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Astrophysics

Astrophysics — Free MYP4 Physics Practice Questions

1QuestionDefinition of a planetConcept Practice

2 marks~3 minCriterion A

The diagram shows a planet in a circular orbit around the Sun. An arrow is drawn from the planet pointing directly toward the centre of the Sun.

(a) Identify the type of force represented by the arrow and state its direction relative to the planet. [2]

Solutions

2QuestionGas giants:Jupiter, SaturnConcept Practice

2 marks~3 minCriterion D

Jupiter's Great Red Spot (GRS) is a persistent anticyclonic storm that has lasted for centuries. Meteorologists study its vortex dynamics to improve Earth-based weather models.

Explain one way in which research on the GRS has contributed to advances in weather prediction models on Earth. [1]

Identify one limitation of using Jupiter's atmosphere to model weather patterns on Earth. [1]

Solutions

3QuestionSteady State Theory (contrast with Big Bang)Concept Practice

2 marks~3 minCriterion A

The diagram below shows two models of the universe's evolution over time.

In Model A, the universe maintains a constant average density and appears uniform at all times.

In Model B, the universe expands from a singular point, with density decreasing over time.

Identify which model represents the Steady State theory. [1]

Justify your choice using one feature visible in the diagram. [1]

Solutions

4QuestionAbundance of light elements (H, He)Concept Practice

2 marks~3 minCriterion B

The graph below shows recessional velocity (km/s) against distance (Mpc) for four galaxies, labelled A, B, C, and D.

Distance (Mpc)	0	100	200	300	400
Recessional velocity (km/s)	0	2000	4000	6000	8000

Point A lies near the origin; Point D lies at the greatest distance.

Identify the galaxy with the greatest recessional velocity. [1]

Deduce the relationship between recessional velocity and distance shown by the trend line, and state what this implies about the origin of the universe. [1]

Solutions

5QuestionFormation of stars and galaxiesConcept Practice

2 marks~3 minCriterion D

Elements heavier than hydrogen and helium — including iron, nickel, and copper — were forged inside stars through nuclear fusion and dispersed across the universe when those stars exploded as supernovae. These heavy elements are now found throughout Earth and are fundamental to human technology and industry.

Outline one way in which heavy elements produced by stellar nucleosynthesis have influenced modern society. [1]

Identify one limitation of depending on stellar nucleosynthesis as the source of heavy elements available on Earth. [1]

Solutions

6QuestionComponents of the Solar System (Sun, Planets, Dwarf Planets, Moons, Asteroids, Comets, Meteoroids)Assessment Practice

10 marks~15 minCriterion B

The table below shows the orbital period

T

(years) and semi-major axis

a

(AU) for eight planets and three dwarf planets.

Object	$T$ (years)	$a$ (AU)
Mercury	0.241	0.387
Venus	0.615	0.723
Earth	1.000	1.000
Mars	1.881	1.524
Ceres	4.600	2.770
Jupiter	11.86	5.203
Saturn	29.46	9.537
Uranus	84.01	19.19
Neptune	164.8	30.07
Pluto	247.9	39.48
Eris	559.0	67.67

Calculate

\log T

and

\log a

for each object and plot the points on the provided grid. Describe the shape of the graph. [2]

Construct a best-fit line on your graph and determine its gradient. Hence express the relationship between

T

and

a

in the form

T \propto a^n

, identifying the value of

n

. [3]

Using the relationship from (b) and Earth's data as your reference, calculate the orbital period of a hypothetical Kuiper Belt object with

a = 100

AU. Justify each step of your calculation. [3]

Discuss two reasons why the relationship from (b) may not reliably predict the orbital period of an object at

a = 200

AU. [2]

Solutions

7QuestionAssessment Practice

4 marks~6 minCriterion D

The asteroid Kleopatra has a small moon, Alexhelios, orbiting it in a nearly circular path. Alexhelios has an orbital period of 2.7 years and an average orbital radius of 2.8 AU.

Kepler's Third Law in Newtonian form is:

T^2 = \frac{4\pi^2}{GM}\,a^3

For the Sun–Earth system:

T_\oplus = 1

year,

a_\oplus = 1

AU,

M = M_\odot

Show that, using the Sun–Earth system,

\dfrac{4\pi^2}{G} = \dfrac{M_\odot}{1\,\text{AU}^3\,\text{yr}^{-2}}

. [1]

Calculate the mass of Kleopatra in terms of

M_\odot

. [2]

Evaluate whether your answer is physically reasonable for an asteroid. [1]

Solutions

8QuestionRole of gravity in maintaining orbitsAssessment Practice

8 marks~12 minCriterion A

A communications satellite of mass 500 kg orbits Earth in a circular path at an orbital radius of

7.0 \times 10^6

m from Earth's centre. The mass of Earth is

6.0 \times 10^{24}

kg and the gravitational constant is

G = 6.67 \times 10^{-11}

N m

^2

^{-2}

State the equation for the gravitational force acting on the satellite and define each variable. [2]

Deduce the orbital speed

v

of the satellite by equating gravitational force to centripetal force, showing all algebraic steps. [4]

A second satellite of mass 1000 kg orbits at the same radius. Evaluate how the orbital speed of this satellite compares to the first, justifying your answer with reference to your expression from (b). [2]

Solutions

9QuestionFormation of the solar system (nebular hypothesis – basic idea)Assessment Practice

4 marks~6 minCriterion C

The nebular hypothesis proposes that the solar system formed from a rotating cloud of gas and dust that collapsed under gravity, flattening into a disk from which planets formed. Space telescopes such as Hubble and James Webb observe protoplanetary disks around young stars without atmospheric distortion, revealing structures such as rings and gaps. Ground-based telescopes face resolution limits due to Earth's atmosphere but are far cheaper to build and operate.

