Comet 62P/Tsuchinshan passed perihelion, the closest point to the Sun in its orbit, on 23 December last year, but is still showing nicely in Virgo in the late evening sky. It’s not a naked eye object and you will need good binoculars or a small telescope to see it.
The comet has a typical green ‘coma’ surrounding its nucleus, caused by excitation of diatomic carbon (C2) in its thin atmosphere. A faint tail has been seen but is now subsiding as the comet starts to recede from the Earth and Sun. During the next month or so, the comet will pass into the ‘realm of galaxies’, an area in Virgo peppered with faint nebula. It will be a challenge to distinguish the comet from these galaxies.
62P is also known at Tsuchinshan 1. The comet was discovered on 1 January 1965 at the Purple Mountain Observatory in Nanjing, China. It orbits the Sun approximately once every 6.2 years, journeying out beyond Jupiter. At its nearest to the Sun, its orbit brings it no nearer than a point between the Earth and Mars.
The brightness of a comet is very difficult to predict, as it depends on the scattering of sunlight from dust in the comet’s coma and tail. The amount of dust varies as the comet rotates and as its distance from the Sun changes. This often results in sudden increases in the comet’s brightness, known as outbursts, as gases sublime from the from the nucleus, bringing dust with it. Comet 62P/Tsuchinshan will probably be around magnitude 9, fading to 10 in the next few weeks.