As skywatchers marvel at the beauty of the annual Perseid meteor shower — set to peak late Sunday and early Monday — astronomers will be thanking their shooting stars for another reason. Airborne pollution from vaporized meteors is proving crucial for the next generation of super-sharp snapshots of exotic moons and distant galaxies.
Pollution of any kind is usually bad news for telescopes, which thrive on clear skies. But shooting stars — flaming bits of debris from comets — leave behind traces of an element astronomers are harnessing to sharpen the focus of their telescopes.
That element is sodium. Traces of it waft in a band encircling the Earth about 55 miles above ground. American astronomer Vesto Slipher, of Arizona, discovered this sodium layer in 1929, but only recently have astronomers found a use for it — by zapping it with lasers.
“We can excite the sodium (with a laser) and make an artificial star,” said Chad Trujillo of the Gemini Observatory, a multinational consortium that operates telescopes in Hawaii and Chile.
Sensors watching these artificial “guidestars” see them twinkle — the effect of atmospheric turbulence. This wavy air usually renders distant targets fuzzy. But by watching the guidestar, sophisticated computers on the ground can calculate the turbulence and send that data to the telescope. Sophisticated mirrors in the telescope then deform hundreds of times per second to compensate for the wavy air.
It’s like adding a pair of glasses with rapidly changing prescriptions to the telescope.
This technique — adaptive optics — has been called the biggest advance in ground-based astronomy since Galileo’s first telescope some 400 years ago.
Earlier this year, the most sophisticated laser guidestar system to date came online at the Gemini South telescope in Chile. The $25 million system sharpens the telescope’s 25-foot mirror onto a wider swath of sky than ever before.
“We’re looking deep into the cores of colliding galaxies now and watching black holes. It’s really fun,” Max said.