Douglas Isbell - Observatories of the Southwest: A Guide for Curious Skywatchers

Astronomical observatories are special places. They share the common goal of seeking deeper understanding of the Universe that surrounds our tiny home planet, but each has its own unique array of equipment and historical lineage. Over time, observatories have morphed from isolated outposts populated by behemoths of steel and glass to high-tech complexes filled with sophisticated imaging and computer-based analysis tools, linked continuously to a worldwide network of telescopes and rich digital archives.

Telescope mirrors have grown lighter and dramatically thinner. (And note that in this book we define the size of a telescopes primary mirror in both English and metric units on first reference, and then defer to the most common modern usage.) Observing tools have changed profoundly. Fifty years ago, the main tools of the astronomer were large photographic plates, which recorded images of the sky gathered with amazing patience by hardy individuals riding in steel cages attached to the telescope superstructureoften in frigid weather conditions. Today, digital cameras that produce files of billions and billions of bits (gathered and analyzed instantly in warm control rooms) have replaced photographic plates, while ever more specialized instruments exploit advances in detector and computer technology to dissect cosmic light in ever more sophisticated ways. These modern digital images and spectral (highly detailed color) maps enable analysis of the Universe beyond Earth with a clarity and sensitivity that would surprise, and perhaps even shock, earlier generations. These previous generations of astronomerslargely menmight also be surprised by the gender revolution in astronomy, which has grown to embrace the talents and imaginations of women and in the process has transformed astronomy into one of the most diverse fields of the physical sciences.

With these new and powerful tools, astronomers are now able to probe the Universe back to the dawn of time, peer into the birthplaces of stars, and study strings of galaxies stretching across hundreds of thousands of light-years.

As a result, astronomers today are able to confront some of the most profound questions regarding our origin as humans and our ultimate fate as a lonely planet in one tiny part of a vast Universe. Throughout its history as a science, astronomy has consistently revealed and challenged the most fundamental conclusions about the basic properties of the Universe and the place of humans within it. Indeed, surprises, new discoveries, and paradigm shifts have accelerated as the power of our tools of exploration has increased.

One recent example is a discovery that has shaken modern cosmology to its core.

In 1998, two competing teams simultaneously announced similar supersensitive and double-checked measurements of the brightness of known types of medium-sized exploding stars known as supernovae, housed in distant galaxies. Each team was initially surprised to find that the supernovae were slightly farther away than the best calculations said they should be. After reviewing their data, and exploring a range of conventional possibilities to explain this discrepancy, they were forced to posit the existence of a mysterious force, dubbed dark energy, that is pushing all of the galaxies and other matter in the Universe apart from one another, at an accelerating speed. What this force might be is completely unknown. The hunt to solve the mystery of dark energy drives curious scientists to propose and make new observations that stretch the state of the art and hold the potential of radically changing the way we understand our physical world.

Using some of the same telescopes (along with many others) and some clever data analysis tools, astronomers have recently discovered planetary bodies in our own solar system the size of Pluto and larger; hundreds of nearby stars surrounded by planets; and huge numbers of strange, dimly glowing, nearly starlike hulks known as brown dwarfs. One group has already staked a claim to taking an image of the first realistic cousin to the gas giant planet Jupiter. Pictures of Earth-like planets may populate the Web pages of tomorrow in fewer than twenty years.

Observatories have also evolved dramatically in recent decades, from entities created by wealthy and well-connected individuals and universities to an egalitarian mixture of public, private, and international facilities sprinkled around the globe on mountains, sand, and ice. Astronomers have deployed telescopes and detectors on Earth, aboard balloons, in Earth orbit, and in distant space that study the Universe not only in optical lightwhere our eyes operatebut across nearly the entire radiation spectrum, from super-high-energy gamma rays with minuscule wavelength to radio waves longer than a football field.

The southwestern United States is unique in this loose federation of like-minded research outposts, in both the quantity and the diversity of its astronomical observatories. Urbanization of the surrounding communities has encroached some upon their dark skies, but the best conditions remain world class, and the natural beauty of the land that surrounds them remains awe inspiring.

This guide is aimed at providing an introduction to these observatories for those eager to see the tools of the astronomer up close, learn what modern telescopes and their sophisticated instruments are doing today, and understand a bit about the role each of these observatories has played in advancing human understanding of the cosmos so far in just the past dozen decades. As such, it seeks to aid both the interested student and the curious adult in planning a trip to one or all of these observatoriesa trip that we hope may be the beginning of a longer journey or quest.

The 200-inch telescope in the moonlight.

Palomar Observatory

North San Diego County, California

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Home of the Giant

The massive 200-inch (5.1-meter) Hale Telescope on Palomar Mountain in southern California is an icon of mid-twentieth-century scientific and engineering prowess. The 200-inch, as astronomers are prone to call it in shorthand, was born in an age when the ability to dream up fantastic new machinesand to be able to sell them to the powers that bedwarfed any serious concerns that it was too difficult or costly to create them.

The mammoth effort to design and build the Hale Telescope tapped into the zeitgeist of the 1920s and 1930s. The nation-spanning pursuit was stoked by the very public nature of the quest of leading scientific figures to understand our place in the cosmos. Edwin Hubbles photographic plates from the 100-inch (2.5-meter) Hooker Telescope on Mount Wilson near Los Angeles showed fuzzy island universes (galaxies similar to the Milky Way) apparent by the dozens. But what was the true scale of the Universe beyond these relatively nearby galaxies? Just how vast was it? Were galaxies far, far away really receding from Earth with a velocity directly proportional to distance, as implied by Hubbles straight-line graph? To answer these fundamental questions, a group of well-connected astronomers with vivid personalities banded together and sought the funds to build a machine of a size matched to the challenges.