Winter Weather Advisory

Comet 46P to glow green in weekend sky during close encounter with Earth

By Brian Lada, AccuWeather meteorologist and staff writer
December 16, 2018, 4:55:39 AM EST

This weekend will feature an uncommon scene in the night sky as a comet glides past the Earth.

Comet 46P/Wirtanen is a small comet that has been growing brighter over the past few weeks.

People who missed the opportunity to see the comet on Saturday night will have another chance to view it on Sunday night.

“On Dec. 16, 46P will be only 7.2 million miles from Earth and will reach an estimated naked eye magnitude of 3 to 7.5, making this comet’s pass the brightest predicted and the brightest close approach to Earth in over 20 years,” NASA said.

This will be the 10th-closest distance that a comet has come to the Earth since the start of the space age in the 1950s, according to the University of Maryland. Despite its close approach, there is no threat of it colliding with the Earth or the moon.

Comet 46p

Comet 46p/Wirtanen as seen from Kaua`i, Hawaii. (Photo/Jim Denny)

Comet 46P will not look like famous comets, such as Halley’s Comet or Comet Hale-Bopp, but it should be bright enough to see from darker spots.

Those looking for it in light-polluted areas, such as Chicago or Los Angeles, may have a difficult time seeing it without the help of a telescope or binoculars.

The comet will look like a bright, slightly green star with a diffuse glow surrounding it.

3 tips for stargazing without a telescope
AccuWeather Astronomy Facebook page
Otherworldly sound of wind on Mars is captured by NASA spacecraft

“It’s not expected to have a big spectacular tail; it’s going to be a smear,” said Matthew J. Holman, senior astrophysicist and director of the Minor Planet Center at the Harvard-Smithsonian Center for Astrophysics.

“It may not be obvious to people what they are seeing, and they may need to use what we call averted vision, meaning you don’t look right at the thing, but you look away from it and look in your peripheral vision,” Holman said.

“Your peripheral vision is more sensitive to light and dark, and so with a little practice, you can see a faint thing in the sky with your averted vision that you can’t see when directly looking at it,” Holman added.

Those with a telescope or pair of binoculars will be able to glean a better look at the celestial object as it glides past the planet.

Where to see Comet 46P in the night sky

Since the comet is making a speedy flight past the Earth, it will appear in a different part of the sky each night.

A sky chart showing the comet's location in the night sky can be found below.

It will be easiest to see on Sunday night on its closest approach to the Earth. This is when it will be at its brightest and will be sitting between the famous constellation Orion and the Pleiades star cluster.

nasa comet viewing .gif


People hoping to see Comet 46P may want to check their local weather forecast and plan accordingly as clouds may interfere with viewing conditions.

"The best viewing will be found in the Rockies and central U.S., where chilly but clear conditions are expected through the weekend," AccuWeather Meteorologist Faith Eherts said.

"A storm impacting the eastern U.S. this weekend means many stargazers from the mid-Atlantic to southern New England could have trouble seeing the night sky," Eherts said.

"In the West, coastal areas from San Francisco northward as well as most of the Pacific Northwest will be encased in clouds," Eherts added.

If it’s too cloudy to see the comet over the weekend, onlookers should be able to see the comet on the days immediately following its close pass. However, it will gradually grow dimmer through the second half of December as it moves away from the planet.

Sunday night viewing Dec 15

Folks heading outside to look for Comet 46P should also keep an eye out for a few shooting stars.

Although the Geminid meteor shower peaked on Thursday night, onlookers may still be able to spot some meteors through the weekend.

Comet 46P 12.16 AM

Comet 46P/Wirtanen is less than a mile across, just a fraction of the size of famous comets such as Halley’s Comet and Comet Hale-Bopp.

“Even though it’s only [0.6 of a mile] across, it’s coming so close to us that telescopes will allow people to observe things that they don’t typically get the opportunity to observe,” Holman said.

“This is a really great opportunity because this is far brighter than most comets that are studied,” Holman said.

After Comet 46P/Wirtanen passes, the next comet to make such a close approach to Earth will be 249P/LINEAR 53 on Nov. 4, 2029.

A sky chart showing the location of Comet 46P in the night sky into early January:

big pictures sky and tellescope.jpg

(Image/Sky & Telescope)

Questions or comments? Email Brian Lada at and be sure to follow him on Twitter!

Report a Typo


Comments that don't add to the conversation may be automatically or manually removed by Facebook or AccuWeather. Profanity, personal attacks, and spam will not be tolerated.

More Weather News