If you have clear skies and are willing to brave the chilly temperatures, you might want to head to a dark site and look for a passing visitor.
Comet 46P/Wirtanen, first discovered in 1948, will have its closest encounter with Earth on Dec.16. But it’s already visible in the sky.
While this is the brightest comet of the year andÂ theÂ 10thÂ closest comet in modern times,Â don’t expect one with a well-defined tail, a hallmark of comets.
At the moment, Wirtanen â€” a small comet at just 1.2 kilometres in diameter â€” is a fuzzy, bluishÂ object in the southern sky. Recent photos do show a thin tail, but nothing very pronounced. Wirtanen will likely brighten as it makes its closest approach to the sunÂ on Dec. 12.
Comets, often referred to as “dirty snowballs,” are leftover collections of dust, gas and ice from the formation of our solar system. Most are from two regions â€” the Kuiper Belt and the Oort Cloud â€” at the outer edge of our solar system. Once in a while they get knocked out of these regions and begin a voyage around the sun.
As a cometÂ approaches the sun, its ice sublimates (changes directly from a solid to a gas, skipping the liquid phase), which produces its characteristic tail. A comet’sÂ brightness dependsÂ on its size and how much ice and gas it contains.
Where to look
The brightness of celestial objects is on a scale that goes from the very brightest â€” the sun â€” to the dimmest. And it doesn’t go in the direction you’d think: the lower the number (negative values) the brighter the object.
At the moment, 46P/Wirtanen is near magnitude 4, so not quite visible to the naked eyeÂ in light-polluted skies. It’s estimated thatÂ when Wirtanen is at its closest position to Earth, on Dec. 16, it should reach a magnitude of 3.
So, if you’re heading out to catch a glimpse of the comet, make sure you try to get to as dark a location as possible. And don’t look at your phone.Â Allow your eyes to adjust to the darkness, which in turn allows you to see dimmer objects.
If you have a pair of binoculars, use them.
Look to the southern sky, where you’ll find the very recognizable constellationÂ Orion, known as the hunter. On Dec. 8, WirtanenÂ will be about 32 degrees to the right of Rigel, the brightest star in Orion’s “foot.” You can use your fingers to measure the distance.
What you’re likely to see, should you find it, is aÂ fuzzy, bluish circle. Over the next week, the comet will continue to rise higher in the sky. OnÂ Dec. 16, it will be near theÂ Pleiades, a cluster of stars visible to the naked eye.
The downside is that the moon will be 65 per cent illuminated on Dec. 16, making it difficult to seeÂ Wirtanen. However, itÂ will set around 1 a.m., so perfectÂ for night owls hoping to get a glimpse.