Archive for August, 2009

Phases of Venus

Sunday, August 30th, 2009

We are all well familiar with the phases of the moon – sometimes too familiar on the nights when a full moon interferes with our ability to see some deep sky object. But did you know the the planet Venus goes through similar phases? The phases result from the orbit of Venus being inside Earth’s orbit. Of course this means Mercury has phases as well. But as Mercury is so small and difficult to see to begin with, it’s phases are much more difficult to observe. However Venus is currently easy to see, shining brightly as the “morning star.” The best time to observe Venus is shortly before sunrise, after the sky has begun to brighten slightly. Not only is venus higher in the sky, but with the contrast between Venus and the sky reduced, details such as phase are easier to see. At this time the phase should be obvious through any small telescope. Some people with sharper eyesight than I have even claim to be able to see the extreme crecent phase with the naked eye. But don’t expect to see major changes over a few nights, as you can with the phases of the moon. While the moon goes through a complete cycle, from new to full and back to new, in about a month, it takes Venus well over a year to complete a similar cycle.

Pegasus’ Fuzzy Apple

Monday, August 24th, 2009

Just off the nose off Pegasus, the winged horse, is a fuzzy cosmic apple it will never quite reach. That fuzzly little apple is the globular cluster M15. With it’s 6.4 magnitude and densely packed structure, M15 has a compact, but striking appearance. To find M15, start low in the east, looking for the great square of Pegasus. Once you’ve found the great square, follow the “neck” of Pegasus to the south. Follow the line formed by the last two stars of the neck, and you’ll find M15 just to the north of that line. Through small backyard telescopes, M15 will look like a large fuzzy star. Bigger telescopes will begin to show individual stars within the cluster. Although it’s unlikely you’ll ever see it through a backyard telescope, M15 houses Pease 1, one of only four planetary nebulae known to reside within a globular cluster. M15 is also unusual in that it contains 112 variable stars, a quite high number. But even if you can’t spot these details, what you can see makes Pegasus’ fuzzy apple a great stop for any late summer night.

Finding M15 in Pegasus

Celestial Royalty

Sunday, August 16th, 2009

Named for the princess Andromeda in Greek mythology, the Andromeda galaxy (aka M31) is a bit of celestial royalty on late summer nights. Andromeda is a spiral galaxy similar in size to (or, depending on who you ask, a bit larger than) our own Milky Way. It is also the nearest spiral galaxy to the Milky Way. These two combine with the Triangulum Galaxy and about thirty smaller galaxies to form the Local Group. While telescopes have captured many stunning images of Andromeda (including the mosaic image found here), the smaller image on the right is more typical of what you can expext to see through a small telescope.

Finding Andromeda

Finding Andromeda shouldn’t be a challenge. Start with the easy to find constellation Cassiopiea, and imaginine a line to the right from it’s “bottom” two stars. (This is earlier in the night, when these constellations are moderately high in the east. And while it’s not a completely straight line, it’ll get you headed in the right direction.) Then look for the bright, magnitude 2 star in the constellation Andromeda, and go up from there. Tracking up from that star toward the line you imagined from Cassiopiea should lead you right to the galaxy. Although, if you have dark skies and keen eyes, all this star hopping may be unnecessary. With an apparent magnitude of 4.4, Andromeda is one of the brighter Messier objects and is visible as a faint smudge to the naked eye under good conditions. At a distance of roughly 2.5 million light years, it is one of the most distant objects visible to the naked eye. While Andromeda is easy to find, seeing how much detail you can resolve is a good test of your telescope’s abilities. Can you see more than a bright core surrounded by a gray smudge? And while looking at Andromeda, don’t miss it’s satellite galaxies; the ellipicals M32 and M110.

The Perseids … Good News, Bad News

Friday, August 7th, 2009

The Perseid meteor shower, annually one of everyone’s favorites, will be at their best within the coming week. Although they’ve already been making a slow start for the last couple weeks, the Perseids will reach their peak late on the nights of August 11th and 12th. Perseus, the constellation from wich the meteors appear to eminate and for which the meteor shower is named, will be high in the East during the early morning hours.

Now for the good and bad news. The good news is that some experts predict this year’s Perseids could be especially intense. The bad news is that moonlight will drown out many of them. Although the full moon will be past, a still bright moon will be just a little to the south of Perseus. So only the brightest of the Perseids will be easily visible. Still, with a display like this, even a few of the brightest are still something worth watching.

Perseid update, August 15: The Perseids produced their best results (at least the best seen by this skywatcher) earlier on the night of the 12th, before the moon got too high. There were a few bursts of bright fireballs, and a fairly consistant display of smaller meteors. For those who missed the show, the next meteor shower will be the Orionids on October 21st and 22nd. Although the Orionids produce only about a third as many meteors as the Perseids, it is known for having colorful fireballs.