Special to CosmicTribune.com, January 13, 2025
Excerpts from weekly Sky&Telescope report.
SUNDAY, JANUARY 12
■ Mars is nearest to Earth tonight, appearing 14.6 arcseconds wide and magnitude –1.4. That’s as bright as Sirius, which sparkles whitely about four fists to Mars’s lower right in early evening, and directly below Mars when they’re highest around midnight or 1 a.m.

Once Mars and Sirius are both high above differential atmospheric effects, compare their brightnesses. If you are getting on in years, Mars may appear to you distinctly brighter than Sirius. As we age our eye lenses yellow to some degree; this means that older people see the world through yellow filters.
This is one more reminder that our experience of the external world (i.e. the sum of its qualia), and the actual external world, are two very different things. In fact they are entirely different orders of being — right down to the bottom. Your experience of things exists only inside the few dark cubic inches of your skull, in a neural model of the outer world that your brain creates from the inputs of your senses. This is the only way that your self-awareness, your personhood, can understand and interact with the external physical world, because your sense of being a self is also a neural phenomenon. The outer world, which exists independently of human awareness, is vastly richer and more variegated than our limited senses perceive or than a brain-sized neural model could ever fully mimic. And internal world-models only evolved in ways that helped creatures survive, thrive, and reproduce. Anything else would be selected out as a distraction and a biologically expensive waste of neural processing power.
The full Moon shines near Mars under Pollux and Castor on Monday evening.
MONDAY, JANUARY 13
■ Full Moon (exactly full at 5:27 p.m. EST). The Moon rises on the east-northeast horizon about five minutes after sunset (for North America). As it climbs and twilight deepens, how soon can you see orange Mars just 2° or less to the Moon’s lower left? That’s about the width of your thumb at arm’s length. And fainter Pollux and Castor above the Moon?
■ And the full Moon occults full Mars this evening for the contiguous U.S., much of southern and eastern Canada, and much of Mexico. Remember when the December 2022 full Moon occulted Mars at opposition? Here comes a repeat!
Bob King writes in the January Sky & Telescope, “During the December 2022 Mars occultation, I tried to keep sight of Mars right up to the lunar limb with just my eyes. I failed miserably, losing the planet in the full Moon’s glare nine minutes before it disappeared. However, it was clearly visible in binoculars right up to the occultation. Viewing with my telescope, what struck me most was the compelling color contrast between the Red Planet and the gray Moon.”
I too was watching that night, from near Boston a little south of photographer Walker, where the Moon made a very near miss — by ¼ of Mars’s apparent diameter. I used a 12.5-inch reflector at 300x and wrote in my observing log, “The dazzling curved limb of the Moon with its irregularities and lines of shadow contrasted with the perfect round ball of the orange planet. Almost science-fictiony!” — it reminded me of a scene from a Star Wars movie. “Mars’s surface brightness was not as bright as the Moon’s, but not as great a difference as I expected. The color contrast added to the clarity and beauty.”
Map and timetables for tonight’s event. The first two tables, with predictions for many cities, are long. The first table gives the times of the star’s disappearance behind the Moon’s limb; the second gives its reappearance out from behind the Moon’s other side. Scroll to be sure you’re using the correct table; watch for the new heading as you scroll down. The first two letters in each entry are the country abbreviation (CA is Canada, not California). The times are in UT (GMT) January 14th. UT is 5 hours ahead of Eastern Standard Time, 6 hours ahead of CST, 7 ahead of MST, and 8 ahead of PST.
For instance: Use the first table to see that for Chicago, Mars disappears behind the Moon’s edge at 8:07 p.m. CST, then reappears from behind the opposite edge at 9:16 p.m. CST. From New York the times are 9:21 and 10:37 p.m. EST. For cities on the West Coast the tables show Mars being covered when the Moon is still low and twilight is still under way (the Sun has a small enough negative altitude to be worth listing).
The limb of the Moon will take about 30 seconds or more to cross Mars’s disk. The closer you are to the edge of the occultation zone on the map, the longer it will take.
