Astrophysics (A-level only) questions

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• AQA 7408 · June 2025 · Paper 3BA · Q3 · 5 marks

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  [3.2] Students often struggled with this question. Talk of a dark or black galactic centre was the main incorrect answer given.

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  The galaxy M87 is 5.3 x 10^7 ly from Earth. Astronomers believe it contains an active supermassive black hole.

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• AQA 7408 · June 2025 · Paper 3BA · Q4 · 10 marks

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  [4.1] Almost 60% of students scored full marks on this question. Those who did not generally failed to follow the “show that” command word and simply did some calculations without giving logical steps or a sensible conclusion. Student’s language was often vague so that in their conclusions many calculated the same number and stated that they were “about” the same.

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  Mintaka Aa1 and Aa2 form a binary system. Aa1 has absolute magnitude -5.4, apparent magnitude 2.5 and spectral class O. Aa2 has absolute magnitude -2.9, apparent magnitude 5.0 and spectral class B.

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• AQA 7408 · June 2025 · Paper 3BA · Q5 · 5 marks

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  Over half of students were able to access the marks for this question although many struggled with the “discuss” command word. Students who did very well on this question provided a logical approach, providing clear calculations for X, clear calculations for Y and then making a logical conclusion based on these. There were several novel approaches which could gain full credit.

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  Early observations of Betelgeuse gave radius r = 700 solar radii, distance d = 548 ly and received intensity I. Recent data give intensity 1.15I at unchanged measured temperature. Group X keeps r and proposes d = 530 ly. Group Y keeps d and proposes r = 750 solar radii.

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• AQA 7408 · June 2024 · Paper 3BA · Q1 · 11 marks

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  This question tested students’ knowledge and understanding of the astronomical telescope in the context of observations of Jupiter. The mark scheme in question 01.1 was designed to give partial credit to students who could do one step in the calculation but not complete it. Over half of the students were awarded both marks. Common errors included mixing up the two lenses, getting the magnification the wrong way round, or not including the focal length of the eyepiece. Question 01.2 was much more demanding. There was evidence of much careless work, failing to take the magnification into account or using the radius rather than the diameter of Jupiter in the calculation. Many students appeared to have no idea of how to approach the question, invoking any equation available to evaluate distance in astronomy, including the magnitudes equation and Hubble’s law. Question 01.3 also proved to be challenging for most students. There was much confusion between diffraction and refraction, for example. Many students also thought that the cap would behave as a filter blocking out some wavelengths and not others. The best answers demonstrated an understanding of the nature of chromatic aberration, and why it affects light entering the edge of the lens the most. Question 01.4 asked about the effect on the image of Jupiter. Most students identified that the image would become dimmer but did not explain their answer in sufficient detail. Some students mentioned reduced resolution without explaining how it was caused or the effect it would have on the image. Some students identified a reduced amount of spherical aberration, which gained credit provided they gave a clear account of what was happening. Some students attempted to say that the image would be both clearer and less clear, referring to resolution and spherical aberration, without realising the contradiction in their answer.

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  A student uses a refracting telescope in normal adjustment to observe Jupiter. The telescope has angular magnification 75 and an eyepiece of focal length 22 mm. A removable cap covers the objective lens except for a smaller circular hole centred on the optical axis, so only the central part of the objective remains exposed.

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• AQA 7408 · June 2024 · Paper 3BA · Q3 · 7 marks

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  This question tested Wien’s law and Stefan’s law in the context of an intensity–wavelength curve. In 03.1 most students simply calculated the temperature of the star using Wien’s law. Some students used an incorrect peak wavelength, either misreading the scale or using the cut-off rather than the peak. The question also required them to show that the graph was consistent with the value given, and therefore some comparison was expected. Other successful routes included calculating a value for Wien’s constant using the data in the question, or a value for the peak wavelength. In both these cases a comparison with the given value was required for full credit. Question 03.2 required the use of Stefan’s law and was answered correctly by almost 60% of students. Common errors included using the volume or area of a circle for the surface area of a sphere and missing out the power of four for the temperature. Partial credit was given for some of these errors. Question 03.3 required students to realise that the radius in 03.2 made the star a dwarf, and that the only option with a compatible spectral class for the temperature was the first one. To obtain both marks in 03.4, students had to identify the effect the absorption would have on the wavelength of the peak, and then conclude the effect this would have on the observed temperature. Some students attempted to argue in terms of Stefan’s law, suggesting that the overall power output would apparently be reduced. This would not affect the estimate unless the absolute magnitude of the star was known, however.

