What’s Up for August 2006

Ahhh… the dog days of summer have arrived. Ever wonder where the term “dog days” comes from?

Over the course of a year, the Sun makes one complete circuit against the background of constellations (from our vantage point on Earth). Imagine it this way: Say you place a lamp in the center of a room, and walk around it. The walls of the room are covered in pictures. Now, if you keep your eyes fixed on the walls around and beyond the lamp as you go around it, at one point or another, you will see the lamp in the same field of view as every picture in the room.

In this context, you are the Earth “orbiting” the lamp, or Sun. The “pictures” are the constellations in our sky. Therefore, over the course of the year, the Sun appears to make a complete circuit against the background of constellations.

Canis MajorSo, what does this have to do with the “dog days” of summer? Well, one of the “pictures” in our sky is the constellation Canis Major, the Big Dog. It’s primary member is the star Sirius, which is the brightest star (other than the Sun) in our sky. Sirius is so bright, in fact, that ancients believed that it wasn’t a coincidence that the hottest days of the year happened when the Sun and Sirius rose and set together. They felt that Sirius “added” to the heat from the Sun, and nicknamed the days when that occurred after Sirius - the Dog’s Star.

What’s New

This month, the astronomical “Old Faithful� returns in the form of the annual Perseid meteor shower. The shower’s peak will occur on the night of the 12th/13th (a nicely timed weekend event). However, the Moon will still be quite bright, and its light will interfere with the shower. Even through the bright moonlight, though, you should still be able to see about 30 meteors per hour – even more if you hang in there until just before dawn.

Image courtesy Astronomy magazine. Click to embiggenate.

Neptune is also brightening, and will reach opposition on the 10th. Of course, you’ll need a telescope and dark skies to see this tiny point of light. You can find Neptune by starhopping a degree northward from iota Capricorni.

What’s Old

the Milky Way in SagittariusNext to May, August has the highest number of Messier objects visible near the meridian at ~23:00 EDT. There are 20 objects, and they represent a perfectly diverse sampling of the Messier catalog, with one interesting exception—no galaxies.

Starting in the north, located in Lyra is the planetary nebula M-57, the “Ring.� Close by is the less-observed globular M-56. Visit Vulpecula to observe M-27 and M-71, another planetary and globular pair. In Scutum there are two open clusters, M-11 and M-26. M-11 is also known as the “Wild Duck Cluster,� due to its Flying-V formation apparent at lower powers.

The Eagle Nebula, M-16 in Serpens, is also visible. An open cluster surrounded by fluorescing gas, the Eagle is one of the most impressive objects ever photographed by the Hubble Space Telescope (the photo was nicknamed “Pillars of Creation�). Of course, in amateur telescopes, it looks a bit different.

As you close in towards Sagittarius and the center of our galaxy, there is M-17, and the open clusters M-18, -21, -24, and -25. Nebulae there include M-20 and M-8, named the Trifid and Lagoon, respectively. You can even see both in the same binocular field, if you wish. Close to these two are the globulars M-28 and M-22; the latter is an often-overlooked beautiful binocular object. Nearby are M-54, -69, and -70. Finally, just to the east of these is M-55, yet another globular.

< - Home

2 Responses to “What’s Up for August 2006”

  • wisconsin sky watcher

    Dog days of summer! I thought we were all going to melt up here in Packerland! With the heat index we hit 120. thanks for the explanation!

  • wisconsin sky watcher

    What a shower we had right in our backyard. I sat out in my backyard with a couple of Corona’s and watched them zoom right over my head! One was so awesome! It had a double tail!(i’m sure there is a more politically correct way of defining that!) But What a sight!

Leave a Reply