To the reader:
The Skywatcher's Diary for July 2001 has been prepared by
David Batch. Credit to the author and to
Abrams Planetarium,
Department of Physics and Astronomy at
Michigan State University, and mention of
our
Sky Calendar, would be
appreciated.
A sample issue of the Sky Calendar is available over the Internet. It
can be viewed via the World-Wide Web at
http://www.pa.msu.edu/abrams/SkyCalendar/Index.html
If you would like a printed sample of the July issue, please send a long,
self-addressed stamped envelope to:
July Sky Calendar
Abrams Planetarium
Michigan State University
East Lansing, MI 48824
Each month, the Department of Physics and Astronomy at Michigan State
University makes the Skywatcher's Diary available over the Internet. It can
be accessed at
http://www.pa.msu.edu/abrams/SkyWatchersDiary/Diary.html
Current and back-issues of the Skywatcher's Diary are available in our
archives
at
http://www.pa.msu.edu/abrams/SkyWatchersDiary/Archives.html
ftp://www.pa.msu.edu/pub/swd/
Skywatcher's Diary: July 2001
Mars blazes in the SSE as evening twilight descends. Its magnificent orange glow makes the planet unmistakable. Mars reaches its highest point, only 23 degrees up (about two fists) in the south, around 2 3/4 hours after sunset. The planet sets in the SW by the start of morning twilight.
The Moon, Mars, and the bright star Antares form a neat equal-sided triangle this evening. The Moon is at the top, Mars is 7 degrees (less than a fist) below the Moon, and the star is to the lower right of the Moon and the upper right of Mars. As the night progresses the Moon slides to the left, and by dawn the figure becomes more nearly a right triangle.
If this year has been tough on you so far, you may take comfort in the news that we have crossed the peak and we're on the downhill slope. The midpoint of the year occurred yesterday at midday. Tonight the almost-full Moon sits about 10 degrees (one fist) to the left of Mars.
Today the Earth is farthest from the sun for this year, just over 94,503,000 miles. The Earth's orbit is almost circular, with just a 3 percent variation in distance between nearest and most distant points. Here's a puzzle to chew on while you wait for the burgers to grill this holiday. Why is our weather now hot when we are farthest from the sun? Obviously, some more significant factor than the sun's distance is at work -- the tilt of the Earth's axis.
The Moon is Full at 11:04 a.m. EDT, but don't look for it then. Remember that the Full Moon is opposite the sun, so it has the night shift. The July moon was traditionally known as the Hay or Thunder Moon. A partial lunar eclipse, centered over Australia, is visible primarily from the Eastern Hemisphere.
Yesterday's Full Moon occurred nearest (14 days after) the Summer Solstice. Consequently, it follows a nighttime path across the sky similar to the sun's arc at the time of Winter Solstice. It you have the opportunity to glance at the Moon on several occasions over the course of the night, notice it never appears high. At maximum it rises to just over 20 degrees above the southern horizon.
Mars reaches its highest point, due south, about 2 hours after sunset. At that same time, one of Mars' more prominent surface markings, Meridiani Sinus, is centered on the disk. Although Martian features are always difficult to spot, if you have access to a telescope, look for a sooty smudge in the middle of the image.
An exciting planetary ballet is taking shape in the early dawn. The principals, in order of appearance, are Venus, Saturn, Mercury, and Jupiter. The Moon is cast in a supporting role. Curtain time is an hour before sunrise. The recital continues through the next two weeks in the ENE sky. Look every morning you can for the constantly changing pattern. A rare opportunity!
Mercury is 21 degrees from the sun today -- its greatest angular separation during this morning appearance. Look for it low in the ENE an hour before sunrise. Brighter Jupiter is 4 degrees (half a fist width) to Mercury's left. More luminous still is Venus, 22 degrees to Mercury's upper right. Between Venus and Mercury, but only 6 degrees from Venus, rests Saturn.
The two brightest stars in the current evening sky are Vega, three-quarters of the way up in the E, and Arcturus, more than half way up in the WSW. The planet Mars, low in the south, is significantly brighter than either star. Can you detect a color difference in the two stars? Hint: Arcturus is the cooler of the pair.
Dusk lingers nearly until midnight this time of year, so to view a truly dark sky requires some late hours. The exquisite summer Milky Way makes the effort worthwhile, however. Bring the binoculars, drag out a lounge chair and a blanket to ward off the chill and insects, lie back, and embark on a celestial journey. Let your eyes and mind roam the subtleties of this vast cloud of stars, stretching the length of the sky from south to north and high across the east.
Tomorrow morning, before dawn, Venus passes within a tenth degree above the 4th-magnitude star Epsilon in the "face" of Taurus, the Bull. The planet is so bright you will probably need binoculars to glimpse the star. Look in the ENE between one and two hours before sunup. Saturn sits 2 degrees to the left of Venus. Much lower, 20 degrees to Venus' lower left, Jupiter and Mercury appear close -- Mercury 2 degrees to the lower right of Jupiter.
The second, and last, Friday the 13th of 2001. Last Quarter Moon occurs at 2:45 p.m. EDT, but sets about an hour before then. Look for it in the morning, before and after sunrise. Over the next several mornings the Moon passes through a faint part of the zodiac which includes Cetus, Pisces, and Aries. That's not a misprint. Cetus is part of the astronomers' definition of "zodiac."
If you have risen early enough to watch the ongoing planetary dance in the eastern sky before sunrise, you have noticed Venus and Saturn cozying up. Tomorrow morning Venus passes closest to Saturn, only seven-tenths of a degree below the Ringed Planet -- just over a moon width. Jupiter continues climbing past Mercury, 20 degrees to the lower left of the Venus-Saturn pairing.