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  A graph of intensity against wavelength for a star has a single black-body-shaped maximum at wavelength approximately 0.48 micrometres; a read-off in the range 0.47-0.49 micrometres is consistent with the plotted curve. The star has radius 9.6 x 10^6 m.

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• AQA 7408 · June 2024 · Paper 3BA · Q4 · 11 marks

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  This question tested knowledge and understanding of black holes and Hubble’s law in the context of merging the Milky Way and Andromeda galaxies. In question 04.1, most students identified Hubble’s law or the Hubble constant as the method of finding the age of the Universe. Far fewer students identified that this was invalid in this situation as the galaxies are approaching and not receding. The calculation in question 04.2 was completed successfully by more than half of the students. Common errors included missing out the factor of 2, incorrectly calculating the mass of the black hole and failing to square the speed of light. The unit mark was linked to the final answer, and any appropriate unit was accepted provided the value was correct. Question 04.3 allowed students to explain what they knew and understood about quasars and their formation. As is typical on this paper, this six-mark question was the most discriminating on the paper, allowing E grade students to gain at least one mark and A* students to get five or six marks. The mark scheme was quite generous. Many students had some idea of the power output and distance to quasars and many managed to link these to their brightness relative to their host galaxies and the redshift, respectively. Fewer students managed to successfully describe the likely process of quasar formation with much confusion with type 1a supernovae being evident, for example.

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  The Andromeda Galaxy is 770 kpc from the Milky Way and approaches it at 110 km s^-1. A supermassive black hole of mass 1.60 x 10^8 solar masses lies at Andromeda's centre. Scientists predict that a quasar will be produced as the Milky Way and Andromeda merge.

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• AQA 7408 · June 2023 · Paper 3BA · Q1 · 7 marks

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  [01.3] Almost 70% of students obtained both marks. Students who got the wrong answer could access one mark for either using m-M correctly or using base-10 antilogs, provided they set out their answers sufficiently clearly so that examiners could spot what they were doing.

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  Rigel has surface temperature 12 000 K, absolute magnitude -7.84 and mass 3.6 x 10^31 kg. For comparison, the Sun has surface temperature 5700 K, absolute magnitude 4.83 and mass 2.0 x 10^30 kg.

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• AQA 7408 · June 2023 · Paper 3BA · Q2 · 9 marks

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  [02.5] Answers contained many misconceptions about the CCD. Many of the best answers explained the difference in quantum efficiency of the CCD and the eye in some detail. Some answers that did not get the mark mentioned the idea that the CCD allows an image to be stored without any idea of why that would allow dimmer objects to be seen. Others discussed resolution, again failing to take into account the context of the question.

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  V1031 and WASP-82 are two stars in Orion. V1031 appears 40 times brighter than WASP-82 from Earth and has apparent magnitude 6.0.

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• AQA 7408 · June 2023 · Paper 3BA · Q3 · 8 marks

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  The questions on the effects of the black hole in M87 proved to be more accessible. They produced a range of marks across the ability range.

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  This question concerns the angular resolution of telescopes observing the black hole in M87 and the Doppler shift of an orbiting star.

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• AQA 7408 · June 2023 · Paper 3BA · Q4 · 6 marks

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  This question was marked using a levels of response mark scheme. Along with 03.2 it was the best discriminating question on the paper. Most students demonstrated an understanding of how the spectral class was related to colour. There was some confusion about apparent magnitude and absolute magnitude, with students unsure whether they were writing about what can be seen from Earth or not. Some students attempted to calculate an absolute magnitude assuming a distance. Calculations were often well done, but a missing factor of 4 for the area of the star in Stefan’s Law was very common. The best answers included the calculation of the difference in brightness as seen from Earth and the difference in power output to show that M40A must be closer than M40B.

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  M40 A and M40 B appear close together from Earth. A true binary should give both stars a similar distance modulus. Their data are: A has T = 6000 K, radius 6.3 x 10^9 m and apparent magnitude 9.7; B has T = 4700 K, radius 1.1 x 10^10 m and apparent magnitude 10.1.

