August 2007
Skywatcher’s Guide for August 2007
The Perseid Meteor Shower Peaks Aug. 11-12; Learn all about it at Flandrau on Saturday August 11
 The Perseid meteors become visible as the radiant (the path where the meteors seem to originate) rises. This graphic shows the sky on August 11-12, at midnight from the southwestern U.S. |
The annual Perseid meteor shower (the Perseids) occurs this year on the nights of August 10th-14th. The Perseids are often the best meteor shower of the year, with at least 10-30 meteors per hour visible even for beginning stargazers. The peak rates of meteors (also called shooting stars) will be seen on the night of Sunday August 12th into Monday August 13th, with as many as 50 meteors per hour or more visible in a clear, dark sky. The new moon this year on August 12 creates an opportunity each night for perfect viewing, if the weather cooperates. If monsoon clouds interfere, viewers will also be able to see meteors in numbers on the nights of August 10-11 and August 13-14. Meteor watchers should seek out a dark sky several miles away from city light and gaze in a wide area of sky high in the eastern and northern sky and overhead after 10:00 p.m. To see the shower well, observers should view until well after midnight (or in the hours before sunrise) in dark skies, far away from city lights. Good locations for viewing include the east end of Speedway at Saguaro National Park East and the Tucson mountains west of town. Observers should expect to drive 30 minutes to out of town, away from city lights, to get good views of the shower.
The debris causing the meteor shower is from a comet that passed Earth in 1992 named Comet Swift-Tuttle. The debris consists of tiny particles of rock, some thinner than a hair and most no larger than a grain of sand. Nearly all the particles of a meteor shower burn up in Earth’s atmosphere. Comets are the source of nearly all meteor showers. Comets are bodies, often potato shaped and less than 6 miles in diameter, made of a loose aggregate of rock and ice that is in orbit around the Sun. As comets come in close to the Sun, they begin to evaporate off dust particles, gases and water vapor, leaving a long tail behind them. This tail leaves a trail of tiny debris in space, which Earth can pass through, resulting in a meteor shower.
To help the public learn about this meteor shower, Flandrau Science Center will offer a special presentation on the Perseids (and about meteor showers in general) by UA Steward Observatory astronomer Dr. Tom Fleming. Dr. Fleming is an Associate Astronomer and Senior Lecturer at the University of Arizona. The presentation, on Saturday night August 11, will be an added feature of the 8:00 p.m. showing of the planetarium show “More than Meets the Eye” and will start after the recorded portion of this program ends. Only patrons attending More than Meets the Eye at 8 p.m. can attend the presentation. The planetarium show and presentation costs $5.00 per person for adults and children 4 and older, and will last about 1 hour and 15 minutes.
For more information visit the news article in Flandrau’s astronomy news section.
A long, early morning total lunar eclipse on Aug. 28
 Please note: The Moon’s appearance during lunar eclipses varies considerably. |
The August full moon provides an early morning treat for North America in the pre-dawn hours of Tuesday August 28 with a long early morning total lunar eclipse. When the full moon rises after sunset on Monday August 27 casual sky-gazers might not suspect anything unusual occurring with the Moon that night but by 1:58 a.m. the Moon’s top limb will start to darken. The Moon at that time will be high up in the south-southwestern sky as seen from southern and central Arizona. This darkening from Earth’s shadow will progress until the entire Moon will be engulfed by Earth’s inner or ‘umbral’ shadow by around 2:58 a.m. The darkest or ‘deepest’ portions of the eclipse will occur at 3:40 a.m. The total phases of the eclipse will end for Arizona at 4:21 a.m. An advantage for Arizonans is that such a predawn eclipse is best weather wise during August, as monsoon clouds tend to clear up after midnight.
From other parts of the world the eclipse is seen earlier the farther you head west on the globe, and later as you head east. The East Coast of North America sees the totally eclipsed Moon setting in the morning twilight. However from Australia and New Zealand the eclipse is seen in the convenient evening hours. A much shorter total eclipse will occur on the evening of February 20, 2008 for North and South America.
