Cosmology (SQA National 5 Physics): Exam Questions

Read the passage and answer the questions that follow.

Making plans for Rigel

Betelgeuse might be regularly mentioned in the news but there are other supergiants in the night sky. One of these is Rigel, a blue supergiant star that makes up the ‘left foot’ of the constellation of Orion. It is approximately 8 million years old and is one of the brightest stars in our night sky.

Blue supergiants, such as Rigel, are short‑lived and are destined to explode as a supernova. Even though Rigel is 860 light‑years from Earth, the supernova will be clear to see. Astronomers believe that it will be as bright as a half‑moon and will be visible in the sky during the day. However, the light show will only last a few months before it fades.

When it explodes, Rigel will throw debris into space at approximately 5% of the speed of light. Intense waves of radiation, including X‑rays and gamma rays, will be radiated into space. The core of the star will collapse into an extremely dense ball of nuclear matter called a neutron star.

It is not possible to predict exactly when Rigel will explode and there is the possibility that it has already happened, it just hasn’t been detected yet! The best estimate scientists have is that it will take place within the next million years, or so.

(i) Calculate the distance, in metres, from Rigel to Earth.

[3]

(ii) Determine the approximate speed of the debris that will be ejected from the star during the supernova explosion.

[1]

(iii) Calculate the time it would take for this debris to reach Earth.

[3]

Explain why the supernova explosion may already have happened but has not yet been detected.

Astronomers can identify elements present in stars by studying the spectrum of the light they produce.

A spectrum from a star is shown.

(i) State the type of spectrum shown.

[1]

(ii) Explain how the spectrum can be used to identify the elements present in the star.

[1]

Astronomers studying a distant star analyse the light from the star that reaches Earth.

The line spectrum from the star is shown, along with the line spectra of the elements hydrogen, helium, mercury, calcium, and sodium.

Determine which of these elements are present in the star.

The star is 97 light-years from Earth.

(i) State what is meant by the term light-year.

[1]

(ii) Calculate the distance, in metres, from the star to Earth.

[3]

A student makes the following statements about the Universe:

I One light-year is the time taken for light to travel from the Sun to the Earth.

II The approximate age of the Universe is 13.8 billion years.

III The ‘Big Bang’ theory describes the origin of the Universe.

Which of these statements is/are correct?

Launched in 2022, the James Webb Space Telescope (JWST) is the world’s premier space-based science observatory.

The NASA website states that the JWST will solve mysteries in our Solar System and probe the mysterious structures and origins of our Universe.

In 2023, the JWST was used to study the exoplanet LHS 475 b.

LHS 475 b orbits a star in the constellation Octans.

The star is 41 light-years from Earth.

Determine the distance, in metres, from this star to Earth.

The line spectrum from a star is shown, along with the line spectra of the elements hydrogen, helium, mercury, and nitrogen.

Determine which of these elements are present in the star.

The distance from the Sun to the star Sirius is 8·6 light years.

This distance is equivalent to

Light from a star is split into a line spectrum of different colours.

The line spectrum from the star is shown, along with the line spectra of the elements X, Y and Z.

The elements present in this star are