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• AQA 7408 · June 2023 · Paper 3BA · Q5 · 5 marks

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  [05.2] Many of the answers demonstrated much confusion about the expanding Universe. Some referred to the Universe itself accelerating, or simply stated Hubble’s Law. The best answers made a clear statement that the expansion of the Universe is accelerating and that the idea of dark energy was introduced to explain it. Any reference to dark matter meant that the second mark point could not be awarded.

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  Galaxy recession-speed data (d in Mpc, v in km s^-1) are approximately: (58,4300), (66,5200), (91,5200), (92,7400), (98,6700), (104,5000), (122,9000), (123,9800), (146,10700), (146,9600), (158,8900), (185,9500).

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• AQA 7408 · June 2022 · Paper 3BA · Q1 · 9 marks

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  [1.4] Many students scored one or two marks on this question as they had a good knowledge of how a CCD works and the advantages it has over the naked eye. They rarely scored the third mark, however, as there was no attempt to link this knowledge to the situation in this question. A significant number of students did not seem to understand that the CCD was attached to the same telescope as was used with the naked eye.

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  Question 1 from AQA A-level Physics Paper 3BA, June 2022.

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• AQA 7408 · June 2022 · Paper 3BA · Q2 · 11 marks

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  [2.6] This proved to be a hard question. Very few students linked their knowledge of white dwarfs and neutron stars to the question.

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  U Cephei is an eclipsing binary: a class-B primary and class-G secondary orbit their common centre of mass with period 2.5 days. A laboratory spectral line is 486.136 nm. In the primary's spectrum its observed wavelength varies from 485.672 nm to 486.498 nm, with mean 486.085 nm.

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• AQA 7408 · June 2022 · Paper 3BA · Q3 · 9 marks

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  [3.2] A large majority of students scored full marks on this question. They were familiar with the equation and could manipulate it. Those who did not score full marks often converted distance between units incorrectly.

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  3C 273 was the first quasar to be discovered. IC 1101 is one of the largest galaxies known. Table 2 shows some information about these objects. Table 2 Absolute magnitude Apparent magnitude Distance / Mpc quasar 3C 273 X 12.8 760 galaxy IC 1101 -22.8 14.7 320

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• AQA 7408 · June 2022 · Paper 3BA · Q4 · 6 marks

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  Many students recognised that this was a black-body curve and correctly calculated the temperature from max λ . When students went on to discuss CMBR in some detail they were half-way to a good mark. Unfortunately, many did not make a real effort to discuss the other predictions of the Big Bang theory. It was surprising that many students made no attempt at any calculation as this was requested explicitly in the question.

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  Question 4 from AQA A-level Physics Paper 3BA, June 2022.

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• AQA 7408 · November 2021 · Paper 3BA · Q1 · 11 marks

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  [1.4] A few students produced an elegant answer to this question. Of those who made an attempt, a number tried to find the radius of Theta Carinae by assuming that its power output was the same as the sun.

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  A Hertzsprung-Russell diagram has absolute magnitude from -10 at the top to +15 at the bottom and spectral class O to M from left to right. A Sun-like evolutionary track passes through W near class M/magnitude +3, X near class G/+6, Y near class F/-5, and Z near the O-B side/+10. Theta Carinae has radius five times the Sun's radius and surface temperature 31 000 K.

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• AQA 7408 · November 2021 · Paper 3BA · Q2 · 4 marks

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  [2.1] Only half of the students got this right. The time scale for a supernova is measured in weeks rather than hours.

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  This question concerns a typical type Ia supernova and one occurring in the Andromeda galaxy, 7.7 x 10^5 pc from Earth.

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• AQA 7408 · November 2021 · Paper 3BA · Q3 · 6 marks

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  There was a full range of marks on this question. Most of those who attempted it realised that the curve was the typical black-body curve. Some went on to find the temperature of the star and to identify the star correctly. Few students could explain the origin of the dips in the graph and that the dips are caused by hydrogen absorption by atoms in the 2 n = state. This was an alternative route to the identification of the star.

