BY now most people will have at least heard about a comet that’s heading our way.
Comet Panstarrs is expected to be visible to the naked eye over the coming few weeks and, like all comets, it gets its name from its discoverer, the Pan-STARRS telescope located on the island of Maui in Hawaii.
Considered to be a non-periodic comet, as it probably took millions of years to come from the outer reaches of the solar system, once it rounds the sun its orbit is predicted to shorten to only 110,000 years.
Although comets are notoriously difficult to predict how they may appear in our skies, Panstarrs has a number of things in its favour.
When it was discovered back in June 2011 it was almost as far out as the orbit of Saturn.
Although only the largest telescopes could glimpse it at this time, the fact that they could at all means it might be large.
Also, by the time it had reached Jupiter’s orbit it was starting to show some activity.
And finally, its closest approach to the sun is quite close by cometary standards so it will heat up a lot more.
To give you an idea on how much activity, a comet is essentially a frozen mix of ices and dust and as it gets close to the sun the ices vaporize and create a cloud of gas that surrounds the comet, known as a coma.
Last time Comet Halley was around it had a coma about 100,000km across at its best.
In October 2012, long before it was anywhere near the sun, Comet Panstarrs’ coma was estimated to be already about 120,000km across.
With all this in mind, Comet Panstarrs may brighten to roughly the equivalent of Venus.
In other words, second only to the moon in the night sky.
Although it will pass closest to the earth on March 5 at a distance of roughly 150 million kilometres, it will come closest to the sun on March 10 March and be about as close as Mercury’s orbit from the sun.
Although these dates are still a couple of weeks away, possibly our best and brightest views will occur in late February to early March. At this time it will be low in the evening twilight sky but after the 10th our view of the tail becomes quite poor as it will be almost parallel to the horizon.
The tilt of Comet Panstarrs’ orbit with respect to the earth’s is nearly perpendicular, which means it will rapidly move from south to north and out of view.
So if the weather is kind and you find yourself outside at sunset, see if you can’t spy within the twilight this year’s best comet.