One of the most eagerly anticipated comets in recent history, Comet ISON, is currently making its final swoop in towards the Sun. Astronomers around the world will be watching closely to check how it performs as it flies perilously close to our home star before heading away again. Here’s a simple guide to help YOU find Comet ISON plus two other comets visible right now. (Update: See our newer post to follow Comet ISON in December.)
When ISON was discovered from Russia, more than a year ago, while still in the depths of the Solar System, there were optimistic predictions that it might become as bright as the Moon and be visible in the daylight sky at its best. The Hubble Space Telescope made a movie of ISON while it was still beyond the orbit of Mars.
Since then, its brightening has been slower than expected as it heads for closest approach, an event dubbed perihelion, on 28 November. Throughout early November, it was only visible with the aid of binoculars or a telescope if you knew just where to look. However, in the last couple of days, Comet ISON, also known as Comet C/2012 S1, has suddenly brightened noticeably by a couple of magnitudes, making it easier to spot and theoretically visible to the unaided eye in a dark sky before dawn. Astronomers have been taking some fine images of its tails of gas and dust.
Unfortunately a bright Moon is beginning to encroach on the morning sky which will impede visibility. However, hopes are still high that it will continue to brighten and develop a longer tail so that it presents a pre-sunrise spectacle in late November. The only way to find out is to look, so the accompanying star chart, produced with the aid of the software Carte du Ciel (Skychart), will help locate it.
The chart shows the constellations visible in the southeastern sky before dawn. Comet ISON is visible low in the East as it travels through the constellation of Virgo, passing close to its brightest star Spica (alpha Virginis) on 18 November, and then heads into Libra as it nears the Sun. (Use the accompanying figure to find Spica by following the curve of the handle of the Big Dipper/Plough). Unless the comet becomes extremely bright, you will need to find it before the twilit sky gets too bright. Binoculars will help, but you MUST stop using them at sunrise as the Sun’s light can seriously damage your eyes if you should accidentally point at it.
Comets are unpredictable and no one really knows what will happen to Comet ISON as it rounds the Sun. It is hoped that it will emerge from its solar encounter looking spectacular with a long and brilliant tail, but some experts fear it will not survive its brush with the Sun.
You will notice that the chart shows not one but two comets. That is because, by coincidence, a more regular visitor called Comet Encke (2P/Encke) is also rounding the Sun this month, with its own perihelion date occurring on 21 November.
Unlike Comet ISON, which is on what is probably its first trip into the Solar System from a region far beyond Pluto called the Oort Cloud, Encke has long been known, having been discovered by Pierre Mechain in 1786, and orbits in only 3.3 years. It is a comet that astronomers believe originally arrived from deep space but had its orbit changed significantly by the planets, particularly Jupiter.
Comet Encke is fainter than Comet ISON and is not expected to become brighter than 6th magnitude, meaning you will need binoculars to glimpse it before twilight becomes too strong. But you should have no trouble finding our third bright comet visible in the sky right now because it is far from the Sun and so may be found much earlier in the morning in a darker sky.
Comet Lovejoy, also known as C/2013 R1, was already just visible with the unaided eye in early November and is expected to reach 4th magnitude later in the month as it heads for perihelion on Christmas Day, 25 December.
Comet Lovejoy was discovered on 7 September by Australian amateur astronomer Terry Lovejoy when it was only 14th magnitude. But it will not be hard to find as it travels below the familiar shape of the Big Dipper or Plough, part of the constellation of Ursa Major. An easy target for your binoculars.
This comet takes around 7,000 years to orbit the Sun.
The tracks for all three comets are indicated by little comet symbols to show their positions at 0h UT on the dates in November marked. These tails are purely symbolic. In reality, comets’ tails point away from the Sun as the solar wind pushes them out into space.
★ Keep up with space news and observing tips. Click here to sign up for alerts to our latest reports. No spam ever - we promise!