What's Up in the Night Sky

March 2013 - Vol. 17, No. 3

This Month's Night Sky - NOTE: The next paragraph describes the sky as it appears at 10 pm EST (11 pm EDT) near mid- month. The sky also looks this way at 11 pm EST (midnight EDT) during the beginning of the month and at 9 pm EST (10 pm EDT) by month's end.

Look S as night falls to see the brightest star of the evening, Sirus (Canis Major). Look to its upper right to find the familiar "hour glass" asterism of constellation Orion with bright white Rigel (lower right) and red Betelgeuse (upper left). Below the three Belt stars, lies the Great Orion Nebula (M42 & M43) visible to the naked eye as a hazy patch of light. Now shift your gaze to the left to find another bright star, Procyon (Canis Minor) the upper star of the "Winter Triangle" mentioned last month. Above Procyon, and to its left, Saturn glows brightly and above Saturn at to its right are the Gemini twins, Pollux and Castor. As the month progresses and winter becomes spring, orange Aldebaran (Taurus) comes into view to the W. Just to the left of Aldebaran, a star cluster, the Hyades, might be faintly visible under dark sky conditions. Above that glows the more famous cluster, the Pleiades (M45). Although smaller that the Hyades, it is much brighter and should be visible as another hazy patch of light. Some may even be able to make out the tiny "dipper" arrangement of its eight brightest stars. High above and a bit to the right is brilliant Capella (Auriga) and farther right is the famous "W" asterism of Cassiopeia.

MERCURY favors observers in the southern hemisphere this month.. VENUS will not be seen this month, reaching superior conjunction on March 28 but will enter the evening sky late next month. JUPITER remains in the evening sky, setting at midnight, still in Taurus and can be seen near the Hyades star cluster. MARS will not be visible this month, will not be in conjunction with the sun until late April 18. SATURN appears late in the evening, and moves retograde through the constellation of Libra.

Review how to determine Angular Measurement.

Calendar of Events

NOTE: For those observers not in the ET zone, convert the calendar times to your zone's time by subtracting one hour for CT, two for MT and three for PT. Don't forget to adjust for Daylight Savings Time when necessary by subtracting one hour from your planisphere's time. Dawn and dusk times must also be corrected. See your local newspaper, TV news, or cable TV's Weather Channel for sunrise and sunset times. Unfortunately some of these events may occur during daylight hours in your area.

DATE	EVENT
01	Spica is.1 deg N of the Moon with occulations possible from the northern Pacific ocean, Southern, and Central America.
03	Saturn 3 deg N of Moon.
04	Mercury in inferior conjunction.
05	Moon at perigee.
10	Daylight Savings time begins.
12	Comet PANSTARRS. Look for this comet low in the W, about 45 minutes after sunset near the crescent Moon. The link will take you to the Earth-Sky PANSTARRS site.
13	The Moon and PANSTARS will be 10 deg apart. Track them as the distance between them grows night after night.
17	Jupiter 1.5 deg N of the Moon. This will be fabulous in the constellation of Taurus near the Hyades and the Pleiades.
22	The Beehive cluster, Castor and Pollux in the early evening hover over the Moon.
19	Moon at apogee.
20	Vernal Equinox.
24	Jupiter 5 deg N of the Aldebaran.
28	Moon within 1 deg of Spica, possible occultation from Southeast Asia, Phillipines and Northern Australia. Venus in superior conjunction.
29	Saturn 3 deg N of the Moon. Uranus in conjunction with the Sun.
31	Mercury at greatest elongation W.

Lunar Almanac for March 2013

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 11	Deep Space Objects
	1st. Qtr 19	Planets & Moon
	Full 27	Moon
	Last Qtr 04	Deep Space & Planets

Topic of the month: Sirius, brightest star in the Night Sky

The northern hemisphere is now deep in the heart of Earth's Winter season. The brightest star of the night sky, Sirius, ruler of the constellation of Canis Major rises as the sky darkens. It marches across the heavens and disappears just before the sky begins to brighten. If you look up in the sky on a February night, Sirius will atttract your attention as the brightest star twinkling in the sky. Just in case, you can't find Sirius, draw a line through the stars of Orion's belt moving eastward. Bingo, Sirius is right on that line. The true brightness of Sirius is -1.47. Sirius is not the largest known star and it should be noted that it owes its brightest star distinction to the fact that it is a mere 8.6 light years distant.

Sirius is a blue star that has a small companion designated Sirius B, sometimes called, "the Pup." This star is the closest known white dwarf star, but it hard to study because the glare from the A component of Sirius is too intense. A very good image was taken by Hubble Space Telescope of Sirius and its companion. The dwarf star was once a normal star, but it expended its store of hydrogen and became a white dwarf in a massive explosion. Sirius A and B are a binary system with a 50-year period.

Sirius was identified in many cultures, but was most revered by the Egyptians, who watched for Sirius to rise just before the Sun on summer soltice. They called Sirius, the Nile Star or the Star of Isis. They watched it carefully because they used it to time to rising of the Nile waters to determine when they would plant their crops. It was known by the proper name, Sothis.

--See You Under the Stars!
Astra for Astra's Almanac