Image credit & copyright: Thomas W. Earle.
Apologies on the title, I’m having withdrawals but the 2018 Perseids meteor shower is really coming. In fact, you may have already been seeing some.
Basics: The night of Sunday, August 12th through the morning of Monday, August 13th, the annual Perseids meteor shower will reach its peak. As with all meteor showers there’s an estimated viewing window or, “active dates” which in this case runs from late-July through late August. However peak viewing is usually narrowed down to a couple days or even a single night through the following morning.
This year’s peak hourly rates will reach upwards of 60-80 per hour and you will want to be looking in the general direction of the constellation of Perseus in the north. This is a worldwide though mostly Northern Hemisphere show and this year that big floodlight in the night sky (the Moon) will be right in its new moon phase so it will have no impact at all. My “Just the Facts” section is below if you don’t feel like reading this whole write up.
Notes: While you’re out there have a look at Venus, Mars, Jupiter and Saturn because they’re all looking great in the night sky at the moment. If you have a decent set of binoculars and average eyesight, you might even be able to see the 4 Galilean moons of Jupiter.
What is a meteor shower/storm? Meteor showers are in short, created by comet or asteroid debris. As comets (2 annual showers are created by asteroids) orbit the Sun, they leave behind a trail of debris from small grains of dust and ice to some decent sized rocks and metal the size of your fist (though rare) and everything in between. As Earth passes though those trails of debris around the same time each year, we run through that debris trail and those fragments light up our night sky as they burn up at an altitude of roughly 80 to 120 km (50 to 75 mi.) in our atmosphere. Almost all the meteors that you see during a meteor shower originate from a piece of rock or metal only 1 gram in size, or about the size of a grain of sand.
What will I see? That depends on a few things such as what time will you be watching, what the meteor is made out of, where is the meteor relative to its radiant point etc. These things aren’t worth worrying about unless you’re a diehard and or trying to image the event but here are the basics.
Morning (pre-sunrise) meteors are hitting the Earth squarely as the Earth is traveling in that direction in the morning, resulting in faster streaks. Evening (post-sunset) meteors are usually slower and less frequent because they have to be moving fast just to make a streak. It’s like being in a car and throwing a baseball at the car’s windshield behind you vs. trying to hit the back window of the car in front of you. The experiment’s been done before I’m sure, so don’t try that at home or, wherever you are. I explain this idea a little differently below in the “When’s the best time to look” paragraph.
Meteors closer to the radiant point tend to be shorter streaks while meteors 20-30 degrees from the radiant point tend to be longer streaks simply because of the path of travel. The streaks further from the radiant point are more glancing impacts than direct impacts.
On occasion you may see a fireball meteor or the even brighter bolide, which is when a meteor explodes in the atmosphere creating an event much brighter than an average meteor streak. There are a few and unclear definitions of bolide and fireball meteors but in short, a fireball meteor and a bolide both basically explode in the atmosphere with the bolide being much brighter than a fireball and a fireball being much brighter than a basic meteor streak. .
You may also catch a meteor train or smoke trail. Smoke trails are usually daytime events so I’m not going to summarize it here but a meteor train is something pretty cool when you first see it. When a meteor streaks by, its energy ionizes the air molecules in that area which creates a momentary (sometimes longer) glowing cloud that will even appear to change shape as it moves with the air. So even if you see a meteor out of the side of your eye, have a quick look, you might see a meteor train.
How many meteors will I see? It’s important to keep in mind that meteor shower predictions are just that; predictions based on past totals so just because it says “X” per-hour you have to understand that predicting these things are about as accurate as weather prediction. Also, when you see “X” per-hour, that rate is assuming that you have an open 360 degree view, at a dark sky location, on a clear night and with the radiant point directly overhead. That being said, your totals (like mine) will probably be half of what’s predicted if you’re viewing from your back yard and you’re within 30 minutes or so of a medium sized city and you can probably half that again if the Moon is up and larger than a small, few day-young or old-crescent.
When’s the best time to look? Peak viewing is typically a given night as well as the following morning with emphasis on the following morning being the absolute best time to watch. In fact, the closer to morning you can get without twilight creeping in the better; here’s why. If you were to view the solar system from the “top” or “above,” you’ll quickly notice that the planets orbit the Sun in a counter clockwise motion and most also rotate in a counter clockwise motion as well, Earth included (Venus and Uranus are the exceptions). That means just before sunrise, Earth is pointed in the direction of travel in its orbit and meteors are mere bugs or snowflakes hitting the windshield of Spaceship Earth.
Where should I look? You’ll want to be looking in the direction of what’s called the “radiant point” of the shower for best results. The radiant point is where it appears that the meteors are radiating from which is usually associated with the constellation they are named after. For example; the radiant point for the Orionids will be the constellation of Orion. Also the higher that the radiant point gets the better observing may become because meteors radiate out in all directions and most aren’t readily visible until they’re approximately 30 degrees or so from their radiant point.
What do I need? As for seeing them all you need is your eyed. No equipment necessary. The most important things you’re going to need are a clear, dark sky, preferably with a nice wide open horizon and no Moon. In fact you really can’t use tools like binoculars or telescopes because the streak is too fast and too long and you simply won’t be able to move your equipment into position in the less than a breath that the meteor streak lasts.
Considerations? Weather and subsequently how you plan to dress for that weather will likely be your biggest considerations. Red flashlights will help save your eyes because dark adaptation is a key in picking out the faint streaks you won’t be able to see after you just finished checking your cell phone (which is a problem for me). Besides that, you’ll want good company, a chair, some blankets, bug spray, food and try not to lie on any ant hills.
Just the Facts:
Active Dates: Late July to late August
Peak Viewing: Looks like Saturday, August 11th through the morning of Monday, August 13th. The better night seems like it’s going to be Sunday the 12th into Monday the 13th.
Hourly Rates: 60-80 per hour
Radiant Point: North in the general direction of the constellation Perseus
Moon Impact = Null! The Moon will be a 1 day old, waxing crescent only 2% illuminated which is pretty close to new phase so it will have no impact at all.
Velocity: 37 mi/sec.
Parent Body: Periodic Comet 109P Swift-Tuttle
Hemisphere Favored: Mostly Northern Hemisphere but the entire planet will be able to catch a glimpse
Time and Date page for this event: https://www.timeanddate.com/astronomy/meteor-shower/perseid.html
Dominic Ford’s “In The Sky” page for this event: https://in-the-sky.org/news.php?id=20180813_10_100
American Meteor Society (AMS) page for this event: https://www.amsmeteors.org/2018/08/viewing-the-perseid-meteor-shower-in-2018/
Moon Giant Moon phase for this event: https://www.moongiant.com/phase/08/12/2018
Perseids Wiki: https://en.wikipedia.org/wiki/Perseids