Comets have been described as dirty snowballs that usually live at the extreme edge of the solar system. Millions of them orbit the Sun in an area known as the Oort cloud but occasionally one of them will get deflected from its orbit and begin to fall in toward the Sun. This journey sometimes takes millions of years. As they get closer to the Sun their speed increases and the heat from the Sun begins to vaporise the comet and produce the characteristic tail. It is only when the comet comes close to the Sun does it become visible from Earth.
There is a comet in the night sky at the moment. Comet C/2015 V2 Johnson was discovered on 3 November 2015 by Jess Johnson. It will reach its closest point to the Sun on 12 June this year but its closest point to the Earth is this coming week.
It won’t be visible to the naked eye but it can be seen with binoculars or a small telescope as it passes through the constellation of Bootes.
To find the comet first locate the Plough which at the moment is directly overhead. The Plough looks a bit like a saucepan with four stars making the bowl of the saucepan and three stars curving away to form the handle. Follow the curve of the handle down toward the horizon and you will come across a bright red-coloured star called Arcturus). Arcturus marks the bottom of Bootes and the rest of the constellation forms a kite-like figure stretching away from Arcturus.
For the next few weeks the comet will pass through the kite-like shape of Bootes toward Arcturus.
Its orbit brings it from above the Earth and sweeps below us before heading back out into space to return again in 14.4 million years’ time.
Even at its closest point to the Sun it never gets closer than between the Earth and Mars which unfortunately keeps it from glowing very brightly but it has developed a rather nice tail.
Comets are notoriously unpredictable and it could suddenly flare up and become brighter. It should remain visible in our sky throughout the summer until it eventually passes into the Southern Hemisphere.
Try and see comet Johnson as this is the best chance of spotting a comet’s tail for quite a few years.