California Wild Spring 2004

The Magazine of the CALIFORNIA ACADEMY OF SCIENCES

SKYGUIDE

April to June

Bing F. Quock

April 4: Spring forward. On the first Sunday in April, is there anything you'd rather do that get up at 2 a.m. to set your clocks ahead one hour for Daylight Savings Time?

April 5: Full Moon - the "Wildcat Moon" to the Choctaw - rises at sunset against the stars of the constellation Virgo, near the bright star Spica. Since this is the first Full Moon of Spring, the next Sunday on the calendar is Easter Sunday.

April 19: New Moon. Tonight at sunset, the 13 1/2 hour old crescent Moon may be too thin to view without binoculars. Count on seeing it with the naked eye tomorrow night to mark the beginning of the Islamic month Rabi-al-Awal.

May 4: Full Moon - the Mohawks' "Time of the Big Leaf" - rises just after sunset against the stars of Libra.

May 15: Astronomers are hoping that the comet NEAT C/2001 Q4, making its closest swing around the Sun, may be bright enough to be seen with the unaided eye.

May 19: New Moon. Tomorrow night at sunset, a thing, almost 23-hour old Moon will be visible. Slightly higher will be Venus, and - just a little higher still - Saturn and Mars.

June 2: Full Moon rises in Scorpius, near the bright reddish star Antares, which represents the Scorpion's heart. The Ponca named this "The Hot Weather Moon."

June 17: New Moon at 1.27 p.m. Look for a nice crescent in the west-northwest tomorrow night (the 18th) after sunset.

June 20: Summer Solstice occurs at 5:58 p.m., marking the beginning of Summer in the Northern Hemisphere. The Sun rises and sets at its most northerly points, making its highest arc across the sky. South of the Equator, this marks the start of Winter.

The Planets

Mercury Having passed a favorable eastern elongation on March 29, Mercury is visible in the evening sky of early April, setting in the West about 90 minutes after the Sun. After the first week of April, however, the elusive planet retreats back into the Sun's glow. It reappears in the eastern predawn sky in early May, but doesn't get very high by sunrise. Mercury lingers in the morning twilight until early June, then once again disappears into the glare of the Sun.

Venus At the beginning of April, the brightest planet is about halfway up from the horizon at sunset and very prominent in the evenng sky, with fainter Mars slightly above it. Don't miss a lovely sight as it passes the Pleiades star cluster on April 2 and 3. It seems to ascend slowly toward Mrs durin ghte month, but never quite catches up with the Red Planet before apparently changing its mind and deciding to retreat back into the Sun's glow. Watch at the beginning of May as it passes the star El Nath - the northern horntip of Taurus - and then slows down and stops by mid-month. Venus diappears by the endof May and reappears in the morning sky by mid-June, rising in the east and dominating the predawn for the rest of the year. The Moon passes nearby on the evening of April 22, May 20 and 21, and then again on the morning of June 16.

Mars The Red Planet spends the coming season in the western sky, visible after sunset against the stars of Taurus in April. Now nearly at its faintest, Mars appears slightly lower in the sky from night to night as it gradually moves through Gemini in May and then into Cancer by June. On May 9, Mars is equidistant between brilliant Venus and fainter Saturn. the crescent Moon visits Mars on the evenings of April 23 (with Venus nearby), May 20 and 21 (with Saturn nearby), and June 19 (very low after sunset).

Jupiter This season, the largest planet lingers in Leo, seemingly ostracized by other planets as they perform their slow, twilight dance. High in the east after sunset in April, Jupiter gradually moves westward through the season, dropping toward the southwest by June. The Moon swings by on the evenings of April 29, May 26, and June 23.

Saturn Located against the stars of Gemini, the Ringed Planet spends the season slowly descending from a point high in the west toward the glow of the setting Sun. It disappears into the sunset by mid-June, not to be seen again until the predawn sky of August. The Moon passes nearby on the evenings of April 24, May 21 and 22, and June 18.

	Sunrise	Local Noon	Sunset
April 1	5:55 AM PDT	12:14 PM PDT	6:32 PM PDT
May 1	6:13 AM PDT	1:07 PM PDT	8:01 PM PDT
June 1	5:49 AM PDT	1:08 PM PDT	8:26 PM PDT
July 1	5:52 AM PDT	1:14 PM PDT	8:36 PM PDT

(Times are for San Francisco, CA, and will vary slightly for other locations.)

Saturn - Gone, But Not Forgotten

Though Saturn disappears into the glow of the Sun by mid-June, it should reappear through the lens of NASA’s Cassini spacecraft. The last of the really big planetary probes, Cassini enters Saturn’s orbit on July 1. Launched in 1997, Cassini is about the size of a school bus and bristles with 12 instruments. It will orbit Saturn for four years, giving scientists a better view of the planet than afforded by the brief glimpses from previous spacecraft flybys. In January 2005, if all goes according to plan, Cassini will release the Huygens probe into the murky, cloud-filled atmosphere of Saturn’s moon Titan. This probe, carrying its own suite of six instruments, should land on the as-yet-unseen surface of the largest of the planet’s 31 known moons. The spacecraft are named after two astronomers of the 17th century: Giovanni Domenico Cassini, who discovered four of Saturn’s moons and the major gap in its ring system and Christiaan Huygens, who was the first to identify the lobes surrounding Saturn as rings.

Bing F. Quock is a member of the Morrison Planetarium staff at the California Academy of Sciences. bquock@calacademy.org