The Night Sky: May 2009

Contents

The Night Sky in May 2009

By Harry J. Augensen
Professor of Physics & Astronomy, Widener University

Moon’s Phases in Month
  Full "Flower" Moon on the 9thNew Moon on the 24th

Stars and Constellations

The nights of May are among the most delightful for observing.  Not only are the nighttime temperatures pleasantly cool, with just a light jacket required, but also the air is perfumed with the scent of newly sprung blossoms of lilac and viburnum.  On the other hand, you need to wait until around 8:30 pm to see the first stars come out at the beginning of the month, and until about 9 pm by month’s end.  Get your last look at Aldebaran and the Pleiades star cluster, Rigel and Betelgeuse, Pollux and Castor, and Sirius and Procyon.  These bright stars of winter are all fading into the twilight during early evening, not to reappear in the night sky until next autumn.  Yellow Capella is setting in the northwest, but you will still be able to see it through June.

The stars of spring rule the May evening sky.  Regulus in Leo (Lion) is high in the south or southeast, and another fairly bright star, Alphard, in Hydra (the Water Snake), is in the southeast, a bit below Regulus.  In Greek mythology, Hydra was a multi-headed serpent which haunted the river Amymone, and was eventually slain by Hercules as one of his twelve labors.  The constellation Hydra has the distinction of being the largest of all the 88 constellations. According to British astronomer Chris Kitchin, Hydra dates back to at least the time of Ptolemy’s Almagest in 145 AD, but may go back even further to the ancient Babylonians (2000 BC).  If you wait until after around 10 pm, you will see yet another bright star, Spica, in the constellation Virgo, rising in the southeast.  The Big Dipper, which is part of the constellation Ursa Major (Big Bear), is now rising in the northeast, and its “pointer stars” point to Polaris, the North Star.  The handle of the Dipper “arcs” to Arcturus, the bright yellow-orange star in the constellation Boötes (the Herdsman), which is rising in the east.  Mizar, the second star from the end of the Big Dipper’s handle is actually a multiple system   To test of your visual acuity, see if you can spot Mizar’s faint companion star, Alcor.

 Naked-Eye Planets In the Evening and Morning Sky

After having made an exceptionally fine appearance at the end of April, Mercury continues to be visible in the western sky after sunset, setting about 1½ hours after the Sun at the beginning of May.  Mercury is moderately bright  and resembles a bright yellow star hovering above the west-northwest horizon in the evening twilight.  However, Mercury fades rapidly as it sinks toward the horizon during the first two weeks of May, ultimately reaching inferior conjunction with the Sun on the 18th; thereafter it moves into the morning sky.  Saturn continues to be in ideal position for viewing for much of the night.  It sets around 3 am at the beginning of May, and by 2 am at month’s end.  Saturn continues its residence in the constellation Leo, and is easily spotted high in the south in mid-evening, resembling a bright yellow star to the east of Regulus.

Jupiter is currently a morning planet, rising in the southeast at around 3 am EDT at the beginning of May, and at about 1 am on the 31st.  Jupiter is easy to spot, looking like a beautiful cream-colored star in the early morning sky.  It is second only after Venus in brightness among the visible planets.  Venus stands out as the most brilliant and easy to spot object (other than the Moon) in the dawn sky.  It rises around 4:30 am at the beginning of May, but at about 3:30 am by the end of the month.   Mars lies a bit below and to the lower left of Venus in the morning sky, and will remain an unimpressive sight until the fall.  Look for Mars above the eastern horizon just before sunrise.  It rises around 5 am at the beginning of May, and by 3:30 am at month’s end.  Mars is still pretty faint, since it currently lies on the opposite side of the Sun from Earth.

 For more information on astronomy and weather, visit the Widener University Public Viewing Website at http://www.widener.edu/stargazing/, then click on Web Links & Resources. A set of free sky maps can be obtained at http://www.skymaps.com/

Some content for this article has been obtained from US Naval Observatory Data Services

Times given apply for observers near to the latitude and longitude of Philadelphia, USA: 40 degrees North latitude, 75 degrees West longitude.