A Perseid Bonus!

Hey, Sky Fans! Tonight’s the big night! Remember, if you can make it outside in the early morning hours, tonight into tomorrow, August 11 into August 12, is the peak of the annual Perseid meteor shower. You might need to set your alarm clock for this one.

There’ll be an extra bonus, though, if you can pull yourself out of bed and the skies cooperate. This actually brings me to something someone asked me a few months ago: Where do the stars go in the daytime?

The short answer, as we all learned in grade school, is they’re still there. The Sun is so bright, though, that we can’t see them. The Sun’s tremendous light scattering in our atmosphere washes out all the other stars. This is all true. The good news, I guess, about living on the Moon or Mercury or Jupiter’s moon Io is the atmospheres in those places are so thin that the Sun would do a much worse job of washing out light coming from the other stars. You might have other problems, but a lack of starry skies wouldn’t be one.

This all works in nicely with something else that’s going on here. Why are the stars we see at night different at different times of the year? What I mean is, if you look at the sky tonight, here in August, you’ll see the bright stars Acrturus, which I’ve been very vocal about as one of my favorites, (in Boötes), Antares (Scorpius), and, of course, the three stars of the Summer Triangle: Vega (Lyra), Deneb (Cygnus), and Altair (Aquila), but where have the stars from the Winter, Rigel (Orion), Sirius (Canis Major), Betelgeuse (also Orion), and Aldebaran (Taurus) gone?

Let’s have a look at this drawing, hot off the ball points from the folks down in Sky Watch’s art department. I cannot make this any clearer: This drawing is not to scale. I guess I could have bold-faced that. I don’t take italics lightly.

IMG_3305
The Earth in February and in August

Imagine how big and close things would be if that were to scale, though.

In this, you’ll see the Earth at a spot in its orbit in February on the left. Across the page on the right, it’s six months later, and the Earth has made its way half way around the block. That flag can be anywhere: Tegucigalpa, Auckland, Marrakesh; it doesn’t matter, but let’s just agree it’s in the same place on both days.

You can see that in February, the kind and generous people of Flag City are on the night side (or, if you prefer, the dark side), and are looking straight at Betelgeuse, Rigel, and the rest of the stars of the constellation Orion. Come August, though, what do you see? Exactly, Flag City’s water slides and hot dog stands are facing Orion again, but since the stars don’t move relative to us here on Earth, it’s daytime. Those glorious stars we see on crisp winter nights are the ones that are up and washed out by sunlight on those thick summer days. You can also see this in reverse by noticing where the Summer Triangle stars are relative to daytime in February and nighttime in August. August’s nighttime stars are the ones that are up and shining invisibly during the day in February.

What does all of this have to do with the Perseids? Well, if you’re like me, you think the skies are the best during the winter. I can’t get enough of the sight of the Orion and Winter Circle taking up what seems like the entire sky. I love watching them appear over the houses across the street in the fall, move little-by-little toward the south all winter, and then across to the east in the spring. It might sound crazy, but I almost think of them as old friends, and I miss them when I’m doing riding roller coasters, doing cannonballs, and eating cotton candy all summer.

This is where that bonus I mentioned at the beginning comes in. Here are two screen captures from Stellarium. This first one is the skies to the south near my house six months ago (or six months from now), on February 11 at about 8:00pm.

feb 11
The Winter Circle and Stuff around 8:30pm February 11.

And now the moment you’ve all been waiting for, the skies looking to the east around 4:00am tomorrow morning:

aug 12
The eastern skies, 4:00am August 12, 2016

Look at that! Most, but, no, not all, of those fantastic winter skies are just rising up into the morning skies right near where the radiant of the Perseids shower will be happening. Do you miss Orion? Well, there he is. Just like that, a quick taste of the winter sky on a steamy summer morning. Sounds great to me, too.

Just as a note, but an important one, I wrote this from the perspective of someone in the northern hemisphere, where winter runs from December to March, and sumer from June to September. In the southern hemisphere, the seasons are reversed, so it’s summer when I mention winter, and vice versa.

I hope your skies are in good shape tonight and you’re able to get out and see the fun. It’ll be terrific, and I can’t wait. Meteors or not, it’ll be great to see the Pleiades again. Clear skies, everyone!

 

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