Once again we return to the first of our four star families, Kekaomakali‘i, the Bailer of Makali‘i, as it makes its nightly east-to-west progression across the horizon.
As we enter 2019, a brief review of what we covered over the past year might be a good refresher for regular readers and useful for those new to the Skywatch column. The star map we always feature is presented upside down and is intended to be held above your head facing south for proper orientation.
We explain directions through an indigenous device called a star compass, which orients the user or a vessel within the circle of the horizon. The circle of the horizon is divided into 32 points defined as houses. Each house is identified by the sidereal or celestial body that resides there: sun, moon, planets and stars.
There are two horizons on the star compass: Hikina, or east, meaning “to arrive,” and Komohana, or west, meaning “to enter.” If you stand with your back toward Hikina, you would be facing Komohana. By extending your right hand 90 degrees from your body, you would be pointing toward ‘Akau, or north. If you extend your left hand, you would be pointing toward Hema, south.
Stars rise in parallel tracks and move from the arriving horizon, Hikina, to the entering horizon, Komohana. Fifteen of the 32 houses form the Hikina side of the star compass, another 15 for the Komohana side of the compass. The remaining two houses, ‘Akau and Hema, are the pivot points that divide the arriving and entering horizons.
Once a sidereal body enters the circle of the horizon, it will climb skyward until arriving at the meridian, the highest point on its westward track formed by an imaginary line that runs between ‘Akau and Hema, the north and south celestial poles. As it crosses the meridian, it begins its descent toward the entering horizon, Komohana, and disappears from sight.
Sidereal bodies are hemispherical; if they rise in the Northern Hemisphere, they set in the Northern Hemisphere; if they rise in the Southern Hemisphere, they set in the Southern Hemisphere. A star rising in the house Hikina, east, will set in the house Komohana, west. The house ‘Akau is marked by the star Hokupa‘a, also known as Polaris.
Kekaomakali‘i forms the shape of a canoe bailer, carrying skyward a series of bright constellations within the scoop. Starting in the direction we call Manu Ko‘olau, or northeast, the scoop is formed by Hokulei, Capella; Nanamua and Nanahope, also known as the twins of Gemini, Castor and Pollux; Puana, Little Dog; and ‘A‘a, Sirius, the brightest star in the night sky.
The handle of the bailer is formed by drawing a line southward between ‘A‘a and Keali‘iokonaikalewa, Canopus, the second-brightest star in the night sky.
The bailer carries within its celestial interior the constellations and stars Kaheiheionakeiki, Orion’s Belt; Kapuahi, Aldebaran in Taurus the bull; and Makali‘i, the Pleiades, the celestial marker for the annual makahiki season.
The star compass is an effective device for orientation and navigation at sea because Hawaii and most of the South Pacific islands inhabit a region that spans the tropics. The tropics lie between the margins of 23.5 degrees north and 23.5 degrees south. Within this region the rising angle is vertical at the equator, tilted slightly southward in Hawaii and tilted slightly northward in Tahiti, making the use of sidereal bodies effective bearing markers along the visual horizon.
January observations
As we welcome the new year, Earth will pass its closest position to the sun. Earth’s orbit is not a perfect circle; it is an ellipse, or oval shape, due to certain points in the orbit where it is slightly closer to the sun and other points where it is farther away.
The orbital position where Earth is farthest from the sun is known as aphelion, and the point where Earth is closest to the sun is known as perihelion. In the last hours of Wednesday, Earth will be at its perihelion point, when we are only about 91 million miles from the sun. In contrast, when we are at aphelion on July 4, we will be about 95 million miles from the sun.
Later into January we will witness some stunning lunar and planetary events. As the moon rises Jan. 20, the moon will be passing through Earth’s shadow in a lunar eclipse.
On that evening, for Hawaii, the moon will rise at 6:07 p.m. (the same time as the sun sets), and as it rises the partial eclipse of the moon will have already started. The full eclipse of the moon will begin a 6:41 p.m., at which time the moon takes on its stunning red color.
At 7:43 p.m. the moon will start to pass out of Earth’s shadow, and its color will shift from red to a dark gray as it passes into Earth’s umbra (the outer part of Earth’s shadow). This will continue until 9:48 p.m. when the eclipse is completely over.
January 2019 Sky Chart 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 Hawai‘i, a center for informal science education at the University of Hawaii at Hilo showcasing astronomy and Hawaiian culture as parallel journeys of human exploration.
