We're nearing the peak of one of the biggest astronomical events of the year — the Perseids meteor shower, which began late last month and can produce up to 100 meteors an hour. Lick Observatory support astronomer Jon Rees spoke with The Six Fifty to offer a scientific explanation behind the celestial spectacle, as well as tips on when and how to view the meteor shower and other night sky happenings this year.
This interview has been edited for clarity and brevity.
For those who are unfamiliar, can you explain what's happening when a meteor shower occurs?
Meteor showers happen when Earth crosses path with debris that's been left behind by a comet. As the comet is orbiting the sun it will eject dust, pebbles — pieces of the comet that get left behind as it orbits the sun. These pieces are very small, typically the size of the piece of a grain of sand, but when these little pieces (called meteoroids) burn up in our atmosphere, it leaves behind the bright trail in the sky.
The Perseids shower is associated with the Comet Swift-Tuttle, which was discovered in 1962. The comet has a 133-year orbit so it's not likely something we're going to see again in our lifetime, but we see the material left behind in the passage through our solar system. On any given night you might see a handful of random meteors, but during meteor showers you get many many more meteors. The frequency of that depends on the meteor shower. The Perseids are one of the best meteor showers of the year: You can get something like 60 to 100 meteors per hour, whereas with some of the smaller meteor showers you might only get five to 10 per hour.
What's special about the Perseids meteor shower?
The Perseids are one of the more impressive and active meteor showers. It varies, but something like 60 to 100 meteors per hour while you're looking at the night sky during the peak of the shower Aug. 11-12, when you'll see most of these meteors, whereas many other meteor showers will only have a handful per hour. It's one of the best you'll see during the year. It started July 17 and will be going on through Aug. 24, but it's Aug. 11-12 when you see the most activity.
What are some factors or conditions that may affect viewing this year?
One of the biggest factors this year is the full moon is on Aug. 11, so you will not be able to see the faintest meteors, so you'll see fewer than in a year when the moon isn't full. But you'll still see a decent number of meteors and the bright ones. As far as the best way to see these, the nice thing about meteor showers is you don't really need a high mountaintop to see these. For the best views at least, you need dark skies and a clear view in the direction of the meteor shower. The Perseids all seem to originate from a single point on the sky known as the radiant, and the radiant for the Perseids is in the constellation Perseus toward the northeast. Find a location with a reasonably dark sky; you'll want to get out of the city and find a nice view toward the northeast. Make sure you bring things that will keep you comfortable because with meteor showers you're staring at the sky for a reasonable stretch of time.
Are telescopes or apps advised for viewing the meteor shower?
One of the nice things about meteor showers is they're actually best without telescopes or binoculars. You want that wide view of the sky to see meteors as they come through the atmosphere. Just using your eyes is the best way to view them. As far as timing goes, Perseus is actually up throughout the night, so once it gets dark enough 30 to 45 minutes after that you should be able to start seeing meteors. It will get better as you move through the night, but the moon is up throughout the night, so realistically these should be visible nicely throughout the night.
What are some of the best local places to go stargazing?
You really just need to get away from the city, so there's no one good location. We typically steer people toward wherever people are familiar with. One thing we do tend to make clear is up here at Lick Observatory for example, during the night we are not open to the public. So other observatories are typically not good for these sort of events because they're usually performing other work and closed to the public. Reach out to your local astronomical societies and see if they're holding any events.
What other astronomical events should people keep an eye out for this year?
There are a few coming up. Right after the Perseids peak, on Aug. 14, Saturn is making its closest approach to Earth which means it'll be the brightest it will be all year, so if you have binoculars or a small telescope you may want to take a look because it's the best view you'll get all year. On Oct. 21 the Orionid meteor shower peaks. It's smaller than Perseids (with) 10 to 20 meteors per hour, but for that one we will not have a full moon. Nov. 8 we have a total lunar eclipse happening which will be visible from California. And Dec. 13 is the peak of another meteor shower, Geminids. These are widely regarded as the best of the year — you get a lot of meteors with that one.
Julia Brown writes for TheSixFifty.com, a sister publication of Palo Alto Online, covering what to eat, see and do in Silicon Valley.