Naked-Eye Comets in 2001

Comet Ikeya-Zhang  (naked-eye comet in 2002)

Comet NEAT (potential bright comet in 2004)

Latest update on comets (December 2005)

Naked-Eye Comets in 2001

Go to latest update (April 1, 2002)

One of the many recent comets discovered by the LINEAR program has become unexpectedly bright. Comet C/2001 A2, discovered on January 15, 2001, was never expected to become especially bright, however it now appears that its nucleus split in two around mid-March, at which time it started to become much brighter than had originally been expected. It continued to brighten from that point, and by the time it ceased to be visible from the northern hemisphere around the beginning of May it had already almost reached naked-eye visibility. Reports that have been received from the southern hemisphere since then indicate that the comet's brightness has continued to increase.

This particular comet LINEAR is at perihelion on May 24, 2001, at a distance of 0.78 AU from the sun. At the end of June it passes 0.24 AU from the earth, and if it maintains its current brightness trend it may be as bright as 4th magnitude around that time. By then it will again be visible from the northern hemisphere, located in the southeastern skies before dawn.

The below two images taken with the Southwest Institute's telescope/CCD system illustrate the comet's dramatic rise in brightness. The left image was taken on March 24 with the 30-cm telescope, the right on April 16 with the 20-cm telescope; both images are 30-second exposures. Observation reports from the southern hemisphere indicate that the comet has now developed a tail at least two degrees long.

UPDATE: Comet LINEAR continued to be a moderately bright naked-eye object from the southern hemisphere during June, becoming visible in the morning sky, and apparently undergoing another brightness increase (to 3rd magnitude) shortly before mid-June. The below photograph was taken by Alan Hale on the morning of June 16 from Harare, Zimbabwe.  


By the end of June the comet had again become visible from the northern hemisphere, and still a moderately bright naked-eye object. At this writing (July 11) it is moving away from both the sun and the earth and is fading, but should probably remain visible to the unaided eye until perhaps the end of the month.
Meanwhile, another recently-discovered comet found by LINEAR also shows some promise of becoming a moderately bright object later this year. Comet C/2000 WM1 was initially discovered on November 16, 2000; at that time it was a very faint and distant object (5.15 AU and 5.79 AU from the earth and sun, respectively) and appeared indistinguisable from an asteroid. According to calculations by Brian Marsden at the Minor Planet Center this particular Comet LINEAR does not pass perihelion until January 22, 2002, at a distance of 0.55 AU from the sun. It approaches 0.32 AU from the earth in early December 2001.

As was demonstrated by Comet C/2001 A2, the brightnesses of comets are notoriously difficult to predict. Initial prediction suggest that Comet C/2000 WM1 may be a moderately dim naked-eye object between 4th and 5th magnitude when nearest Earth, and possibly a magnitude brighter when near perihelion. At the time it is brightest the comet will only be visible from the southern hemisphere, but should remain accessible from the northern hemisphere until late December.

We expect to have a special page devoted to information and images of this comet as we get closer to its main appearance. Check back for more details as that time approaches.

UPDATE (August 3, 2001): As expected, Comet LINEAR C/2001 A2 faded quite a bit during July, and is no longer visible to the unaided eye. Currently about 7th magnitude, it can still be viewed with an ordinary pair of binoculars; by mid-August it will be visible in the evening hours after sunset in the constellation Vulpecula (south of Cygnus).
Meanwhile, Comet LINEAR C/2000 WM1 continues to remain faint. The above CCD image is a 2-minute exposure that was taken with the Southwest Institute's 20-cm telescope on the morning of August 3; the comet appears as an essentially starlike object of about 15th magnitude. It would still be premature to say too much right now about what Comet LINEAR's brightness might be near the end of this year, but at present the chances of a brilliant cometary display do not seem especially promising. Time will tell.
UPDATE (September 19, 2001): This CCD image of Comet C/2000 WM1 is a 2-minute exposure taken with the Southwest Institute's 20-cm telescope on September 18. The comet has both brightened dramatically and developed a significant tail over the course of the past month, and can presently be viewed in larger backyard telescopes as an object of 13th magnitude. It is still running somewhat fainter than expected, and thus it seems unlikely right now that it will be especially bright at the end of this year; however, there does seem reason to be optimistic that, at the very least, it will be an attractive object for binoculars and small telescopes at that time.
UPDATE (October 12, 2001): The image of Comet LINEAR C/2000 WM1 at right is a "stacked" series of CCD images (total exposure time 8 minutes) taken with the 20-cm telescope on October 12. The tail can be seen extending to the upper right from the very bright central region.

The comet is now approximately 11th magnitude, bright enough to be visible in moderate-sized backyard telescopes. It continues to brighten and develop nicely as it approaches perihelion, however it is still running a little over one magnitude fainter than the original predictions for this time. If this trend keeps up, the comet will be a dim naked-eye object of 5th or 6th magnitude when it is closest to the earth in December.