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  Miaplacidus is spectral class A and Avior class K. A measured stellar spectrum has an overall black-body curve peaking in the near ultraviolet at about 320 nm, with narrow intensity dips at visible wavelengths including the Balmer series.

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• AQA 7408 · November 2021 · Paper 3BA · Q4 · 6 marks

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  [4.2] More students performed better on this question than on any other in the paper. Some students, however, lost marks through unnecessary attempts to change the unit from Mpc. This unit is usually used and is the easiest to find.

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  Galaxy IC2497 once contained a quasar that stopped emitting several thousand years ago. Its redshift is 0.0516.

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• AQA 7408 · November 2021 · Paper 3BA · Q5 · 8 marks

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  [5.1] Few students scored marks on this question though versions of it have appeared many times and it is simple recall. One of the key words is ‘minimum’; this was often missed.

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  This question concerns telescope resolution and two 21 cm radio telescopes: Arecibo, diameter 305 m with a spherical dish, and Lovell, diameter 76 m with a parabolic dish.

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• AQA 7408 · November 2020 · Paper 3BA · Q1 · 10 marks

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  [01.2] Most students realised they had to calculate the resolution of the instrument and did so accurately. Many then either calculated the angle subtended by the crater or the smallest detail that could be resolved by the telescope. Only a few explained that it was suitable to study detail in the crater because the resolution was much smaller than the crater. Some students thought that the telescope would be inappropriate because it could only ‘see’ objects up to 27m across and so would not ‘see’ the crater.

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  This question is about astronomical telescopes.

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• AQA 7408 · November 2020 · Paper 3BA · Q2 · 11 marks

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  [02.2] Most students were able to calculate the temperature correctly from the peak wavelength on the graph, though there were a number who had difficulties in reading the wavelength from the graph. The link between colour and either the spectral class or the emitted wavelengths was less well made. Those who went down the spectral class route often scored better. There were no marks for stating the colour; this was in the table above.

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  Table 1 gives data for four stars in Cassiopeia: Caph (white, apparent magnitude 2.3, distance 55 ly), Ruchbah (blue/white, 2.7, 99 ly), Schedar (orange, 2.2, 228 ly), and Tsih (blue, 2.2, 610 ly).

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• AQA 7408 · November 2020 · Paper 3BA · Q3 · 10 marks

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  [03.2] There were many excellent graphs. Some scored marks without being very well drawn. It was common to see the peak at +19.3 and/or the magnitude axis going in the wrong direction. Time scales seen ranged from a few seconds to millions of years. The time scale should be such that it takes around 100 days for the absolute magnitude to decrease through 5 magnitudes.

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  Type 1a supernovae can be used as standard candles.

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• AQA 7408 · November 2020 · Paper 3BA · Q4 · 4 marks

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  [04.1] Many students did this calculation faultlessly. Common errors, however, were using the formula for volume instead of area, failing to raise temperature to the fourth power, and giving the final answer to only one significant figure.

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  Table 2 compares the supergiant star Melnick 34 (radius 1.4 x 10^10 m, surface temperature 53 000 K) with the Sun (radius 7.0 x 10^8 m, surface temperature 5700 K).

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• AQA 7408 · June 2019 · Paper 3BA · Q2 · 13 marks

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  [2.3] This question scored the full range of marks, with some very well-argued answers. Many students were able to state that the two stars had similar temperatures due to being the same spectral class. Some students used the 5log10 d m M = − equation to work out d, thinking this was the diameter of the star. There were issues with statements about absolute and apparent magnitude. It is difficult to describe this due to the reverse nature of the scale, so students should take care to express themselves clearly. A brighter magnitude takes a smaller (more negative) value.

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  The four brightest stars in Canis Minor have the following properties: Gamma A, apparent magnitude 4.46, absolute magnitude -0.50, class K; Gomeisa, 2.89, -0.70, class B; HD 66141, 4.39, -0.13, class K; Procyon, 0.34, 2.65, class F.

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• AQA 7408 · June 2019 · Paper 3BA · Q3 · 9 marks

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  [3.5] Most students attempted this question and around half scored at least 2 marks. The reason for missing the third mark was either because they only considered temperature or absolute magnitude, or because they considered only one of the two objects.

