The Life and Death of Stars

Overview

Gain a better understanding of these spectacular celestial bodies in this enthralling course which features dazzling imagery from Hubble, informative graphics, and animations.

Long ago, the magnificence of the star-filled sky and its clock-like motions inspired people to invent myths to explain this impressive feature of nature. Now we understand the stars at a much deeper level, not as legendary figures connected with constellations, but as engines of matter, energy, and the raw material of life itself. And thanks to powerful telescopes, our view of the stars is more stunning than ever. The Life and Death of Stars introduces you to this spectacular story in 24 half-hour lectures that lead you through the essential ideas of astrophysics—the science of stars. Your guide is Professor Stassun, an award-winning teacher and noted astrophysicist. He provides lively, eloquent, and authoritative explanations at a level suitable for science novices as well as for those who already know their way around the starry sky. The Life and Death of Stars takes you to some otherworldly destinations, including stellar nurseries, planetary nebulae, the core of the sun, and protoplanetary systems. You also become familiar with the periodic table of elements, discovering how fusion reactions inside stars forge successively heavier atoms, producing some in abundance, temporarily skipping others, and creating everything heavier than iron.

Course Content

01: Why the Stellar Life Cycle Matters

View the life cycle of a star in its broadest context, seeing how stars serve as agents of alchemy, transforming the simplest element—hydrogen—into the panoply of heavier elements that compose life and all other material objects in the universe.
Duration: 32 min

02: The Stars’ Information Messenger

Discover that there is much more to light than what we can see with our eyes. Investigate the properties of light and the electromagnetic spectrum, which extends from gamma rays to radio waves. Then learn how astronomers read a star’s spectrum to determine the star’s elemental composition.
Duration: 29 min

03: Measuring the Stars with Light

Uncover more information encoded in starlight, learning how color and patterns of emission and absorption reveal the surface temperature of a star and its motion relative to Earth. Examine the scientific laws that explain stellar spectra, and find out how stellar distances are measured.
Duration: 31 min

04: Stellar Nurseries

Probe the places where stars begin their lives: stellar nurseries. Use what you’ve learned about light to interpret the incredible colors and sculpted shapes in glowing clouds of gas and dust. See how star death leads to a new generation of stars. Close with a virtual fly-through of the stellar nursery in the Orion Nebula.
Duration: 28 min

05: Gravitational Collapse and Protostars

Chart the stages of star birth in stunning astronomical images. From Bok globules and Herbig-Haro objects to protoplanetary disks, these phases develop as gravity brings together material within denser regions of a stellar nursery. Clumps of matter eventually collapse into stars, which often include surrounding planetary systems.
Duration: 31 min

06: The Dynamics of Star Formation

Hundreds of stars can form inside a single cloud of collapsing gas and dust. Zoom in on the intricate details of this process. First, watch a computer simulation of star formation. Then, see how double, triple, and other gravitationally bound combinations of stars arise.
Duration: 27 min

07: Solar Systems in the Making

Follow the formation of newborn planets as they jockey for position close to their parent stars. Computer simulations show how some planets can be ejected out of their solar systems. Such models suggest that our sun and its planetary system might have looked markedly different in the past than it does now.
Duration: 30 min

08: Telescopes—Our Eyes on the Stars

Focus on the instruments that observe and measure stars: telescopes. Investigate the major types and the detectors they use to extract the maximum amount of information from starlight. Telescopes on Earth and in space can survey the entire range of the electromagnetic spectrum.
Duration: 30 min

09: Mass—The DNA of Stars

Learn how mass is like a star’s DNA, as it determines all of a star’s physical characteristics. Astronomers can measure a star’s mass by observing another star in orbit around it. Explore the Hertzsprung-Russell diagram, which shows that stars of different masses fall into well-defined classes.
Duration: 31 min

10: Eclipses of Stars—Truth in the Shadows

Investigate the remarkable usefulness of eclipses. When our moon passes in front of a star or one star eclipses another, astronomers can gather a treasure trove of data, such as stellar diameters. Eclipses also allow astronomers to identify planets orbiting other stars.
Duration: 29 min