UPDATE (April 1, 2002): During early December 2001 Comet LINEAR reached a peak brightness of magnitude 5 to 5 1/2, dimly visible to the unaided eye. The photograph to the right was taken on the evening of December 7; the bright star above and slightly to the left of the comet is Diphda (Beta Ceti).

The comet faded as it receded from the earth, and was about magnitude 6 when it became invisible from the northern hemisphere during late December. During January it was only observable from the southern hemisphere, and it remained near 6th magnitude through perihelion passage on January 22. However, near the end of January it underwent an apparent outburst, for a brief time becoming as bright as 3rd magnitude, although at that time it was in conjunction with the sun and was difficult to observe.

Comet LINEAR had faded to 6th magnitude by the time it again became visible from the northern hemisphere, during the latter part of February. It has continued to fade since then, being almost 9th magnitude by the end of March. It will continue fading during the coming months as it exits the inner solar system.

The CCD image to the right was taken on the morning of March 15.


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On February 1, 2002, a new comet was independently discovered by Kaoru Ikeya in Japan (discoverer of five comets during the 1960s, including the daylight comet Ikeya-Seki in 1965) and by Daqing Zhang in China. The comet was then 9th magnitude but has brightened dramatically since then as it has approached both the earth and the sun. Perihelion passage (0.51 AU from the sun) took place on March 18, and the comet will pass 0.40 AU from Earth on April 29.

The photograph to the right was taken on the evening of March 9, at which time Comet Ikeya-Zhang was 5th magnitude. By the end of March it had brightened further to 3rd magnitude, becoming the brightest comet to appear since Hale-Bopp five years ago. (Further photographs will be posted in the near future.)

Perhaps the most dramatic development concerning Comet Ikeya-Zhang is that it appears to be identical to a bright comet that appeared in February and March 1661 and which was observed by, among others, the Polish astronomer Johannes Hevelius (one of the top astronomers of that era). If this identity is conclusively verified, Comet Ikeya-Zhang would earn the distinction of being the longest-period comet that has been positively seen on two separate returns.
UPDATE (April 11, 2002) Comet Ikeya-Zhang is now primarily a morning-sky object, visible in the northeastern sky southwest of Cassiopeia. It is still about 3rd magnitude, with a naked-eye tail up to eight degrees long. The apparent tail length may continue to increase as the comet approaches the Earth.
The above photograph was taken on the evening of April 1, from a location on New Mexico Highway 6563 between Cloudcroft and Sunspot, overlooking the Tularosa Basin some 5000 feet (1500 meters) lower. The streak to the lower right of the comet is due to an airplane.
UPDATE (June 7, 2002) Comet Ikeya-Zhang has now -- finally -- faded below naked-eye visibility, although it continues to remain a relatively bright and easy object as seen with a pair of binoculars. It can presently be found in the constellation of Serpens Caput; it is near opposition, and is visible all night.

The comet's past history of returns is still being sorted out. In addition to its probable identity with the comet of 1661, Comet Ikeya-Zhang has also been tentatively identified as possibly being identical to comets that were observed in A.D. 1273 and in A.D. 877.

Other than the fading Ikeya-Zhang, there are no bright comets presently visible, although numerous faint comets are being tracked at the Southwest Institute and elsewhere. (See the NEA images page for images of some of these objects.) The next expected bright comet is Comet NEAT C/2001 Q4, which should be bright during the early months of 2004 (see below); another bright comet could always appear at any time, however.

UPDATE (September 5, 2002) Although still accessible to CCD imaging, Comet Ikeya-Zhang has now faded beyond the range of visual observations. It is currently located in the southwestern evening sky, a few degrees north of the "head" of Scorpius.

Calculations have now firmly established that Comet Ikeya-Zhang is indeed the same comet that was observed by Johannes Hevelius (among other astronomers of that era) in 1661. It has been assigned the periodic comet designation 153P, and the current orbital period is approximately 367 years; thus, our descendants should see this comet again sometime around the year 2370. It is also possible that comets observed in A.D. 1273 and A.D. 877 were earlier returns of Comet Ikeya-Zhang, but the available observations are such that we can't make any definitive statements about this one way or the other.


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On August 24, 2001, the Near-Earth Asteroid Tracking (NEAT) program, which utilizes (among other telescopes) the 1.2-meter (48 inch) Schmidt telescope at Palomar Observatory in California, discovered a very faint comet which was subsequently found to be located beyond the orbit of Saturn. Recent orbital calculations indicate that this comet does not pass perihelion until May 15, 2004, when it will be located 0.96 AU from the sun. A week prior to that it will approach to within 0.33 AU of the earth.

At this time it is all but impossible to make any accurate predictions as to how bright Comet NEAT will become, but if it behaves in any way "normally" it has the potential to be a rather bright naked-eye object around the time it is nearest the sun and earth. This page will carry more information about the comet as it makes its way into the solar system.

UPDATE (September 4, 2002) After being in conjunction behind the sun for the past several months, Comet NEAT has now reappeared in the morning sky. At 16th magnitude, it is still too faint to be observed visually with moderate-sized telescopes, but can be imaged with modest CCD equipment.

