Subjects: Astronomy

The discussion of galaxies continues in this lesson by focusing on a special group of galaxies with very energetic cores called active galaxies. Different types of active galaxies are introduced, from Seyfert galaxies and blazars to quasars.

Scientists discuss the possibility that the early seeds of life on Earth were delivered by comet impacts and the reasons why it is believed that the first life began on the deep seafloor near hydrothermal vents. The discussion continues with a look at Europa’s subsurface ocean and the pros and cons of life forming in that hostile location. The life zone or habitable zone of a star is defined and the efforts to detect signatures of that life using future spacecraft missions are described. The efforts and difficulties of communicating with an intelligent extraterrestrial civilization are discussed.

This lesson takes students on a journey from planet Earth to the distant galaxies and superclusters. It is illustrated with stunning computer animation and photographs from NASA, the Jet Propulsion Laboratory (JPL), and astronomical observatories. This journey introduces the planets, stars, and galaxies that will be presented and discussed throughout the course.

Explaining the concept of a scientific model, this lesson introduces the celestial sphere as a model to help describe and organize the night sky. Several specialists explain how different cultures named stars and constellations, and brought the aspects of the sky into their buildings and structures, such as those of Chaco Canyon in the southwestern United States.

This video lesson explains the motion of Earth around the sun and its yearly cycle. Astronomers explain the unique orbital and size relations between the rotation of Earth, the sun, and the moon and how this makes a total solar eclipse possible at predictable intervals, known as the Saros cycle. The lesson concludes with a description of the ecliptic and explains how that differs from constellations that are contained in the zodiac.

A presentation on the foundations of astronomy, The Birth of Astronomy examines the observations, theories, and contributions of Aristotle, Ptolemy, and other ancient scientists and philosophers. Copernicus, Tycho Brahe, Kepler, Galileo, and Sir Isaac Newton’s contributions are discussed throughout this lesson.

Astronomers are the only scientists who do not manipulate the objects they study. Instead, they do two basic things: collect light and analyze it. Accordingly, this lesson answers two basic questions: (1) What is light? and (2) What tools are used to collect it?

Students will discover the interactions of atoms and light and what spectra can tell us about a star. The fascinating history of spectral classes and the intriguing group of women who were responsible for much of our stellar classification system today is also presented.

This lesson describes the thermonuclear process in the core of the sun, identifying the layers of the interior and atmosphere showing spectacular pictures of surface features, such as granulation and sunspots. The magnetic cycle and magnetic effects on the surface are also introduced. Discussions of how the sun affects Earth’s climate conclude the lesson.

To determine how bright a star actually is, we need to know how far away it is. This lesson illustrates how to find distance to nearby stars and how to plot them on an H-R diagram. It also shows why binary stars are important for the study of stars and their mass-luminosity relation.