Topic 3: Galaxies

3.1

Nature of science:

• Forming a hypothesis: Although dark matter cannot be directly observed it can be inferred due to gravitational effects on the Milky Way

Understandings:

• Structure and constituents of the Milky Way

• Electromagnetic radiation

• Neutrinos

• Rotation curve for the Milky Way and the evidence for dark matter

• Mass distribution curve

• Dark matter

• Spiral arms

• Winding dilemma

Applications and skills:

• Describing rotation curves as evidence for dark matter

• Interpreting rotation and mass distribution curves

3.2 Measuring galaxies

Nature of science:

• Classification: Using the vast amount of data collected through observing galaxies, scientists have been classifying types of galaxies based on observed features.

Understandings:

• The Hubble classification for naming galaxies

• Features of elliptical, lenticular and spiral galaxies

• Irregular galaxies

• Formation of galaxies as a result of density fluctuations in expanding gas produced by the Big Bang

• Cosmic distance ladder: Trigonometric parallax; Cepheid variables: period-luminosity relationship; Type Ia Supernovae: maximum luminosity is a constant

Applications and skills:

• Describing the reason for the variation in the luminosity of Cepheid variables

• Determining the distance of galaxies using data on Cepheid variables

3.3 Active galaxies

Nature of science:

• Observing: Technology has allowed for the collection of large amounts of data on galaxies which has enabled scientists to classify them according to specific properties

Understandings:

• Spectral peculiarity

• Active Galactic Nucleus (AGN)

• Starburst galaxies

• Quasars

• Radio galaxies

Applications and skills:

• Explaining the power sources for different types of active galaxies

• Describing the methods used to observe different types of galaxies