The most easily observed dark feature on Mars, Syrtis Major, is centered on the planet's disk at prime observing time, when Mars is highest and due south. Look 1 1/2 hours after sunset. When viewed through an inverting (upside-down image) telescope, the shape of Syrtis Major is reminiscent of the Indian subcontinent.
The Moon joins the morning planetary gathering for the next few days. Tomorrow morning's sight will be worth the effort of getting up early. The beautiful crescent sits among two planets and a bright star. Saturn is 2 degrees (four moon diameters) to the Moon's left. Venus is 2 degrees to the lower left of the Ringed Planet, and Aldebaran, the eye of Taurus, is 2 degrees to the lower right of the Moon.
The Moon passes in front of Venus this afternoon, blocking our view of the planet for just over an hour. Since the event occurs in broad daylight, a telescope is needed, although binoculars may work if the sky is clear enough. The occultation, as astronomers call it, begins just after 2:15 p.m. EDT (in Michigan), but you will want to test your ability to find the Moon well ahead. Look for it about halfway up in the west. Venus will be above the Moon, nearest the bright crescent.
Tomorrow morning the Moon is within 3 moon diameters (1 1/2 degrees) of Mercury. Look low in the ENE an hour before sunrise. Mercury is to the Moon's lower left. Jupiter is the brighter planet 6 degrees to the Moon's upper right. Inhabitants of the northwest U.S. will be able to watch the Moon occult Mercury.
Mars has been retrograding -- traveling westward against the background stars -- for the last two months. Today it reaches a stationary point and then resumes the more common direct, or eastward, motion. Look for it in the south at the end of dusk. Five degrees to the planet's right is Antares, the bright star marking the scorpion's heart. The separation between planet and star is now minimum, as Mars begins to pull away.
The Moon is New at 3:44 p.m. EDT. No moonlight means dark skies all night long. From a dark location, trace the glimmering path of the Milky Way across the sky. If the night is quite clear and you have a low southern horizon, use binoculars to explore the various star clusters and gas clouds in that region. The Lagoon Nebula, a famous stellar birthplace, sits just above the "spout" of the "teapot" pattern of Sagittarius.
The Moon reenters the evening sky. Look for a hairline crescent very low in the WNW 45 minutes after sunset. Use binoculars. Don't be tardy because the Moon sets about 20 minutes later.
The young crescent Moon will be easier to see tonight. It sets an hour and 45 minutes after sunset. Regulus, the brightest star in Leo, the Lion, is 4 degrees (8 moon diameters) below Luna. Leo, one of the first celestial signs of spring, is now giving way to the stars of summer, found high in the southern sky, and autumn, now just rising in the east.
Pegasus, the Winged Horse, and one of the early stellar indicators for autumn, sits above the ENE horizon at the end of twilight. Look for the Great Square of Pegasus, now rotated so that it looks more like a diamond. Draw a line across the middle corners of the diamond and extend it to the left its own length. You are in the vicinity of the great Andromeda Galaxy. Use binoculars in a dark sky to look for a softly glowing oval.
If you have not seen the early morning sky in a week or more, you might be caught off guard by Venus' swift motion. Nine days ago it was near Saturn. Now it straddles the gap between Saturn and Jupiter. Continue following it through early August when it passes underneath Jupiter.
The Moon is near Spica, the brightest star in Virgo, the next two nights. This evening the star is 10 degrees (one fist) to the lower left. In the next 24 hours the Moon hops over Spica, so tomorrow night look for the star 9 degrees to the lower right.
The Equation of Time, the difference between sundial time and standard time, is currently at a maximum. If you would like to check your sundial, add 6 and a half minutes to what your sundial reads and compare it to an accurate clock. Remember to add an hour for daylight saving, too.
The Moon is at First Quarter phase at 6:08 a.m. EDT. Tomorrow morning the Delta Aquarid meteor shower reaches its predicted peak of one meteor every 3 or 4 minutes. While the number of meteors is not substantial, the peak is broad, so activity continues at nearly the same rate for a number of days. Don't fear getting pelted by meteorites. Meteor showers rarely contain pieces of material large enough to reach Earth's surface before disintegrating. Typically they are the size of a grain of sand.
The constellation Cassiopeia, Queen of Ethiopia, is high enough in the NE by the end of dusk to easily be picked out. Not much of the constellation resembles its namesake queen, but the shape, once learned, is memorable. Look one-third of the way up for a "W-shaped" group of 5 stars. The pattern is somewhat compressed and fainter on the left side. None of the stars are brighter than 2nd magnitude, but, then, nothing else in that part of the sky competes for your attention.
The Moon is near Mars the next two nights. This evening it is 9 degrees to the upper right of the Red Planet, and 6 degrees (12 moon diameters) above Antares, in Scorpius. Tomorrow night the Moon is 7 degrees on the other side of Mars, to the planet's upper left. The following night the Moon stands directly above the "teapot" of Sagittarius.
Neptune is at opposition tonight, meaning it is opposite the sun in the sky. Around opposition is always a good time to look for a faint planet because it is then brightest. Even so, Neptune only reaches 8th magnitude, two notches fainter than the typical eye can see under the best of conditions. If you want to spy the pale blue-gray dot, you will need a moderate-sized telescope and a good finder chart.
An hour before sunrise Orion, the principal winter constellation, is now completely above the eastern horizon. Look for Venus and Jupiter to the hunter's upper left. Try to coerce yourself into rising early enough to keep track of those two planets for the next week. Venus is barreling toward Jupiter and will pass 1 degree below it on August 6.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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