On Monday evening, the first full moon of the year will slide across the sky. For lucky stargazers in some parts of the world, it will also pass in front of a brighter red Mars than usual in an event known as a lunar occultation.
But that’s not all the January sky has to offer. The new comet, expected to be the brightest this year, makes its closest approach to the sun on Monday – although spotting it, at least in the northern sky, will be difficult.
What is a lunar occultation?
According to NASA, a lunar occultation occurs when the Moon passes in front of an object, such as a distant planet, that appears much smaller in the sky. An occultation is similar to a solar eclipse – when the Moon blocks the Sun – but is much smaller.
Occultations of the Moon can occur several times a year and when the Moon is in any phase. Earlier this month, a crescent moon that slipped over Saturn was visible to people in Europe, North Africa and parts of Greenland and Russia.
What is special about this?
Mars appears larger and brighter in the night sky as it approaches Earth. It is approaching what is known as opposition, which occurs when Mars is on the opposite side of the Earth from the Sun. During opposition, Mars is closer to us than usual and its side is completely illuminated by the sun as seen from our world, creating spectacular views of the Red Planet.
Mars is in opposition every 26 months. This year, it reaches opposition on January 15th at 9:32 PM ET. But the planet has been steadily getting brighter since November.
How can I see a lunar occultation?
Only people in North America and parts of Africa will be able to see the occult moon Mars on Monday. Elsewhere, Mars will only appear near the Moon, a celestial phenomenon known as a conjunction. The occultation will last more than an hour in some places and will be visible to the naked eye, although binoculars or a telescope will improve the view.
The event will start at different times depending on where you live. According to a map published by the International Occultation Timing Association, Mars will disappear behind the Moon on Monday at 6:21 PM in Seattle, 9:16 PM in Washington, DC, and 9:21 PM in New York City, all local times. Observers in Montreal will see the occultation begin at 9:25 p.m., and those 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 its name with many other comets detected by the network of telescopes, including Tsuchinshan-ATLAS, which last flashed across the sky in 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 January 13 and come within 8.4 million miles of the Sun’s surface.
Some comets disintegrate from the heat. But if they survive the encounter, they are expected to be at their brightest at perihelion – although they are hard to see so close to the sun.
How can I see comet ATLAS?
Some Northern Hemisphere observers have already spotted Comet ATLAS, a faint dot with a short tail, low on the eastern horizon before sunrise. Because of its altitude and the dawn light, it is difficult to see, especially without binoculars or a telescope.
Closer to perihelion, those with an unobstructed view of the western horizon might catch the comet in the evening near the setting sun. Interactive star charts like this one can help you determine where and when to look.
If comet ATLAS survives perihelion, it will migrate to the southern hemisphere sky in the second half of January and will be visible there in the evening after sunset. As the comet moves away from the sun, it will climb higher in the sky, but will become fainter every day.
