StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

JULY 2001

JULY STAR MAP | INDEX | MOON PHASES

253 JULY 1, 2001: Lunar Fireworks Frozen in Time: The Fourth of July is nearly upon us, and as you watch Wednesday’s fireworks displays against a moonlit sky, keep in mind that our nearest neighbor has also experienced its own pyrotechnics over the last five billion years. The moon may have even been born with a bang, from the near collision of Earth and Mars very early in the history of our solar system. When the dust cleared, there had been enough material ejected into space to form our moon, originally a hot molten body. The moon cooled during its early history as meteorites of all sizes rained onto its surface, creating the lighter heavily cratered lunar highlands. But the worst was still to come. About 3.9 billion years ago the moon was struck by truly colossal meteorites that gouged into its surface basins 50 to 100 miles deep. This was followed by several hundred million years of volcanism which filled the basins with slightly darker and denser lava, forming what even modern astronomers refer to as the seas. Since the creation of the seas the moon has had an occasional large meteorite strike its surface. These newer impact scares can be seen with binoculars or small telescopes as bright spots. Often these craters are associated with bright lunar rays, the splash marks created from rock ejected far from the impact sites. As the moon sweeps up dust in its journey through space, its surface has darkened. Recent impacts stand out as brighter regions because the meteorites have disrupted the soil and have splashed debris far from these craters exposing the fresher and brighter materials beneath. Use binoculars to view these celestial fireworks frozen in time or view them at this week’s web version of StarWatch.
This CCD image of the nearly full moon showing the rayed crater Tycho was imaged at Chaco Culture National Historical Park near Nageezi, New Mexico by Sam Hopkins, Brandon Velivis, and Gary A. Becker in May 2001. South is up.
254 JULY 8, 2001: Great Cluster in Hercules: Globular clusters are large assemblages of geriatric stars numbering in the hundreds of thousands to millions that were formed in the very early history of galaxies like our Milky Way. They form a halo around the galaxy, revolving in paths which are highly tilted. As they plunge headlong through the galactic plane, they stir up the interstellar mix and probably lose members en route. However, because they are composed of some of the oldest stars in the galaxy, astronomers feel that they have been present as long as the galaxy has been around. With the moon on the wane this week, the finest globular cluster visible from the Northern Hemisphere is culminating right after dark. It’s called M13 or the Great Cluster in Hercules. M13 contains about 500,000 stars and is 22,000 light years distant. From the darkest locations around the Lehigh Valley, M13 is visible as a faint, small circular smudge with the unaided eye, but it is quite distinct through binoculars, and it can be a truly impressive object through medium-sized telescopes, especially when its stars can be resolved. Unfortunately, the constellation of Hercules, the Strongman, can be a difficult one to spot, even from these same dark locations. However, since Hercules is nearly overhead right after dark, its identification will be simplified. Face south at 10 p.m. and look overhead for Hercules’ keystone-shaped body. A line stretched between the bright stars of Vega and Arcturus will pass nearly across M13. See the M13 finder map found on the web version of this week’s StarWatch, as well as a photo of M13 taken by the author from Chaco Culture National Historical Park last year.
The Great Globular Cluster in Hercules, called M13... Photography by Gary A. Becker, John Prince, and John Sefick.
255 JULY 15, 2001: The Comet LINEAR Show: News of any kind at Chaco Culture National Historical Park, near Nageezi, New Mexico is almost nonexistent unless you are a permanent resident and privy to TV. Volunteers like myself are not. The Internet is also glacially slow at best. Time flows at its own pace in the Canyon, and the days merge into a rhythm which is very different from the world of schedules which I am normally accustomed to. So it was no surprise to me when a Park visitor casually mentioned that he would like to see the "bright" comet that was currently in the sky. A number of us scurried to the Net and came up with a few scraps of information. Meanwhile, the weather had soured, so seeing Comet LINEAR, or more precisely C/2001 A2 LINEAR, a product of MIT’s Near Earth Asteroid Project based in Socorro, NM had to wait. The night of July 4th looked promising, so Liz Churchill, an astronomy colleague from St. Charles, IL and I bagged the local Chaco fireworks display to prepare for a more informed look at LINEAR. Lying out on moonlit sandstone still warm from the day’s heat was delightful, and the hours quickly melted away. By 3 a.m. LINEAR was easily spotted with binoculars entering the Circlet of Pisces, the Fish, a distinct frothy spot almost as big as the full moon. It was much brighter than expected and a beautiful sight to behold in our larger scopes here at Chaco. View LINEAR in the moonless morning sky this week by following its path as plotted on the sky chart found on the web version of this article. As one sky enthusiast wrote, LINEAR "...has become the kind of comet that astronomers love--truly unpredictable." Enjoy this comet!

