California Wild Summer 2005

The Magazine of the CALIFORNIA ACADEMY OF SCIENCES

Skyguide

July to September 2005

Bing F. Quock

July 6: New Moon at 5:04 AM PDT. Just after sunset, a thin, 16-hour-old crescent should appear very low in the northwest. This sighting begins the month of Jumada-at-Thani in the Muslim calendar-for most of the world, that sighting doesn't happen until the following night, the 7th.

July 17: The Moon is in conjunction with the star Antares in Scorpius. In the southern United States, an occultation will be seen in which the Moon blocks Antares from view.

July 20: The 36th anniversary of the first moonwalk. A day before Full Moon, the large Sea of Tranquility, where the footprints of Armstrong and Aldrin lie undisturbed, is clearly visible as the left eye of the famous "Man in the Moon."

July 21: Full Moon at 4:02 AM PDT. With perigee-or the Moon's closest approach to Earth-occurring about nine hours later, the Moon's pull will be a little stronger, resulting in higher tides than usual. One of the Algonquin names for July's Full Moon is the "Thunder Moon." To the Choctaw, it was the "Crane Moon," and to the Mohawk, it was the "Time of Much Ripening."

August 4: New Moon at 8:05 PM PDT. The first crescent won't be visible until tomorrow, the 5th, marking the start of the month of Rajab in the Muslim calendar.

August 12: Peak of the annual Perseid meteor shower. This is a good year for the shower, which comes a day before first quarter Moon. Best viewing is between midnight and dawn, by which time the Moon will have set, so its light won't interfere with the display. Expect about 50 meteors per hour, radiating from the constellation Perseus in the northeast.

August 19: Full Moon about twelve hours from perigee, resulting once again in higher-than-usual tides. This Moon is also known to Native American tribes as the "Autumn Moon" (Taos), the "Women's Moon" (Choctaw), and the "Blueberry Moon" (Ojibway).

September 3: New Moon at 11:45 AM PDT. There is no crescent visible tonight; look tomorrow, on the 4th, which will mark the start of the month of Sha'ban in the Muslim calendar.

September 17: Full Moon at 7:01 PM PDT. As the Full Moon nearest the equinox, this one is traditionally called the "Harvest Moon," which comes from the Algonquin. Other names for September's Moon include the "Moose-Calling Moon" (Micmac), the "Wild Rice Moon" (Ojibway), and the "Moon When the Elk Bellow" (Ponca).

September 22: Autumnal equinox at 3:23 PM PDT, marking the start of Fall in the Northern Hemisphere-the Sun crosses the celestial equator and enters the southern hemisphere of the sky, rising due east and setting due west. Theoretically, day and night are of equal length. South of the Equator, this is the beginning of Spring.

The Planets

Mercury
The world closest to the Sun is always a difficult object to spot. This season, it makes a brief appearance in the evening sky of early July, soon disappearing back into the Sun's glow, then leaping up before dawn in late August. Look for it close to Venus in early July, closest on the evening of the 6th. The Moon pairs up with Mercury on the evening of July 8 (with Venus between them), on August 4 (too close to the Sun to observe), and on the morning of September 2.

Venus
Just emerging from late June's spectacular clustering with Mercury and Saturn, the brightest planet is visible in the evening sky after sunset and has a few more interesting pairings. On July 7, it's one degree from fainter Mercury, and the following night, the crescent Moon sweeps by. On the evening of July 22, it's two Full Moon widths from the star Regulus (the heart of Leo). Closing in on Jupiter, it pairs beautifully with the giant planet on September 1. The crescent Moon is nearby on the evenings of July 8 (along with elusive Mercury), August 7, and September 6 (when it forms a photogenic foursome with Jupiter and the bright star Spica).

Mars
Approaching its November opposition, the Red Planet is now beginning to brighten noticeably. It rises shortly after midnight in July against the stars of Pisces and inches toward Aries. By September, it rises shortly before midnight. The Moon is nearby on July 27, August 24, and September 21.

Jupiter
An evening object, the largest planet in the sky lingers against the stars of Virgo, located high in the southwest at sunset in July and gradually dropping lower and lower toward west. Watch for the stunning close pairing of Jupiter and Venus on September 1. The Moon swings by on the evenings of July 12 and 13, August 9, and September 6 (with Venus and the bright star Spica nearby).

Saturn
In conjunction with the Sun on July 23, the Ringed Planet is not visible until late August, when it rises in the east just before dawn against the faint stars of Cancer. The Moon is nearby on July 6 and 7 and August 4, but these encounters are too close to the Sun to be observed. More visible are the Moon's pairings with Saturn on August 31 and September 27 and 28.

	Sunrise	Local Noon	Sunset
July 1	5:52 A.M. PDT	1:14 P.M. PDT	8:36 P.M. PDT
August 1	6:13 A.M. PDT	1:16 P.M. PDT	8:18 P.M. PDT
September 1	6:40 A.M. PDT	1:09 P.M. PDT	7:38 P.M. PDT
October 1	7:06 A.M. PDT	12:59 P.M. PDT	6:52 P.M. PDT

(Times are for San Francisco, CA, and are accurate to within two minutes.)

The Milky Way Panorama

Summer months are the best time to observe the galaxy in which we live. Disk-shaped, our galactic island of several hundred billion stars looks like a band of light arching gracefully across the sky. On summer nights, particularly away from the interference of bright city lights, we're looking at its brightest sections. Running from the "W" of stars forming the constellation Cassiopeia in the north, it passes through the Summer Triangle overhead and descends toward hook-shaped Scorpius in the south. Within the Summer Triangle, sharp eyes will see the Great Rift, a dark lane of dust that seems to split the band in two. Southward, where the Milky Way meets the horizon, the stars of Scorpius stand between us and the center of the galaxy itself, about 30,000 light years (or 180,000,000,000,000,000 miles) away. It's hidden from direct view behind yet more dust lanes and billions of densely-packed stars. However, using instruments that can see forms of light our eyes cannot, astronomers have detected what lies at the heart of our galaxy and most others: a giant black hole. This one has the gravity of nearly 3 million suns.

Bing F. Quock can be reached at bquock@calacademy.org.