Hooray for the Perseids!

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[This Commentary originally appear in the August 10, 1989 issue of The Mendon-Honeoye Falls-Lima Sentinel.]

CarosaCommentaryNewLogo_259It’s not been a very good summer for stargazing – at least on Monday nights. The hazy skies tend to catch too much light. Remember, the full moon we had a few weeks back. It lit up the entire atmosphere.

Of course, the omnipresent haze does lend itself to some interesting night-time sights. For instance, did you ever watch a descending jet? When the plane puts its landing lights on, an arrow of humid sky blazes into illumination. It sort of looks like the craft is shooting weak phasers.

The haze isn’t the only problem that could hurt stargazing. Fortunately, we don’t live too close to the city of Rochester. Light pollution from the city makes it impossible to see all but the brightest stars.

Light pollution is an astronomer’s nemesis. They constantly lobby for municipalities to use street lights which don’t ooze luminous photons into the sky. The Kitt Peak scientists would applaud the kind of lights used at Mendon Square. Take a drive by that place. You can see they put out a lot of light. Now, go two miles away and look in the sky. You’ll see no evidence of those lights. Maybe the Kitt Peak Observatory should move to Mendon.

Admittedly, even I – a die-hard astronomy enthusiast – contribute to light pollution. I live on Lantern Lane, an appropriately named street. In fact, one of my friends came visiting one evening and said Lantern Lane looked like an RG&E commercial.

Well, that’s what they made back yards for, I guess. Whenever I get the urge to do some summertime stargazing, I just hide behind the shadow in the back of my house and look up. So many stars! It’s wonderful!

On any given night, we could see about 2,000 stars (unless we live in the city). With a pair of large binoculars we can see a hundred times more. Stars are great and they offer an amazing story – but not the one I’m going to tell now.

For most people, stars tend to be boring (or romantic). They aren’t exciting because, except for the Earth’s rotation, they don’t move. Regular folks generally demand something more dynamic. This weekend, if the sky is clear, we can all see some of that excitement. The forecast for Saturday, August 12th, is the same for all previous August 12th’s – day light, followed by night and showers – meteor showers!

Falling stars – or meteors – are not really stars that fall. Stars are far away. The nearest star (besides the sun) is more than 24 trillion miles away. The Sun itself is 93 million miles away. By comparison, the Earth’s atmosphere goes up only about 100 miles, and most of the weather we experience occurs within the first couple miles from the ground.

Stars are far away. Meteors are not. Meteors, in fact, are atmospheric phenomena. That brilliant flash you see happens inside our atmosphere (about 50 miles high), and not out in space.

The tiny chips of rock, though, do come from space. They are usually debris associated with comets and are no bigger than a fingernail. When the Earth’s orbit brings it past these tiny specks of dust, they “shower” down upon the planet. That’s why we call them “meteor showers.”

Since the cometary fallout remains in the same part of the Earth’s orbit, meteor showers occur the same time every year. Unlike sporadic meteors (which are lonely chunks of rock meandering randomly in space), specific meteor showers appear to come from specific parts of the sky. Meteor showers get their names from the particular star or constellation they seem to emanate from. The Perseids peak on or about August 12 every year. Most of them appear to be shooting from the constellation Perseus. You remember Perseus, don’t you? He’s the one who killed Medusa and saved Andromeda, for you Greek mythology buffs. For you movie buffs, try seeing any one of the various Class of the Titans films.

How can you see the Perseids? There are five easy steps:

  1. Take out your lawn chair (this makes it more comfortable for you);
  2. Apply liberal quantities of Off (this makes it less comfortable for hungry mosquitoes);
  3. Turn off your houselights (optional – this makes the viewing a little easier);
  4. Put the Frank Sinatra CD on the stereo (optional – Johnny Mathis works just as well); and,
  5. Look up in the sky.

The last part is really easy if you have a lawn chair that folds back. Also, you’ll want to point yourself in a northeasterly direction. While not all the meteors will come from there, most of them do. For best viewing, look straight up (and keep your eyes open).

Start your viewing past eleven, because the night is darker then. If you’ve got good peripheral vision, you ought to see about 50 or so meteors an hour. Also don’t worry about getting hit by a meteor. Meteors are so small they usually burn up in the sky. Every once in a while, though, one will hit the ground. Then we call it a meteorite. Meteorites generally come from sporadic meteors, not meteor showers.

One final note on our quick stargazing lesson. If you are pointed to the northeast and looking somewhat straight up, you may see three bright stars which form a triangle (the brightest of the three being almost directly overhead). This is the Summer Triangle and the brightest star in the summer sky. It’s the star called Vega. Vega is a giant blue-white star shining 27 light years (or about 170 trillion miles) away. It is more than twice as big as the sun and nearly fifty times as bright.

Through the Summer Triangle seeps a milky white stream. It’s not a cloud in the sky (although it does look like one). It’s actually the Milky Way Galaxy (or the part we can see). Our solar system is inside the Milky Way, and the Milky Way consists of hundreds of thousands of stars. The fuzziness that we see is really thousands upon thousands of stars. They are too far away for us to make them out individually, but, together, their light combines to form a cloud of stars.

Last Week #20: What Do You Think? (originally intended to be published August 3, 1989)

Next Week #22: Adiós Opus (originally published August 17, 1989)

[What is this and why is here? See Interested in Discovering My Time Machine? for more details.]

Comments

  1. Chris Carosa says:

    Author’s Comment: After a week in the wilderness of hiatus, I returned with one of my most-read Commentaries. Of all the things I’ve done, my background in astronomy is the one experience people seem most interested in. This Commentary was timely, coming two days before the weekend when the Perseids peak (as for this actual posting, well, today’s the day folks). What made this the most read, though, was the fact it went viral. I passed it out at my Summertime Stargazing astronomy classes each year and to various groups I would make astronomy presentations to. The original contained a lot of typos. Hopefully I removed most of them.

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