The Night Sky: February 2009

Contents

The Night Sky in February 2009

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

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

Stars and Constellations

During February, the winter stars and constellations seem to stare down at us with icy brilliance.  Nearly overhead by 8 pm is Auriga, the Charioteer, with the bright yellow star Capella as its "eye."  Just south of Auriga is Taurus, the Bull, with its bright orange star Aldebaran and the Pleiades, or Seven Sisters, star cluster.  The Pleiades cluster actually contains about 500 stars, but, appropriately, only about seven are bright enough to be seen with the naked eye.  The Pleiades group lies just over 400 light years away, and so we are seeing light which left the cluster when Shakespeare and Galileo were alive.  Following Taurus to the east is Gemini, the Twins, and its two brightest stars Pollux and Castor.  Their proximity to each other is merely perspective:  in reality they are about 10 light years apart.  Pollux has a slight yellow or orange tinge to it, while Castor is more white in color.  Remarkably, the Castor system consists of a total of six gravitationally bound stars, five of which can be seen individually in a telescope.

The midwinter night sky is dominated by Orion, the Hunter.  Standing high in the south by around 9 pm during February, Orion's two brightest stars, Betelgeuse and Rigel, form his left shoulder and right foot, respectively.  Look with binoculars at Orion's "sword" and see if you notice that one of these stars is fuzzy.  This object is in fact the Great Orion Nebula, a vast complex of star formation nearly 1500 light years from our solar system.  Just below and to the left of Orion is Sirius, the brightest star in the sky, in Canis Major, and just a bit further to the east is its neighbor Procyon in Canis Minor.  Well below Sirius is the second brightest star in the night sky, Canopus, but it never rises above the horizon for most of the United States.  You would have to travel to one of the far southern states, say to Florida or south Texas, to see it.

One winter constellation that often goes unnoticed by sky watchers in the northern hemisphere is Eridanus, the River.  Eridanus starts from just to the west (right) of Orion and meanders southward to below the horizon, ending with the first magnitude star Achernar. In fact, the name Achernar means "river's end" in Arabic.  Achernar is not visible to observers lying north of about 30 degrees north latitude, and this includes all but the southernmost fringes of the United States.  Another far less luminous member of Eridanus is the faint star epsilon Eridani.  At only about 10 light years distant, it is considered one of our Sun’s interstellar neighbors. Astronomers have detected what they believe may be a Jupiter-sized planet in orbit about its otherwise unremarkable parent star.

 Looking toward the east-northeast after about 8 pm, you should be able to spot the star Regulus in the constellation Leo, rising above the horizon.  Further to the left, the Big Dipper, a part of the constellation Ursa Major, or Big Bear, is rising in the north-northeast.  These are the celestial signs that spring is is just around the corner!

 Naked-Eye Planets In the Evening and Morning Sky

Over the past several months, Venus has been a dazzling sight in the southwestern sky during the early evening hours, and its spectacular display will continue through February.  Venus blazes like a brilliant yellow star in the southwest for several hours after sunset, reaching its maximum brightness during the latter part of the month.  At the beginning of February, Venus sets about 4 hours after the Sun, but this interval decreases to 3 hours by the end of the month, a sign that Venus will soon be departing from the evening sky.   Indeed, it does so next month. Saturn is nowhere near as bright as Venus, but it is still easy to spot in the east-southeast below Regulus during the late evening.  Saturn rises around 8:30 pm EST on the 1^st and by 6:30 pm at month’s end.  Around midnight, Saturn is easily located, resembling a bright yellow star roughly halfway between the first-magnitude stars Regulus and Spica. 

 Mercury, Mars, and Jupiter are all located in the morning sky during February, and all are difficult to find. Mercury reaches its greatest morning elongation with the Sun on the 14^th, when it rises a little over one hour before sunrise. It resembles a bright yellow star.  Nevertheless, an unobstructed southeastern horizon will be needed to locate it. Toward the end of February, Mercury aligns closely with Mars and Jupiter in the dawn sky.  Mars was in conjunction with the Sun back in December, and it is still too close to the Sun to be seen during much of February. On the 28^th, Mars and Mercury may be spotted together just above the southeastern horizon shortly before sunrise.  Jupiter was in conjunction with the Sun last month, and will remain lost in the glare of morning twilight until nearly the end of February, when all three morning planets cluster together very low above the southeastern horizon just before sunup.

 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