TUESDAY, JANUARY 14
■ After dinnertime, the enormous Andromeda-Pegasus complex runs from near the zenith down toward the western horizon. Just west of the zenith, spot Andromeda’s high foot: 2nd-magnitude Gamma Andromedae, slightly orange. Andromeda is standing on her head. About halfway down from the zenith to the west horizon is the Great Square of Pegasus, balancing on one corner. Andromeda’s head is its top corner.
From its bottom corner run the stars outlining Pegasus’s neck and head, ending at his nose: 2nd-magnitude Enif, due west. It too is slightly orange.
WEDNESDAY, JANUARY 15
■ Mars is at opposition tonight, its closest to being exactly opposite the Sun in our sky. The three-day offset from its closest approach to Earth on the 12th is due to the ellipticity of Mars’s orbit (which has an eccentricity 0.093) and to a lesser extent the ellipticity of Earth’s (e = 0.017).
■ At this coldest time of the year, Sirius rises in late twilight. Orion’s three-star Belt points down almost to its rising place.
Right after Sirius clears the horizon, it twinkles surprisingly slowly and deeply through the thick layers of low atmosphere. And if you’ve ever watched Sirius rise from an airplane window at cruising altitude, you may have been struck by its doubly deep and slow twinkling. This happens because you’re seeing Sirius through almost twice as much lower atmosphere. The light from the star skims near the Earth’s surface where a ground observer would be, then continues on through more of the lower atmosphere and up again to the airplane.
Sirius twinkles faster and more shallowly as it gains altitude. Its flashes of color also moderate, blending into shimmering whiteness as it climbs to shine through thinner air.
All stars show these effects, but the brilliance of Sirius makes them more salient.
THURSDAY, JANUARY 16
■ Zero-magnitude Capella high overhead, and zero-magnitude Rigel in Orion’s foot, have almost the same right ascension. This means they cross your sky’s meridian at almost exactly the same time: around 9 or 10 p.m. now, depending on how far east or west you live in your time zone. (Capella goes exactly through your zenith if you’re at latitude 46° north: near Portland, Montreal, Minneapolis, central France, Odesa, Kherson.) So whenever Capella passes its very highest, Rigel always marks true south over your landscape, and vice versa.
This winter, brighter Jupiter is a little to the right of the midpoint between them, trying to steal the show. They don’t seem to care.
FRIDAY, JANUARY 17
■ Here it is the coldest very bottom of the year on average. But the Summer Star, Vega, is still barely hanging in! Look for it twinkling over the northwest horizon during and shortly after nightfall. The farther north you are the higher it will be. If you’re as far south as Florida it’s already gone.
You think they’re close together? At distances of 5 and 86 light-minutes from Earth, Venus and Saturn are 17 times farther apart than Venus is from us.
■ Venus and Saturn, in the southwest during and after dusk, now appear just 2¼° apart as shown above. That’s about the width of your thumb at arm’s length. Saturn is left of Venus. How early can you first see it?
SATURDAY, JANUARY 18
■ This evening Venus and fainter Saturn are 2.2° apart, just a trace closer together than they appeared yesterday. And, Saturn is now lower left of Venus. Today is their actual conjunction date (i.e. in ecliptic longitude). From now on Saturn will move away farther below Venus.
■ On the other side of the sky in the southeast, Sirius twinkles brightly after dinnertime below Orion. Around 8 or 9 p.m., depending on your location, Sirius shines precisely below fiery Betelgeuse in Orion’s shoulder. How accurately can you time this event for your location, perhaps by judging against the vertical edge of a building? Of the two, Sirius leads early in the evening; Betelgeuse leads later.
SUNDAY, JANUARY 19
■ Right after dark, face east and look very high. The bright star there is Capella, the Goat Star. To the right of it, by a couple of finger-widths at arm’s length, is a small, narrow triangle of 3rd- and 4th-magnitude stars known as “The Kids.” Though they’re not exactly eye-grabbing, they form a never-forgotten asterism with Capella.
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