Lighthouse of the Skies

The Smithsonian Astrophysical Observatory probes the universe for the unimaginable

The largest budget in the Smithsonian belongs not to any museum but to one of our research centers, the Smithsonian Astrophysical Observatory (SAO). As far back as 1838, when the disposition of the bequest that would establish the Smithsonian was still a matter of debate, John Quincy Adams proposed that the money be used for an astronomical observatory—"a lighthouse of the skies." A different sort of Smithsonian emerged from that early debate, but the Institution did make room eventually for Adams’ celestial lighthouse. In 1890, Secretary Samuel Langley, an astronomer and a pioneer of flight, founded SAO, which today is one of the glories of the Smithsonian. It embodies an aspect of the Institution that’s less visible to the public than our museums but that’s no less essential to our mission: to probe the deepest secrets of nature through basic scientific research.

Since 1973, SAO has been a partner with Harvard University in the Harvard-Smithsonian Center for Astrophysics, an enterprise involving some 900 researchers, staff and students. Their work reflects the separate but linked contributions of astronomy and physics to the study of the universe. The first task is to observe how the universe behaves, using instruments fixed to Earth (telescopes at facilities in Arizona, Chile, Hawaii, Massachusetts and at the South Pole) and in orbit aloft (including the Chandra X-Ray Observatory, conceived at SAO and launched by NASA in July 1999). Researchers then set about making models—formulating theories—to explain the observed behavior. As technology advances, more powerful instruments are built, disclosing new information requiring better models, in a never-ending sequence.

Until 1998, SAO used a multiple-mirror telescope in Arizona that had six 1.6-meter mirrors. When technology allowed, the six mirrors were replaced with one mirror 6.5 meters in diameter; it provides a field of view nearly 400 times larger than could be achieved with the previous instrument. Now SAO is involved in plans for a 20-meter telescope, which will extend our reach and enable us to view events such as the birth of the first galaxy many billions of years ago. But not all the benefits of SAO’s work are at a distance: a recently developed capacity to stop light, store it, and then—the significant part—re-create it with all its properties intact, may one day transform how computers operate.

Because SAO encompasses so generous a range of subfields of astrophysics, it brings unsurpassed breadth to the study of the universe. It has the resources, human and technological, to observe objects and phenomena along the entire electromagnetic spectrum, from long radio waves to ultra-short gamma rays. Among the observatory’s great achievements, let me cite just three: the discovery, through optical telescopes, that galaxies are not distributed randomly in space but mostly form enormous sheets and bubbles; the discovery, using radio observations, of supermassive black holes; and the shocking discovery (made simultaneously by scientists at UC Berkeley) that the universe is accelerating in its expansion. A model to account for the acceleration? Scientists haven’t a clue. Not yet.

The distances, dimensions and temperatures of the cosmic objects studied at SAO are vastly beyond our ordinary experience of measurement. Thanks to the Chandra X-Ray Observatory, for example, we can hold in our hands images the size, shape and color of ordinary photographs that show, with unprecedented clarity, something astonishing: the Crab Nebula, the remnant of a supernova 6,000 light-years from Earth. The images are a wonder, but so, too, is the human mind responsible for them—a mind determined to conceive the inconceivable and imagine the unimaginable size and distance they portray. Human beings have always had good reason to be humbled when they look to the heavens, and a better reason not to be deterred.

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