For the best views of the eclipse get to a dark location away from city lights. From a dark sky the darkened Moon gives a 3-D effect, as it set against the background of the starry night sky. Other information about the eclipse and the night sky is available by calling the Science Center’s free Astronomy News-line at 621-4310 (and a menu option off of 621-STAR).
PLANETS
Bright Jupiter dominates the August sky for the first few hours of the evening. Jupiter appears as a very bright, almost brilliant white star-like object, high above the southern horizon in the early August evening twilight. By late August Jupiter moves above the southwestern horizon in evening twilight. The largest planet in our solar system, Jupiter is the brightest star-like object most often seen in the night sky, although Venus is substantially brighter, and Mars can be brighter every 15 years or so. Jupiter in early August is still close to its brightest this year (at magnitude -2.3) and largest in a telescope (at 41 arc seconds wide). The giant gas world, although dimming slightly, remains nearly this bright in the skies of Earth all month long. August 2007 continues to be a good time for viewing the giant planet as appears well up in the southern sky this year during the convenient evening twilight. When looking at Jupiter in a telescope to view its cloud belts and festoons, the sharpest views should be in evening twilight, when it’s highest. As with any planet, viewing is dependent on atmospheric stability and conditions, and of course, the quality and size of the telescope used. However to view its moons, a good pair of binoculars is all that’s needed. Finally, the 8-day old gibbous Moon can be seen well below Jupiter starting around 7:45 p.m. on Tuesday night, August 21.
Mars continues to brighten and is 0.3 magnitude by August 21st. It’s now about 45 degrees in altitude in the eastern half of the sky, 90 minutes before sunrise, mid-month. Mars drifts eastward out of the southern portions of Aries, the Ram and into Taurus the Bull. Mars is rising now above the east-northeastern horizon at around 12:00 a.m. in middle and late August. The waning crescent Moon will rise well above and before Mars around 1 a.m. on Sunday, August 6, while a thinner waning crescent Moon will be slightly closer and rise left (or north) of Mars the following morning.
The brilliant planet Venus moves into the glare of the Sun in the evening sky early this month but then rockets out of glare of the Sun and into the morning twilight. Venus, once grouped wonderfully close to Saturn early in July, sinks out of view during the first few days of August. On August 1 Venus sets a little about one hour after the Sun and is difficult to find a few degrees above the western horizon 30 minutes after sunset. Venus then reappears in the morning twilight by August 21. By August 31, Venus will be seven degrees in altitude at 5:15 a.m. in the eastern morning twilight. Whether you try for Venus in the evening the first few days of August or in the morning late in the month, view it in a good quality pair of binoculars or a low power telescope as the phase of Venus will be a fascinating, thin crescent. Venus will climb high into the morning twilight in September and reach its highest.
The elusive planet Mercury and the ringed planet Saturn are both lost into the glare of the Sun for naked eye viewing.
Visitors to Flandrau’s 16-inch telescope should note that only the planet Jupiter is visible this month in the telescope after it opens at 7 p.m. The telescope normally closes at 10 p.m.
Finally, remember that in spotting planets there is a general rule: ’stars twinkle, planets don’t’. This is because stars are point sources of light; therefore starlight is easily disturbed and shifted by air currents in the Earth’s atmosphere. However when looking at Mercury right now, note that it may appear to twinkle somewhat; however, this twinkling is of a slower nature than the bright stars.
AUGUST EVENING STARS
August evenings are an excellent time to see the bright constellations of the summer months (especially Scorpius and Sagittarius), along with the Milky Way. To see the brightest areas of the Milky Way in the south, look before 10 p.m., as the star rich regions in Scorpius and Sagittarius start to lose altitude in Arizona skies early. Start by finding the brightest star in Scorpius: Antares. These evenings, its orange-red twinkling enlivens the southern sky, giving reason to its name “the rival of Mars”. From the southern United States Antares does not get very high, only about 30 degrees (or three fists held at arm’s length) above the southern horizon, because of its position in the southern sky. Antares is the brightest part of a most impressive scroll of stars, sort of like a long letter S fallen halfway forward. And in this case the S stands for the constellation it is part of: Scorpius, the Scorpion.
