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McDonald Observatory: Searching for Dark Energy

The two large domes in the foreground house the 2.1-meter (82-inch) Otto Struve Telescope (left) and the 2.7-meter (107-inch) Harlan J. Smith Telescope (right). Between these two, the Hobby-Eberly Telescope (HET) can be seen, atop neighboring Mt. Fowlkes
(Image credit: Tim Jones/McDonald Observatory)

McDonald Observatory is a Texas-based astronomical site that is known not only for work gazing at the stars, but also for educating the public about them.

The observatory produces a daily program called StarDate, which runs on nearly 300 radio stations across the country.

A research facility of the University of Texas at Austin, McDonald has several telescopes perched on Mount Locke and Mount Fowlkes, part of the Davis Mountains range in western Texas.

Among them is the Hobby-Eberly Telescope, a 30-foot (9.2-meter) observatory that is one of the world's largest optical telescopes.

Improving farmers' fortunes

McDonald came to be due to an "unexpected legacy" from a banker in Paris, Texas, according to the Texas State Historical Association.

William Johnson McDonald died in 1926 at age 81 and arranged for $850,000 (the equivalent of $11 million in modern dollars) to be used for starting up an astronomical observatory.

"McDonald is said to have thought that an observatory would improve weather forecasting and therefore help farmers to plan their work," the association stated.

Because the university didn't have any astronomy expertise, it made a work arrangement with the University of Chicago for three decades where the Illinois institution would provide astronomers that would use the new Texas observatory.

The first major telescope – Struve – was finished in 1939. With a mirror spanning 82 inches (2.1 meters), that telescope is still in use today. The university, however, added other telescopes through the decades.

Notable telescopes include Hobby-Eberly (dedicated in 1997) and the 2.7-meter (107-inch) Harlan J. Smith Telescope, then the third-largest in the world when completed in 1968.

Dark energy and distant comets

McDonald's most notable scientific effort these days is the Hobby-Eberly Telescope Dark Energy Experiment.

Hobby-Everly Telescope
(Image credit:

Billed as the first major experiment searching for the mysterious force pushing the universe's expansion, it could answer questions such as "if the laws of gravity are correct, and reveal new details about the Big Bang in which the universe was born," the project website stated.

HETDEX will make observations of a minimum of one million galaxies to produce a large map showing the universe's expansion rate during different time periods. Any changes in how quickly the universe grows could yield differences in dark energy.

Observations are expected to start later in 2013, after the telescope gets a new wide-field corrector that should allow it to see a larger part of the sky, as well as several spectrographs.

In recent years, astronomers using the observatory's telescopes have discovered a huge massive magnetic star pulling charged particles along with it, and tracked "likely" comets in alien planet systems, among other findings.

"This is sort of the missing link in current planetary formation studies," stated lead author Barry Welsh, of the University of California, Berkeley, concerning the comet discoveries. The discovery brought the number of known stars with "exocomets" to 10.

Wildfire shelter

On a non-astronomical note, McDonald Observatory also served as a makeshift shelter during widespread 2011 fires that blanketed much of Texas.

Although the observatory was without power at the time, astronomers did their best: "We just put them up and fed them and did whatever we could," said Anita Cochran, the associate director of the West Texas observatory, in an interview at the time.

Wildfires are not an uncommon occurrence in the dry area, but the 2011 fire was a little more severe than most, Cochran added.

The observatory was undamaged in the fires, although for a while it appeared to be directly in their path. The Texas Forest Service did controlled burns as a precaution, to remove wood and any other fire-friendly material in the mountains nearby.

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