It’s a phrase that’s often repeated but at least now it’s especially true…. You wait patiently for something and all of a sudden there are several at once – buses, opportunities, or in this case, Comets.
Comets are interstellar wanderers, spending most of their lives living in the frozen outer reaches of the Solar System, well beyond Neptune, merrily orbiting the Sun, minding their own business. Occasionally though, their peaceful existence gets perturbed by the gravity of other objects – perhaps they come too close to a large asteroid, perhaps they have a collision with some of the other remnants of the formation of the Solar System and as a result, their quiet, mundane orbits are transformed and they are sent on a new journey – into the inner Solar System where they can come close to the other Planets and eventually the Sun.
As it gets closer to the Sun, the “dirty Snowball” (a description for comets coined by American astronomer Fred Whipple) warms and the ices that make up a good portion of its mass are transformed into vapour and stream away from the comet – creating the familiar beautiful, awe inspiring tail.
Comets often used to be thought of as “portents of doom” since they appeared apparently from nowhere and occasionally coincided with major events. We, of course, now know this is all coincidence, but Comets are still a big deal – especially the ones that are bright enough to be seen with the naked eye. And to the point – this winter we have at least two good comets coming in and maybe, just maybe, one of them will be bright enough to be visible to the naked eye.
Firstly, in the next few weeks, we have a comet known as C/2021 A1 ( Leonard ) – which makes its closest approach to the Sun around the turn of the year. Its currently a binocular object but "might" get bright enough to see with the naked eye by the end of the year... Over the next couple of weeks it can be found under the plough so is best seen in the hours before morning twilight as it moves westwards. (graphic Stuart Atkinson)
Secondly, we have the return of the comet 67P/Churyumov-Gerasimenko which you may remember was the one that the wonderful European Space Agency's Rosetta probe visited back in August 2014 and the lander, Philae, bounced around the comet's surface in November 2014, becoming the first spacecraft to land on a comet nucleus. This is still going to be faint - it needs binoculars to be seen at Magnitude 8 but its an interesting one to keep an eye on.
You might remember that last year we were treated to the amazing sight of Comet C/2020 F3 (NEOWISE) in the autumn twilight sky, this one was unexpected and bright and was probably the best northern Hemisphere comet we have had for more than twenty years...
We say could, because comets are notoriously fickle things, but watch this space, things could get even more interesting “up there”.