Shooting stars, Falling Stars, and Meteors!
Most everyone who has been outside and enjoyed the night sky has on occasion witnessed dazzling, brief streaks of light from meteors, sometimes called “shooting or falling stars.” On any given night from a dark location, one can expect so see a handful of meteors as close to 100 metric tons of space dust falls through the atmosphere each day. Some meteors are very faint, barely at the limit of human visibility. Others are very bright even outshining the brightest of planets and stars. On rare occasion we witness “fireballs or bolides,” exceptionally bright ones that light up the sky or shatter into multiple pieces. If any of these pieces reach the ground it is then called a meteorite.
One might think that we “see” meteors because the debris is burning up or being incinerated, but actually this is not the case. Meteors are bits of interplanetary debris slamming into Earth’s atmosphere at altitudes 50 to 75 miles (80 to 120 kilometers for those of you who use internationally accepted units). The debris particles themselves are typically about the size of a grain of sand but they hit the atmosphere going between 25 to 50 miles per second causing the air molecules along its path become flash-heated to thousands of degrees. As this energy is dissipated it lights up as the flash we see in the sky, or the meteor streak. The larger the particle, the brighter the streak, so if you have something that is the size of say a Maine blueberry, it will create a dramatically bright meteor.
I often get asked about the best time to see meteors, and while on any given night you might see a handful if you watched the sky from dusk to dawn, the best time to see them is during meteor showers.
Meteor Showers and Comets – A Cosmic Connection
Multiple times each year the Earth’s orbital path carries it through a cloud of debris from the passage of a comet, and the result is a meteor shower. During meteor showers one can expect a greater number of meteors to be visible and it enhances your chance of seeing these fleeting cosmic sights. The meteor showers are named for the constellation where the meteors appear to emanate from which astronomers call the radiant point. So if the radiant is in the constellation of Orion, the meteor shower is called the Orionids for example. All of these particles causing the shower are traveling in parallel but our perspective on Earth makes them appear to come from one area of the sky. A good way to think of this is like the way snow or rain appears on our automobile windshields. While the snow or rain is travelling parallel, it appears to radiate outward in all directions as it encounters the glass barrier.
Meteor showers usually peak during the early morning hours and have a peak date (best day) for viewing. However one can expect to see activity a couple of nights prior to and after the peak date with sky conditions playing a factor in the number visible. For best viewing conditions, get out to a dark location free of light pollution and avoid (when possible) viewing during the Full Moon which also brightens the sky. The darker the sky, the easier it is to see meteors, especially some of the fainter ones.
While we do pass through the same debris cloud from comets each year, the passage of a comet that is the parent object or source for a particular shower can enrich the potential number of meteors viewed. Prediction for meteor showers often have something called the ZHR or Zenith Hourly Rate. It is the number or meteors one would expect to see in an hour of time at the peak of the shower under the best conditions, so use it as a guide.
To maximize your meteor shower viewing experience, find a dark location, wear of warm clothing, and take a reclining lawn chair with you so you can recline while watching the sky. It also helps to have a star chart so you can find the constellations, especially the one with the radiant point for the meteor shower you plan to observe. A great place to get star charts is at Heavens-Above.com and you can print them out or use their mobile app to take the chart with you.
Annual Meteor Showers
Here is a list of some of the best annual meteor showers…
The Lyrids: April 16 to 25, peak on April 21
A medium strength shower that producing good rates near the peak night. While the meteors of this shower often lack persistent trains/streaks, it is known for producing an occasional bright fireball. The shower produces 10-20 meteors per hour at its ZHR and is a result of the debris from comet Thatcher which typically has observed speeds of 30 miles per second. The radiant point is in the constellation of Lyra the Harp, near its border with Hercules.
The Eta Aquariids: April 20 toMay 26, peak on May 6
This annual shower originates from Halley’s Comet, and these meteors are fast with average speeds of 40 miles per second. The shower’s radiant in the Water Jar asterism of Aquarius never gets very high above the horizon for observers in the Northern Hemisphere. Still the shower can produce 10 to 30 meteors per hour at its ZHR. While the shower is just shy of a month in length, the best chances of good visibility are 4 or 5 days prior to and following the peak day.
The Perseids: July 13 to August 26, peak on August 12
One of the most popular and well known of the meteor showers which put on a show during the warm summer evenings in the Northern Hemisphere with excellent numbers of meteors. It often can deliver at least one meteor per minute from the debris cloud shed by comet Swift-Tuttle. The radiant in Perseus the hero is relatively easy to locate as well, and meteors from this shower move at speeds of around 35 miles per second. One nice thing about this shower is that the radiant point rises around 10:00 pm unlike other showers which normally peak after midnight or in the early morning hours.
The Orionids: October 4 to November 14, peak on October 21
The second meteor shower of the year from Halley’s Comet produces a medium strength with occasional high activity of 20 to 25 per hour. This shower lasts nearly a month, and the radiant point is near the bright star Betelgeuse marking Orion’s shoulder. The best time for observing this shower is around 3:00 am when Orion will be high in the sky.
The Leonids: November 5 to 30, peak on November 17
The Leonid shower is known for its spectacular shows every 33 years when its parent comet, Tempel-Tuttle reaches perihelion. The next time it does so will be in 2031. While one normally can expect 10 to 15 meteors per hour, in the years of its parent comet reaching perihelion there have been times of over 100 per hour or even more. The shower often has bright meteors with persistent trains which sometime show greenish colors. Meteors will radiating from Leo’s sickle or backward question mark shaped mane. In 1999 I witnessed a spectacular display in the early morning hours from 3 to 5 am, and it was like watching nature’s fireworks.
The Geminids: December 4 to 16, peak on December 13
A highly reliable end of the year shower, with upward of 100 meteors per hour radiating from a point near the bright star Castor in Gemini The radiant is well up in the sky by 9 p.m. as seen here in Maine. These meteors are often bright and intensely colored but move a bit slower than other showers averaging about 20 miles per second. Unlike most showers which are associated with comets, this shower’s parent is the asteroid 3200 Phaethon.
There are other minor meteor showers that take place during the year and more information can be found at the American Meteor Society website which has annual predictions and other great information.
Grab a lawn chair, some blankets and/or warm clothes, your favorite warm beverage (coffee in my case) and stretch out under a dark sky and enjoy nature’s fireworks during these meteor showers!