August 2017: A Big Month for Astronomy
Sky watchers in the United States have been waiting for this date for years. On Aug. 21, 2017, there’s going to be a total eclipse of the Sun. With the path of totality stretching from Oregon to South Carolina, people can see the eclipse from coast to coast. The timing of the eclipse will provide the opportunity for viewers to see one of the biggest astronomical events of the century just a few weeks after enjoying one of the biggest meteor showers of the year.
Every August, Earth passes through a stream of debris from Comet Swift-Tuttle, source of the annual Perseid meteor shower. This year the shower will peak on the nights of August 11, 12, and 13.
Although the comet is far away, currently located beyond the orbit of Uranus, a trail of debris from the comet stretches all the way around its orbit back to where it nears Earth’s orbit. As our planet crosses the debris zone, the upper atmosphere will be pelted by specks of comet dust traveling 132,000 mph. At that speed, even a flimsy speck of dust makes a vivid streak of light when it disintegrates--a meteor. Because, Swift-Tuttle's meteors streak out of the constellation Perseus, they are called "Perseids."
Astronomer Bill Cooke of NASA’s Meteoroid Environment Office offers these observing tips:
“If it’s not cloudy, get away from bright lights, lay on your back, and look up. Remember to let your eyes get adjusted to the dark (it takes about 30 min) – you’ll see more meteors that way.”
“You don’t need to look in any particular direction. Meteors can generally be seen all over the sky.”
“Not all of the meteors you’ll see belong to the Perseid meteor shower. Some are sporadic background meteors. Others are from weaker showers also active in August, including the Alpha Capricornids, the Southern Delta Aquariids, and the Kappa Cygnids.”
But the vast majority will be Perseids.
Cooke says, “If you see a meteor, try to trace it backwards. If you end up in the constellation Perseus, there’s a good chance you’ve seen a Perseid.”
Under ideally dark skies, observers can often see dozens or even more than a hundred Perseids per hour when the shower peaks. This year, the glaring light of a bright waning gibbous Moon will interfere, reducing the number of visible meteors.
Now for the good news: That same Moon is heading toward the Sun, narrowing as it goes, until the thinning crescent disappears into a black disk that will perfectly cover the Sun on August 21st.
A meteor shower followed by a total solar eclipse: August doesn’t get much better than that!
For more news about backyard astronomy stay tuned to science.nasa.gov.