6.2.2

Stars

Cambridge IGCSE Physics (0625)  · Unit 6: Space physics  · 6 flashcards

Stars is topic 6.2.2 in the Cambridge IGCSE Physics (0625) syllabus , positioned in Unit 6 — Space physics , alongside The Earth, The Solar System and The Sun as a star.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical).

The deck below contains 6 flashcards — covering the precise wording mark schemes reward.

What the Cambridge 0625 syllabus says

2026-2028 syllabus, in our words

What the syllabus expects you to be able to do in this topic, in plain English. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks. For the exact wording, see the official syllabus (PDF).

  1. State State that: (a) every galaxy has many billions of stars in it; (b) our Sun is one of the stars in the Milky Way galaxy; (c) compared with the Sun, every other star in the Milky Way is far more distant from the Earth; (d) distances in astronomy can be expressed in light-years, a light-year being how far light travels in one year through (the vacuum of) space.
  2. Know Know the value of a light-year: 1 light-year = 9.5 × 10¹⁵ m. Supplement
  3. Describe Describe the life cycle of a star: (a) stars form from interstellar clouds of gas and dust containing hydrogen; (b) a protostar is such a cloud collapsing and heating up because of its own internal gravitational attraction; (c) a protostar becomes a stable star once the inward pull of gravity is balanced by an outward force caused by the high temperature at its centre; (d) every star eventually runs out of the hydrogen that fuels its nuclear reactions; (e) once most of the hydrogen at the centre has become helium, most stars expand into red giants, while more massive stars expand into red supergiants; (f) a less massive star's red giant becomes a planetary nebula, with a white dwarf left in the middle; (g) a red supergiant ends in a supernova explosion, creating a nebula of hydrogen and newly formed heavier elements, with a neutron star or a black hole left at the centre; (h) the nebula left by a supernova may go on to form new stars with planets orbiting them. Supplement
Key Concept Flip

Light travels at approximately 3.0 x 10^8 m/s in space. Calculate the distance, in metres, of one light-year.

Answer Flip

Distance = speed x time.
Time = 1 year = 365.25 days x 24 hours x 60 minutes x 60 seconds = 31,557,600 s
Distance = (3.0 x 10^8 m/s) x (31,557,600 s) = 9.47 x 10^15 m. One light-year is the distance light travels in a year, so we multiply the speed of light by the number of seconds in a year.

Key Concept Flip

State three facts about the Sun's location and relation to other stars and galaxies.

Answer Flip

1. The Sun is a star.
2. The Sun is located in the Milky Way galaxy.
3. Other stars in the Milky Way are much further away from Earth than the Sun is.

Key Concept Flip

Calculate the distance, in meters, that light travels in 4.6 years. State your answer in standard form. You may use the following value: 1 light-year = 9.5 x 10¹⁵ m

Answer Flip

Distance = (Number of light-years) x (Distance of 1 light-year)
Distance = 4.6 x 9.5 x 10¹⁵ m
Distance = 4.37 x 10¹⁶ m

This calculation uses the definition of a light-year to find the distance light travels in 4.6 years.

Key Concept Flip

Describe what is meant by the term 'one light-year'.

Answer Flip

One light-year is the distance that light travels through a vacuum in one year. It is equal to 9.5 x 10¹⁵ meters.

Key Concept Flip

Describe the key stages in the life cycle of a star, starting from an interstellar cloud of gas and dust and ending with either a white dwarf or a black hole.

Answer Flip

1. Interstellar Cloud: Stars form from interstellar clouds of gas and dust, mainly hydrogen.
2. Protostar: The cloud collapses under gravity, increasing temperature.
3. Stable Star: Nuclear fusion begins; outward pressure from fusion balances inward gravity.
4. Red Giant/Supergiant: Hydrogen fuel depletes; core contracts, outer layers expand and cool.
5a. White Dwarf: For smaller stars, the red giant sheds its outer layers as a planetary nebula, leaving behind a white dwarf.
5b. Supernova/Neutron Star/Black Hole: For massive stars, the red supergiant explodes as a supernova. The core collapses to form a neutron star, or a black hole if the star is massive enough.

Key Concept Flip

Explain why a protostar increases in temperature as it collapses under its own gravitational attraction.

Answer Flip

As the interstellar cloud collapses, its gravitational potential energy is converted into kinetic energy. The increased kinetic energy results in increased particle motion, causing the temperature of the gas and dust to rise.

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6.2.1 The Sun as a star 6.2.3 The Universe

More topics in Unit 6 — Space physics

Stars sits alongside these Physics decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

6.1.1 The Earth

8 flashcards
6.1.2 The Solar System

20 flashcards
6.2.1 The Sun as a star

4 flashcards
6.2.3 The Universe

22 flashcards

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How to study this Stars deck

Start in Study Mode, attempt each card before flipping, then rate Hard, Okay or Easy. Cards you rate Hard come back within a day; cards you rate Easy push out to weeks. Your progress is saved in your browser, so come back daily for 5–10 minute reviews until every card reads Mastered.