There is a full slate of phenomena in April’s night sky—planets, a meteor shower and even a supermoon! But first, a little mythological lesson on one of the most recognizable constellations in the sky, Ursa Major—the Great Bear.
Ursa Major contains another recognizable “constellation”—the Big Dipper. In actuality, the Big Dipper is not a constellation but an asterism, a distinctive pattern formed by a group of stars within a constellation. Another great astronomy term associated with the Big Dipper is circumpolar, meaning that it never sets below the horizon for the mid-northern to polar latitudes in the Northern Hemisphere. Usually, the handle of the Big Dipper is seen as Great Bear’s tail and the cup is the flank area above the back leg.
As with all constellations, the myth of the Great Bear varies depending on the legend. The most popular comes from the Greeks. Callisto was a huntress companion of Artemis and swore to never wed. Zeus saw Callisto and fell in love, but she would never agree to be with Zeus and break her oath to Artemis. So, as the way of Greek gods, he tricked her to be with him and the result was a son named Arcas. Angered by Zeus’ cheating, Hera turned Callisto into a bear that roamed the forest for 15 years. One day, Arcas encountered his mother-bear in the forest. Frightened, he drew his sword, ready to fight. Zeus, seeing this disastrous encounter from Mount Olympus, intervened by flinging Callisto and Arcas into the heavens. Arcas became Boötes, the Herdsman and Callisto, the Great Bear. Zeus’ meddling made Hera even angrier, so she persuaded Oceanus and Tethys to never let the bear bathe in the waters. Hence why the Great Bear never sets below the horizon in the north.
Variations on the myth of the Great Bear include Artemis or Zeus turning Callisto into the bear; Artemis killing Callisto, not realizing she isn’t a real bear. Zeus turning Arcas into the Little Bear instead of Boötes; Arcas being turned into the star Arcturus before he can kill his mother. And this is just the Greeks. Many Native American stories say the bowl of the Big Dipper is the bear while the three stars in the handle are hunters chasing it. Whichever story you settle on, it certainly helps to find and identify them in the sky.
April Planets: At dawn, the waning crescent moon will glide past Saturn on April 6 and then Jupiter on April 7. Between April 15 and 17, around 45-minutes after sunset, face west and you will find Mars in between the horns of Taurus. On April 16, look for Mars above the waxing crescent of the moon which also sits in the middle of the horns, just below the tips. Mercury appears at dusk on April 26 but very low in the west-northwest. It’s worth using binoculars or a low-powered telescope that day as it will have a conjunction with Venus—they will be separated by just over one degree.
Lyrids Meteor Shower April 22-23: Chinese astronomers first reported the Lyrid Meteor Shower in 687 B.C., making them the oldest known meteor shower ever recorded. This year, the glare of the nearly full moon will cause some problems, but with patience, you can view some good ones after midnight. Another option is to get up pre-dawn, after the moon has set, to see if there are still some meteors hanging around. The Lyrids runs annually from April 16 through the 25. This year, the peak is expected on April 22 and 23. The Lyrids are an average meteor shower with about 20 meteors per hour at peak but can sometimes produce bright dust trails that last for several seconds. They are produced by dust particles left behind by comet C/1861 G1 Thatcher, discovered in 1861. Meteors will radiate from the constellation Lyra but can appear anywhere. Look for the blue-white star Vega, the brightest spot in the constellation, to catch the show.
April 26 Supermoon: This month’s full moon is known as the Pink Moon. Various Native American tribes named it so because it marked the emergence of pink moss or wild ground phlox. It is also called Sprouting Grass Moon, the Growing Moon, and the Egg Moon. Coastal tribes called it the Fish Moon. April 26 will also be a Supermoon. So, what is a Supermoon? The term has only been around for the past 40-years and signifies when the full moon is near its closest approach to Earth and so appears slightly larger and brighter than usual. The closer the moon is to the horizon, the larger and brighter it appears. The Farmer’s Almanac reports just two Supermoons this year (April and May), but other astronomers have bumped that up to four, adding March and June.
Another great thing to see with the moon this month happens on April 8 and 9. The waxing and waning crescent moon lets you see earthshine, that unlit part of the Moon that is visible in the sky. It is also known as Da Vinci glow.
Historical Events: April was a big month for Charles Messier. While he was only interested in finding comets, he kept a list of the other objects he found during his comet search. That list became his Catalogue of Nebulae and Star Clusters and includes 110 astronomical objects like nebulae, clusters, and galaxies.
This is what he discovered in April:
1772: The open cluster M50 in Monoceros.
1779: The spiral galaxy M58 in Virgo.
1780: The globular cluster M68 in Hydra.
Other notable discoveries and happenings include:
1790: Caroline Herschel discovers Comet Herschel.
1960: Project Ozma begins, the first attempt to locate extraterrestrial intelligence.
1961: Yuri Gagarin becomes the first human in space.
1990: Hubble Space Telescope launches.