2018 will end with a naked eye level comet, predicted to be bright enough to be seen with the naked eye when it makes its closest approach on December 16! While this will by no means be considered a “great comet,” it will still be the brightest comet of the year! Read on and find out how to look!
Most comets are very dim and are even hard to spot in telescopes. It is mainly due to their size, their distance from the Sun, and their distances from Earth ie the closer the brighter! The comet known as 46P/ Wirtanen will have its perihelion on December 14, and make its closest approach on the night of December 16.
Wirtanen is a very small comet, only 3/4 of a mile across! It has a short orbit, and even though it never gets further than Jupiter, it usually isn’t a very noticeable comet in the sky due to its small size. But the approach to Earth on December 16 will make it much easier to spot! Wirtanen will be 7.2 million miles away, which may seem far, but considering the nearest planet is currently 40 million miles away, it will be very close!
How Bright Will it Be?
To understand the brightness, it helps to know what apparent magnitude means. Apparent magnitude is how bright objects appear in the sky, and the lower the number, the brighter – hence a magnitude 1 is brighter than magnitude 2. Under rural and suburban skies, your naked eye level limit is around magnitude 6. From a city sky, it drops to mag. 4 as long as the skies are clear.
Currently, Wirtanen is around mag. 4 as of 12/13, and it is predicted to reach as bright as mag. 3.8 on the night of its close approach. This means it should be as bright as the Orion Nebula – which can be glimpsed with the naked eye under suburban skies with good conditions.
But not so fast!
Remember that you’re not looking for a sharp star-like object, but rather for something that is spreading light out over a wider area. A magnitude 4 star, which is a sharp point can be spotted easily from the city skies, but a diffuse object will be much harder to spot.
The comet will appear ghostly, even under dark skies.
The comet is still practically invisible from heavily light polluted skies, so places deep within large cities like Griffith Observatory in Los Angeles will NOT be able to see it! If you come up to the observatory expecting to see it, we’ll just tell you to go to the mountains and deserts!
My home location is not as bright, as it is transitioning from city to suburban skies, but it is still light polluted. From my location, I can spot the comet with my 8″ telescope but it appears very dim. Long exposure on the other hand does brighten it up, and shows the distinct green color.
If you want your best chances at spotting the comet with just your eyes, get away from the cities and/or get in touch with someone that has a telescope or a good pair of binoculars.
So Where Do I Look?
The comet will be well positioned in the southern skies over North America. Currently, the comet is in the constellation Cetus, and it is approaching Taurus. You can use the following maps to find it near familiar stars. These maps come from Comet Watch – you can click here to go to the page containing more maps and info on the comet!
On the night of the close approach, the comet will be near a very familiar star cluster, the Pleiades! It will be between the main stars of Taurus, which has the bright orange star Aldebaran, and the Pleiades. Taurus will be visible in the eastern sky after nightfall, and be high up in the southern sky around 9:30 pm, along with Orion and the other winter constellations.
The following is a simulated image showing you where to look on December 16. The comet will not appear as big or as bright as the image simulates, it’s just there to help you find it!
The Moon will gradually become more prominent near the peak days, which may wash the comet. However, if you have a beautiful clear sky, the chance to spot a comet, and add the fact that the Geminids meteor shower will also be just after their peak, these factors make good excuses to go outside and look up!