|The Double Comet Show of 2004|
How bright will they get? With a little luck, one or both could become distinctly visible to the naked eye. Or they could remain targets only for binocular users who know just where to look. Predicting the brightness of “new” comets — those freshly arrived from the outermost reaches of the solar system, like these — is fraught with risk. Some such comets in recent years have broken up and dissipated completely as they neared the Sun, the most recent being C/2002 O7 (LINEAR). Others suddenly ebbed in their brightening after a promising start; famous cases are comets Kohoutek in 1973-74 and Austin in 1990, both of which were supposed to become bright to the naked eye but ended up only 3rd or 4th magnitude when easily visible, much to the world’s disappointment.
|View from the Northern Hemisphere
For skywatchers living at north temperate latitudes, Comet NEAT promises the easiest show to watch. In early May, just when NEAT is brightest, it will rapidly climb out of the Sun’s glare into good view above the southwest horizon after sunset. By the middle of May it will be high in the dark sky of late evening even as it begins to fade. It will remain ideally placed for viewing high in the northwest after dark through June and July as it dwindles away into the distance, eventually becoming visible only in telescopes.
Comet LINEAR may get a little brighter, but it will act more coy. In April and the first days of May it just peeks over the eastern dawn horizon, appearing quite low in the brightening dawn; bring your binoculars. When LINEAR is at its brightest in mid-May, it will be hidden in the Sun’s glare (well to the Sun’s south). Then in late May and June it will show itself a little higher above the west-southwest horizon at dusk, fading all the while.
View from the Southern Hemisphere
Here is a timetable of noteworthy events during the long comet show. Tables listing each comet's position and its predicted magnitude, based on projections by John Bortle, can be found on the next page.
In the first week of April, NEAT is passing 7° north of the Small Magellanic Cloud, creating an inviting target for far-southern astrophotographers. Around April 22nd NEAT will pass a little less than 10° from the Large Magellanic Cloud.
Meanwhile, on April 23rd Comet LINEAR passes through perihelion, its closest approach to the Sun. At 0.615 astronomical unit (91.9 million kilometers), LINEAR’s perihelion is substantially closer to the Sun than NEAT’s three weeks later.
On May 5th Comet NEAT passes 9° from Sirius, the sky’s brightest star. On the 6th NEAT is closest to Earth (0.321 a.u.) and should be about at its peak brightness, perhaps magnitude 2.5. On May 7th NEAT passes just 1° northwest of the 5th-magnitude open cluster M47 in Puppis.
Comet NEAT reaches perihelion on May 15th, 0.962 a.u. from the Sun, barely closer to the Sun than Earth is. At this time the comet will be just a couple of degrees away from M44, the Beehive Cluster.
May 19th brings Comet LINEAR’s closest approach to Earth (only 0.266 a.u.) and its time of greatest brightness: perhaps magnitude 2. By this time Southern Hemisphere viewers will be seeing both comets in the evening sky at once (see the lower chart on the previous page). On the 22nd (local date for North America), only about 3° will separate LINEAR’s head and Sirius.
During June both comets should fade to below naked-eye visibility. NEAT will become lost to Southern Hemisphere observers in June; conversely, it will turn circumpolar for those in north temperate latitudes. As LINEAR fades, by contrast, it will move back into the glare of the Sun for northerners, but from the Southern Hemisphere it should remain a telescopic sight through July and August, glowing dimly at perhaps 11th magnitude by the end of that period.
The May issue of Sky & Telescope contains a large chart that shows the comets’ paths (and tail direction) among the constellations. The comets’ positions are marked for 0:00 Universal Time on the indicated dates, for worldwide use. The same issue also includes tables indicating each comet’s altitude above the western horizon in very late dusk, and/or the eastern horizon in very early dawn (when the Sun is 15° below the horizon), for skywatchers at midnorthern and midsouthern latitudes. The May S&T will be available on newsstands March 30th.
|Positions for NEAT and LINEAR
Use our interactive sky chart to follow Comet NEAT as it moves through the skies of the Southern and Northern Hemisphere during April and May 2004. The southern chart shows the sky for 8:00 p.m. on April 20th at 35° south latitude; the northern chart is set to 10:00 p.m. on May 7th at 40° north. To adjust the date and time, highlight the month, day, hour, or minute and click the "+" or "-" button. To alter your viewing location, press the "Change" button on the location bar.
The double comet apparition should provide us with many treasured memories. If you don't normally use binoculars much on the sky, now's certainly the time to get them out. The chance to follow the progress of comets LINEAR and NEAT every clear night will make this a fascinating time to be an amateur astronomer.
|©2004 Sky Publishing