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LASCO SOHO专家 K.B发布的2006P1资料和预测
December 26, 2006 -- We know when, we just don't know how bright...
For those of you who follow the goings-on in the world of comet astronomy, you may have noticed that one particular object has been the source of much discussion recently. That object is the comet C/2006 P1 (McNaught). It was discovered on August 7th, 2006 by the hugely successful comet discovered Rob McNaught (Siding Spring Survey), and is the 31st comet to bear his name. (Admittedly, the SOHO satellite scoffs at such a small tally, but among us humans it's a formidable achievement.) At time of discovery, the comet was a very faint mag17 object, but the published orbit -- giving a perihelion distance of just 0.17AU and a perihelion date of January 12, 2007 -- indicated that the object has the potential to be a very bright object indeed. The question was, and still remains, just how bright will it be?
Ordinarily, (pre-perihelion) estimates of a comet's maximum brightness are accurate to within a magnitude or two, often better. In the case of this comet, however, I have seen estimates that range from magnitudes of +6 to -5! So why the huge uncertainty? Well, the single biggest problem is that for several weeks the comet has been at a small elongation (apparent proximity to the Sun as viewed from Earth) and so it has been extremely difficult for observers to get good measurements of it. (Important aside: Never, ever, point a telescope at or near the Sun without the correct solar filters!!)
So nobody really knows just what this comet will look like at its closest point to the Sun... and that is where SOHO comes in! As you are probably aware, the LASCO instrument on-board SOHO has the ability to watch comets as they get extremely close to the Sun. Fortunately for us, C/2006 P1 is going to pass right through the LASCO C3 field of view in just over two weeks' time!
The image opposite (click for a larger version) shows the expected track of the comet through LASCO C3. Unfortunately this object will not come close enough to the Sun for it to also be in the C2 instrument field of view, but hopefully we will get a spectacular view of the object, maybe even rivaling the comet NEAT or comet Bradfield passages through LASCO C3!
The comet will appear in C3 at around 1000UT (0500 EDT) on January 12th (a few hours before perihelion) in the upper-left of the images and travel almost vertically down, exiting C3 in the lower-left at roughly 0300UT on January 16th.
It is worth making one final note that this comet should also be visible in the "Heliospheric Imager 1 (HI-1)" instrument on STEREO-A spacecraft. However, while these images will be publicly available, we do not currently have processing routines in place to produce a regular stream of "pretty pictures" from any of the STEREO instruments. I will try and post some HI-1/A images of this comet as soon as we have them. |
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