“Guam’s Tropical Skies” with Pam Eastlick


Guam -“Guam’s Tropical Skies”,  news of the cosmos from Pam Eastlick.  

There are a couple of interesting events coming up on Monday.  We’ve got a meteor shower in the morning and an occultation in the evening.  Read on!

1. Perseid Meteor Shower

We’ll be experiencing what is usually the best meteor shower of the year this weekend and Monday morning.  Meteor showers are comet leftovers and
the meteors (small sand-grain sized rocks) are concentrated in the comet’s path through the solar system.  Comets are the solar system’s worst litterbugs.  If the comet’s path happens to cross the orbital path of the Earth, we smack right into the dirt at over 66,000 mph.  These small rocks enter the Earth’s upper atmosphere, and the friction of their passage causes them to catch fire and burn.  There are usually a lot of rocks and we call the burning debris a meteor shower.

One of the most famous meteor showers is called the Perseid shower because we hit the dirt in the direction of the constellation Perseus the Hero.

The Perseids are the leftovers of a comet named Swift-Tuttle.  This comet is apparently particularly ‘dirty’ as its entire orbit path near the Sun is full of dirt and rocks.  This makes the Perseids one of the most reliable meteor showers around.

So, how do you watch the Perseids?  If you know the compass directions from your house, you’ll need to face north.  If you don’t, just watch the Sun go down tonight.  That direction is west.  Turn 90 degrees to the right from west and you’ll be facing north.

Although the peak of the shower should be Monday morning, Comet Swift-Tuttle has been through the neighborhood lots of times and the Perseids are particularly drawn out.  So you’ll see Perseids tomorrow morning and probably Tuesday as well.  To see the fiery rain, set your alarm for about 5:00 a.m. tomorrow morning and Monday morning.  When it goes off, look out the window.   If it’s raining or overcast, go back to bed.

If it’s relatively clear, go outside, face north, pull up a lawn chair and sit down.  Look about halfway up from the horizon and you should see a starry M in the sky.  That’s the constellation Cassiopeia the Queen. Measure one fist-width up and two fist-widths to the right and you’ll be in the middle of Perseus the Hero.  You should see streaks of light that come from this point and radiate all over the sky; at least one a minute.

See if you can find the bugs hitting the windshield tomorrow and Monday morning!

2. Moon occults Spica
We’ll have a lovely crescent Moon in our evening sky this weekend, and it will visit our two evening planets in turn.  But the real news is that the moon will actually pass directly between us and a bright star on Monday night.

Start your moon and planet observations tonight.  You’ll discover that the crescent Moon will be less than a fist-width to the left of Venus in the western sky.  They’ll make a pretty pair.  But the really spectacular sight happens on Monday night August 12th.  If the clouds let us see it, there will be a really nice prime time occultation of the 15th brightest star.  An occultation occurs when one sky object moves directly between the Earth and another one.  On Monday night, our Moon will move directly between us and the bright star Spica.

If you measure two fist-widths up from the Moon tonight and then two fist-widths to the left, you find a bright star.  That’s Spica, the 15th brightest star.  On Monday as it begins to grow dark, the crescent Moon will be just below Spica and will appear to cradle it like a cup.

Although we don’t think about it much, our Moon circles us at over 2000 mph.  Monday night you’ll actually be able to watch the Moon move as it gets closer to Spica.  The occultation starts at 8:03 p.m. and by 8:12 p.m. Spica will completely disappear as it is hidden behind the part of the Moon that’s not being lit up by the Sun.

I’ve mentioned that watching lunar eclipses is sort of like watching paint dry and there are similarities here.  Once Spica has vanished, there won’t be much to see.  But go outside again an hour later at quarter after nine Monday night and you can watch Spica emerge from the lit side of the crescent Moon.  By 9:20 Spica will re-emerge in all its glory.  Hope the sky is clear on Monday night.  It’s not often you can watch the Moon move.

Of course, if you wait a day or two you can figure that out and by next Tuesday night, the Moon appear closer to Saturn than it was to Venus.

Watch celestial mechanics in motion this weekend!