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April welcomes the sun back to the northern hemisphere and the star family Kaiwikuamo‘o, the Backbone, back to the spring night sky. This string of stars running in a line from the North Star to the Southern Cross represents the backbone or vertebrae of a celestial genealogy.
To identify this star family, first locate the constellation Nahiku (the Seven), the Big Dipper in the northeast. The first two stars in the bucket of the dipper, Hikukahi and Hikulua, Dubhe and Merak, point toward the direction of Hokupa‘a, Polaris, the North Star.
Following the sweep of the Big Dipper’s handle toward the east-northeast, look for the red giant and fourth brightest star in the night sky, Hokule‘a (Arcturus) in the constellation Bootes. Next, arc from Arcturus and cross the celestial equator to connect to Hikianalia, Spica, in the constellation Virgo.
Hokule‘a is the zenith star for Hawaii, passing directly over Kau on Hawaii island; Hikianalia passes just south of the Marquesas island chain. To the west and in between Hokule‘a and Hikianalia is the star Kau‘opae, Regulus, in the constellation Leo. To the naked eye Kau‘opae appears as a singular star, but it is actually a quadruple-star system — four stars organized into two pairs. These three stars — Hokule‘a, Hikianalia and Kau‘opae — make up the Spring Triangle.
As we continue south from Spica, the next constellation in the celestial vertebrae is Me‘e, Corvus, a trapezoid-shaped constellation. Drawing a line through the center of Corvus and down toward the southern horizon we come to Hanaiakamalama (Cared for by the Moon), the Southern Cross. To the east of the Southern Cross is the constellation Nakuhikuhi, the Pointer Stars, which points the direction toward the Southern Cross.
Nakuhikuhi consists of two stars, Kamailemua (Beta Centauri) and Kamailehope (Alpha Centauri). Kamailehope is the third brightest star in the night sky and is the planetary system closest to our solar system. Both Alpha and Beta Centauri are triple-star systems, appearing to the naked eye as one star even though each of them comprises three separate stars.
The sun is now in the northern hemisphere, having crossed the celestial equator for time zones in the United States on March 19, the vernal (spring) equinox. This year’s spring equinox was the earliest it’s been for more than a century. An excellent explanation for this can be found in Bob Berman’s online article, “Signs of Spring From the Sky: A Crescent Moon Smile,” in The Old Farmer’s Almanac (almanac.com). The last early spring equinox that occurred on March 19 was 124 years ago, in 1896. Equinox stems from the Latin word for “equal night,” aequus (equal) and nox (night). The sun crosses the celestial equator northward in March, causing the length of day and night to be nearly equal.
SPECIAL EVENTS
The moon’s orbit around Earth is not a perfect circle. As such, there is a point in the moon’s orbit where it is at its closest position to Earth, and this point is called perigee. The moon passes through the perigee point once a month, and each year there are a couple of months when the full moon phase lines up with the perigee point. Many observers claim that this is when the moon appears to be bigger in the sky, hence the term “supermoon,” which will next be visible on April 7.
The Lyrids meteor shower is the oldest known shower ever recorded, as chronicled in the Zuo Zhuan in 687 B.C. This year’s shower is expected to occur from April 16 to 25, but the best time to see the meteors will be around 8 p.m. on April 21. At its peak, there would be about 20 shooting stars per hour, or about three meteors a minute.
EVENING OBSERVATION
Throughout April, the extremely bright planet Venus will continue to stand out in the early evening sky. As one of the brightest objects in the sky, Venus will be clearly visible as the sun sets and into the early evening.
Venus appears to be so extremely bright due to its proximity to Earth and the thick layers of clouds in its atmosphere. While Venus is similar to Earth in size, its environment couldn’t be more different. In the earlier days of the solar system, the liquid water on Venus evaporated into the atmosphere, where it mixed with the noxious gases coming from Venus’ many volcanoes, thereby creating a thick layer of clouds. These clouds act like a blanket for Venus, trapping heat between the surface and the cloud layer and creating a runaway greenhouse effect and a surface temperature of at least 880 degrees Fahrenheit, hot enough to melt lead.
MORNING OBSERVATIONS
Early-bird stargazers will enjoy a very different perspective of the stars in April. The sun will rise between 6 and 6:23 a.m., with dawn beginning to color the sky just before 5 a.m. In these early-morning hours, observers will be able to see at least three planets — Jupiter, Saturn and Mars — high in the southeastern sky.
On the morning of April Fool’s Day (April 1), the mischievous planets Saturn and Mars will go through a conjunction. Conjunctions occur when two celestial objects, typically planets, appear to be less than 1 degree away from each other in the sky from our perspective on Earth. In ancient times, a conjunction of planets was a very significant event, as the motion of planets in the sky was thought to predict the future. While conjunctions are not considered significant today, it can still be stunning to watch two planets merge into one light.
Observers with an extra careful eye may also be able to catch the planet Mercury as it rises just before the sun comes up. Mercury is often the hardest of the visible planets to spot, as it is so faint and always appears to be quite close to the sun.
APELILA (APRIL) SKIES AT 8 … by Honolulu Star-Advertiser 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.
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