The best hours to watch the Perseid meteor shower – in some ways the most viewer-friendly show of shooting stars in the northern hemisphere – will begin just before midnight Sunday and persist through Monday night.
It is one of the annual can't-miss events for stargazers – promising abundant shooting star-sightings and coming during the height of vacation season, when late-night temperatures are pleasant and folks have more time to dawdle under the night sky.
This year, it might be more of a can't-miss event than normal. Next year, the moon will be in a waning gibbous phase (a three-quarter moon on the way from full to half) during the the best time for viewing meteor showers – after midnight. That means the light of the moon will wash out much of the night sky right when viewing should be peak.
So if you want to see the Perseids at their best, catch them overnight Sunday or Monday – or wait for summer 2015.
Here are a few basic questions answered about the Perseid meteor shower:
Is watching a meteor shower easy? Yes, mostly. You don't need any equipment; in fact, using binoculars is counterproductive since it prevents you from seeing the meteors streak across the wide field of the night sky. Viewing meteor showers entails laying on your back with your eyes open. That's it.
But certain factors make the experience more or less impressive. First, meteor showers are at their most intense just before dawn, which should come at about 4:30 a.m. in the United States Monday and Tuesday morning.
Though the moon is relatively dim now (in its waning crescent phase) viewing will improve when it sets after 10 p.m. So peak viewing hours are from just before 11 p.m. to just after 4 a.m., with the show getting better as it goes on. For die-hard viewers, that means a long night or a very early morning.
And obviously, in a bright city where light pollution is strong, the faintest meteors won't be visible. So if you want to see the Perseids in all their glory, and you live in New York City, you've got a long way to drive. This map of the world at night gives a sense of how prevalent light pollution is in the Northeastern US.
What do the Perseids look like in the darkest skies – far from any cities? Check out this stunning video of the Perseids from Joshua Tree National Park in 2010.
A meteor shower is considered intense if it generates one meteor a minute. The Perseids generally generate about 90 to 100 an hour.
Why "Perseids"? The meteors appear to originate from one section of the night sky. That section is located near the constellation Perseus, hence the name. For American stargazers, Perseus will be in the northeastern sky this week.
What are the Perseids? Basically, the Perseids are cosmic leftovers. A comet called Swift-Tuttle orbits the sun every 133 years, and Earth just happens to cross its orbital path once a year. When Earth crosses that path, it plows through the bits and pieces that have broken off Swift-Tuttle as the comet moves around the sun. As this happens, those bits and pieces vaporize in Earth's atmosphere. These are "shooting stars."
Scientists estimate that most meteors during the Perseid shower are the size of sand grains. The largest are the size of a marble.
Viewing is best just before dawn because, at that moment, that side of the Earth is facing "forward" – the direction of the Earth's movement around the sun. In other words, just before dawn, a viewer on Earth will see the planet plowing through Swift-Tuttle's debris head-on, which makes for a more spectacular show.
Will Swift-Tuttle hit Earth? Scientists have forecast that Earth and Swift-Tuttle will have a near-miss (by cosmic standards) in 3044, when the two will swing within 1 million miles of each other. Asteroid 2012 DA14, which is 150 feet wide, caused a stir when it came within 17,500 miles of Earth in February. Swift-Tuttle is 16 miles across – roughly the same size as the asteroid thought to have caused the extinction of the dinosaurs.
Swift-Tuttle's last closest approach to Earth was in 1992. The Perseids were particularly intense that year, as well as a few years preceding and following. Its next rendezvous with Earth will occur in 2126. It was discovered by two different astronomers working independently, Lewis Swift and Horace Parnell Tuttle, during a close approach in 1862.