SCOPE on the SKIES Flipped Constellations by BOB RIDDLE

SCOPE ON THE SKIES Flipped constellations BY BOB RIDDLE any people may not real- of stars that are often named after constellation. The Summer Trian- ize that the term constella- figures from Greek mythology. gle, for example, is made up of Al- Mtion refers to a particular Other patterns, known as aster- tair in Aquila the Eagle constella- region of the starry sky around isms, can also be found within a tion, Deneb in Cygnus the Swan, the Earth and not just to a pat- single constellation, such as the and Vega in Lyra the Harp. tern of stars found in that region. Big Dipper. Other asterisms, such One thing that both types of These regions are, however, iden- as the Summer Triangle, may be patterns have in common is that tified by the recognizable pattern made up of stars from a different they typically are made up of the l FIGURE 1: The Winter Hexagon asterism (SCHATZ AND FRAKNOI 2016) 74 Ask students what the evening the map that best represent the l skies of January would look like FIGURE 2: Members of the sky and the relative locations of from their home using the same Winter Hexagon bright stars with the horizon and degrees of latitude, but set to south the center of the map. Encourage Constellation Star latitude rather than north latitude. students to use the map at home Orion Rigel Download the southern hemi- to see how the map matches the Taurus Aldebaran sphere version of the January star night sky and to locate the Winter Auriga Capella map so they can compare the two Hexagon and other bright stars. Gemini Pollux maps. Students should be able to Switching perspectives point out the changes in position Canis Minor Procyon Canis Major Sirius l FIGURE 3: A local horizon brightest stars in our sky. Conse- quently, when attempting to locate a constellation in the night sky using a smartphone app (see Re- sources), sky map, or other means, you should focus on locating the brightest stars in the sky instead of trying to visualize a horse, lion, or other imagined shape. Wintertime in the northern hemisphere is a good time to learn about constellations because some are visible during the early evening hours. During the winter evenings, go outside to a shadowy area where most of the l FIGURE 4: Locating the South Celestial Pole with the Southern light sources are blocked. Wait a Cross few minutes to allow your eyes to adapt to the darkness. Face toward the southern horizon and look about halfway up to see the center of a group of six constellations, each of which provides a bright star to make up the asterism known as The Winter Hexa- gon (see Figures 1 and 2). When learning and observing constellations, it’s a good idea to use a star map, such as Evening Sky Map from the Skymaps website (see Resources). Allow time for students to become familiar with the January star map, in terms of the dates and times of January 2017 75 of the stars above the horizon. ern latitude decreases toward the south of the equator show some The stars over the southern ho- equator, Orion gets higher in the of the constellations visible from rizon are higher on the southern sky. At the equator, Orion’s belt is north of the equator. But they are hemisphere star map, whereas directly overhead. (Download the oriented differently relative to the stars over the northern horizon January star map for the equator horizon; many constellations are are lower or no longer visible. to see Orion directly overhead.) upside down from the perspec- We see Orion, for example, facing When continuing south, Orion’s tive of the northern hemisphere. us with his feet toward the hori- stars start to get lower over the Until European explorers sailed to zon. Near his left foot is the dim northern horizon. When stopping southern latitudes, constellations star Lambda Eridani, which is at at the mid-southern latitude of in the southern hemisphere were the northern end of Eridanus the 43° South, Orion is now seen as unknown or at least unnamed by River, a long constellation that upside down over the northern Europeans. The names (e.g., Tele- meanders south of the equator. At horizon. scope, Microscope, Sextant) for the mouth of the celestial river is The southern hemisphere star these constellations reflected the the bright star Achernar. As north- map reveals that the night skies time period instead of names from Greek or Roman mythologies. Students can use the southern hemisphere constellations website January (see Resources) to learn more about 1 Waxing crescent Moon near 17 Cassini distant flyby of Titan the stars and constellations of that Venus part of the celestial sphere. From 19 Waning gibbous Moon near Moon at descending node the southern latitudes