| Jan 27, 2005

Feature Article January 27

Feature article January 27, 2005

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Three Bright Planets and the Stellar Ring Around Orion

The month of February still gives us the spectacular winter constellations high in the southern sky during the evening hours, along with a few of the distinct, but less spectacular, spring constellations that now begin to make their way into our sky to be noticed by those who linger into the late evening to do their observations. For those who rise in the early morning hours, there are even a few of the summer constellations to be seen in the eastern sky during the hour or two before sunrise.


After the end of evening twilight, we are bound to recognize the very distinctive and bright stars of Orion, the Great Hunter, marching westward across the southern part of the sky. He and his attendants, both human and animal, still provide us, as they certainly did in the earlier parts of the winter, with a huge array of bright stars, the gems of the winter evenings. Seven bright stars mark the shoulders, the knees, and the belt of this giant figure, as it was pictured in the minds of our ancestors long ago. In addition, six other very bright stars (and this month, one bright planet) surround him, almost filling the southern half of the sky. Lets first consider the eastern half of the great circle of stars surrounding Orion. Looking downward and to the left from the three stars of Orions Belt, we can easily see the first of the Dog Stars, Sirius, the brightest star in the whole sky, to mark the eye of the large canine, Canis Major, and then to the left and up a bit from it, Procyon, the eighth brightest star in the sky, marking the head of his smaller sibling, Canis Minor. Continuing upward in the huge semi-circle to the left of Orion, we have the planet Saturn, which currently is a visitor in this region of the sky and currently a suitable addition to the bright objects found here. Above Saturn we see Castor and Pollux, the Heavenly Twins, the two brightest stars in the constellation Gemini. High above those two stars and also in a line upward from the head of Orion, is Capella, the Goat Star, the skys sixth brightest star, accompanied by three much fainter stars called the Kids, with Capella being a part of a very large pentagon of stars making up the constellation Auriga, the Charioteer. Capella is the first of the huge semi-circle of stars on the right side of Orion completing the semi-circle (just mentioned) on his left side. The second star of the semi-circle on the right side of Orion is the reddish Aldebaran, the Eye of the Bull Star in the Head of the Bull, the group of stars representing the animal that Orion appears to be attacking as he marches westward. This red eye is the skys 14th brightest star. The third star of this semi-circle is Rigel, the right knee star of Orion, and the seventh brightest stars in the heavens. Although when put together, these two semi-circles do not form a perfectly symmetrical circle, they are actually close to a circle, and they do contain, as is already evident, four of the eight brightest stars seen from any location on earth. In addition, Castor and Pollux, are on the list of the 30 brightest stars, as are both of the stars marking the shoulders of Orion, as well as one of the three stars in his belt. In summary, from the seven stars in the Great Circle, and the six remaining bright stars in Orion, no less that eleven of those 13 are among the 30 brightest in the whole sky.

Among the five bright planets, Mercury and Venus, the two inner planets (meaning their orbits are within the orbit of planet Earth), which were seen in the morning sky last month, are now in a direction that is close to the direction of the sun, and so they will not be easily seen this month. Saturn, Jupiter and Mars, however, are well spaced around the sky and can be seen at different times during the night. Saturn is well up in the east at the end of evening twilight and can be seen marching across the sky during the entire night. As mentioned above, it is found just below the bright stars Castor and Pollux and almost in a line with them. Over the month, careful observers will notice that Saturn moves slightly to the right and away from these two stars. Those who own a small telescope may see, not just the planet Saturn, but also its impressive ring system and its brightest moon, Titan, which has been in the news so much lately. After a seven-year journey from Earth, the surface probe Huygens (named after the discoverer of this moon in 1655) separated from the spacecraft Cassini (named after the discoverer of the gap in Saturns ring system in 1675), and landed on the Titan to reveal a rocky and frozen surface where liquid methane had recently rained down upon the landscape. This first of the outer planets moons to be explored in great detail has revealed some startling information in just the past three weeks. Remember these events as you study Saturn. Jupiter has risen in the eastern sky by 11:00 p.m. in early February, and rises a little earlier each evening until by the end of the month it may be seen before 9:00 p.m. With Venus absent from the sky, Jupiter is the brightest planet, considerably outshining Sirius, the brightest star. It is in the constellation Virgo not far from the very bright star Spica, and after rising, it is seen throughout the night, being high in the southwestern sky by sunrise. Reddish Mars is low in the southeastern sky in the very early morning, rising between 4:00 and 4:30 a.m. It is best seen between two hours and one hour before sunrise, and it is to the left of the red star Antares by about twice the width of a fist held at arms length. Antares has a colour similar to that of Mars, and our ancestors looked upon this reddish star as a rival of Mars. That is the meaning of the name Antares.

The moons passage by these three planets will present some very interesting views this month. On the four mornings from February 3 to 6, watch the eastern sky about an hour before sunrise to see the waning crescent moon passing both Antares and Mars. On the 3rd, the moon is above and to the right of Antares; on the 4th, it is below and to the left of that star. On the 5th, it is below and to the right from Mars; on the 6th, a very thin crescent is below and to the left from Mars. In the evening sky on February 19th, the waxing gibbous moon is seen to the right of Castor, Pollux and Saturn. Looking in the same place the following evening, February 20, will easily show how far the moon has moved in 24 hours, since it will now appear to the left of Saturn. Three nights after Full Moon, the waning gibbous moon will appear above Jupiter and the star Spica in the eastern evening sky of February 26. On the morning of February 27, an hour before sunrise, as Jupiter and the moon are setting in the southwestern sky, try to catch the view of the moon and Jupiter in a very close conjunction. That same evening, on February 27, observe them again to see how much the moon has moved in a single day, since it will now be below Jupiter and the star Spica.

Those who are interested in more information about the constellations, planets and other objects of the night sky are invited to purchase a copy of the book The Beginners Observing Guide, which is now available at Sharbot Lake Pharmacy and The Valley Book Shop in Perth.

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