Discuss one benefit and one limitation of using space-based telescopes to observe protoplanetary disks. [2]

Explain how observations of protoplanetary disks support the nebular hypothesis. In your answer, refer to one specific feature visible in these disks. [2]

Solutions

10QuestionNuclear Reactions in Stars - fusionAssessment Practice

6 marks~9 minCriterion B

In stars, hydrogen fusion reactions occur in the core. The table below shows how the relative fusion rate (number of fusion events per second, normalised to 1 at 10 million K) varies with core temperature.

Core temperature (million K)	10	12	14	16
Relative fusion rate	1	4	16	64

On the grid provided, construct a graph of relative fusion rate (y-axis, 0 to 300) against core temperature (x-axis, 10 to 18 million K). Plot all four data points and draw a smooth curve through them. [2]

Deduce the relative fusion rate at a core temperature of 18 million K. Show your reasoning clearly. [2]

Analyse whether the relationship between relative fusion rate and core temperature is consistent with an exponential model. Use all four data points in your answer. [2]

Solutions

11QuestionAssessment Practice

3 marks~5 minCriterion C

Astronomers classify asteroids by composition. The table below shows albedo and surface temperature for three asteroid types.

Asteroid Type	Albedo	Surface Temperature (K)
C-type (carbonaceous)	0.05	250
S-type (silicate)	0.20	200
M-type (metallic)	0.40	170

State the relationship between albedo and surface temperature shown in the table. [1]

Explain why higher albedo produces a lower surface temperature, using the concepts of energy absorption and reflection. [1]

An asteroid scientist argues that composition is the root cause of surface temperature differences between asteroid types. Evaluate this claim using evidence from the table and your knowledge of each asteroid type's material properties. [1]

Solutions

12QuestionRole of gravity in structure formationAssessment Practice

8 marks~12 minCriterion D

Physicists are proposing a next-generation dark matter detector — a 10 km³ neutrino observatory — to be built either within the Antarctic ice sheet or beneath a remote desert. Construction would require years of drilling or excavation, continuous energy supply, and a permanent research presence in a currently undisturbed environment.

Explain why detecting dark matter is scientifically significant in the context of gravity's role in large-scale structure formation. [2]

Discuss the ecological disruption and resource consumption that construction of this facility would cause. [2]

Analyse the impact on indigenous land rights and local communities in either proposed location. [2]

Evaluate whether the ethical justification for building this detector is strengthened or weakened by the uncertainties in current dark matter models. [2]

Solutions

13QuestionCosmic microwave background radiationAssessment Practice

5 marks~8 minCriterion B

Cosmic microwave background (CMB) temperature maps at three angular resolutions are shown below. Each map covers the same region of the sky.

Angular resolution (degrees)	2.0	1.0	0.5
Number of hot/cold spots visible	4	16	64

Deduce the relationship between angular resolution and the number of visible spots. [1]

Explain how many spots would be visible at a resolution of 0.25 degrees, using the pattern in the data to support your answer. [2]

A cosmologist claims that finer angular resolution always improves our understanding of CMB temperature fluctuations. Analyse this claim, referring to both the mathematical relationship and a physical limitation of real instruments. [2]

Solutions

14QuestionSteady State Theory (contrast with Big Bang)Assessment Practice

7 marks~11 minCriterion C

In the 1960s, a team of astronomers is designing a space telescope to study the early universe. They must choose between two competing cosmological models: the Steady State theory, which proposes that the universe has always existed and maintains the same large-scale appearance at all times, and the Big Bang theory, which proposes that the universe evolved from a hot, dense state and predicts that faint remnant radiation — the cosmic microwave background (CMB) — should be detectable across the sky.

Identify one key prediction of the Steady State theory about the large-scale appearance of the universe over time. [2]

Describe how the detection of the CMB in 1965 challenged the Steady State theory. [2]

Analyse the limitations of the Steady State theory as a foundation for the telescope's observation strategy, and justify why the Big Bang theory provides a more dependable framework for planning observations. [3]

Solutions

15QuestionDefinition of CMBAssessment Practice

4 marks~6 minCriterion A

The hydrogen H-alpha spectral line has a rest wavelength of 656.3 nm. In the spectrum of a distant galaxy, this line is observed at 670.0 nm.

v = c \times \frac{\Delta\lambda}{\lambda_0}, \quad \Delta\lambda = \lambda_{\text{observed}} - \lambda_{\text{rest}}, \quad c = 3.0 \times 10^8 \text{ m/s}

v = H_0 \times d, \quad H_0 = 70 \text{ km/s/Mpc}

Calculate the recessional velocity of the galaxy. Show your working. [2]

Deduce the distance to the galaxy in megaparsecs (Mpc). Show your working. [1]

The Hubble-Lemaître law assumes a constant expansion rate. Analyse one reason why this assumption may not accurately represent the actual expansion history of the universe. [1]

Solutions

16QuestionDefinition of CMBAssessment Practice

2 marks~3 minCriterion C

The Cosmic Microwave Background (CMB) has a measured temperature of approximately 2.725 K, uniform across the sky to about 1 part in

10^{5}

State the fundamental cosmological assumption that this near-perfect uniformity supports. [1]

Discuss one limitation of relying on data from a single satellite, such as WMAP or Planck, when using CMB measurements to support this assumption. [1]

Solutions