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May is a good time for star and planet gazing. All five naked-eye planets are visible; the islands experience the first of the two "overhead sun" days of the year; moon conditions are good for one of the lesser-known meteor showers; and we say goodbye to Orion and the other great winter constellations.
While the other naked-eye planets are visible all month, you’ll have to wait until to May 6 to catch Mercury. Look west around 7:20 p.m. on May 6 and 7 for a brilliant dot just above where the sun set. On May 6, Mercury shines at an intense minus 1.16. In early May, the planet will set by 7:45 p.m. so you have only about a half-hour to catch it.
From then until the end of the month, Mercury will be a little higher in the sky at dusk. By the end of the month, Mercury will be down to first magnitude, but will also be well above the sun at dusk. Search for it around 7:45 p.m. about 12 degrees (well more than the diameter of your fist) above the western horizon. The planet sets in late May around 8:45 p.m.
In early May, Jupiter is about halfway up in the west at dusk and sets by 11:30 p.m. Jupiter will be a little lower at dusk each day through May. By May 31, it will be about one-third of the way up in the west at dusk and will set just before 10 p.m. Jupiter shines at minus 2 magnitude, several times brighter than Sirius, the brightest star. Jupiter has been a regular beacon in the evening sky for many months, but we’ll lose it by early July in the light of the setting sun. Look for an early crescent moon just to the left of Jupiter on May 3 and again on May 31.
As Jupiter blazes in the west on May evenings, look for Mars as a bright orange spark high in the southeast. In early May, Mars is about two-thirds of the way up in the south at 10:30 p.m. and sets at 4:30 a.m. By the end of May, look for Mars high in the south at first darkness, and setting by 2:30 a.m. When Mars is due south in May, you can look down to the horizon and catch the Southern Cross just above the south horizon.
Mars hit its peak brightness of minus 1.5 magnitude (as bright as the brightest star, Sirius) in early April and the red planet’s brightness does fade fast in May. Look for the waxing gibbous moon next to Mars May 10.
Saturn on May 10 the planet is in opposition, exactly opposite the sun. It rises in the east at sunset and sets in the west at dawn. In the middle of the night, when due south, Saturn is about halfway up in the sky. By the end of the month, Saturn will be about a third of the way up in the east as it gets dark enough to see the planet at dusk, is due south at 11 p.m., and sets by 4:30 a.m. Look for the almost-full moon next to Saturn on May 13.
Venus remains a constant in the morning sky, rising in the east at 3:45 a.m. all month long and shining brilliantly at minus 4 magnitude. It is so bright that it should remain visible until about 30 minutes before sunrise.
LAHAINA NOON
In the tropics, the sun passes overhead twice during the year. On these two days, at local noon, the sun will be exactly overhead and an upright object such as a flagpole will have no shadow.
Here in the islands, a term we often use for zenith noon is "Lahaina Noon." This is a modern term, selected by Bishop Museum in a 1990 contest. "La haina" means "cruel sun," and while the sun in the islands is almost never cruel, it can be pretty intense as it shines directly down from the zenith.
The dates vary depending on how far north or south you are: South Point, 12:19 p.m. on May 15 and 12:28 on July 28; Kailua-Kona, 12:20 on May 18 and 12:30 on July 24; Hilo, 12:16 on May 18 and 12:26 on July 24; Hana, 12:20 on May 23 and 12:30 on July 18; Kahului, 12:22 on May 24 and 12:32 on July 18; Lahaina, 12:23 on May 24 and 12:33 on July 18; Lanai City, 12:24 on May 24 and 12:34 on July 18; Kaunakakai, 12:24 on May 25 and 12:34 on July 16; Honolulu, 12:28 on May 26 and 12:37 on July 16; Kaneohe, 12:28 on May 27 and 12:37 on July 15; Lihue, 12:35 on May 31 and 12:42 on July 11.
ETA AQUARID SHOWER
This meteor shower peaks on the evenings of May 4-5 and May 5-6. The portion of Aquarius where the shooting stars radiate rises in the east about 3:45 a.m. One claim to fame: This is one of two showers caused by debris from Halley’s Comet, along with the Orionids in October. This is a light shower, 10 meteors or so per hour. As always, viewing is better from midnight until dawn on both evenings. Focus your attention on the eastern sky, though the streaks could appear anywhere. A waxing crescent moon sets well before for the peak meteor viewing: at 11:30 p.m. May 4 and 12:20 a.m. May 6.
STARS IN MAY
May is an ideal time to try and spot the Southern Cross, due south around 10:15 p.m. in early May and 8:15 p.m. in late May. The bright stars Alpha and Beta Centauri, to the left of the Cross, are visible by these times and serve as a pointer to the more elusive cross.
May is also the last chance to see the winter constellations. If you look west at 8 p.m. in early May you’ll still be able to see Orion, Taurus, Canis Major and Minor, Auriga and Gemini. By May 15, Taurus will be lost in the light of the setting sun; by the end of the month we’ll have lost Orion.
By 11 p.m. in early May and 9 p.m. in late May, the Big Dipper is high in the north and Hercules and three of his 12 labors (Leo, Hydra, Draco) are visible. Arcturus (or Hokule‘a) is nearly overhead, and Scorpio has just cleared the southern horizon.
Mike Shanahan is director of visitor experience and planetarium at Bishop Museum. For more information, go to www.bishopmuseum.org/planetarium/planetarium.html.
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