Skywatchers’ Guide for May 2010
PLANETS
 Saturn and the constellation Leo in the eastern evening sky on May 1 at around 7:45 p.m. This sky chart is most useful for the entire United States, southern Canada and northern Mexico.  Venus and the constellations of the winter sky setting in the evening twilight sky on May 1, 50 minutes after sunset, facing west. This sky chart is most useful for the entire United States, southern Canada and northern Mexico.  Saturn, Mars and the Moon looking overhead on May 21 at 8 p.m. This sky chart is most useful for the entire United States, southern Canada and northern Mexico.  Jupiter, Mercury, and the Moon in the morning sky looking east on May 9, one hour before sunrise. The positions of other planets are also shown. This sky chart is most useful for the entire United States, southern Canada and northern Mexico. |
HIGHLIGHTS: Saturn, in the eastern evening sky, is conveniently high up in the sky for evening telescopic viewing. The rings of Saturn appear very thin, as we view them nearly edge-on from Earth. The Eta Aquarid meteor shower is visible in early May after 2 a.m. and until dawn. Brilliant Venus is our ‘evening star’ in the west while Jupiter is in the eastern morning twilight sky as our ‘morning star’.
May 2010 continues to be a very good time to see Saturn and its ring system as Saturn doesn’t set until well after midnight. Saturn fades slightly to around magnitude 1.0 during May. Although the ringed planet is somewhat dimmer this year (compared to previous years) because its rings are more edge-on, it is found conveniently overhead in the constellation Virgo the Virgin during the evening hours (well placed for telescopic viewing).
Saturn’s rings are nearly the most ‘narrow’ they will be this year. The ringed world stops its retrograde motion on May 31, when it is stationary and resumes eastward or ‘direct’ motion that day. The 10 day old gibbous Moon passes about 9 degrees below (south) of Saturn on the evening of May 22.
Best views of any planet should be when it is highest in the sky, but viewing is dependent on atmospheric stability and conditions, and of course, the quality and size of the telescope used. Large, high quality amateur telescopes in good “seeing” (stable atmospheric conditions) will best reveal any features on a planet’s disk.
The brilliant planet Venus gains altitude, rising higher, earlier during the entire month in the western evening twilight. As it does so, it passes out of Taurus, the Bull and moves into Gemini, the Twins. Venus is moving rapidly against the background stars and is only 1/2 of a degree from the fairly bright star Mebsuta in Gemini, the Twins, on May 27 (use binoculars or a wide-field telescope at low power). In a fairly dark sky, with binoculars or a wide-field telescope, you can see Venus only 3/4 of a degree north of the open cluster M35 in Gemini, the Twins on the evening of May 21 (M35 appears as a patch of fuzzy light in binoculars). Also look for the razor thin, 2 day old waxing crescent Moon to pass 3 degrees south of Venus on the evening of May 15 and the 3 day old Moon ‘above’ Venus on May 16.
Mars continues to fade this month and is in the western half of the sky after the end of evening twilight, in Leo the Lion. On May 4 it appears at 0.8 magnitude in brightness, and is only 7.1 arc seconds in diameter. Mars is a long way off from Earth (hence its faintness compared to Venus) and so is currently an unremarkable object in a telescope. Mars, like Venus, is moving rapidly against the background stars as Earth continues to recede from it in our solar system. Look for the nearly 1st quarter, 6.5 day old waxing crescent Moon to pass 5 degrees ‘below’ (southwest of) Mars on May 19. On May 20, the first quarter Moon will appear about 4 degrees from the bright star Regulus in the constellation Leo, the Lion.
Bright Jupiter continues to gains altitude and rise earlier each morning this May in the east-southeastern sky, and is now high enough for quality telescopic viewing, starting one hour before sunrise (especially during the last half of May). By May 26 Jupiter is 30 degrees above the east-southeastern horizon, 45 minutes before sunrise. The razor thin 25 day old waning crescent Moon passes about 5 degrees above (northeast) of the giant gas planet on the morning of May 9.
Mercury has a difficult to see and dim morning apparition and is lost in the glare of the Sun this month for casual observers. It is much better seen from the Southern Hemisphere. It is at greatest elongation from the Sun on May 26, when it appears at 0.6 magnitude, some 4 degrees above the eastern horizon, 45 minutes before sunrise.
Visitors to Flandrau’s 16-inch telescope should note of the planets Saturn is visible in the telescope during public hours, and other celestial objects will be shown in the telescope, weather permitting. Flandrau’s telescope remains open for viewing during public hours from 7-10 p.m., weather permitting, Wednesday through Saturday nights (excluding select holidays).
Finally, remember that in spotting planets there is a general rule: ’stars twinkle, planets don’t’. This is because stars are point sources of light; therefore starlight is easily disturbed and shifted by air currents in the Earth’s atmosphere. However when looking at Mars this month, note that it may appear to twinkle somewhat when near the horizon; however, this twinkling is of a slower nature than that of the bright stars.