July 15 and 16 (Sunday/Monday):: Estimating the brightness of Comet LINEAR has been difficult because it is a large and diffuse object. I observed LINEAR from Wahweap Marina, near Page, Arizona on the evenings of July 15th and 16th. On the 15th, I thought the comet was naked eye when I saw it around midnight, but it was on the threshold of my visual abilities. I used binoculars to spot it, then sighted LINEAR visually. On the 16th I could not see LINEAR without optical aid, but I was observing around 9:30 p.m. MST and the comet was much lower to the horizon. The sky was also hazier than the day before. I believe the magnitude of LINEAR to be between +4.5 and +5.0. This is comparable to some of the fainter stars of the Little Dipper. The comet was definitely fainter than the Andromeda Galaxy (+3.95) and much brighter than the Great Globular Cluster in Hercules, M13 (+5.90). Based upon the size and circular shape of LINEAR in comparison to the oval shape of the Andromeda Galaxy, I feel LINEAR’s brightness estimate to be closer to the Andromeda Galaxy than to M13.

July 17 (Tuesday):: Comet LINEAR seems to have faded. Based upon the same method described above, the brightness of the comet was between +5.0 and +5.5. LINEAR was observed from Wahweap, Arizona.

July 18 (Wednesday):: Comet LINEAR seemed to be still fainter, but plainly visible through binocular from Wahweap, Arizona.

256 JULY 22, 2001: Flying Giraffe: The world’s greatest astronomical observer, Sir William Herschel, was a musician until the age of 42. When his vocation changed after discovering Uranus in 1781, his perceptions of how to conduct research were unconventional, but changed the science forever. Herschel swept the night sky charting anything that looked strange, and in the end discovered thousands of new objects--clusters, galaxies, nebulae, and double stars--which made him legendary. His son, John, continued charting objects in the Southern Hemisphere. William entered astronomy without any of its preconceptions and approach viewing the heavens with a fresh perspective. Such is the case for Elizabeth Churchill’s flying giraffe constellation. Who is Liz Churchill you’re asking? She is researching indigenous science and currently working at Chaco Culture National Historical Park’s astronomical observatory near Nageezi, NM. Her perceptions of the night sky are unique. For example, take the Big Dipper, really the Big Bear, Ursa Major, now in the Northwest right after dark. Even from a remote site like Chaco, it is usually pretty much of a "bear" of a constellation to perceive. However, Liz sees the Bear as a flying giraffe crossing the sky right side up. In Liz’s interpretation, the three stars which form the Bear’s bushy tail become the neck and head of the giraffe. The body of the Bear, the bowl of the Big Dipper, remains the body of the giraffe. The giraffe’s legs are also the same as the Bear’s, but instead of making the Bear look like he is awkwardly skidding to a stop, the giraffe gracefully strides the sky. The head of the Bear is the giraffe’s long tail. See Liz’s flying giraffe at this week’s web edition of StarWatch.
More About Comet LINEAR...
July 23-24 (Monday/Tuesday):: Comet LINEAR was easily spotted under clear skies from Coopersburg, PA at 3 a.m. on the 23rd. LINEAR appear diffuse with a small tail about 1/2 to 3/4 degree in length. The tail was seen with adverted vision. Under hazier conditions on the 24th, at 1:15 a.m., LINEAR was visible with adverted vision only. A small tail could still be seen.

257 JULY 29, 2001: Planet Alert: The planets and the moon have been on parade for several weeks, and you can catch some very nice groupings in the early evening, as well as the morning sky. Over the next three evenings starting Sunday you can watch the waxing gibbous moon cruise past Mars, which has been the dominant planet gracing our summer sky. Now on the wane with regards to brightness, Mars is still outshining by leaps and bounds its rival, the great red supergiant star, Antares, just to its right. However, over the next several weeks you’ll notice Mars pulling away from Antares, as well as beginning to fade more noticeably in brightness as the Earth gets ever farther from our neighboring Red Planet. By the end of August, Mars will be only six times brighter than Antares, having faded by a factor of four since mid-June, when Mars was at its brightest. Switching to the morning sky about 5 a.m., one hour before sunrise, will reveal three bright planets if your eastern horizon does not have trees or buildings obscuring it. In addition, many of the brightest stars of winter, such as Aldebaran, Capella, Betelgeuse, Bellatrix, and Rigel will also be on the rise. The dominant planet will be Venus, bright enough to cast shadows in rural Lehigh Valley locations if you are up slightly before 4:30 a.m. Below, and to Venus’ left will be Jupiter, now having regained its title as second brightest planet after Venus. During June, when Mars was only 44 million miles from Earth, the God of War was brighter than Jupiter. Venus and Jupiter are side-by-side on Sunday and Monday, August 5th and 6th. Above and to Venus’ right will be Saturn. Download a map of these planets, as well as the location of the brighter stars at this week’s web edition of StarWatch.