This upcoming Sunday and Monday the annual Perseids meteor shower event will reach its luminous peak. Stargazers are predicted to view a spectacular meteor shower August 12 from4 pm to 4 am, localized around Earth’s northern hemisphere. It is estimated that viewers will see up to 60-70 meteors per hour at peak times.
Every year around summer time, Earth passes through the path of comet Swift-Tuttle (formally designated 109P/Swift-Tuttle). The debris from the comet manifests as the spectacular Perseid meteor showers; thousands of shooting stars light up the night sky as Earth makes its way through the debris trail. Meteors entering our atmosphere leave glowing “wakes” of light as they disintegrate from the heat and friction.
Experts say that the best time to view the showers is during the late evening to the early dawn hours in the Northern hemisphere, in locations away from the light pollution of cities. The Perseids meteor showers are also visible from the southern hemisphere, just not in as great quantities.
The Perseid meteor showers, named after the constellation Perseus from which the meteors seem to emanate, are one of the most well-known and consistently recurring celestial events. The Perseids were first formally observed in the 1830s independently by American astronomer Edward Herrick, Belgian statistician Adolphe Quetelet, and John Locke, a headmaster at an American all-girls school. Despite these three often being listed as the discoverers of the Perseids, civilizations have astronomical records of annual August meteor showers stretching back to ancient history. Catholics. for example, had long referred to the event as the “Tears of St. Lawrence” as the showers take place around his feast day. August 10.
Herrick’s work on the subject is notable as, unlike his contemporaries, he believed that meteor showers were celestial bodies, not atmospheric or terrestrial effects. Herrick is also credited with correctly linking the phenomena of meteor showers to the activity of comets. He wrote, “It is not impossible that these meteoric showers are derived from nebulous or cometary bodies which, at stated times, the earth falls in.” Herrick’s postulate was spot on and now, scientists can examine the composition of meters that survive the fall to earth to determine which parent body it spawned from.
109P/Swift-Tuttle is a periodic comet that orbits the sun once every 133 years. It has a nucleus approximately 26 km in diameter and it is the parent body of the Perseid showers. As the comet barrels through its orbit around the sun, it leaves a trail of dust and debris in its wake. When the earth goes through this debris trail, material from the comet trail is burned up as it enters our atmosphere. The disintegrating material is responsible for the spectacular light show that we see every year.
Records indicate that ancient Chinese astronomers had recorded appearances of the comet since at least 69 B.C., but the formal discovery is credited to Lewis Swift and Horace Tuttle, who both independently observed the comet in July of 1862. The next passage of the comet was predicted to be in 1992, when it was successfully observed by Japanese astronomer Tsuruhiko Kiuchi.
109P/Swift-Tuttle has caused astronomers concern in the past as its orbital path can bring it into perilously close distances to the Earth. Observations show that the comet has an Earth-minimum-orbit-intersection-distance of .0009 AU (~84,000 mi.). The comet is the largest body that passes so close to the Earth. Given that its average velocity is 60km/s, it is estimated that were the comet to hit Earth, the energy release would be about 27 times greater than the Cretaceous-Paleogene impact, the event that killed off the dinosaurs. Due to these concerns, American radio astronomer, Gerrit Verschuur has labeled 109P/Swift-Tuttle as “the single most dangerous object known to humanity.”
How To See/Photograph the Showers
Get away from city lights.
Naturally, the Perseids event drums up a lot of excitement so here are some tips to maximize your viewing pleasure should you chose to watch the showers. Firstly, it is recommended to go to an area away from city lights. Although you will be able to see the showers from most cities, the best viewing takes place about 15 miles away from any dense source of city lights.
Pick the right time.
Next, plan on viewing the showers between midnight and the early dawn. The soft glow of the moon in the sky provides a good backdrop upon which the individual wakes are easily visible. Also, make sure that you are in a place that is supposed to have clear weather for the night. There is nothing worse than planning a trip only to have bad weather ruin the experience.
Have the right tripod/lens
If you are planning on capturing the event on camera, you will need to bring the right equipment. Taking photos of the night sky requires some exposure, so a tripod is useful to hold the camera still long enough. Heavier tripods tend to work better as they won’t get shaken by any wind or nearby vibrations in the ground. You want to capture as much of the night sky as you can, so a wide angle lens is the best choice. The wider the lens, the more meteors you can get in your shot.
Choose the right exposure length
Picking the right amount of exposure can be difficult. The longer the exposure the more the stars appear to move. The trails of the moving stars can obscure the trails of the meteors, so you need to pick an exposure time that is just long enough to capture the trail of a moving meteor, but not the trail of the moving stars. The appropriate exposure time can be estimated by using the 500 rule. Take the number 500 and divide it by camera lens diameter. The resulting number is how long you can expose your camera without recording the movement of the stars. So far a camera with a 35mm lens, the maximum exposure time is 500/35mm = ~14 seconds.