NASA JPL

It has been a month since the discovery of the first Russian comet, and tonight the Minor Planet Center has released a circular with a refined, official comet orbit. The eccentricity is greater than one, which means the comet has a hyperbolic orbit. The perihelion date is September 9, 2011 with a precision of +/- 1.7 days. The perihelion distance is 0.4762 (+/-0.008 a.u.).

Changes in the orbit did not favorably affect estimates of the maximum brightness of the comet; now it is estimated at mag. 6-8. So the comet will be accessible for observations by binoculars and spotting scopes, but it is possible that it will also be observable with the unaided eye by people located far from city lights in places where the atmosphere is also stable and transparent.

The maximum brightness of the comet will be ten days after perihelion, but at that moment the comet will not be observable from Earth – it will be at conjunction with the Sun. After the comet emerges from conjunction, by the beginning of October, the brightness of the comet will have already have slowly begun to fade. The come will come closest to the Earth, a distance of 0.27 a.u. (40.5 million km.), in the middle of October. By the end of the year, the brightness of C/2010 X1 may fall to mag. 14-16, in other words, the practical limit for visual observations in larger amateur telescopes. In moderate-sized telescopes equipped with color CCD cameras, the comet will be observable for another whole year after its closest approach to the Earth.

At the moment there are 67 comets known with hyperbolic orbits and a perihelion inside the orbit of the Earth. The most recent of them, C/2009 R1 (McNaught), was observed at our observatory in the middle of June 2010. In this list you will notice the beautiful comets C/2006 M4 (SWAN) and C/2006 P1 (McNaught), the first of which decorates the top of our site. At the moment, comet C/2010 X1 (Elenin) is in third place in this list according to the size of its eccentricity.

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