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PISGAH ASTRONOMICAL RESEARCH INSTITUTE Text by Dr. Bob Hayward Astronomer/Educator Graphic by TheSky Software Bisque Mountain Skies June 20, 2016 SUMMER BEGINS TODAY The Earth: Today is the first day of summer! At least this evening is. At 6:34 p.m. EDT today we have the summer solstice which marks the first moment of summer in the northern hemisphere. This is the point in the Earth’s orbit when the northern hemisphere reaches its maximum tilt towards the sun. Thus, the sun is highest in the sky at noon and the days are longest. In Brevard sunrise was at 6:17 a.m. EDT this morning and sunset will occur at 8:49 p.m. this evening. This gives us 14 hours 32 minutes of daytime. The sun rose at 6:15 a.m. in Asheville giving those folks two more minutes of daylight. Happy Solstice! The planets: The planets and the moon circle our sky along a path that goes through twelve very famous constellations and one not so famous (Ophiuchus). As we look at the planets in the sky, we notice that they are not scattered all about but lie close to being in a straight line across the heavens. This is because the solar system is pretty much a plane and, when we look at this plane from our vantage point inside it, it looks like a line that traces a circle around us. This invisible line is called the ecliptic. It is apparent in tonight’s sky as we see from west to east the planets Jupiter, Mars and Saturn and then the moon. Jupiter is the brightest of the planets up tonight. (Venus is brighter but is now hidden behind the sun.) As soon as the sky darkens, we’ll find Jupiter just a bit west of due south and high up in the sky since he is hanging around the hind feet of Leo the lion. Down and to the east we’ll note Mars at close to its brightest. The red planet was closest to the earth on May 30 so it is still quite bright and, through a telescope, relatively large. Its reddish-brown hue is readily apparent when it is this bright. A bit farther to the east and still lower is the ringed planet Saturn. If you think Jupiter or Mars is spectacular through a telescope, then take a look at Saturn. Saturn’s beautiful rings are tilted towards us by just over 26 and, at that angle, present a glorious sight. They also contribute to Saturn’s brightness. Finally, down and to the east of Saturn is the full moon. So the line goes from west to east from Jupiter to Mars, Saturn and the moon. Venus is behind the sun so the only one missing is Mercury. Recall that on May 9 Mercury transited the sun, i.e., passed directly in front of it as it moved from the evening to morning skies. So, now Mercury is very low in the morning twilight before sunrise. The stars: In the last column we described Boötes the herdsman or bear driver, perhaps better visualized as a kite. Boötes, with the bright “ginger-colored” star Arcturus being most prominent, is high in the south on a June evening an hour or two after sunset. Now, look to the east of the herdsman for an almost complete circle of moderately bright stars that marks the location of Corona Borealis, the Northern Crown. Then, to the east of the crown, a pattern of six stars forms a great letter “H” in the sky. Appropriately, this is the constellation of Hercules (known as Heracles to the Greeks). One cannot study Greek mythology without hearing of the labors of Hercules and many of these stories are illustrated among the constellations in the sky. Hercules is pictured upside down as we view him from the northern hemisphere. Thus, the lower two stars in the letter “H” mark his shoulders, the middle two his waist, and the upper two his legs. In some ways the constellation is similar to that of Orion the hunter but by no means as obvious. Perhaps of most interest is the Great Cluster in Hercules, also known as Messier 13 (M13). It can be spotted with a pair of binoculars or a small telescope on the upper western leg of the letter “H.” Celestial Calendar: June 20 - The sun appears to move from Taurus into Gemini. June 20, 7:02 a.m. EDT – Full Moon June 20, 6:34 p.m. EDT - Summer Solstice, Summer begins! Longest day of the year June 27, 2:19 p.m. EDT – Last Quarter Moon July 4, 7:01 a.m. EDT – New Moon July 4, Noon EDT - Earth at aphelion (farthest point from the sun) * * * * * * * * * * PARI is a public not-for-profit public foundation established in 1998. Located in the Pisgah Forest southwest of Asheville, NC, PARI offers educational programs at all levels, from K-12 through post-graduate research. For more information about PARI and its programs, visit www.pari.edu. Follow PARI on Twitter at http://twitter.com/Astronomy_PARI. “Like” PARI on Facebook at www.facebook.com/Pisgah.Astronomical.Research.Institute. For further information or questions about this Mountain Skies column, contact Dr. Bob Hayward at [email protected]. Graphic produced by the author with TheSky Astronomical Software, Software Bisque.