MAY EVENING STARS
 The northern sky at 9:45 p.m. in early May, and at 8:45 p.m. in middle May. Find Polaris, the North Star off the pointer stars of the Big Dipper. This star chart is most useful throughout the southern United States and northern Mexico.  This sky is shown facing east and overhead at 9:45 p.m. in early May, and at 8:45 p.m. in middle May. This star chart is useful for the entire United States. 'Arc to Arcturus' and then 'speed on to Spica' off the handle of the Big Dipper. |
Face west in May, 1 hour after sunset, to see the bright winter constellation Orion, the Hunter, and his hunting dog, Canis Major, still visible in spring evenings. In its middle is a horizontal row of three stars, Orion’s Belt. The belt points left to the bright star Sirius. Orion, Canis Major and Taurus set early and are all progressively lost in the glare of the Sun during May. Turn around to face north and look high up to view the famous Big Dipper twinkling upside down. The Big Dipper is part of the larger constellation, Ursa Major, the Great Bear. It forms the bear’s hindquarters and unnaturally long tail. In England the Dipper is called the plow, even today! The star at the bend in the Dipper’s handle is named Mizar, for “the horse”, but the original Arabic name was the “girdle”. If you have normal (or well-corrected) eyesight and a clear sky, Mizar can be seen to have a faint, very close companion star, Alcor, whose name now means “the rider”. In ancient times it was often called “the test” as it was used to test eyesight. Since then the star may have brightened somewhat, because it is now no longer truly a difficult naked eye object. Binoculars help to easily distinguish Mizar and Alcor.
The Big Dipper is an amazing signpost in the heavens, useful in finding many notable sights in the sky. The two stars forming the outside end of the Big Dipper’s bowl — the part opposite from the handle — are called “the Pointers.” A line drawn through them points quite near the North Star, Polaris. Polaris closely marks the north celestial pole, and hence appears not to move in the sky to the unaided eye. Polaris is also the end of the handle of the Little Dipper, whose other name is Ursa Minor, the Little Bear. Continue straight down from Polaris to the horizon to find true north. Polaris always remains at almost exactly the same point over the northern hemisphere landscape, day and night, and is always there to mark almost exactly due north. Polaris is not a very bright star, but it’s in a dim part of the sky where there’s nothing else to confuse it with. Come back to the Big Dipper and follow the curve of the Dipper’s handle back across the sky by about two handle-lengths and you will see the brightest star of spring, the bright yellow-white star Arcturus. Continue down from Arcturus to “spike” or speed onto the blue star of spring, Spica.
The Milky Way Prominent in the Late Night Hours!
 The Milky Way as seen above the southern horizon on May 15 at 2 a.m. from the Desert Southwest |
The Milky Way, the galaxy of stars, gas and dust our solar system resides in, is prominent all summer long, and rises in the early May morning sky after 1 a.m., but earlier, by 11 p.m. in late May. To see it, you’ll need to get away from city lights to a dark location, and look on a night when there’s not much interference from the moon. The Milky Way will appear as a “cloudy” band clear across the sky. High power binoculars and telescopes reveal the Milky Way to be clouds of stars, millions of them, with attendant star clusters and gas clouds making up some of the “fuzzier” spots you’ll see.
Eta Aquarid Meteor Shower Visible
 The eastern sky and the radiant of the Eta Aquarid Meteor Shower is shown for May 5/6 at 4 a.m. |
Although better observed from the Southern Hemisphere, the Eta Aquarid meteor shower is visible in early May after 2 a.m. and until dawn. This year the last quarter Moon in the morning sky and limits the number of meteors visible with this year’s pre-dawn shower. The Eta Aquarid meteors are particles from Halley’s Comet, and have a sister shower in October, called the Orionids, after the constellation Orion. To see the shower simply sit outside in a reclining lawn chair, far away from city lights, face towards the southeastern horizon and look overhead. At the shower’s peak, around 3:15 to 4:15 a.m. on Thursday morning May 6 you can typically expect to see up to 10 meteors an hour from dark sky locations, but less than this from suburban Arizona skies, away from the glare of artificial lights. Some observers may see less than this count while experienced astronomers may see upwards of 15 meteors an hour from dark sky locations far away from city lights this year.
MOON PHASES
The May last quarter Moon occurs on Sunday morning May 6. The May 2010 new moon will occur on Sunday, May 13. The May first quarter Moon will occur for the first time on Friday evening, May 21. The May Full “Flower Moon” rises on the evening of Friday, May 27 and sets on the morning of Saturday, May 28.
These dates and times are for southern Arizona, and are not necessarily Greenwich Mean Time dates, the moon phase dates used for calendars.
Note: Additional information can be accessed by phone at Flandrau Science Center’s Astronomy Newsline at (520) 621-4310 or as a menu option at 621-S-T-A-R.
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