May 2009
Skywatchers’ Guide for May 2009
Special note: Astronomy Day is May 2: For information on the special event at Flandrau click here.
PLANETS
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. Three planets, Venus, Mars and Jupiter are widely spaced in the east-southeastern area of the morning twilight sky.
May 2009 continues to be a very good time to see Saturn and its ring system as Saturn and Earth are not far from their closest approach back in March, and Saturn doesn’t set until well after midnight (by 1:20 a.m. near the end of May). Saturn fades slightly from around magnitude 0.5 and 19.5 arc seconds across during May to a 0.8 magnitude star-like object in 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 high overhead in the constellation Leo the Lion during the evening hours (well placed for telescopic viewing).
Saturn’s rings are the most ‘open’ they will be this year but will narrow by month’s end as we view them more edge-on. The ringed world starts May in retrograde motion but is stationary on May 17 and resumes eastward or ‘direct’ motion that day, drifting farther from Leo’s brightest star Regulus after-wards. Also, the 10 day old waxing gibbous Moon is nearest Saturn in our sky this month on Sunday evening May 3.
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.
Fading Mercury ends its best evening apparition this year, and is best visible this month for the first few days of May above a clear west-northwestern horizon starting 30-40 minutes after sunset. On May 1 Mercury is seen nearest the Seven Sisters or Pleiades star cluster. Viewing both in wide-field binoculars makes for an interesting sight. Either way you’ll probably need binoculars to spot faint Mercury in a clear unobstructed horizon, before it moves into the glare of the Sun during the second week of May.
Bright Jupiter continues to gains altitude and rise earlier each morning this May in the southeastern sky, and is now high enough for quality telescopic viewing, starting one hour before sunrise (especially during the last half of May). By the end of May the giant planet is easily seen over 40 degrees above the south-southeastern horizon 45 minutes before sunrise (from the southern United States). Jupiter is located in the constellation of Capricornus, the Sea Goat. The waning gibbous Moon will lie closest to Jupiter in our sky in the dawn twilight of Sunday morning, May 17.
The brilliant planet Venus starts May some 15 degrees above the eastern horizon in the bright morning twilight, 30-35 minutes before sunrise and gains altitude, rising higher, earlier during the entire month to reach 22 degrees in altitude at that time by May 31. As it does so its crescent phase thickens and becomes smaller to almost half lit by the end of May, as Venus moves farther away from Earth (the opposite of its phase changes and visibility in February-March). Venus is over 6 degrees from faint Mars (below and ‘left’ of the brilliant world) and the two close to 5 degrees apart by the end of May above the eastern dawn horizon. The razor thin 26-day-old waning crescent Moon will lie closest to Mars and Venus in our sky in the dawn twilight of Thursday morning, May 21. Mars is still a long ways off from Earth (hence its faintness compared to Venus) and so is currently an unremarkable object in a telescope.
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 main building is now closed on Thursday nights due to state budget cuts but the 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 Mercury or even Mars this month, note that they may appear to twinkle somewhat; 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 gibbous Moon sets late (especially by the shower’s predicted peak on May 6, it does not set until 3:45 a.m. MST), making it a fairly good year to see this 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 Wednesday morning May 6 you can typically expect to see up to 15 meteors an hour from dark sky locations, and around 10 meteors an hour 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 30 meteors an hour from dark sky locations far away from city lights. If you can’t do Wednesday morning, then Tuesday morning May 5 is also expected to be fairly good.
MOON PHASES
The May first quarter Moon will occur for the first time on Friday evening, May 1, and for the second time on Saturday evening, May 30. The May Full Flower Moon rises on the evening of Friday, May 8 and sets on the morning of Saturday, May 9. The May last quarter Moon occurs on Sunday morning May 17. The May 2009 new moon will occur on Sunday, May 24.
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.
Graphics done using Starry Night Pro, Starry Night Enthusiast and Adobe Photoshop. To purchase Starry Night Pro or Enthusiast, go to http://StarryNight.com