What's Up in the Night Sky

February 2013 - Vol. 17, No. 2

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.

A large asterism, the "Winter Triangle", appears directly overhead. It is an inverted triangle formed by three bright stars: Procyon (Canis Minor) upper left, Betelgeuse (Orion) upper right and Sirius (Canis Major) below center. The Big Dipper (Ursa Major's famous asterism) stands high in the NE with its "handle" still pointing towards the horizon. Follow the handle's curve to orange star Arcturus (Bootes). Look for Cassiopeia's "W" asterism high in the NW. To the S, Orion dominates the sky while Aldebaran (Taurus) followed by the Pleiades star cluster drops below the horizon by 3 AM. Regulus (Leo) now rises in the SE. If you live in a dark site region, don't forget to observe the Milky Way's (our spiral galaxy) arm hat passes through Cassiopeia. It will not be visible in bright Moon light or in the cities.

MERCURY will be visible from the northern hemisphere for three weeks this month in one of its best appartitions, check the calendar below for various events of interest. VENUS will vanish from the morning sky for superior conjunction on March 28 and won't be seen until she enters the evening sky late next month. JUPITER remains in the evening sky, setting after midnight, still in Taurus. MARS sets in the early evening, the red planet disappears this month, not to be seen again from Earth until June. SATURN appears earlier every morning, moving into Libra. Outer planets: NEPTUNE is no longer visible and URANUS sets in the early evening..

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	Saturn and Spica dance with the last quarter Moon as the month opens.
02	Spica within 1 deg of the Moon, occultation south Africa, small pat of E Austalia.
03	Saturn 3 deg N of Moon.
04	Mars .4 S of Neptune.
07	Moon at perigee. Mercury .3 deg N of Mars.
08	Mars .4 deg N of Neptune.
11	Mars 6 deg S of Moon. Mercury 5 deg S of Moon. With a good horizon, this will be a splendid sight just after sunset. Don't take chances with your vision--take care when observing the sky near sunset.
12	Mercury at ascending node.
16	Mercury at greatest E. elongation.
17	Mercury at perihelion, fades rapidly and can be used as a early evening test of vision acuity. How many days can you see it before it disappears completely?
18	Jupiter .9 deg N of the Moon, occultation from South Australia.
21	Neptune in conjunction with the Sun. Watch the next few nights as Jupiter "mixes it up" with the stars and clusters in Taurus.
19	Moon at apogee. Saturn begin retrograde motion and will once again approach Spica. What a splendid naked eye sight they are.
26	Full Moon near the Beehive cluster. How many bees (stars in the cluster) can you see?
27	Look W from a dark location, at about an hour after sunset, to view zodiacal light. ("Zodiacal light" is a vertical band of white light believed to be sunlight reflected from meteoriods found in the plane of the ecliptic, the apparent "path" of the Sun, Moon and Planets as they travel across our sky.) It will appear to be a very large, but very dim, pyramid of of white light, "leaning" to the left. This effect may be visible for the next two weeks on dark nights.

Lunar Almanac for February 2013

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 10	Deep Space Objects
	1st. Qtr 17	Planets & Moon
	Full 25	Moon
	Last Qtr 03	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