This lecture looks at radio telescopes, adaptive optics for ground-based infrared telescopes, and NASA's Great Observatories, which include the Hubble Space Telescope, Chandra X-Ray Observatory, and Spitzer Space Telescope.

This lecture turns back the clock to almost the moment of creation-a fraction of a second after the Big Bang-and follows events as they sort themselves out, from what may have been packages of space-time foam winking in and out of existence, to conditions conducive for star and galaxy formation.

The surface temperature of a star determines its apparent color. The hottest stars are bluish in color, and the coldest stars are reddish; stars at intermediate temperatures appear white. The Sun is a white star.

Earth is one of the four innermost, or terrestrial, planets; the others are Mercury, Venus, and Mars. All are relatively small, rocky, and dense. This lecture examines Earth's structure, properties, and the forces that affect it.

Delving deeper into the nature of light, you explore the strange duality between electromagnetic waves (light waves) and particles (photons), which is a fundamental feature of quantum theory.

In 1995, the first extra-solar planet was discovered around a Sun-like star. Since then, about 200 have been found. The easiest to detect are those with large masses, close to their host stars, and with brief orbital periods.

Apparent brightness is the observed brightness of a star. Because stars are at different distances, astronomers need a standard reference by which to compare stars in absolute terms, as if they're all at the same distance. This standard is called intrinsic brightness, or luminosity.

In 1987 a Type II supernova only 170,000 light years away became visible. Earlier photos of the region showed that the exploded star was a blue supergiant, a previously unsuspected candidate for this fate. Ghostly neutrinos were detected from this supernova.

Because they don't emit any light, black holes can't be seen directly. But they reveal their presence through their gravitational influence on other objects. This lecture looks at the methods astronomers use to track them down.

Why is the sky dark at night? In an infinitely old and large Universe the sky should be ablaze with light at all times. There are several possible answers to this paradox, each of which has profound cosmological implications. The relative youth of the Universe is now known to be the main explanation.