Night-sky patterns: constellations as defined regions; daily/annual sky motions
Seasons from Earth’s axial tilt and geometry; causes of changing day length
Eclipses, Moon’s orbit, and synchronous rotation keeping one face toward Earth
Solar system overview and orbital properties (e.g., which planet is most circular)
Star/planet formation: nebular theory, accretion, and gravitational contraction heating
Planetary geology drivers: internal heat, impacts, volcanism; Moon maria vs highlands
Earth’s active surface via plate tectonics; Venus’s heat via runaway greenhouse effect
Atmospheres: structure (ozone heating stratosphere), exospheres, climate & CO2 sources
Light and spectra: speed of light, absorption lines, and inverse-square brightness law
Sun and stars: fusion conditions, sunspot cycle patterns, stellar classification & H-R diagram
Stellar evolution and endpoints: protostars, fusion ashes, Chandrasekhar limit, NS vs BH
About the free online course
Look up at the night sky and it can feel both familiar and mysterious. This free online course helps you turn that curiosity into real understanding by connecting what you see overhead to the science that explains it. You will learn to think like an astronomer: using models, evidence, and simple physical principles to make sense of motions in the heavens, the changing seasons, and the patterns we recognize as constellations.
The journey starts with how people have interpreted the sky across history and why major shifts in thinking mattered. You will explore the ideas that led from ancient explanations to the Copernican revolution, and how improved ways of reasoning about motion and forces made the universe more predictable and understandable. From there, the course grounds big concepts in everyday experience, showing how perspective, reference frames, and physical laws shape what we observe.
As your skills grow, you will connect Earth-based phenomena to celestial mechanics: why day length changes through the year, how the Moon’s motion produces eclipses, and what makes planetary orbits and sky cycles appear the way they do. You will also take a guided tour of the solar system, learning how planet properties reflect where and how they formed, and how impacts, heat, and internal structure drive the geology of terrestrial worlds.
Atmospheres become another lens for understanding worlds. You will compare the terrestrial planets, see why greenhouse effects differ so dramatically, and learn how atmospheric layers work on Earth along with the role of the magnetic field. The course also links planetary science to our present, examining long-term climate change and how human activity influences atmospheric composition.
Finally, you will move outward to the stars and beyond by learning the language of light. By interpreting spectra, you can infer temperature, composition, and motion, and understand why the Sun shines. You will explore stellar structure, classification, and the Hertzsprung-Russell diagram, then follow how stars are born, evolve, and end their lives—sometimes quietly, sometimes in spectacular supernovae that leave behind white dwarfs, neutron stars, or black holes.
Throughout, quick questions and exercises help you check understanding and build confidence. By the end, you will not only recognize key astronomy ideas, but also be able to explain them clearly—making every clear night an opportunity to read the universe with informed eyes.
Course content
Video class: General Astronomy: Lecture 1 - Introduction57m
Exercise: What unit of measurement is used to describe the average distance between the Earth and the Sun?
Video class: General Astronomy: Lecture 2 - The Ancient Views of the Heavens26m
Exercise: According to ancient Greek beliefs, which celestial body did NOT exhibit retrograde motion?
Video class: General Astronomy: Lecture 3 - The Copernican Revolution23m
Exercise: What was the key flaw in Copernicus's model that affected its accuracy in predicting planetary positions?
Video class: General Astronomy: Lecture 4 - Making Sense of the Universe40m
Exercise: What law explains why passengers feel no sensation of motion while traveling in an airplane on a smooth flight?
Video class: General Astronomy: Lecture 5 - Patterns in the Night Sky35m
Exercise: How do astronomers define the term 'constellation'?
Video class: General Astronomy: Lecture 6 - The Reason for Seasons23m
Exercise: What causes the varying lengths of daytime and nighttime experienced on Earth?
Video class: General Astronomy: Lecture 7 - Eclipses and the Motion of the Moon31m
Exercise: What term describes the moon's rotation that results in the same hemisphere always facing Earth?
Video class: General Astronomy: Lecture 8 - A Tour of the Solar System41m
Exercise: Which planet's orbit is most nearly a perfect circle?
