Astronomers from South Africa and abroad use the research facilities at SAAO to conduct a wide range of research in optical/infrared astronomy. They look for answers to unsolved questions about stars, extrasolar planets, the dust and gas of "empty space", galaxies containing hundreds of billions of stars, and the structure and scale of the universe.
Beyond our own spiral of stars, 100000-light-year-wide, lie billions of other galaxies. Recent extragalactic work has explored the structure of the universe by mapping obscured galaxies behind the Milky Way. Dim galaxies whose matter is primarily in interstellar gas rather than stars have been searched for. Information has been gathered about active galaxies where giant black holes turn matter into energy on a scale such that some may be seen billions of light years away.
Investigations centering on our nearest neighbour galaxies, the Magellanic Clouds, have yielded new information about the late stages of the lives of stars like the Sun, as have investigations of similar stars in the central regions of our own Milky Way galaxy. Studies of massive "Cepheid variable stars" have helped establish the distance scale of the universe more firmly, and other projects have investigated the life cycles and behaviour of "Be" and other hot, mass-losing stars, surveyed the halo of our galaxy for hot stars of various kinds, probed the nature of cool stars shrouded by dust (sometimes clouds of soot), and established the properties of a new class of red giant stars which pulsate at far shorter periods than were thought possible. Spectroscopy ("dissecting" starlight in detail) and photometry (precise measurements of the brightnesses of stars through filters) are the most common techniques applied by researchers, aided by the clear, dark skies of the desert hills of the Karoo.