Auriga, the Charioteer
Plus the planets for March.
Just north of the zenith you will find a group of bright stars that form the constellation of Auriga, the Charioteer. While constellation diagrams often show this as a diamond-shaped constellation, you can pull a fifth star from the adjacent constellation Taurus to form a squat triangle on the side of a rectangle. These stars are easy to find, with Alpha Aurigae (Capella) being the sixth-brightest star in the sky.
Auriga, the Charioteer, is actually identified with at least three Greek heroes. It is most often identified with Erichthonius of Athens. Erichthonius is credited with the invention of the quadriga, a four-horse chariot, made in the image of the Sun's chariot. He used this chariot in a battle against Amphictyon, a usurper trying to take the Athenian throne. Erichthonius' defense of the throne with his chariots placed him next in line of succession, and he eventually became king of Athens. Upon Erichthonius' death, Zeus placed him in the sky because of his ingenious chariot design and his heroic deeds.
Auriga's brightest star, Capella, is actually a multi-star system. The two main components are both G-type stars. They are not dwarf stars like our Sun, but yellow giants. The larger is almost 12 times the diameter of our Sun while the smaller is almost 9 times the Sun's diameter. These two stars are only 67 million miles apart and swing around each other every 104 days. There is also pair of red dwarf stars 0.17 light-years away from the two main stars that completes this star system.
Another interesting star in the southern part of Auriga is AE Aurigae. It is labeled as a variable star, based on observations in 1926. More recent observations show little or no variation in brightness, however. Shining around magnitude 6.0, this is a spectral class O9.5 dwarf star about 1,460 light-years away. It is currently in a cloud of dust and gas that it illuminates, giving us the Flaming Star Nebula. The name comes from the nebula's wispy red color, which makes it look as if the star is on fire.
"Runaway" star AE Aurigae is the bright star at top plunging at high speed into the gas and dust clouds at left. This Moon-sized patch of sky was photographed with a 10-inch telescope. (Photo by David Cortner)
AE Aurigae has just entered this cloud. It is a fast-moving star, what astronomers call a runaway star; every hundred years it moves 4.3 seconds-of-arc in our sky. At such a great distance, this is a very fast mover.
Tracing the star's motion backward, astronomers believe it originated in the area that would eventually become the Trapezium in Orion's Sword. There is a multiple star there called Iota Orionis. Iota's primary is 15-solar-mass O-type star. Orbiting far from it are an A-type star some 1.9 trillion miles away and a B-type star some 409 billion miles distant. Close to the primary is a hot B1-type star in an eccentric orbit, from as close as 10 million miles from the primary all the way out to 74 million miles and back again. What gave this companion such an eccentric orbit?
About 2.5 million years ago, there were two double stars in the area where the Trapezium, the center of the Orion Nebula, would form. These two double stars had a very close encounter. Each lost its companion stars, which went shooting off in opposite directions, leaving the remaining two now-single stars to form a new double star, Iota Orionis. Of the two stars that were flung off, one headed south and we now know it as Mu Columbae (in Columba, the Dove), a fourth-magnitude star some 26 degrees south of Iota Orionis. The other star headed north and is now 40 degrees from Iota Orionis — the light of the Flaming Star Nebula, AE Aurigae.
The Planets for March
As night falls you can find Jupiter 77 degrees up in the northeast. Its disc is 40.4 seconds-of-arc across and is a brilliant magnitude -2.4. The King of the Gods is moving slowly eastward in western Gemini and sets by 3:30 a.m. MDT.
Mars is the next planet up, rising at 9:30 p.m. MDT. It is moving slowly westward in eastern Virgo, picking up speed as the month progresses. The God of War is magnitude -0.9 and its disc is 13.3 seconds-of-arc across at midmonth.
Saturn is moving slowly westward in central Libra. Its rings are tilted down 22.6 degrees with the northern face showing, 40.2 seconds-of-arc across. Saturn's disc is 17.7 seconds-of-arc across. Saturn rises at 11:30 p.m. MDT in the east-southeast and shines at magnitude +0.4.
Watch the SkiesMarch 1, 1 a.m. — New Moon
March 8, 6:27 a.m. — First Quarter Moon
March 9, 2 a.m. — Daylight Savings Time begins
March 14, 1 a.m. — Mercury furthest west of Sun (28°)
March 16, 11:08 a.m. — Full Moon
March 20, 10:57 a.m. — Vernal Equinox, spring begins
March 22, 2 p.m. — Venus furthest west of Sun (47°)
March 23, 7:46 p.m. — Last Quarter Moon
March 30, 12:45 p.m. — New Moon
10 p.m. — Mars 5° north of Spica
The brilliant Venus rises around 5 MDT in east-southeast, shining at magnitude -4.5. During March, it moves eastward from eastern Sagittarius into Capricornus, across a corner of Aquarius and back into eastern Capricornus. The Goddess of Love has a disc 26.9 seconds-of-arc across and is a 46% illuminated crescent. By the end of the month, it will be just past the "half-Venus" phase.
Mercury starts the month in Aquarius, crosses into a panhandle of Capricornus, and back into Aquarius, where it ends the month in the eastern end of that constellation. This is a great apparition for southern hemisphere observers, but for us, Mercury will be only six degrees up as it starts to get light. As the month progresses, Mercury will not get higher, but will slide from the east-southeast to the east. At mid-month, Mercury rises around 6 a.m. MDT with a disc 57% illuminated and 7.1 seconds-of-arc across, becoming fuller as the month progresses.
Spring begins in the northern hemisphere as the Sun crosses the celestial equator heading northward at 10:57 a.m. MDT on March 20. The location where the Sun is at that instant is the zero-point for the celestial coordinate system. It is zero hours in right ascension and zero degrees in declination. Daylight Savings Time begins on March 9. After that, we will have an extra hour of daylight in the evening and lose an hour in the morning. So remember to set your clocks ahead one hour and "keep watching the sky"!
An amateur astronomer for more than 40 years, Bert Stevens is co-director
of Desert Moon Observatory in Las Cruces.