[重要] 本月底将是观测T7和Q4的最后机会，请千万别错过！

LINEAR Puts in an Appearance
By David Shiga

 
On May 22, 2004, Comet LINEAR passed near the open star cluster M41 in Canis Major. Sirius is the bright star at the top of the frame. The image was shot at Hakos Farm in Namibia. Courtesy Michael J鋑er and Gerald Rheman.


 
 
Until late June, Northern Hemisphere observers can catch both Comets NEAT and LINEAR before they become difficult (or impossible) to observe. LINEAR (C/2002 T7) emerged from the Sun抯 glare in late May, and by early June had faded to about 4th magnitude. At this time its head was approximately 10 arcminutes wide, followed by a 1°-long tail. The comet is expected to fade to 9th magnitude by the end of June as it moves away from both the Earth and the Sun. It will also move lower in the evening sky throughout June until, in early July, it becomes unobservable from the Northern Hemisphere.
 
S & T illustration.


 
 
You can use our interactive sky chart to find Comet LINEAR in the dusk skies of the Northern Hemisphere during June 2004. The chart is set to 10:05 p.m. starting on June 1st 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.

Meanwhile, Comet NEAT (C/2001 Q4) glowed at magnitude 5.4 as of June 2nd, with a 10-arcminute-wide head and a 30-arcminute-long tail. This comet will likely fade to 7th magnitude by the end of the month, though it will remain high in the sky near Merak, the bottom-right star in the bowl of the Big Dipper.

Our interactive sky chart will also show Comet NEAT as it moves through Ursa Major during June and July 2004. The chart is set to 10:00 p.m. starting on June 15th at 40° north.

The past three years have each seen a comet of brightness comparable to that of NEAT and LINEAR, but not two at once. (The comets were C/2002 V1 NEAT, which peaked in February 2003 at magnitude 3.0, 153P/2002 C1 Ikeya-Zhang in April 2002 at magnitude 3.3, and C/2001 A2 LINEAR in June 2001 at magnitude 3.4.) In fact, since 1950, there have been only three other instances where two naked-eye comets have graced the sky simultaneously, and all three pairs were dimmer, between 5th and 6th magnitude.


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David Shiga is an editorial intern at Sky & Telescope.

T7可能是最后机会了，但Q4的观测条件还是很不错的，位置高，亮度也不算太低，一直在6.5等左右徘徊，下个月可能会降到8等，还是适合观测的。

K4的消息？？

K4正在变亮，而且位置也非常好，目前亮度约8等，整夜可见。

大家一共见过几次2001Q4彗星？

我至少见到10次，最后一次太暗不敢确认，如果算上就是11次了。

第一次：5月7日兰州北山（离学校800米）彗星在M47旁，3.8等，直径7-8’。
第二次：5月10日兰州交通大学宿舍（以下简称“宿舍”）小犬座β向α延长1倍，3.7等，8’。
11日，北山，3.7等。
15日，宿舍，位于M44旁，4.5等，6’。
16日，宿舍，位于巨蟹座γ北略偏西1度，5.0等。
17日，宿舍，位于巨蟹座γ北3-4度，5.2等。
18日，宿舍，位于巨蟹座ι旁，5.2等。
20日，宿舍，位于巨蟹座σ2σ3附近，5.3等。
21日，宿舍，位于巨蟹座σ3北2度，5.5等.
22日，宿舍，位于天猫座α以西3-4度，5.8等。

唯一的Q4照片，5月7日在兰州北山拍摄，当时Q4在天狼星左上方，M47旁边。右下的亮星是天狼星，50毫米标准镜头1.8光圈固定1分钟，400度胶卷。有的人说看不到彗星，有人却可以看到，大家试试看，能够看到的就是高手！

没有人试着在照片中找一找？

提示一下，彗星在照片中央偏右的位置。