A Stargazers’ Guide to Watching the Full Moon Pass Mars and the a New Come

The first full moon of the year will glide through the sky on Monday night. For lucky stargazers in some parts of the world, it will also pass in front of the more-brilliantly-red-than-usual Mars in an event known as a lunar occultation.

But that’s not all January’s sky has to offer. A new comet, expected to be the brightest of the year, is nearing its closest approach to the sun on Monday — though spotting it, at least in northern skies, will be tricky.

What is a lunar occultation?

According to NASA, a lunar occultation occurs when the moon passes in front of an object, like a distant planet, that appears much smaller in the sky. An occultation is similar to a solar eclipse — when the moon obscures the sun — but much less grand.

Lunar occultations can happen several times a year and when the moon is in any phase. Earlier this month, a crescent moon that slipped over Saturn was visible for people in Europe, northern Africa and parts of Greenland and Russia.

What’s special about this one?

Mars has been appearing bigger and brighter in the night sky as it nears Earth. It is approaching what is known as opposition, which occurs when Mars is on the opposite side of Earth as the sun. During opposition, Mars is closer to us than usual and its face is fully lit by the sun as viewed from our world, making for spectacular views of the Red Planet.

Mars is in opposition every 26 months. This year, it reaches opposition on Jan. 15 at 9:32 p.m. Eastern time. But the planet has been steadily growing more brilliant since November.

How can I see the lunar occultation?

Only people in North America and parts of Africa will be able to see the moon occult Mars on Monday. Elsewhere, Mars will just appear close to the moon, a celestial occurrence known as a conjunction. The occultation will last for more than an hour in some places and be visible with the unaided eye, though binoculars or a telescope will enhance the view.

The event will begin at different times, depending on where you live. According to a chart published by the International Occultation Timing Association, Mars will disappear behind the moon on Monday at 6:21 p.m. in Seattle, 9:16 p.m. in Washington, D.C. and 9:21 p.m. in New York City, all local times. Observers in Montreal will see the occultation start at 9:25 p.m., and in Accra, Ghana, at 4:53 a.m., before sunrise on Tuesday.

What about the comet?

Comet ATLAS, or C/2024 G3 to astronomers, was spotted last April by the Asteroid Terrestrial-impact Last Alert System and shares the name of many other comets discovered by the network of telescopes, including Tsuchinshan-ATLAS, which blazed through the sky last October.

Like all comets, C/2024 G3 is a frozen chunk of material left over from the formation of the solar system that has begun to melt as it approaches the sun. It will reach perihelion, or its closest approach to the sun, on Jan. 13, and come within 8.4 million miles of the solar surface.

Some comets disintegrate from the heat. But if they survive the encounter, perihelion is when they are expected to be brightest — though being so close to the sun can make them difficult to see.

How can I see Comet ATLAS?

Some observers in the Northern Hemisphere have already spotted Comet ATLAS, a fuzzy dot with a short tail, low on the eastern horizon before sunrise. Because of its altitude and the light of dawn, it is difficult to see, especially without binoculars or a telescope.

Closer to perihelion, those with an unobstructed view of the western horizon may be able to catch the comet in the evening near the setting sun. Interactive star maps like this one can help with figuring out where and when to look.

If Comet ATLAS survives perihelion, it will migrate to skies in the Southern Hemisphere in the latter half of January, and be visible there in the evenings after sunset. As the comet moves away from the sun it will climb higher in the sky, but also grow dimmer each day.