Backyard Stargazer: February 2017
By Francis Parnell
On January 31st, the moon formed a close triangle with Venus, and Mars. On February 1st, the waxing crescent moon will be upper left of the two planets and forming a line 20-degrees long. Red Mars is only 5.4 -degrees from Venus, but Mars’ eastward motion slowly widens the distance to 12-degrees by months end.
Celebrated by the ancient Romans, Brits, Celts, and others, February 2nd is a “Cross Quarter Day”, halfway between the December Solstice and the March Equinox. The other Cross Quarter Days are May 1st, August 1st, and October 31st. The “Quarter Days” are the summer and winter solstices and the spring and fall equinoxes.
Venus blazes in the west-southwest all month and sets about 3 hours after the Sun. On the 16th, Venus reaches “Greatest Brilliancy” at magnitude -4.8, the brightest it will be all year! Under dark skies, away from the ever-increasing light pollution, Venus can actually cast shadows, especially on snow or light colored buildings.
After sunset on the 10th, the Full “Snow Moon” undergoes a deep Penumbral Eclipse. This isn’t a total lunar eclipse; that only happens when the Moon enters the Umbra, the darkest part of Earth’s shadow. We hardly notice a Penumbral Eclipse because it occurs in the pale outer part of Earth’s shadow. This time it’s different. According to both Sky & Telescope and Astronomy magazines, the northern part of the Moon misses the Umbra by about 100 miles, so the shading should be easily visible. Start watching around 7p.m., mid-eclipse is at 7:44 p.m. What time will the Umbral shading disappear? Watch and see!
One half hour before sunrise on the 15th, the waning gibbous Moon, bright yellow Jupiter, and “Spica”, the brightest star in Virgo, form a shallow arc about 7-degrees long.
Saturn is lower left of the waning crescent before dawn on the 20th.
At dusk on the 28th, the waxing crescent Moon is 10-degrees to the lower left of Venus.
If you used the constellation chart in January’s column to find ORION, the “Belt stars” will show the way to one of his hunting dogs – CANIS MAJOR, the Greater Dog. Follow the line from the belt stars down to the left and you’ll see the brilliant white star “Sirius”, the Dog Star. Sirius is only 8.6 light years (ly) away, 1.8 times the diameter and 25 times the luminosity of the Sun. Let’s look at a couple of other stars. “Wezen” is 1800 ly away, 410 times the diameter and 48,000 times brighter than the Sun. “Aludra” is 1760 ly away, 94 times the diameter and 66,000 times the Sun’s luminosity. We’ve got the dog, now let’s go star hunting!
Happy Cross Quarter Day everyone; winter will be half over! Stay warm and “Keep looking up!”
Francis Parnell of Darlington has been an amateur astronomer for over 46 years, and was on the staff and helped out at the Francis Marion University Observatory from 1982 until 2006 by showing visitors “what’s out there.” With the help of a friend, Mr. Ernest Lowry, he built his own telescope in 1986. And, because of light pollution, for the last 31 years he has been advocating for the advantages of using fully-shielded lighting at night.