To the ‘left’ or east of Scorpius is the “Teapot” of Sagittarius. Not technically a constellation, the Teapot is actually part of the larger constellation Sagittarius, the Archer. Like steam emerging from the spout of a real teakettle, look for bright portions of the Milky Way off the spout of the Teapot; This region marks the central area of our galaxy and is fascinating to scan in binoculars. High power binoculars and telescopes reveal the Milky Way to be clouds of stars, millions of them, with attendant star clusters and gas clouds making up some of the “fuzzier” spots you’ll see.
Overhead in the August evening sky look for the bright stars of the Summer Triangle: Vega, Deneb, and Altair. Each night every August the widely spaced triangle of Vega, Deneb, and Altair brighten the evening sky. Vega, Altair, and Deneb are each the brightest stars of three constellations that make up the Summer Triangle. Vega is the brightest star in the small constellation of Lyra, the Lyre (a small ancient harp). Vega, one of the closer stars to Earth (only 25 light years away), was the Pole Star (our North Star) some 12,000 years ago, and will again be the North Star in 12,000 A.D. when Earth’s cyclical wobbling motion brings in near the pole once more. Deneb is the tail of Cygnus the Swan, but also marks the bottom of the cross-shaped pattern whose other name is the Northern Cross. Deneb is a huge supergiant star over 1,600 light years from Earth. Aquila, the Eagle is the home of the bright star Altair, the first star of the three in the triangle to set late at night and the closest of the three to Earth at only 16 light years distant. Aquila looks more like a diamond or kite than an Eagle. Aquila and Cygnus (or the Northern Cross) mark some of the brightest areas of the northern Milky Way.
Finally, the Big and Little Dippers are only briefly visible in the August evening sky. The Big Dipper will start to sink from view in from southern Arizona by around 9:30 p.m. in early August. Take the pointer stars and point to Polaris, our North Star (a star of ordinary brightness, but one that hardly moves at all in our sky).
The Milky Way Prominent in the Late Night Hours!
 The bright star clouds of the southern Milky Way surround the Teapot of Saggitarius |
The summer Milky Way is brightest towards the south in the late night hours in August. This sky chart shows the southern sky from southern Arizona at around 11:30 p.m. in early August, 10:30 p.m. in middle August, and 9:30 p.m. in late August.
Look for the Milky Way to rise late on moon-less August evenings; It will be brightest around the constellation Scorpius, the Scorpion. The Milky Way, the galaxy of stars, gas and dust our solar system resides in, is prominent all summer long, but is brightest after midnight in August. To see it, you’ll need to get away from city lights to a dark location, and look on a night when there’s not much interference from the moon. The Milky Way will appear as a “cloudy” band stretching clear across the sky. High power binoculars and telescopes reveal the Milky Way to be clouds of stars, millions of them, with attendant star clusters and gas clouds making up some of the “fuzzier” spots you’ll see.
MOON PHASES
August’s last quarter Moon will occur on Saturday morning, August 5th. The August new moon occurs on August 12, allowing for great views of the Perseid meteor shower from August 10th through the 14th. The first quarter Moon will be on the evening of Monday August 20. The August full moon can be called the full ‘Sturgeon or Red’ Moon and occurs this year in North America on Monday night August 27 into the morning of Tuesday August 28. That night a total lunar eclipse occurs for North America, the Pacific Ocean, Australia, New Zealand and parts of Asia. For Arizona the total eclipse phases start in the pre-dawn hours at around 2:58 a.m., with mid-eclipse at 3:40 a.m. The total phases of the eclipse for Arizona ends at 4:21 a.m.
These dates and times are for southern and central Arizona, and are not necessarily Greenwich Mean Time dates, the moon phase dates used for calendars.
<U>Note:</U> Additional information can be accessed by phone at Flandrau Science Center’s Astronomy Newsline at (520) 621-4310 or as a menu option at 621-S-T-A-R.
<i>Graphics done using Starry Night Enthusiast and Adobe Photoshop. To purchase Starry Night Enthusiast go to http://StarryNight.com </i>