Video class: General Astronomy: Lecture 9 - The Origin of the Solar System25m
Exercise: What process explains how the gravitational energy of a contracting cloud of gas is converted into thermal energy during the formation of a star?
Video class: General Astronomy: Lecture 10 - The Formation of the Planets28m
Exercise: Which region of the early solar nebula was cold enough for hydrogen compounds such as water, methane, and ammonia to condense into solid ices, thus setting the stage for the formation of jovian planets?
Video class: General Astronomy: Lecture 11 - An Introduction to Planetary Geology42m
Exercise: Which factor is the most significant in determining the geological activity of a terrestrial world?
Video class: General Astronomy: Lecture 12 - Geology of the Terrestrial Planets38m
Exercise: What is the primary reason the Mare regions on the Moon have fewer craters compared to the Highlands?
Video class: General Astronomy: Lecture 13 - The Unique Geology of Earth23m
Exercise: What is the primary reason for the constant shaping and reshaping of Earth's surface?
Video class: General Astronomy: Lecture 14 - An Introduction to Planetary Atmospheres25m
Exercise: What is the primary reason Venus has such high surface temperatures?
Video class: General Astronomy: Lecture 15 - Earth's Atmospheric Structure and Magnetic Field29m
Exercise: Which atmospheric layer of Earth is characterized by an increase in temperature with altitude due to the absorption of ultraviolet radiation by ozone?
Video class: General Astronomy: Lecture 16 - Atmospheres of the Terrestrial Planets30m
Exercise: How do the exospheres of the Moon and Mercury contribute to the appearance of the sky on their surfaces during daylight?
Video class: General Astronomy: Lecture 17 - Earth's Atmospheric History and Climate Change40m
Exercise: Which human activity has been responsible for the increase in carbon dioxide levels affecting the Earth's climate according to the lecture?
Video class: General Astronomy: Lecture 18 - The Nature of Light27m
Exercise: What is the speed of light in a vacuum?
Video class: General Astronomy: Lecture 19 - Learning From Light31m
Exercise: When astronomers observe the spectrum of a distant star, what can they determine about the star from the presence of absorption lines in its spectrum?
Video class: General Astronomy: Lecture 20 - Why the Sun Shines34m
Exercise: Which of the following is NOT a reason why the Sun's core temperature sustains nuclear fusion?
Video class: General Astronomy: Lecture 21 - The Structure of the Sun37m
Exercise: What occurs during the sunspot cycle in terms of sunspots forming at different latitudes on the Sun?
Video class: General Astronomy: Lecture 22 - The Nature of the Stars28m
Exercise: What is the significance of the inverse square law for light in astronomy?
Video class: General Astronomy: Lecture 23 - Stellar Classification and the H-R Diagram32m
Exercise: Which property of main-sequence stars is directly correlated with their luminosity?
Video class: General Astronomy: Lecture 24 - The Formation of a Protostar23m
Exercise: Which term refers to regions in space where young stars are formed and are recognizable by their dense concentrations of gas and dust?
Video class: General Astronomy: Lecture 25 - The Evolution of a Protostar30m
Exercise: Which of the following stellar evolutionary tracks on the Hertzsprung-Russell (HR) diagram is correct for varying stellar masses?
Video class: General Astronomy: Lecture 26 - The Lives of Stars40m
Exercise: What element serves as the 'ash' of helium fusion in the cores of stars?
Video class: General Astronomy: Lecture 27 - The Fates of Low and Intermediate-Mass Stars26m
Exercise: What is the ChandraSekhar limit?
Video class: General Astronomy: Lecture 28 - The Fates of High-Mass Stars34m
Exercise: What is the minimum initial mass required for a star to potentially leave behind a neutron star after a supernova explosion?
Video class: General Astronomy: Lecture 29 - Neutron Stars and Black Holes43m
Exercise: What determines whether the core remnant of a supernova explosion will become a neutron star or a black hole?
This free course includes:
15 hours and 56 minutes of online video course
Digital certificate of course completion (Free)
Exercises to train your knowledge
100% free, from content to certificate
Ready to get started?Download the app and get started today.
