The Double Comet Show of 2004

Comet NEAT
Comet NEAT was high in the evening sky on May 8, 2004, when Chris Schur caught it with an 8-inch f/1.5 Schmidt camera on Supra 400 film. He took this 5-minute exposure under a very dark, transparent Arizona sky at an elevation of 6,800 feet. 'The comet had a 2° tail to the naked eye,' he writes, 'however, in binoculars over 7° of tail was seen without much effort. Three tails are seen here: a greenish tail pointing upward, a blue ion tail, and a brownish dust tail. The green tail points away from the Sun.'
Photo by Chris Schur.
Two nice comets are currently coursing through the inner solar system. They will continue to be visible from various latitudes on Earth — with binoculars, and perhaps with the naked eye — for the next few weeks.

Comets C/2001 Q4 (NEAT) and C/2002 T7 (LINEAR) were discovered in August 2001 and October 2002, respectively, by the automated sky-survey programs for which they’re named: Near-Earth Asteroid Tracking (NEAT) and Lincoln Laboratory Near Earth Asteroid Research (LINEAR). Amateurs tracked the comets with telescopes for more than a year as they approached the inner solar system and gradually brightened. Now that they're here, they are not living up to astronomers' early brightness predictions ("hopes" might be a better word), but they are still well worth seeking out.

Frequent updates on the comets' brightnesses and visibility, including when and where to look, can be found in Sky & Telescope's online column This Week's Sky at a Glance.

View from the Northern Hemisphere

Path of Comet NEAT
In early May, Comet NEAT climbs higher every day above the southwestern sunset horizon. The comet could be visible to the naked eye, but binoculars provide a much better chance of seeing it. By mid-May, NEAT will be well up in the west even after twilight gives way to darkness — though the comet will be fading daily. The dates plotted are civil dates for North America. The horizon is drawn for early May; later in the month the horizon will be higher at dusk with respect to the stars.
S&T illustration.
The two comets will put on rather different performances in each 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 evening sky 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 will act more coy. In April and the first days of May it just peeked over the eastern dawn horizon, appearing quite low in the brightening dawn. It was only seen from low latitudes. 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

Paths of Comets NEAT and LINEAR
Observers in the world’s midsouthern latitudes — Australia and New Zealand, southern Africa, and southern South America — get a grand view. Comet NEAT stays very high in the evening sky throughout its brightest times, while Comet LINEAR shows itself well during both its morning and evening displays. Click on the image to see the complete chart.
S&T illustration.
Southern Hemisphere observers have a much better vantage point for both of these comets. Seen from south temperate latitudes, NEAT will remain beautifully placed high in the evening sky after dark throughout May, including its early-May period of peak brightness. At the same time LINEAR is much less shy about showing itself before dawn until mid-May, and then after dusk from then on.


Comet Highlights

Here is a timetable of noteworthy events during the long comet show. Tables listing each comet's position and its predicted magnitude, initially based on projections by John Bortle and updated in early May based on actual observations, can be found on the next page.

Comet NEAT reached perihelion on May 15th, 0.962 a.u. from the Sun, barely closer to the Sun than Earth is. At this time the comet was 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.

Comet LINEAR at dusk for Northern Hemisphere observers
After it ducks back around the Sun, Comet LINEAR will be visible to observers in the US and Europe in the west during evening twilight.
Sky & Telescope illustration.
Late in May midnorthern observers get their turn to see both comets at once — NEAT high in the western evening sky at about 4th magnitude, LINEAR emerging low in the west-southwest a little past its prime.

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.


Where to Look for NEAT and LINEAR

The double comet apparition should provide us with many treasured memories. If you don't normally use binoculars much on the sky, now's 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.

Comet NEAT

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&deg 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.

Comet C/2001 Q4 (NEAT)
Date
2004
R.A. (2000)
h   m
Dec.
°   '
Magnitude
Constellation
May   1  6 14-44 303.4Pup
May   4  6 54-32 003.2Cma
May   7  7 28-16 483.0Pup
May 10  7:56-  1 303.0Mon
May 13  8 19+11 243.4Cnc
May 16  8 38+21 183.7Cnc
May 19  8 54+28 494.0Cnc
May 22  9 07+34 064.3Lyn
May 27  9 24+40 244.8Lyn
June   1  9 38+44 365.2UMa
June   6  9 49+47 365.6UMa
June 11  9 59+49 546.1UMa
June 2110 15+53 006.7UMa
July   110 30+55 067.3UMa

Comet LINEAR

You can also use our interactive sky chart to follow Comet LINEAR as it moves through the sunset skies of the

Southern

and

Northern

Hemisphere during May and June 2004. The southern chart shows the sky for 7:00 p.m. on May 18th at 35° south latitude; the northern chart is set to 10:05 p.m. on May 29th at 40&deg north.

Comet LINEAR is also visible before dawn until about mid-May for
southern observers.
This chart is set for 5:00 a.m. on May 1st at 35° south latitude.

Remember, to adjust the chart's 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.

Comet C/2002 T7 (LINEAR)
Date
2004
R.A. (2000)
h   m
Dec.
°   '
Magnitude
Constellation
May   1  0 06+  0 363.9Psc
May   6  0 26-  2 123.6Psc
May 11  1 07-  6 483.1Cet
May 16  2 43-14 302.7Cet
May 19  4 24-19 122.6Eri
May 22  6 14-20 003.0CMa
May 25  7 34-17 423.6Pup
May 28  8 22-15 124.4Pup
May 31  8 53-13 125.0Hya
Jun.   5  9 23-11 005.9Hya
Jun. 10  9 42  -9 366.7Sex
Jun. 2010 03  -8 068.0Sex
Jun. 3010 17  -7 249.0Sex