April announces the arrival of the second of our star families, Kaiwikuamo‘o, or “the Backbone,” back to the spring night sky.

“Four Star Families” is a heuristic tool created by modern-day voyagers to simplify the organization of the tropical night sky into a culturally significant context. It reduces the 88 recognized constellations into four simple patterns that run north through south and follow a culturally appropriate storyline.

The star lines are understood as a pattern of stars that tell a story and their relationship to the stars around them. Kaiwikuamo‘o represents the spinal backbone of a person and speaks to a person’s genealogy, where they came from and the story they represent.

The string of stars in Ka­iwikuamo‘o, 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, or 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. Hokule‘a is the zenith star for Hawaii and passes above Kau on Hawaii island.

Next, arc from Arcturus and cross the celestial equator to connect to Hikianalia, Spica, in the constellation Virgo. 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, a system of four stars organized into two pairs. These three stars — Hokule‘a, Hikianalia and Kau‘opae — comprise the Spring Triangle.

As we continue south from Spica, the next constellation in the celestial backbone is Me‘e, or Corvus, a trapezoid-shaped constellation. From Me‘e we encounter the southernmost parts of the star line, which will be rising in the later evening hours. Drawing a line through the center of Me‘e and down toward the southern horizon, we come to Hanaiakamalama (“Cared for by the Moon”), also known as the Southern Cross, which will rise closer to 8:30 p.m.

To the east of Hanaiakamalama is the constellation Nakuhikuhi, the Pointer Stars, which points toward the Southern Cross. Nakuhikuhi consists of two stars, Kamailemua (Beta Centauri) and Kamailehope (Alpha Centauri), which will rise around 10:30 p.m.

Kamailehope is the third-brightest star in the night sky and is the planetary system closest to our own solar system. Both Alpha and Beta Centauri are triple-star systems, appearing to the naked eye as one star even though each of them includes three separate stars.

Special events

The full moon on April 26 will appear to be slightly larger in the sky as we have 2021’s first supermoon.

The moon’s orbit around Earth is not a perfect circle, as it travels in an elliptical path with Earth as one focus. As such, there is a position in the moon’s orbit known as perigee, where the moon is closest to Earth. The moon completes an orbit around Earth every month, and it passes through this position once a month.

However, for a couple of months each year, the full moon is often referred to as the supermoon, as it will appear to be somewhat larger in the sky while it is passing through the perigee position.

The annual Lyrids meteor shower will occur in mid- to late April with a peak in activity on April 22 at approximately 2 a.m. This average meteor shower originates from the debris cloud left by the comet C/1861 G1 Thatcher, which passed through the inner solar system in 1861 and will not return until 2283.

Every year, as Earth passes through the debris cloud, rocks and ice fall through our atmosphere and create shooting stars.

The shooting stars of the Lyrids, which you can expect to see around 10 p.m., will appear to come from the constellation Lyra. There could be about 18 to 20 shooting stars each hour at the peak of the meteor shower.

Featured Mauna Kea discovery

Every day, astronomers discover more and more planets that are orbiting around other stars. These “exoplanets,” or planets outside our solar system, would have been the stuff of science fiction just a couple of decades ago.

Recently, University of Hawaii astronomers utilized the W.M. Keck Observatory to observe and discover what seems to be the oldest exoplanet. The small rocky planet, named TOI-561, orbits a star that is estimated to be about 10 billion years old; this also infers that the planet itself is likely about 10 billion years old. This planetary system is located away from the main plane of the Milky Way galaxy, meaning that the planet would also witness a beautiful and unique view of the galaxy’s spiral arms across its sky. Learn more about this unique discovery observed here in Hawaii at ifa.hawaii.edu/info/press-releases/TOI561.

Evening observations

In the early evening sky toward the western horizon, observers will note a triangle of three distinctive red objects: the red giant stars Kapuahi (Adebaran) and Kauluakoko (Betelguese), and the planet Mars, which will sit just beneath the shape of Hokulei. Kapuahi and Kauluakoko gain their characteristic red color as they are red giant stars.

These stars have completed the first stage of their lifetimes and have moved on to a secondary stage where they are utilizing a different fuel source; when the stars switched to a less efficient fuel source, they grew larger and took on a unique red color.

At some point in the future, both of these stars will eventually explode as supernovae.

The star Kauluakoko grabbed astronomers’ attention last year when it suddenly dimmed and remained quite faint for three months. However, after it regained its brightness, astronomers at the James Clerk Maxwell Telescope on Mauna Kea determined that Kauluakoko was just covered by a high amount of sun spots.

Kauluakoko is the closest red giant star to our solar system, and its eventual supernova will be sure to grab the world’s attention.

The third object of our April red triangle — the planet Mars — is much closer to home. Our sibling planet gains its notable red color from the unique soil on the planet’s surface. The soil on Mars is iron oxide or rust and is actually quite similar to the basalt rocks that are found on the mountains of Mauna Kea and Mauna Loa — so much so that numerous NASA projects utilize Hawaii as analog sites to test missions that will one day travel to Mars.

Morning observations

As we enter the spring season, the days will get noticeably longer once again at the beginning of April; the sun will rise at about 6:25 a.m., and by the end of April, the sun will be rising at 6 a.m. with dawn coloring the sky starting at about 5:10.

Celestial observers who prefer the early morning sky will see a very different section of the sky from evening observers.

In these early morning hours, the most notable objects will be the two largest planets in the solar system: Jupiter and Saturn. These two distinctive planets will be the final objects to fade into the light of dawn as the sun rises, and can be viewed climbing out of the southeastern sky in the early morning hours.

High up above, approaching the center of the sky, early morning observers will be able to view the three bright stars —Deneb, Vega and Altair — that form the summer triangle, signaling that summer is just around the corner.

April 2021 Sky Chart by Honolulu Star-Advertiser

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.