Reply To: A good year for Japanese astronomers

Forums Comets A good year for Japanese astronomers Reply To: A good year for Japanese astronomers

Nick James

The Japanese are very dedicated observers. The key strategy for amateur comet discovery is to scan the morning twilight since if a comet is in the right orbit it may appear here without being detected by the surveys. The attached plot shows the elongation of this comet, i.e. how far it appears to be from the Sun in the sky, as the purple line. The comet’s distance from the Sun and distance from the Earth are shown by the green and blue lines respectively. These lines are based on astrometry of the comet up to August 18 assuming that the orbit is a parabola, i.e. e=1.

You can see that the comet has been at an elongation of < 40 deg since the beginning of May and that Nishimura discovered it as it reached around 34 deg rising out of the morning twilight. As it approaches perihelion in September the elongation will drop rapidly and when the comet is at its brightest in September it will only be 12 deg or so from the Sun. To see it then you will probably want to be high up a mountain but we'll see. The surveys could have picked it up back in April when the elongation was much larger but it was then over 3au from the Sun and so would have been much fainter. I would expect that, once we have a better orbit, we'll find it somewhere in the survey data.