of Argen- Jupiter tina, for example, there is no North 2 Waxing crescent Moon near Mercury at west elongation: Star, simply because Polaris is be- Mars 24° W low the northern horizon from any Quadrantid shower peak Last quarter Moon latitude south of the equator. There 4 Earth at perihelion 21 Moon at apogee: 404,900 km is instead what is known as the (251,593 mi.) SCP, or South Celestial Pole, which 5 First quarter Moon may be found by using the stars 24 Waning crescent Moon near 8 Waxing gibbous Moon near of Crux, known as the Southern Saturn the Hyades Cross. The SCP is approximately 25 Moon at southernmost 9 Mercury near Saturn 26° South from Acrux, the bottom declination: 19° S Waxing gibbous Moon near star in the cross shape, but there Aldebaran 26 Waning crescent Moon near is no visible star there (see Figure Mercury 4). During January, the Southern 10 Moon at perigee: 363,200 km Cross will rise around midnight (225,682 mi.) 27 New Moon and follow an apparent circular 11 Moon at northernmost 29 Moon at descending node path around the SCP, known as declination: 19° N circumpolar motion, which refers 31 Jupiter near Spica to any star that always follows an 12 Full Moon Moon near Venus and Mars apparent circular path around the Venus at east elongation: 47° E celestial pole. To locate the SCP, 15 Waning gibbous Moon near observe the sky every couple of Regulus hours or, more practically, set up a Moon at ascending node camera either for a long-time exposure to get “star trails,” or to make 76 SCOPE ON THE SKIES a time-lapse video. jpl.nasa.gov the_universe/Constellations/south_ To see star trails, aim the cam- Dates of Earth’s seasons—http:// constellations.html era toward the North Star and aa.usno.navy.mil/data/docs/ Universe Discovery Guide: January— EarthSeasons.php http://nightsky.jpl.nasa.gov/ set it for a long exposure for sev- Quadrantids meteor shower—http:// download-view.cfm?Doc_ID=537 eral minutes. The resulting im- meteorshowersonline.com/ Free smartphone apps age should show streaks of light quadrantids.html Mobile sky map—http://sites.google. curving around the North Star. Circumpolar Motion—www.bobs- com/site/pyopyostudioapp (Android, Another way to see star trails re- spaces.net/2015/06/04/ Apple , and a virtual reality version) quires the use of software to stack circumpolar-motion Ready, Jet, Go—www.pbskids.org/apps/ Skymaps—www.skymaps.com/ or merge all of the images taken ready-jet-go-space-explorer.html downloads.html (Android, Apple, and some tablets) during a time lapse into one im- South America—http://1drv.ms/f/ Sky Map—http://play.google.com/store/ age (See “Circumpolar Motion” in s!AhTmME0SAmy6g4gHEC8ISjJ apps/details?id=com.google.android. Resources). • 4p4C4EA stardroid&hl=en (Android Only) Southern Hemisphere Constellations— RESOURCES www.windows2universe.org/ Cassini Saturn mission—http://saturn. Bob Riddle ([email protected]) is a science educator in Lee’s Summit, Visible planets Missouri. Visit his astronomy website at www.bobs-spaces.net. Mercury will rise about 1–2 hours before sunrise and will be For students visible over the eastern horizon. 1. Where is the horizon? It is sometimes described as “where the Venus will be visible sky meets the ground,” a good visual for those living in or familiar over the western with the geography and “long distance” views of the Great Plains. horizon at sunset and Actually, the horizon is measured as 90° from the zenith, or will set about four straight overhead, regardless of the compass direction faced or hours after sunset. what is along the horizon. Mars will be visible over 2. What is meant by “your local horizon”? This is a horizon whose the western horizon distance from the zenith varies based on human-made or natural at sunset and will set objects along the horizon (see Figure 3). about five hours after 3. Apparent sky motions: In the southern hemisphere, stars rise and sunset. set in which direction? Which direction is circumpolar motion in Jupiter will rise around the southern hemisphere? The Earth always rotates from west midnight local time to east, so despite being south of the equator, stars will still and will be visible over rise in the east and set in the west. Circumpolar motion in the the southern horizon southern hemisphere is around the South Celestial Pole and is at sunrise. in the opposite direction from the northern hemisphere. It is an apparent clockwise motion in the southern hemisphere. Saturn will rise 3–4 hours before sunrise 4. Download the January Universe Discovery Guide (see Resources) and will be visible over for some engaging activities about Betelgeuse, the red giant star the eastern horizon.

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