2

why the observed brightness at P is different from the observed brightness at Q.

Determine the angular velocity of the binary system.

Early observations of the star Betelgeuse indicated that:

radius r of Betelgeuse = 700 × radius of the Sun distance d of Betelgeuse from the Earth = 548 ly intensity received from Betelgeuse = I.

Recent data suggest that the intensity received from Betelgeuse is actually 1.15 I.

Based on these recent data, two groups of students reach different conclusions.

Group X suggest that:

• r is correct

• d is actually 530 ly.

Group Y suggest that:

• d is correct

• r is actually 750 × radius of the Sun.

Discuss for each group whether their conclusion could be correct. Assume that the measured temperature of Betelgeuse is constant.