Just four days after it passed in front of the Pleiades star cluster, the moon will cross paths with another noteworthy celestial object on Monday evening, Jan. 13, when it will cover the planet Mars, now shining as bright as it will get in this new year of 2025.
An opportunity to see the moon occult a bright planet at night does not happen too often; for Mars, a specific location on Earth can see it happen (on average) once about every 14 years. So, if you are fortunate to live in the occultation zone and the weather cooperates, this upcoming event is one that really should not be missed.
The moon will be mere hours past full phase during the occultation. Traditionally, the January full moon is known as the "Wolf Moon." At the moment it officially turns full — 5:27 p.m. EST (2227 GMT) — it will be diametrically opposite to the sun in the sky. By sheer coincidence, Mars is also opposite to the sun, though its actual moment of "opposition" will not come until late on Wednesday, Jan. 15. Still — both objects, the moon and Mars will be near enough to each other so that during Monday evening, the moon will temporarily hide the planet from view, and much of North America has a ringside seat to observe it.
Mars no match for the moon
Looking for a telescope for the next night sky event? We recommend the Celestron StarSense Explorer DX 130AZ as the top pick for basic astrophotography in our best beginner's telescope guide.
The zone of visibility for this event encompasses practically all of the contiguous (lower 48) United States, as well as much of central and eastern Canada. Since Mars will be near opposition when it has its lunar rendezvous, it will be shining at its very brightest for this current apparition; glowing at magnitude -1.3, just a trifle less prominent compared to the brightest star in the sky (Sirius).
And yet, just before Mars disappears and later reappears from behind the moon, it likely will be overwhelmed by the moon's brilliance. The moon will be nearly 40 thousand times brighter than Mars, so in order to actually see it vanish or reappear you will need a telescope or at the very least, good binoculars. Be sure to also check out our guides for tips on how to photograph the planets or photograph the moon during this lunar occultation.
A few hours before, or after the occultation however, Mars will be plainly visible with unaided eyes, glowing brightly near to the dazzling disk of this first full moon of the winter season. People, who are unaware or have no advance notice will almost certainly wonder, as they cast a casual glance toward our nearest neighbor in space on this second Monday in January, just what is that "bright orange-yellow light"?
Sometimes, such occasions bring with them a sudden rash of phone calls to radio and television stations, local planetariums, weather offices and police precincts. Not a few of these calls excitedly inquire about "the mysterious UFO" (or nowadays, maybe a drone?) that's closely hovering in the vicinity of our natural satellite!
A gradual fade-out
Unlike a star which is a pinpoint of light and would disappear and reappear in an instant, Mars appears as a small disk in telescopes; owing to its relatively large angular size (14.6 arc seconds in diameter), the occultation will occur at a rather "leisurely" pace. So, the disappearance of Mars behind the moon's bright limb for most places, will take anywhere from about 30 seconds to almost a minute (or even longer in locations where the moon's limb approaches it obliquely at a slant).
From Washington D.C., for instance, the moon's slow eastward drift will take about 30 seconds to completely cover the planet's disk. The planet's reappearance will also be gradual. Moving to the east against the background stars at its own apparent diameter each hour, the moon will appear to approach Mars from the west (right) and ultimately pass in front of it, and then shortly thereafter, uncover it, and leave it behind as the moon continues to move to the east.
Grazing circumstances
In the United States, the northern limit of visibility for this occultation will pass southwest-to-northeast through Jefferson and Clallam counties of Washington state, including Olympic National Park, as well as nearby Skagit and Whatcom counties. Here, along a strip measuring approximately 25 miles (40 km) wide, a spectacular partial occultation will be visible in which Mars' disk will be seen skirting the edge of the moon. For instance, Port Angeles, Washington will be within this zone and will be able to see the moon partially cover Mars for roughly 7 minutes starting at around 6:27 p.m. Pacific Time.
To the north, outside of this zone, for places such as Vancouver Island, Mars will appear to barely miss touching the limb of the moon.
Meanwhile, the southern limit of the occultation will skirt the Florida Keys.
Schedule of events
The table below provides the specific details for 16 selected U.S. cities. Civil times of Mars' disappearance and reappearance from behind the moon are provided. Both the disappearance and reappearance of the planet, can last anywhere from 30 seconds to over a minute, depending on whether Mars passes centrally behind the moon (and is covered for an hour or more) or, as is the case for Seattle or Miami, near its outer rim at a slant (and is covered for less than a half hour).
Disappearance and reappearance times are for Mars' center. The Table was adapted from data provided by the International Occultation Timers Association (IOTA). This webpage provides specific disappearance and reappearance information in Universal Time for over 600 locations in North America and western and central Africa. It is also accompanied by a Mercator map which shows the region where the occultation will be visible.
In addition to the timetable, we have also prepared a diagram which depicts the path behind the moon that Mars will take for seven cities: Seattle, Los Angeles, Helena, Dallas, New York. New Orleans and Miami.
The next favorable occultation of Mars for North America will take place on Feb. 5, 2042. The moon will be a waning gibbous about 4 hours past full. Mars comes to opposition the very next day.
All Mars oppositions are not alike
Mars travels a little more than half of its orbit each year, and thus has oppositions every 2 years plus about 50 days (its "synodic period"). Prior to 2025, the last opposition was Dec. 8, 2022; after 2025, the next will come on Feb. 19, 2027. It reaches opposition this year at 9:31 p.m. Eastern Time on Jan. 15.
On the average, Mars is 48.2 million miles (77.6 million km) away when Earth passes it. In 2025, Mars will be farther-than-average from Earth. On Jan. 12 at 8:37 a.m. Eastern Time, Mars will be 59.7 million miles (96.1 million km) away. The greatest distance occurs when the Earth passes Mars at a time when the planet is farthest from the sun.
Such a circumstance will happen in 2027: On March 4 of that year, Mars will be at aphelion, its farthest point from the sun. Less than two weeks earlier, as the Earth passes Mars in our respective orbits, they will be separated by as much as 63 million miles (101.4 million km); that will be the greatest distance for any opposition since 1948.
The minimum distance occurs when the Earth passes Mars at a time when the planet is at the point in its orbit nearest the sun (perihelion). These exceptionally close approaches — called perihelic oppositions — occur at intervals of 15 or 17 years. They always occur in either August or September, since the Earth passes the point on the orbit of Mars nearest the sun about this time of year.
One of the closest approaches of Mars in nearly 60,000 years occurred in 2003, when on Aug. 27, Earth passed Mars at a distance of only 34,646,000 miles (55,746,000 km). At that time, Mars appeared nearly 42% larger and shone nearly four time brighter than it appears in our current night sky!
The next perihelic opposition will occur in September 2035. Mark your calendars!
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications.
Editor's Note: If you snap a good photo of the celestial pair and would like to share it with Space.com's readers, send your photo(s), comments, and your name and location to spacephotos@space.com.
