This article reprinted from http://www.astroday.net/bishopsky.html
SKY GEOMETRYThe patterns we see in the sky exist only in our imagination. The points of light we group to create the shapes we call constellations are arbitrary and usually don’t have any connection with each other at all except that they happened to line up in someone’s mind at one time. The 88 “official” constellations are recognized by a group of professionals called the International Astronomical Union to help keep order and structure to the science of astronomy. Otherwise, imagine what chaos might reign—how would anyone know how to distinguish one part of the sky from another if names were random? For instance, the constellation Crater the Cup in the southern sky next to Corvus looks remarkably like my Weber grill, but I can’t very well start referring to it as such. As it is, we sometimes “shorten” the constellations anyway. Sagittarius is often referred to as the Teapot, and part of the Big and Little Bears are called the Big and Little Dippers, respectively.
Informal groupings or segments of constellations are called asterisms. They are usually parts of constellations that are more easily recognized, like the Dippers and the Teapot, and at times the references are updated. Some constellations are simply easier to recognize by these nicknames. I have heard the constellation Boötes the Herdsman referred to as a “bowtie” or “ice cream cone”, which most people relate to better.
Sometimes asterisms include groups of stars or constellations, like the Summer Triangle. Known anecdotally as a basic element of celestial navigation, the Summer Triangle is comprised of the three brightest stars in three separate constellations forming a large, distinctly triangular shape in the sky. First to rise in the east is the star Vega in the constellation Lyra the Lyre. Lyra is a small constellation that takes a bit of effort to imagine the harp-shaped instrument from the parallelogram of stars, but it is an area rich in telescopic sights. One is the famous Ring Nebula, M57—a little smoke-ring object that is the remains of a dying star seen at the center of the ring.
Vega is a white star and the fifth brightest star in the sky. Twelve thousand years ago Vega used to be our North Star, but because the Earth slowly “wobbles” (think of a spinning top, except our wobble is 26,000 years long!) the North Pole points toward different stars periodically. Right now, almost halfway through the wobble’s circle, Polaris is our North Star but in another 14,000 years Vega will take that title again.
Almost two hours after Vega rises the second point of the Triangle appears in the east in Cygnus the Swan. Although this constellation can be easily visualized as a bird, it does have an asterism associated with it. Part of the body and wingspan of the Swan is known as the Northern Cross. The star Deneb is the tail feather of the bird and is the brightest star in that constellation. Opposite from Deneb is an interesting star called Alberio. With a low powered telescope or even binoculars what looks like a single star will split into a beautiful sapphire blue and golden
pair of stars.
A half hour later, Altair in Aquila the Eagle makes its appearance over the eastern horizon. Altair and Vega represent two figures in Japanese folklore that are celebrated with a national holiday in the country. Altair is the handsome herdsman Hikoboshi (also known as Kengyu) that fell in love with Orihime (Vega), the beautiful fabric-weaver. Their preoccupation with each other began to interfere with their duties, and as a result the gods separated them across a vast river in the sky. You can see that “heavenly river” in the dark sky as the white band of light called the Milky Way.
Fortunately, the story doesn’t end here—the gods heard the unhappy cries of the two lovers and took pity on them. On the seventh day of the seventh month, the two are united for one day as a flock of magpies build a living bridge to bring the two together. Today this occasion is celebrated by a festive holiday called Tanabata in Japan on July 7, although in early times this date was determined by the lunar calendar.
Following the Summer Triangle (and the parallelogram of Lyra) is the big Square of Pegasus. But because it is not included on this month’s map, I will save that “astro-geometry” lesson for another month!
The Planets Earth:
Summer kicks off, at least astronomically, with the solstice on June 20. At 2:00 P.M. HST the sun crosses from the southern hemisphere into the northern hemisphere, marked by the celestial equator. (The celestial equator is an imaginary line that extends the Earth’s equator into space)
Mercury:
Mercury is passing in front of the sun for most of the month and will reappear in the morning sky during the last week of June. It hangs over the red “bull’s eye” of Taurus in the light of the rising sun.
Venus:
Venus is behind the sun right now, what is referred to as superior conjunction. It will be another month before it will appear back in the evening sky and blaze in the west after the sun sets.
Mars:
Mars quickly moved from Gemini through Cancer last month and will settle in the constellation Leo during June. Saturn has also been a resident of Leo recently and the two planets are heading for a conjunction in July. You can watch the Red Planet edge closer to yellowish Saturn over the month, with Regulus (the brightest star in Leo) in the middle.
The NASA mission to Mars, called Phoenix (see May’s article) will make its descent to Mars on May 25. Unfortunately I cannot update the status of this mission because this article is filed before this date, but I will definitely talk about Phoenix next month.
Jupiter:
The King of Planets rules the night, shining brighter than any other object besides the Moon this month. Jupiter rises by 10:00 P.M. in early June and about two hours earlier by the end of the month. On June 18, the full Moon enters Sagittarius, the same constellation as Jupiter, and the next evening the waning Moon moves just south of the giant planet.
Saturn:
Look for Saturn high in the west at nightfall during the first half of June, then only about halfway up in that direction by the end of the month. The rings of the gas planet is continuing to tip edgewise to our line of sight and well worth watching over the upcoming months. You will need a telescope to really appreciate this sight, however.
Questions? Contact Carolyn Kaichi @ hokupaa@bishopmuseum.org or 847-8203. For information ad videos about visiting Hawaii in general and touring the Big Island in particular, visit
www.tourguidehawaii.com and
www.lovingthebigisland.wordpress.com.