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  Use a Hertzsprung-Russell diagram with surface temperature decreasing from 50 000 K at the left to 2500 K at the right. The main sequence runs from the hot, luminous upper left to the cool, dim lower right; giants lie above it and white dwarfs below it.

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• AQA 7408 · June 2019 · Paper 3BA · Q4 · 5 marks

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  This question was about quasars and galaxies.

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  NGC 936 has redshift z = 4.8 x 10^-3 and distance 6.8 x 10^7 ly. NGC 3379 has z = 3.0 x 10^-3 and distance 3.2 x 10^7 ly.

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• AQA 7408 · June 2018 · Paper 3BA · Q1 · 8 marks

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  [01.3] This question required students to make a judgement to demonstrate their understanding of the Rayleigh criterion as a limit. Many answers were seen that compared the angular size of the asteroid with the resolution of the telescope correctly, but then simply stated that the asteroid could be seen without any comment about the level of detail. Students who calculated the separation of objects that could be just resolved at the distance of the asteroid made better progress, but an answer that went on to suggest that this would not allow detail to be seen were rare. Only 3% of students scored all three marks; the proportion failing to gain even a single mark was 43.6%. Surprisingly, 9.4% of students made no attempt at all at this question.

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  The Griffith refractor has objective diameter 305 mm and focal length 5.03 m. Its minimum angular resolution is 1.8 x10^-6 rad; a typical eye resolves 3.2 x10^-4 rad.

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• AQA 7408 · June 2018 · Paper 3BA · Q3 · 9 marks

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  [03.1] Many answers to this question focused on simple properties of the three objects rather than the relationship between them. Some students, who did see what was required, suggested incorrectly that quasars are black holes, or that galaxies orbit a black hole in a similar way to planets orbiting stars, perhaps. Only 18.2% of students gained both marks here.

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  Quasar Markarian-231 is 5.81 x10^8 light year away with redshift z=0.0415. A typical quasar outputs about one thousand galaxies' power.

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• AQA 7408 · June 2018 · Paper 3BA · Q4 · 6 marks

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  [04.2] A similar lack of detail or clarity was often seen in answers to this question on the relative abundance of hydrogen and helium. It was rare to see answers that explained why virtually no heavier elements were produced after the formation of helium. Many incorrect answers were seen that focused on fusion processes within stars. There was also some confusion between fission and fusion. Only 3.9% of students gained all three marks; the proportion that failed to gain even a single mark was 47.4%.

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  Evidence for the Big Bang includes cosmological microwave background radiation and cosmic hydrogen/helium abundance.

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• AQA 7408 · June 2017 · Paper 3BA · Q1 · 2 marks

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  Much of the work on ray diagrams has been removed from the specification but the two main types of telescope remain. Most students were able to draw this ray diagram without difficulty. However, a large number of refracting telescopes were seen. Other issues included drawing a convex or flat secondary mirror, or drawing the primary as two curves so they look like two mirrors, rather one continuous curve, with or without a gap. Problems with the rays tended to be related to where they cross with several students drawing them so they crossed before the secondary mirror rather than after, or drawing them so that they meet at the eyepiece.

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  A Cassegrain reflecting telescope receives two rays initially parallel to its principal axis.

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• AQA 7408 · June 2017 · Paper 3BA · Q5 · 6 marks

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  This question was related to another aspect of current astronomical research: the search for planets orbiting other stars. Most students were able to recall the transit and radial velocity methods of detection, without making much more progress. More success was made by those that mentioned problems of direct observation. Very few students related any of these methods to the particular situation of an Earth-like planet orbiting a Sun-like star or made any attempt to discuss which method would be most successful in this situation. The most successful students were able to point out that most of the planets discovered so far have been so-called ‘hot Jupiters’ and that the Earth, being relatively small and far from the Sun, would make little impact on the apparent magnitude of the Sun, or affect its motion significantly. Use of statistics Statistics used in this report may be taken from incomplete processing data. However, this data still gives a true account on how students have performed for each question.

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  Nearly 2000 exoplanets had been discovered by 2016. One aim is to find an Earth-like planet orbiting a Sun-like star.

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• AQA 7408 · sample1 · Paper 3BA · Q4 · 6 marks

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  A planet was discovered orbiting a star in Pegasus using the radial-velocity method, then confirmed from changes in the star's apparent magnitude.

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