Skywatch: Summer solstice brings longest period of daylight
Hokule‘a, Arcturus in the constellation Bootes, is the zenith star for Hawaii, passing above the Kau desert on Hawaii island.
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June will be the last month where we can clearly see Hanaiakamalama, the Southern Cross, in our early evening sky. Throughout early June, this notable shape will be directly over the direction of Hema — south on our star compass — in our early evening sky; however by the end of June it will begin to set into Manu Kona, the southwest horizon. It will reappear once again in the early morning sky in December.
Hanaiakamalama is the end of the star line, Kaiwikuamo‘o, the Backbone. Beginning with Nahiku, the Big Dipper in the northeast, the two pointer stars in its bucket point toward the direction of Hokupa‘a, Polaris, the north star.
If you follow a curving line from the handle of the Big Dipper southward, the next brilliant star in its path is Hokule‘a, Arcturus; then Hikianalia, Spica; then the trapezoid box Me‘e, Corvus; and finally the line terminates in Hanaiakamalama.
The Southern Cross is a significant constellation for oceanic explorers heading north toward Hawaii as it points toward the direction Hema, south on our sidereal star compass.
Compasses, sidereal or magnetic, all work on the same principle: By pinpointing one known location along the horizon, magnetic north on the magnetic compass or polaris on the sidereal compass, you can identify the 32 headings of the magnetic compass or the 32 houses of the oceanic sidereal compass.
The stars and our islands
At Kahikinui, Maui, along the southern coastline, winds from the ‘Alenuihaha Channel sweep the rugged shoreline constantly. In the shadow of Haleakala are two puu, or cinder cones, known as Pimoe, the name of the magical ulua that the demigod Maui fished for, and Hokukano, meaning proud star. To the southeast of these cinder cones lies the panana at Hanamauloa at Luala‘ilua. The panana is a pre-contact navigational structure or “sighting wall” designed to identify the point we call Hema.
The wall is approximately 29 feet long, 5 feet wide and 5 feet tall with a 2-foot notch at the center of the wall. Seaward of the wall sits an ahu, or stone cairn. Looking through the notch toward the cairn provides a relative line southward along the celestial meridian.
When Hanaiakamalama is upright, it stands directly above the notch and frames the direction to the southern horizon. The panana at Hanamauloa serves as navigational monument to voyagers from generations past.
June 21 marks the summer solstice, the day when the Northern Hemisphere is at its farthest tilt toward the sun and experiences its longest period of daylight of the year. The day length for Honolulu on the solstice will be 13 hours and 25 minutes.
Featured astronomical project
Using high-resolution adaptive optics imaging from the Gemini Observatory, astronomers have uncovered one of the oldest star clusters in the Milky Way galaxy, HP1. This star cluster is estimated to be about 12.8 billion years old, making these stars among the oldest ever found in our galaxy.
This ancient cluster is a part of the fundamental building blocks that assembled our galaxy’s central bulge. To learn more about this amazing study and how it unlocks the secrets of our own origins visit: gemini.edu/node/21165.
Throughout June, the bright planet Jupiter will be rising out of Manu Malanai, the southeast horizon, in the early evening. This gas giant planet is the fourth-brightest object we see in the sky, after the sun, moon and Venus. On June 10 Jupiter will be in a unique position known as opposition, when an outer planet (a planet farther from the sun than Earth) is lined up with the Earth and the sun. As Jupiter will be on the opposite side of the sun, from our perspective, it will rise at the same time as the sunset and will be in the sky the whole night. When Jupiter is at opposition it is at its closest physical position to us and will appear to be brighter in our sky.
In the early evenings of June 16-19 the planets Mercury and Mars will be going through a conjunction near Manu Ho‘olua, the northeast horizon. A conjunction is when two planets appear to be very close together (less than 1 degree away from each other) in the sky. The best time to see the two planets in conjunction on these days will be between sunset and 8:30 p.m.
As summer season approaches, the days will be longer and the sun will be rising earlier in the morning. Throughout June the sun will rise at or around 5:50 a.m., and dawn will start to color the sky just before 5 a.m. If you are up before sunrise keep an eye out for the incredibly bright planet Venus, which will rise just before the sun does in the eastern sky. At the same time the fainter planet Saturn will be high in the southwestern sky.
Skywatch, May 26 by on Scribd
Chad Kalepa Baybayan (Kalepa.Baybayan@hawaii.edu) serves as navigator-in-residence and Emily Peavy (Emily.Peavy@hawaii.edu) as planetarium technician support facilitator at the ‘Imiloa Astronomy Center of Hawaii, a center for informal science education at the University of Hawaii at Hilo showcasing astronomy and Hawaiian culture as parallel journeys of human exploration.