D e s e r t E x p o s u r e 
February 2006
D e s e r t E x p o s u r e |
 Constellation of the Month: Taurus, the Bull (Part I) It's a lot of bull—Taurus, the Bull, that is, our constellation of the month. There is so much to say about this constellation, we will be covering it both this month and next. This is a truly ancient constellation. The caves of Lascaux in France contain wall paintings that are over 16,500 years old. There, in the Hall of Bulls, are many paintings of bulls, including one where there is a small group of stars near it. This group represents the Pleiades, which is near Taurus in our sky, making Taurus the oldest known constellation.
In more recent times, only about 6,000 years ago, the Egyptians would hold their bull festivals at the beginning of spring when the Nile would overflow its banks, depositing a new layer of fertile silt for the summer growing season. In those days, the Sun would enter the constellation Taurus around each spring equinox. For the Greeks, this constellation is the bull that Zeus disguised himself as when he wanted to woo the Phoenician princess Europa, whose father kept her guarded at all times. This disguise as a white bull with golden horns allowed Zeus to mingle with the king's herd. When Europa saw the beautiful bull, she went over to it, talked to it, and fed it. Charmed by the friendly bull, she climbed on his back and he slowly ambled toward the sea. Before she knew it, the bull had carried her out into the sea and it was too late to dismount. The bull carried her to Crete. After wooing Europa, Zeus realized he could not marry her, and gave her in marriage to Asterius, king of Crete. Their child was half man, half bull: the Minotaur, ultimately slain by Theseus (see the July 2005 Starry Dome featuring Corona Borealis). Even more recently, in 1054 AD, Chinese astronomers noticed a new star in Taurus, which they called a "Guest Star." The Anasazi Indian artists here in Arizona and New Mexico also made drawings that depict the new star near the crescent Moon as it would have appeared July 4, 1054. These drawings can be found in Navaho Canyon and White Mesa, Arizona, and Chaco Canyon National Park, New Mexico. This star was near the horns of Taurus and shined at magnitude -6, so bright that it was easily visible in the daytime for 23 days and at night for over two years. This was the famous 1054 supernova.
The supernova is some 6,300 light-years away, so the explosion actually occurred while the Egyptians were holding their bull rituals. Seven hundred years after the supernova was seen, John Bevis of England found a faint nebula in Taurus. It was rediscovered by Charles Messier, which prompted him to start his famous catalog, in which it became M1, the first entry. Lord Rosse's drawing of M1 resulted in the name Crab Nebula. The 1054 supernova was a type II supernova. A
supergiant star 10 times more massive than our Sun had reached old
age, and was "burning" (fusing)
silicon and sulfur to make iron. Iron does not fuse, and built up in
the core of the star. When the iron core reached 1.4 solar masses, gravity
was so strong that the core collapsed, shrinking from 5,000 miles across
to just a dozen. The electrons and protons of the iron core were forced
together by gravity to become neutrons, emitting vast quantities of energy.
Most of the energy was carried off by tiny massless particles called
neutrinos. The rest of the star fell toward the new smaller core. The
energy of this collapse created a shockwave that traveled upward through
the star, causing explosive fusion throughout and creating all the elements
heavier than iron. This tremendous release of energy flung the outer
layers of the star into space, forming the Crab Nebula. The core, composed
solely of neutrons, was spun-up by the collapse, and still had the magnetic
field of the parent star. One of the poles of this field points toward
the Earth as the core (now a neutron star) spins and we see a bright
flash of light, radio and X-rays on each rotation. This happens an amazing
30 times every second. The Planets for February 2006 Mercury makes an appearance in our evening sky this month. Because Mercury travels along the ecliptic, and the ecliptic is almost vertical against the western horizon, this will be the best apparition of Mercury for this year. Mercury will appear low in the west around midmonth and will reach its greatest height on Feb. 24, when it will be magnitude -0.3 and 7.4 seconds-of-arc across. Mercury will be almost full when it first appears, shrinking to a thin crescent when it disappears in early March. Having passed between the Earth and Sun, Venus is now in the morning sky. It begins the month low in the east before sunrise and will get higher every day. Remaining in Sagittarius all month, Venus is a thin crescent that will plump out as it races away from us. At midmonth, Venus will be magnitude -4.6 and 41.0 seconds-of-arc across, slowly shrinking. Mars slips from Aries into Taurus just after the beginning of the month. Its eastward motion among the stars will keep it in Taurus for the rest of the month as it appears to shrink and dim. It is now only 7.7 seconds-of-arc across at magnitude 0.5. Mars is high overhead in the south as it gets dark, and sets around midnight. Saturn is already up in the east as the Sun sets. Still in Cancer, Saturn is just past opposition, so this is a good time to take a telescopic look. The Ringed Planet is 20.2 seconds-of-arc across; its rings are 45.8 seconds-of-arc across, with the southern face showing, and tilted up 19 degrees to our line-of-sight. Jupiter is in Libra all month. The King of Planets rises just before midnight as Mars is setting. Jupiter remains visible the rest of the night. At midmonth Jupiter will be at magnitude -2.1, stretching 37.8 seconds-of-arc across. Jupiter is one of the most fascinating planets to view, so take a peek with your telescope and "keep watching the sky"!
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