It is also a paved path to the past.
Some of the equipment here has sat unchanged since the 1920s when Edwin Hubble used the mountain's 100-inch telescope to discover that our universe is expanding.
Now, eight decades after Hubble ushered in a new era of cosmology, and on the heels of a complete shutdown, the Mount Wilson Observatory is alive again and being repositioned for the future by going back to basics. It is a future expected to unlock fundamental secrets about ordinary stars, objects that have lost some of their "star power" in an era of pretty pictures made by exotic space-based telescopes. Like the one named after Edwin Hubble.
Under the steady air at Mount Wilson, scientists are building an array of telescopes that will combine to work as one and effectively become among the most powerful stargazing tools ever built.
The setup is so complicated that no one person understands how it works.
It is called the CHARA array, and later this month scientists plan to start normal operations as they bring the third telescope in the complex array online. The longest distance between two of the telescopes, known as the array's baseline, will be 1,148 feet (350 meters), nearly the length of four football fields. By comparison, the largest conventional optical telescopes do not exceed 36 feet (11 meters).
CHARA is expected therefore to allow astronomers to measure and weigh stars and calculate distances to them with a precision not previously possible.
Out of the age of occultations
Other telescopes -- including Hubble, Chandra, Hawaii's Keck and the European Southern Observatory's Very Large Telescope -- are better equipped to look beyond our Milky Way to explore distant galaxies or to marvel at supernovae, exoplanets and other enigmatic objects. If those are an astronomer's most elegant power tools, then CHARA could be considered a supercharged slide rule.
And unlike a handful of similar telescopes that perform diverse tasks, CHARA will be dedicated to the basic measurement of stars in visible and near-infrared light. Such measurements have until now relied heavily on lunar occultations, a moderately reliable method of studying how a star's light goes out during the seconds when the Moon chances to pass in front of it.
CHARA (Center for High Angular Resolution Astronomy) is expected to give significantly improved measurements of the mass of stars, a crucial factor in learning what the objects are made of and how they evolve.
Other research has indirectly measured the mass of stars by observing how two stars orbit around one another in what's called a binary system. But these observations have relied on noting changes in the star's light as it moves away from us, and then toward us, in its orbit.
This Doppler effect, identical to the change in sound as an ambulance moves toward and then away from you, is an indirect measurement tool that, again, has only provided reasonably close estimates.
What CHARA's interferometry can do that the Doppler method and conventional telescopes can't is to actually locate points around the perimeter of a star, thus providing an exact "picture" of a star's diameter. Other methods use a star's luminosity to estimate other parameters.
"If you can resolve these binary stars ... then you can directly measure the masses of the two stars as well as the distance to the stars from Earth," says Harold A. McAlister, a Georgia State University professor and director of the 14-person CHARA team. "The measure of mass is the most fundamental parameter scientists would like to know" about stars.
Duplicitous by nature
Stars are often duplicitous by nature, doubling up just to confuse observers and even, at least in the past, being perceived as evil. CHARA will help untangle stars' deceptive properties.
Roughly half of all the points of light in the night sky are actually binary star systems, in which two stars orbit around a common gravitational midpoint. Such systems give off confusing light signatures that in some cases move in the sky, sometimes sending airliners off course and generally confounding attempts to measure their size, distance, substance and movement.
One such binary system was once thought to be a single star. Its frequent winking gave the ancients the creeps, and so they gave the strange object the name Algol, meaning Eye of the Demon.
Algol, modern-day astronomers learned, has a small faint companion star that orbits
around it, explains Bill Hartkopf of the U.S. Naval Observatory. Every few days the smaller star passes in front of the big star, making the system dimmer.
Hartkopf is interested in using CHARA to learn more about star systems like Algol, as well others that appear to actually move around in the sky.
"Consider a star sitting out there in space all by itself, a perfect directional beacon for a jet to use to plot its course," Hartkopf said. "Unbeknownst to the pilot, however, the star slowly, imperceptibly moves -- and not even in a straight line -- enough to throw the jet off course."
The moving beacon, Hartkopf explains, is a bright star accompanied by a faint star.
"They're too close together to be seen as two stars," he said. "Instead we see the blended light from both. As the brighter star moves from, say, left of the fainter star to above it, then to the right of it, the center of light of that blended image appears to move in a circle."
Hartkopf says CHARA may help answer other important questions:
- Do binaries stay together forever?
- What role does a binary system play in stellar evolution?
- Do all stars form in pairs? Recent evidence has shown that current estimates of binary systems may be incomplete. Or some stars may form in pairs and later be forced apart.
Next Page: How CHARA will work, and why it sits near L.A.
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