As with last month, it remains possible to catch all five naked-eye planets in June. Three eclipses occur but will not be visible in the islands. Summer starts on June 21. As always, June is the final month to catch the Southern Cross in the evening sky in Hawaii. The early summer constellations include Hercules; three of his 12 labors; the Scorpion; and the Summer Triangle.
Saturn remains the only naked-eye planet in the evening sky. Saturn is pale yellow and shines at 0.75 magnitude (brighter than most of the stars). In early June, Saturn will be high in the south at dusk (8 p.m.), halfway down the western sky at 10 p.m., and will set at 2:30 a.m. in the west.
Once Saturn sets, no planets will be visible for an hour, until the bright planet Jupiter rises in the east. Jupiter shines at minus 2.2 magnitude, brighter than any dot of light in the sky except Venus. At the start of June, Jupiter rises in the east at 3:30 a.m. and is about one-quarter of the way up in the east as day starts to break around 5 a.m.
Venus rises in the east at 4:40 a.m. at the start of June and at 5 a.m. at the end of the month. This means you have a very short window to catch Venus in June, since day starts to break around 5:15 a.m. Still, blazing away at minus 3.9 magnitude, Venus is so bright that you should still be able to catch it, low in the east.
Look for Mars low in the east about 4:45 a.m. all month. It is very pale orange and still shining at 1.3 magnitude, as bright as a fairly bright star. At the start of June, Mars is just above Venus but 100 times dimmer. In mid-June, look for Mars just to the right of the Pleiades star cluster. Look for the slender, waning crescent moon next to Mars on the morning of June 28.
Mercury reappears in the evening sky by June 23. For the rest of the month, catch Mercury low in the west around 8 p.m. It shines at minus 0.5 magnitude, bright enough to pierce the dusk glow if you have a clear western horizon.
Summer begins at 7:17 a.m. June 21 in Hawaii. This is the longest day of the year for the Northern Hemisphere and the shortest day for the Southern. In Hono-lulu the sun rises at 5:50 a.m. and sets at 7:16 p.m., providing 13 hours and 26 minutes of daylight. Being near the equator, Hawaii does not have wide swings in day length.
For more on the changes in the seasons in Hawaii, see Bishop Museum’s planetarium show "Tropical Skies" at 3:30 p.m. daily except Tuesdays.
JUNE SKY MAP
The map for June 2011 is good for 11 p.m. at the start of the month, 10 p.m. in the middle and 9 p.m. at the end. The map is set for Honolulu’s latitude, 21 degrees N.
June is the last month to catch the Southern Cross, called Crux on the map. It sets in the south-southwest. On the star map for June, only the top star (Gacrux) and the two stars that form the crossbar (Mimosa on the left, Delta Crucis on the right) are above the horizon.
If you go out a little earlier (10 p.m. at the start of the month, 8 p.m. at the end), you should still be able to see the entire Southern Cross, including Acrux, the brilliant star that marks the bottom of the cross.
Alpha and Beta Centauri are just to the left of the cross. These two bright stars are generally easier to spot than the cross itself. These two stars will point you to the cross; go right from Alpha and Beta Centauri and you’ll come to the crossbar of the cross.
Scorpius has also returned. The distinctive constellation really does look like a scorpion. It also looks like a big fishhook; its Hawaiian name is, of course, the Big Fishhook of Maui.
Look for the Big Dipper in the northwest. The pointer stars of the Big Dipper — the two stars in the cup that don’t have the handle attached — point to the North Star. The handle of the Big Dipper is bent, or has an arc to it. If you follow the handle, it points you to the bright star Arcturus ("arc to Arcturus," as the saying goes). Arcturus is high overhead on this map.
In the eastern sky the Summer Triangle is rising. These are three bright stars from three different constellations that form a giant star triangle: the star Altair in Aquila the Eagle, Vega in Lyra the Harp, and Deneb in Cygnus the Swan.
This is the season for Hercules. Hercules the Kneeler is high in the eastern sky. The stars of Hercules are not bright, and it takes some hunting to find the constellation. The core of the constellation is a butterfly shape of six stars that look like a watered-down version of Orion.
Hercules shares the June sky with three of his 12 labors. Low in the west is Leo the Lion; fighting the lion was the first of Hercules’ labors. Killing the Hydra was his second labor. Every time Hercules cut off one head of Hydra, two more heads appeared. Hercules seared off each neck of the Hydra with a hot sword before the new heads could appear. The long, snaky constellation of Hydra is down below Leo.
In the north, the constellation of Draco winds its way between the Big and Little dippers. Collecting golden apples was the 11th labor of Hercules; Draco was the dragon that guarded the apples. Hercules, leveraging his past successes, killed the dragon with arrows that he had dipped in the poisonous blood of the Hydra.
Mike Shanahan is director of education, exhibits and planetarium at Bishop Museum. Reach him at firstname.lastname@example.org.