Astrophysics

The universe consists of over 100 billion galaxies like ours, each containing tens or hundreds of billions of stars. This course will highlight what we know (and what is still unknown) about this vast and varied frontier.

By the end of this course, you’ll have discovered a world of cosmic wonders, followed a star from diffuse nebula to dense star remnant, traversed the scales of space and time from planetary to intergalactic, and crunched data to determine the Universe's ultimate fate.

• Astrophysics Toolbox: Gear up with the basic physics tools that astrophysicists use to understand the universe.
• Matter: A quick review of temperature, density and the ideal gas law.
• Gravity: The primary driver of star cycles, planetary motion, and galactic evolution.
• Radiation: Light and other types of radiation are our window into the Universe.
• HR Diagram: What does a star's color have to do with its size?
• Atomic Spectra: Each different kind of atom leaves its fingerprint in the light it gives off.
• The Round Earth: Use precision measurement and reasoning to prove for yourself that the Earth is not flat.
• Sizing the Universe: Here we develop meter sticks to measure the cosmos, starting with insights from the ancient Greeks.
• Greek Estimates: The Greeks first estimated the distance to the Moon over 2,000 years ago. How did they do it?
• Trigonometric Parallax: This clever geometric trick can reveal how far we are from distant stars.
• Standard Candles: Meet standard candles, the brightness benchmarks of the Universe.
• Apparent Magnitudes: Learn about the logarithmic scale astronomers use to classify the brightness of stars.
• Supernovas: These stellar explosions are more common than you might think.
• Hubble's Law: Observing standard candles in nearby galaxies, Hubble was surprised to find they're running away.
• Life Cycles of Stars: Everything on Earth is made of the remnants of stars. Find out how stars consume matter as they live and die.
• Star Formation: When there's too much dust in one place, you might just end up with a black hole.
• Static Stars: Build a simple model of a star that gives predictions about its core temperature.
• Energy Production in Stars: The Sun releases more energy in an instant than Earth uses in a year.
• Solar Energy Transport: Follow the trail of energy as light escapes the core of the Sun.
• Stellar Evolution: Investigate what happens to a star as its fuel supply runs out using the virial theorem.
• Stellar Remnants: White dwarf, neutron star or black hole—which is it going to be?
• Black Holes: If no light escapes a black hole, what should we look for to observe one?
• Worlds Beyond Earth: Is extraterrestrial life possible? Could we live anywhere other than Earth? We don't know yet, but we're looking.
• Goldilocks Zone: This planet's too cold, that one's too hot, where do you find one that's just right?
• Exoplanets: How would an exoplanet look in a telescope? How would a grain of sand look from a kilometer away?
• Transits: We've found 2,000+ exoplanets with the method in this quiz, but there are many more we've missed...
• Gravitational Wobble: Every planet is in a gravitational tug-of-war with its star. How does this affect the light we see?
• Interstellar Travel: To send a space probe to an exoplanet in our lifetime, we'll have to get creative...
• Cosmology: The fate of our universe is decided by matter we cannot see. Its identity is one of the great mysteries of our time.
• Cosmological Principle: Homogeneous? Isotropic? Learn the basics of cosmology.
• The Fate of the Universe: The Universe is expanding, but will gravity ever reel it in?
• Dark Matter: Gravity moves galactic matter in a predictable way, but we can't see most of it.
• Cosmic Microwave Background: A signal from the beginning of the Universe...
• Shape of the Universe: How light travels across the Universe is closely related to the shape of the Universe.
• Dark Energy: In the end, the more we know, the more mysteries we reveal.