Michael Werner - More Things in the Heavens: How Infrared Astronomy Is Expanding Our View of the Universe

Picture a telescope with a mirror no larger than a hula hoop. On successive days, it can measure the size of an asteroid smaller than a stretch limo, which has passed between the Earth and the Moon; characterize the atmosphere of a planet orbiting a sunlike star 100 light-years from Earth; and help determine the mass of a distant galaxy more than 13 billion light-years away. The telescope you are picturing is the Spitzer Space Telescope, NASAs Great Observatory for infrared exploration of the Universe. Since 2003, Spitzer has provided the international scientific community with the data required to address these and many other questions at the cutting edge of astronomical research. Spitzer builds on a foundation established by physicists and astronomers who pioneered infrared studies of the heavens starting around the middle of the last century. This book describes our infrared view of the Universewhich often differs dramatically from what is seen in visible lightas it has emerged from those studies, culminating with Spitzers contributions and setting the stage for yet more powerful observatories in the future.

Contemporary astronomical research addresses fundamental questions about the Universe and humanitys place in it:

Where did we come from? What processes gave birth to the earliest observable stars and galaxies?

How did the Universe evolve? What drives the growth and development of the astonishing variety of astronomical phenomena that have emerged since those earliest days?

Are we alone? Has that evolution led to conditions favorable to the development of life beyond the solar system?

Spitzers contributions are fundamental to addressing these questions, as we shall see throughout this book.

The authors are privileged to be explorers of the Universe. We both have worked on Spitzer for decades. Werners association with Spitzer began in 1977, and he assumed his current position as Spitzer Project Scientist in 1983. In those early days, what is now Spitzer was called SIRTF (Shuttle/Space Infrared Telescope Facility); it was renamed Spitzer in 2003 following launch and initial operations. Eisenhardt joined Werners SIRTF team in 1987, working on issues ranging from the choice of orbit to the telescope focus procedure and serving at one time or another as the Instrument Scientist for all three of Spitzers instruments before settling on the Infrared Array Camera. From these positions, we have witnessed the turbulent history of Spitzer leading up to launch. We have also reveled in the remarkable scientific results that Spitzer returned, beginning with its very first observations in October 2003, which started a flow of discovery and understanding that has continued for more than 15 years.

Most of what we know about the Universe beyond our solar system has come to us based on observing and then decoding the information carried by electromagnetic radiation,. The completion of the Great Observatories with the launch of Spitzer in 2003 was a scientific and technical milestone that fulfilled a vision traceable in part to our namesake, Lyman Spitzer, Jr. Spitzer was an astrophysicist and scientific statesman at Yale and Princeton. His 1946 paper Astronomical Advantages of an Extra-Terrestrial Observatory foresaw the power of observatories in space.

The accompanying wavelength scale shows that the higher the temperature is, the shorter the wavelength of the radiation will be. Finally, the atmospheric transmission curve shows that apart from visible light, a few infrared windows, and the radio band (not shown but important for astronomical studies), the atmosphere is opaque to electromagnetic radiation. As a result, observations from space are essential for a complete picture of the Universe.

We devote this book to a discussion of the scientific results from Spitzer, frequently including contributions from the other Great Observatories. After introducing the infrared view of the Universe, we start the scientific discussion with a fanciful tour of the sky as seen by Spitzer, which provides a broadbrush overview of the infrared sky and of Spitzers contributions to our understanding of it. We then go back over the topics addressed in this tour, examining the work of Spitzer in greater depth. Like NASAs other major observatories, Spitzer is open to the international scientific community, which has responded by producing more than 8,000 peer-reviewed papers based in whole or in part on Spitzer data. We make no pretense of having reviewed even 10% of these papers while writing this book. Instead, we present a selection that touches on many of the scientific highlights from