A Comet Is Growing in Our Sky: Watch It Bloom As It Moves
+ Von Del Chamberlain +
Its roots go back a dozen-billion years or so to the beginning of the universe. Somehow the material of which it is composed got into the batch that eventually became the solar system about 4.5 billion years ago. Growing from that seed, it has hovered out beyond the planets, a goodly- way toward the nearest stars, in a region that astronomers labeled the Oort Cloud, named for Jan Oort, a Dutch astronomer who proposed the idea that trillions of comets orbited at the edge of the solar system. A complicated series of tiny, yet significant, gravitational events, probably involving near-by stars and the big planets in the outer solar system, altered its movement to cast it inward. Now it is here, visible in our sky. That, in a nut shell, is the theory of where comets come from. Thus, we see that this interloper into our region is a sample of the ancient past, filled with primordial material that has been preserved in deep freeze. Studying such old stuff can give us information about the origin and history of the planetary system we live in and about the rest of the universe.
Contemporary astronomers must have been living right to be blessed with a pair of fine comets within just two years. Many readers will recall, with good memories I hope, Comet Hyakutake that graced our skies a year ago. Although it was not one of the brightest comets in history, it was a classic one. From a dark location on a clear night last April it was a wonderful sight, especially through binoculars. That was the prologue. Now for the main event.
On July 23, 1995 two individuals, Alan Hale of New Mexico and Thomas Bopp of Arizona, simultaneously discovered a new comet. Thus, it bears their name, Comet Hale-Bopp. The discovery was unusual because the comet was still so far away. Only rarely has such a distant new comet been seen. Once discovered, it has been watched coming in toward the Sun.
Last November Hale-Bopp was a small, fuzzy ball of light difficult to find in binoculars. It has been hiding in the glare of the Sun for the past two months while many of us have waited with hope. That hope was fulfilled for me on the morning of January 30 when I arose early and drove up to Little Mountain to find the comet now that it was back in dark sky just before sunrise. Wow! No problem seeing it this time. Right where it should be was an easy to see fuzzy star. Binoculars revealed a glowing cloud, the "coma," with a broad fan-shaped tail beginning to become apparent. I could easily see all of this even through thin clouds that picked up the light of the last-quarter moon.
Now, more than anything else, I want my readers to see this space-and-time probe as it goes hurtling through our region. I hope you will mark your calendars now. You will have three excellent opportunities to watch how it grows in brightness, to see the tail develop and to follow its march across the sky. Several factors regulate the visible characteristics of a comet: its composition determines how solar energy evaporates its gasses and releases its dust particles so that the coma and tail can grow; the relative positions of comet, Earth and Sun determine just how, where and when we see it; all of this combined with waxing and waning moonlight and weather patterns provide our opportunities to see it at its best.
There will be periods in each of February, March and April when the comet should be visible in dark sky. From now until about February 19 you can see it between 5:30 and 6:30 a.m. and watch its tail develop. Then, the Moon will brighten the sky until early March, the comet remaining visible, but moon light lessening its beauty. From early until mid-March the morning sky will be dark again for prime viewing of the comet as it brightens and moves northward. Hale- Bopp will be closest to Earth, about 194 million kilometers (120 million miles) on March 23. The full Moon of March 23, when there will be a partial lunar eclipse, will dampen viewing conditions for a few days, but by March 25 the comet will be visible in the evening sky after sunset. Thus, itis expected that most people will see it from then until about the middle of April when the Moon will again become an important obstacle and the comet should be dimming. Finally, we should be able to watch it fade through the month of May.
Again, I plead with you to begin now watching this celestial "motion picture" and enjoy it as the prime feature of our sky going into spring. Here is how you can find it during the next few days.
The best time for viewing this month will be about 1 1/2 hours before sunrise. For top results, get out of city lights. After you have looked around to enjoy the beauty of the morning sky and get your bearings, turn east and find the bright star Vega, in the constellation Lyra, well up north of east. Now, still farther north and lower, find another bright star, dimmer than Vega, the star Deneb in Cygnus the Swan. Lower still, but almost straight east is a third bright star, Altair in Aquila the Eagle. These three stars form the Summer Triangle. Right now, the comet will be about one-quarter of the way along the line from Altair toward Deneb, the brightest object in that vicinity. It will move northward as the days go by. When you find it, look with binoculars. If you see a glowing cloud, rather than a star, you will know that you have found the comet. Feast your eyes upon it. Study the tail pointing upward from where the Sun will rise.
Now that you have located Comet Hale-Bopp, you can continue to watch it unveil its visual secrets to become the flower of our spring-time sky. Share it with family and friends. You can maximize enjoyment of the comet by attending any of the many comet events sponsored by various organizations. Consider becoming a local expert and arrange some neighborhood comet watch parties, a good excuse to get better acquainted with others living around you.