Stellar Evolution (Edexcel IGCSE Physics (Modular): Unit 2)

The diagram shows some incomplete notes about a stellar process. An astronomer left the notes to a colleague for them to decipher. 

Identify the process described in the diagram.

The colleague wants to include some extra detail in stage 3.

Which of the following correctly describes the physical process outlined in stage 3 and the 'smaller nuclei' and 'bigger nuclei' that are mentioned?

The longest stage in this process is

(i) State the name given to the star in stage 4.

(1)

(ii) Explain what happens in stage 4.

(3)

The colour of visible light a star emits tells us how hot or cold it is.

The table contains the colour classifications of the visible light emitted from stars. 

Place a number from 1 − 7 in each box to put them in order from hottest (1) to coolest (7). 

(i) Identify and explain the coolest stage of a star's life cycle.

(2)

(ii) Identify and explain the final stage and colour in the life cycle of a star similar in size to the Sun.

(3)

Explain how stars like the Sun are formed.

What are the properties of luminosity and temperature for a main sequence star? 

A Hertzsprung-Russell (H-R) diagram is a plot of luminosity against temperature for a range of stars.

One group on the H-R diagram is the main sequence.

Once hydrogen fusion has ceased in its core, the Sun (labelled S) will move to a new position on the H-R diagram above.

What is the new position of the Sun?

State the letter for the position of a white dwarf on the H-R diagram and describe its temperature and luminosity in relation to the Sun. 

Most of the stars in the universe are main sequence stars, including the sun. 

Describe the similarities between main sequence stars.

The table gives some statements about the relationship between a star's colour and its surface temperature. 

Add ticks (✔) to the table to show which two statements are correct.

The table shows the colour and surface temperature of several known stars.

(i) Identify a star with a temperature of 7000 K.

(1)

(ii) Identify a star with a temperature of 2000 K.

(1)

(iii) State and explain which of the stars you identified is likely to be the largest.

(2)

Define what is meant by the absolute magnitude scale.

Identify two statements that correctly describe the relationship between the absolute magnitude of a star and its brightness.

A selection of celestial objects and some information about their apparent brightness is detailed below. 

 Write each object into the correct place on the apparent brightness scale. 

The Hertzsprung-Russell diagram is shown below. 

Label the axis and complete the missing numbers on the scale.

State and describe the type of star each of the letters A, B, C and D represent.

Add the following to the diagram.

(i) A cross (X) to show the position of the Sun.

(1)

(ii) Draw an arrow on the diagram to show the direction the star labelled (*) would move as it cools down and emits less energy.

(1)

The table shows the 5 stages of the life cycle of a star that has a similar mass to the Sun. 

(i) State and explain what happens in stage 2 of the diagram.

Include specific references to the relationships between

• the masses of the bodies involved and the forces acting between them

  • the separation of the bodies involved and the forces acting between them

(4)

(ii) State and explain what happens in stage 4 of the diagram.

(4)

The timescale of stage 3 is in the order of

Explain why the star remains stable during stage 3 for the length of time you selected in part (b).

For stars with much larger masses than our Sun, stages 1 to 3 are almost exactly the same as lower mass stars. For the later stages, 4 and 5, the processes begin to differ. 

Compare and contrast the final two stages in stars with much larger masses than our Sun and stars with similar masses to our Sun.

The table contains information on the mass of different stars.

(i) Compare the masses of Proxima Centauri and VY Canis Majoris to the Sun.

(1)

(ii) Explain how these differences will affect the time these stars can remain stable.

(3)

Describe what will happen to each of the stars after they leave the main sequence stage.

Separate: Physics Only

A Hertzsprung‑Russell diagram shows how different astronomical objects may be classified according to their colour and absolute magnitude.

The diagram shows three stages of evolution for stars of similar mass to the Sun.

(i) Add an S to the Hertzsprung-Russell diagram to show the position of the Sun.

(1)

(ii) Star X has the same surface temperature as the Sun but would be brighter than the Sun if it were the same distance away from Earth as the Sun.

Add an X to the Hertzsprung-Russell diagram to show the position of star X. 

(1)

(iii) Star Y has a hotter surface temperature than the Sun but would be dimmer than the Sun if it were the same distance away from Earth as the Sun.

Add a Y to the Hertzsprung-Russell diagram to show the position of star Y.

(1)

Describe the evolution of stars of similar mass to the Sun.

You should refer to the temperature and brightness of the stars in your answer.

Separate: Physics Only

An amateur astronomer is compiling a list of stars he can see through his telescope along with their temperature, colour, absolute magnitude and brightness relative to our Sun. 

His observations so far are detailed in the table.

Present the data on a suitable graph using the grid below.

Canopus has already passed through the red giant branch after exhausting all of the hydrogen in its core. The rest of the stars listed are either in their main sequence or red giant stages.

(i) On your graph, identify the following regions:

• Main sequence

  • Red giants

  • Red supergiants

  • Blue supergiants

(4)

(ii) Draw an arrow on your graph to show the path Canopus is likely to take in its next evolutionary stage.

(1)

Separate: Physics Only

The editor of a science magazine is writing an article on the Hertzsprung-Russell diagram.

All objects on a Hertzsprung-Russell diagram emit electromagnetic radiation. The editor is particularly interested in objects R and S, as shown in the diagram.

Which of the following statements about object R and object S is correct?

Describe the relationship between the colours and values of temperature on the Hertzsprung-Russel diagram.

The editor requires more information to complete the article. 

(i) The Moon is the brightest object in the night sky.

Suggest why the Moon cannot be shown on the Hertzsprung-Russell diagram.

(1)

(ii) Suggest why black holes are not plotted on the Hertzsprung-Russell diagram..

(1)

The editor plots the location of the Sun on the Hertzsprung-Russell diagram.

He states that object R will eventually move to the same position as object S someday.

(i) Comment on the validity of the editor's statement.  

(2)

(ii) The editor wants to compare the evolutionary path of the Sun with the path of object R.

Draw the evolutionary paths of the Sun and object R on the Hertzprung-Russell diagram.

(4)

(iii) Explain the paths you have drawn in (ii).

(2)

Separate: Physics Only

An astronomer is collecting data for stars with a range of spectral classes and wants to plot a graph of spectral class against absolute magnitude to see if any patterns can be identified.

The data the astronomer has collected is shown in the table below.

Complete the data from the table using the conversion table below.

(i) On the grid below, plot a graph of absolute magnitude against star class using the data from the table in (a).

(2)

(ii) On your graph, indicate the following regions:

• Main sequence

• Red supergiants

• Blue supergiants

• White dwarfs 

(4)