ASTRONOMY CLUB NEWSLETTER

CLUB EVENTS:
Join us at Explorit at 8:00 Saturday night, June 20.
The topics will be the Constellation Libra, Making Craters, and Making Magnitude Indicators. Everyone is invited to this astronomical pot-pourri!

Libra , or the Scales, is the only constellation of the zodiac that is not named for either a real or fanciful living creature. The zodiac is the twelve constellations that the Sun appears to move through during a year. The most interesting aspect of the constellation, to me, is the name of its two brightest stars: Zubenelgenubi (zoo ben el gen U bee) and Zubeneschamali (zoo ben es sham AL ee). The names mean "Southern Claw" and "Northern Claw" and medieval Arab astronomers used these names, recalling the ancient days when the stars in "Libra" made up the forepart of its larger neighboring constellation, Scorpius, the scorpion.

Libra was recognized as a separate constellation by the ancient Roman astronomers at least since the time of Julius Caesar, but the association of the stars with the Scorpion continued to be popular with poets. Did the Romans invent Libra? According to the late Julius Staal, around 1190 B.C. the sun visited this constellation during the autumnal equinox and so, he believed that at that early date, Libra came to represent the "balance" between night and day. At least 3 other constellations, all obsolete, have occupied the area of Libra in various European maps of the sky over the last couple of centuries: the Hermit Bird, the Solitaire, and Noctua (the Night Owl).

Some interesting sights in Libra are:

• Zubenelgenubi, an easily resolved double star with one component yellowish and the other a pale blue;
• Iota Librae, consisting of a very close (0.1 seconds of arc) binary pair orbiting each other every 22 years and a third companion star which is nearly 1 minute of arc away
• 48 Librae, a star surrounded by an outer shell of gas that rapidly expands and, when it does, makes it appear that the star is rapidly approaching
• Zubeneschamali has been described by some observers in the late nineteenth and early twentieth centuries (T.W. Webb and W.T. Olcott) as green, or pale-emerald--but is it? Green stars usually only appear so when viewed next to bright red stars (perhaps we will view , for example, the companion to Antares in Scorpio).

In addition to a look at Libra, we will construct "stellar magnitude indicators" from cardboard and plastic strips. We will see how successful these devices can be in measuring differences in brightness between various stars. Are they more accurate than our own eyes in estimating the relative brightness of stars?

We will also have some fun making impact craters to help us visualize what happens when a meteoroid hits a solid surface like that of the Moon. What are the structural elements of an impact crater? How important are the factors of size and speed of the meteoroid to the size and shape of the crater? This demonstration uses a pan of flour and three different size rocks, and is taken from the Astronomical Society of the Pacific's astronomy activity and resource notebook: "The Universe at Your Fingertips."

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The topic of our meeting on May 16 was "Virgo and the Two Bears". We saw slides on the mythology surrounding the constellations of Virgo (the Virgin), Ursa Major (Big Bear) and Ursa Minor (Little Bear). Thanks to Alvin Huey, we saw slides of objects of interest to astronomers (amateur and professional) that lie within these areas of the sky. The area around Virgo is well known for its clusters of galaxies. Because our usual meeting room was filled with materials for an Explorit science class on chemistry, we held our slide show in front of the building. Approximately 20 friendly people attended the meeting. The weather cooperated and gave us a very clear sky, though the temperature was a little brisk for this time of year--around 50 degrees. We had the use of two 16 inch telescopes, courtesy of Jeff and Ben Granett and Alvin Huey. Many deep sky objects were seen. One experienced amateur from Sacramento treated us to views through his Meade ETX 90 mm Maksutov, which provided excellent images.

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What's Up in June? Planet watchers must continue to rise early in the morning, since all the planets are west of the Sun this month and most visible (if at all) before dawn. Best time is around 5:00 a.m!

• On Wednesday the 17th the Moon will be close to Jupiter in the East Southeast.
• Two days later (Friday the 19th) our natural satellite visits Saturn, and on Sunday, the 21st, the slim crescent moon is near the horizon and below bright Venus.
• At 7:03 a.m. Sunday June 21st, the summer solstice occurs: official beginning of summer for the Northern Hemisphere.

On the evening of Wednesday, May 6 Valley Oak School presented a large Science Fair event on campus with guest speakers including myself. Members of the club, Jeff and alumnus Ben Granett, brought their large telescope and, in spite of the partly cloudy skies, it drew a crowd of children and their parents of observe the Moon and other celestial attractions. We also demonstrated how to model the head of a comet with dry ice and presented a slide show on Leo. The sky cooperated with the Leo presentation by clearing enough for us to observe the entire constellation from the playground. The Science Fair was a great success due in large part to science teacher at Valley Oak and member of this club, Bill Storm.

The Astronomy Club is hosted by Dennis Smith with the assistance of Tim Feldman and other eager astronomy buffs. The club is for everyone - adults, children, knowledgeable or ignorant. Come to listen, look and learn, or to share your expertise or experience.