11: Stellar Families

Survey the two major types of star clusters. Open clusters typically form within the disk of a galaxy and represent recent generations of stars, enriched in heavier elements. By contrast, globular clusters form a halo around the centers of galaxies and are some of the most ancient stars in the universe.
Duration: 30 min

12: A Portrait of Our Star, the Sun

Explore the nearest star, the sun, in an imaginary voyage through its fiery photosphere down to the center. Discover the sun’s rich inner structure, with strata ranging from the extremely hot and dense core—denser than solid lead—to the more rarefied outer layers.
Duration: 30 min

13: E = mc²—Energy for a Star’s Life

Probe the physics of nuclear fusion, which is the process that powers stars by turning mass into energy, according to Einstein’s famous equation. Then examine two lines of evidence that show what’s happening inside the sun, proving that nuclear reactions must indeed be taking place.
Duration: 30 min

14: Stars in Middle Age

Delve deeper into the lessons of the Hertzsprung-Russell diagram, introduced in Lecture 9. One of its most important features is the main sequence curve, along which most stars are found for most of their lives. Focus on the nuclear reactions occurring inside stars during this stable period.
Duration: 30 min

15: Stellar Death

Stars like the sun end as white dwarfs, surrounded by an envelope of expelled material called a planetary nebula. Explore the complicated and beautiful structure of these dying outbursts. Then investigate the spectacular end of the most massive stars, which explode as supernovae, forging the elements of life in their violent demise.
Duration: 32 min

16: Stellar Corpses—Diamonds in the Sky

Analyze three major types of stellar remains. Low mass stars like the sun leave behind white dwarfs, composed of carbon in a compact diamond-like state. Heavier stars collapse into super-dense neutron stars. And stars weighing more than 20 solar masses end as bizarre black holes.
Duration: 30 min

17: Dying Breaths—Cepheids and Supernovae

Stars vary in brightness during their final phases. Study two phenomena that allow astronomers to measure distances with great accuracy across vast reaches of space: Cepheid variable stars and white dwarf supernovae. Zoom in on the processes that produce these valuable cosmic yardsticks.
Duration: 29 min

18: Supernova Remnants and Galactic Geysers

Explore amazing images of the remnants of supernova explosions, charting how these cosmic catastrophes unfold as if in slow motion. Expanding clouds of supernova debris can trigger new star formation nearby and even carve enormous chimney-like structures in a galaxy.
Duration: 28 min

19: Stillborn Stars

Follow the search for brown dwarfs—objects that are larger than planets but too small to ignite stellar fires. Hear about Professor Stassun’s work that identified the mass of these elusive objects, showing the crucial role of magnetism in setting the basic properties of all stars.
Duration: 29 min

20: The Dark Mystery of the First Stars

Join the hunt for the first stars in the universe, focusing on the nearby “Methuselah” star. Explore evidence that the earliest stars were giants, even by stellar standards. They may even have included mammoth dark stars composed of mysterious dark matter.
Duration: 29 min

21: Stars as Magnets

Because stars spin like dynamos, they generate magnetic fields—a phenomenon that explains many features of stars. See how the slowing rate of rotation of stars like the sun allows astronomers to infer their ages. Also investigate the clock-like magnetic pulses of pulsars, which were originally thought to be signals from extraterrestrials.
Duration: 29 min

22: Solar Storms—The Perils of Life with a Star

The sun and stars produce more than just light and heat. Their periodic blasts of charged particles constitute space weather. Examine this phenomenon—from beautiful aurorae to damaging bursts of high-energy particles that disrupt electronics, the climate, and even life.
Duration: 29 min

23: The Stellar Recipe of Life

Survey the periodic table of elements, focusing on the elements that are vital to life. From carbon, oxygen, and nitrogen to phosphorus, copper, and zinc, virtually every constituent of life was forged in a star during some phase of its life cycle.
Duration: 30 min

24: A Tale of Two Stars

Close your introduction to stellar evolution by contrasting the life cycles of two markedly different stars: one like our sun and another 10 times more massive. Professor Stassun compares their histories to milestones in the lives of humans, bringing a personal dimension to the science of stars.
Duration: 32 min