Feature Article May 5, 2004
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Four Bright Evening Planets and Two Comets!
In this area at the beginning of May, sunset is just after 8:00 p.m. (Eastern Daylight Time), and sunrise at 6:00 a.m. By months end, sunset is at 8:40 p.m. and sunrise at 5:30 a.m. Over the same period of time, the end of evening twilight moves from about 10:00 p.m. to about 11:00 p.m. Morning twilight moves from 4:00 a.m. to just after 3:00 a.m. By months end, complete darkness is only within the four hours between 11:00 p.m. and 3:00 a.m.
However, if the weather cooperates, the long evening twilights this month do provide us with a chance to observe the brightest of the stars of the spring constellations, as they begin to appear in the late evening, and also four of the five bright planets that can be seen in the western half of the evening sky. As twilight darkens, we may notice what our ancestors saw as the emerging patterns of the two dominant spring constellations, Leo the Lion and Virgo the Maiden. High in the south, in the first of these two constellations, the star Regulus, marking the animals front paws, emerges first in the twilight, and later to its left, the star Denebola which marks its tail. Meanwhile, in the southeast, Virgos brightest star, a brilliant whitish jewel called Spica, has appeared to mark the place where the Maiden holds an ear of wheat in her hand. As you gaze in wonder at these three stars, try to remember that they are at vastly different distances: Regulus is 69 light years away; Denebola, 40 light years away; and Spica, an inconceivable 275 light years distant! (Each light year is over 9 trillion kilometres!)
Among the four bright evening planets, Venus, well above the western horizon, is most remarkable this month for several reasons. After reaching its greatest brilliancy in the first week of May, a brightness so great that those who know exactly where to look have been able to see it fairly easily in the daytime, it starts to fade in the latter part of the month, but more noticeable than its fading is its changing position in the sky. It begins the month quite high in the west at sunset, and can be seen for 3 hours before setting, but by the end of the month it is very low in the western evening twilight when first seen and sets less than one hour after sunset. Those who view it with good binoculars or a small telescope can easily see that its orbit is carrying it closer to the earth since the width of its disk increases, while the lighted portion of the disk grows thinner, changing from about a quarter-phase to a very slim crescent.
Well above Venus, bright Saturn is easily seen below the stars Castor and Pollux in the constellation Gemini. Its position changes very little. Fainter than both of these planets is reddish Mars which begins this month 1/3 of the distance from Venus up to Saturn. By May 10 it appears half way between the two brighter planets, and on May 24 Mars can be seen passing very close to Saturn. On the last weekend of the month, Mars is seen well above Saturn in the constellation Gemini.
As in the previous several months, Jupiter is in the constellation Leo the Lion, appearing to the left of the brilliant star Regulus, and high in the southwestern twilight. The fifth bright planet, Mercury, has a limited appearance this month, observable in the week of May 10 to 17 for those who look low in the eastern morning twilight sky about an hour before sunrise.
The moons passage near several planets provides for some very interesting views this month. On the morning of May 16th, the crescent moon appears to the upper right of Mercury in the eastern dawn sky. On the evening of May 20th, challenge yourself to see the slim crescent below Venus in the evening sky about 60 minutes after sunset. The following evening, May 21st, at the same time, notice that the crescent is now above Venus. On May 22nd, it is just above Saturn and Mars, and on the evening of the 23rd, it is beside the stars Castor and Pollux. On May 26 the First Quarter Moon forms a triangle with Jupiter and the star Regulus in the constellation Leo. The following night the moon has moved eastward enough to appear just to the left of Jupiter.
This is a rare month, one that amateur astronomers have awaited for a long time, because it brings the rare possibility of seeing two bright comets, in fact, two comets that may even be bright enough to view with the unaided eye! The first one, commonly called Comet NEAT (or officially C/2001 Q4 NEAT) was discovered on August 24, 2001 by the robotic telescopes of the Near Earth Asteroid Tracking program in California and Hawaii. The second comet, commonly called Comet LINEAR (officially called C/2002 T7 LINEAR) was discovered on October 14, 2002 by the Lincoln Near Earth Asteroid Research program with the use of a pair of robotic telescopes in White Sands, New Mexico. Both comets will almost certainly become bright enough this month to see easily in ordinary binoculars, and probably even with the unaided eye (but that is still not absolutely for certain), and both of them may have a long, easily-visible tail that may be whitish or slightly yellow in colour. To enjoy a view of Comet NEAT, look low in the southwestern sky any clear evening between May 6 and May 22, about an hour after sunset. To see Comet LINEAR look low in the western sky about 40 to 60 minutes after sunset any clear evening from May 26 to June 21. I would be happy to hear from anyone who enjoys a good view of either of these two comets.