The image at right is a two-minute exposure obtained on the morning of August 12, 2002. This was taken during the early stages of dawn, so it is a bit "noisy," but the comet nevertheless shows up moderately well.

Comet NEAT, currently about 7 AU from both the sun and Earth, should remain accessible for the next few months, and presumably should brighten slowly. At a declination south of -30 degrees it is more favorably placed for observations from the southern hemisphere, although northern hemisphere telescopes should still be able to access it.
UPDATE (February 7, 2003) Over the past several months Comet NEAT has brightened slowly, and currently is perhaps slightly brighter than 15th magnitude. For the most part it has remained too faint for visual observations, but has been relatively easy to image with CCDs. At this writing Comet NEAT (presently 5.8 AU from the sun) is about ready to disappear into conjunction with the sun, but should reappear in the morning sky in five to six months. By that time it should be bright enough to be detected visually (perhaps 12th magnitude) but will be at a declination of about -40 degrees and heading southward; observations will be difficult, at best, from the northern hemisphere, but should be relatively easy from the southern hemisphere.

Meanwhile, another recently-discovered comet may also be quite bright during early 2004. This is Comet C/2002 T7, discovered by the LINEAR program on October 14, 2002, at which time it was a faint object of about 17th magnitude located 6.9 AU from the sun. It passes perihelion on April 23, 2004, when it will be 0.62 AU from the sun; it passes 0.26 AU from Earth four weeks later. Beginning in late May both it and Comet NEAT will be simultaneously visible in the evening sky, and both objects could be prominent naked-eye objects at that time. At this writing, meanwhile, Comet LINEAR is located in the constellation Taurus (in the evening sky) some ten degrees north of the Hyades star cluster, and is approximately 15th magnitude, too faint for visual observations. These may become possible around August when the comet emerges into the morning sky at about 13th magnitude.


Images of Comet NEAT C/2001 Q4 (left) and Comet LINEAR C/2002 T7 (right), both obtained with the 20 cm telescope on December 1, 2002.
UPDATE (December 3, 2003) Both approaching comets appear to be brightening fairly nicely as they continue towards perihelion. Comet NEAT is currently deep in southern circumpolar skies, and according to reports from comet observers in the southern hemisphere it appears to be between 10th and 11th magnitudes -- bright enough to be detectable in moderate-sized telescopes. Comet LINEAR, visible from both hemispheres, is now somewhat brighter than 10th magnitude and can be detected with binoculars; it is developing nicely and is already showing a short, bright tail in small telescopes.
The CCD image of Comet LINEAR at right was taken on the evening of November 1, 2003; this is a 2-minute exposure obtained with the 20-cm telescope.
UPDATE (December 13, 2005) Because of our primary focus upon getting the Earthrise project developed, this page has not been updated in some time. We nevertheless feel it is appropriate to provide a quick review about the appearances of the above comets.

Neither Comet NEAT nor Comet LINEAR lived up to their expectations. Comet LINEAR never became brighter than 4th magnitude as observed from the northern hemisphere, and even when brightest was fairly close to the horizon and not especially easy to observe. Comet NEAT, meanwhile, reached 3rd magnitude during May 2004, but although easily visible to the unaided eye it did not develop a bright or conspicuous tail.

By a remarkable coincidence, the above two comets were joined by a third relatively bright comet, Comet Bradfield C/2004 F4, which had been discovered by Australian amateur astronomer William Bradfield in March 2004. When Comet Bradfield became visible in the northern hemisphere's morning sky in late April it was about 4th magnitude and was exhibiting a long and moderately conspicuous tail. The show was brief, however, with the comet's fading below naked-eye visibility by mid-May.

LEFT: Close-up photo of Comet NEAT C/2001 Q4, on the evening of May 5, 2004. RIGHT: Comet Bradfield C/2004 F4, on the morning of April 26, 2004.
Yet another fairly bright comet was discovered by California amateur astronomer Don Machholz on the morning of August 27, 2004. At that time Comet Machholz C/2004 Q2 was about 11th magnitude, but it brightened steadily over the subsequent months as it approached the sun and earth. It passed 0.35 AU from Earth in early January 2005, and passed perihelion on January 24, at 1.205 AU from the sun. When brightest in early January Comet Machholz was about 3 1/2, and was well placed for viewing high in the sky; however, because it was beyond Earth's orbit the tail was directed more or less away from us and thus the comet appeared primarily as a large fuzzball.
LEFT: CCD image of Comet Machholz on September 23, 2005. RIGHT: Photograph of Comet Machholz, near the Pleiades star cluster in Taurus, on the evening of January 5, 2005.
At this time there are no known comets that are expected to become conspicuous naked-eye objects within the near future. However, Comet 73P/Schwassmann-Wachmann 3 will be passing only 0.079 AU from Earth on May 12, 2006, and may very well reach 6th magnitude or brighter. This comet split into several fragments at its 1995 return and was unusually bright then; whether or not this increased brightness will persist through the current return remains to be seen.
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