The Evening Sky in March 2015
Whole sky chart for Mar 2015
Two bright planets light up the twilight sky. Silver Venus appears low in the west. Golden Jupiter appears in the north-east. Venus soon sets, but Jupiter stays in the northern sky all night, setting in the northwest in the morning hours. Bright stars are overhead and down into the southeast sky.
Jupiter is the biggest planet by far. Its mass is greater than all the other planets put together. In a telescope it shows parallel stripes. These are zones of warm and cold clouds, made narrow by Jupiter's rapid rotation. Any telescope shows Jupiter's disk with its four bright 'Galilean' moons lined up on either side. They are roughly the size of our moon. Sometimes one or two moons can be seen in binoculars, looking like faint stars close to the planet. Io, the smallest and closest to Jupiter, has massive volcanoes. The other moons have crusts of ice, some with oceans beneath, around rocky cores. Jupiter is 680 million km from us in March. The Moon will be near Jupiter on March 3rd and 30th.
Northwest of overhead is Sirius the brightest star in the sky. It is fainter than star-like Venus and Jupiter. Southwest of the zenith is Canopus, the second brightest star. Below Sirius are Rigel and Betelgeuse, the brightest stars in Orion. Between them is a line of three stars: Orion's belt. To southern hemisphere star watchers, the line of three makes the bottom of 'The Pot'. Orion's belt points down and left to a V-shaped pattern of stars. These make the face of Taurus the Bull. The orange star is Aldebaran, Arabic for the eye of the bull. Continuing the line from Orion down and left finds the Pleiades or Matariki star cluster.
Sirius is the brightest star in the sky both because it is relatively close, nine light years* away, and 23 times brighter than the sun. Rigel, above and left of Orion's belt, is a bluish supergiant star, 40 000 times brighter than the sun and much hotter. It is 800 light years away. Orange Betelgeuse, below and right of the line of three, is a red-giant star, cooler than the sun but much bigger and 9000 times brighter. It is 400 light years from us. The handle of "The Pot", or Orion's sword, has the Orion Nebula at its centre; a glowing gas cloud many light-years across and 1300 light years away.
Near the north skyline are Pollux and Castor marking the heads of Gemini the twins. Left of Jupiter is the star cluster Praesepe, marking the shell of Cancer the crab. Praesepe is also called the Beehive cluster, the reason obvious when it is viewed in binoculars. The cluster is some 500 light years from us.
Crux, the Southern Cross, is in the southeast. Below it are Beta and Alpha Centauri, often called 'The Pointers'. Alpha Centauri is the closest naked-eye star, 4.3 light years away. Beta Centauri, like most of the stars in Crux, is a blue-giant star hundreds of light years away. Canopus is also a very luminous distant star; 13 000 times brighter than the sun and 300 light years away.
The Milky Way is brightest in the southeast toward Crux. It becomes broader lower in the southeast toward Scorpius. Above Crux the Milky Way can be traced to nearly overhead where it fades. It becomes very faint in the north, right of Orion. The Milky Way is our edgewise view of the galaxy, the pancake of billions of stars of which the sun is just one. We are 30,000 light years from the galaxy's centre.
The Clouds of Magellan, LMC and SMC are high in the south sky, easily seen by eye on a dark moonless night. They are two small galaxies about 160 000 and 200 000 light years away.
Saturn rises in the southeast before midnight at the beginning of March. It is on the lower end of a curve of stars making the Scorpion's claws. To its right, slightly higher in the sky and fainter, is orange Antares, marking Scorpio's heart. By the end of the month, Saturn is up around 10 p.m. A telescope magnifying 20x shows Saturn's rings. Saturn is 1430 million km away in mid-March. The Moon is by Saturn on the 12th.
Mercury (not shown) ends its best morning sky appearance of the year during March. At the beginning of the month it rises around 5 a.m., a little south of due east. It is the brightest 'star' in that part of the sky. By the end of the month it is rising at 7 a.m. less than an hour before the sun. It is tiny in a telescope.
*A light year (l.y.)is the distance that light travels in one year: nearly 10 million million km or 1013 km. Sunlight takes eight minutes to get here; moonlight about one second. Sunlight reaches Neptune, the outermost major planet, in four hours. It takes four years to reach the nearest star, Alpha Centauri.
Notes by Alan Gilmore,
University of Canterbury's Mt John Observatory,
P.O. Box 56,
Lake Tekapo 7945,