Topic 1: The Stars

1.1 The Sun

Nature of science:

  • Curiosity: Humans have had a long term fascination with the objects visible in the sky and have developed many ideas to help explain the observations they were able to make.

Understandings:

  • Historical development of the layout of the solar system

  • Eclipses

  • Newton’s Law of gravitation

  • Kepler’s Laws

  • Mass-distribution curve for the solar system

  • Luminosity

  • Black-body radiation and Wien’s Law

  • Limb darkening

  • Sunspots

  • Granulation of Sun’s surface

  • Chromosphere and corona

  • The interior of the Sun

  • Nuclear fusion

  • Proton-proton chain

  • Gamma radiation travels from the stellar core to the Earth

Applications and skills:

  • Solving problems involving planetary orbits including Newton’s law of gravitation, gravitational field strength, gravitational potential energy and kinetic energy and speed

  • Describing the relationship between gravitational force and centripetal force

  • Applying Newton’s law of gravitation to the motion of an object in circular orbit around a point mass

  • Solving problems involving gravitational force, gravitational field strength, orbital speed and orbital period

  • Determining the resultant gravitational field strength due to two bodies

  • Deriving Kepler’s 3rd law

  • Solving problems involving black body radiation

  • Applying nuclear reactions to the processes taking place in stars

  • Describing the composition, temperature and energy transport mechanisms of the interior of the Sun

  • Explaining that for fusion to occur high temperatures are required to overcome the electrostatic repulsion between like charges

1.2 Measuring stars

Nature of science:

  • Reality: The systematic measurement of distances and brightness of stars and galaxies has led to an understanding of the universe on a scale that is difficult to imagine and comprehend.

Understandings:

  • Constellations

  • Light pollution

  • Movement of stars

  • Astronomical distances

  • Methods of measuring, size, surface temperature, composition and luminosity of stars

  • The electromagnetic spectrum

  • Stellar spectra

  • Stellar parallax and its limitations

  • Luminosity and apparent brightness

  • Harvard Spectral Classification

  • Stefan’s law

  • Hertzsprung-Russell (HR) diagram

Applications and skills:

  • Using the astronomical unit (AU), light year (ly) and parsec (pc)

  • Describing the method to determine distance to stars through stellar parallax

  • Solving problems involving luminosity, apparent brightness and distance

  • Explaining how surface temperature may be obtained from a star’s spectrum

  • Relate the colour of light to the frequency of the radiation emitted

  • Describe the different regions of the electromagnetic spectrum

  • Describing emission and absorption spectra to explain how the chemical composition of a star may be determined from the star’s spectrum

  • Sketching and interpreting HR diagrams

  • Identifying the main regions of the HR diagram and describing the main properties of stars in these regions

1.3 The birth, life and death of stars

Nature of science:

  • Evidence: Our understanding of the processes taking place in stars has come about through the observation of many stars using telescopes and deducing the nature of stars based on this.

Understandings:

  • Star formation from a nebula

  • Jeans criteria

  • Star clusters

  • Protostars

  • T-Tauri phase

  • The nature of stars

  • Proton-proton chain reactions and the CNO cycle

  • Brown dwarfs

  • Death of a star

  • Electron and neutron degeneracy pressure

  • Triple alpha process (3∝) to produce beryllium

  • Secondary fusion to produce elements up to iron

  • r-process to produce elements heavier than iron

  • Stellar evolution on HR diagrams

  • Black holes and escape velocity

Applications and skills:

  • Applying the Jeans criterion to star formation

  • Sketching and interpreting evolutionary paths of stars on an HR diagram

  • Describing the evolution of stars off the main sequence

  • Describing the formation of elements in stars that are heavier than iron including the required increases in temperature

  • Understanding the instability strip for a protostar and be able to describe how this affects the luminosity

  • Describing the s and r processes for neutron capture qualitatively

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