The moon: January is a good time to anticipate the coming of spring, a welcome three months away. Look for the crescent moon on the night of Jan. 1, and you will be looking very nearly at the vernal equinox, where the sun will be when spring commences. A heartwarming thought! The first quarter moon is on Jan. 2, and the waxing gibbous moon passes above Aldebaran (in Taurus) on Jan. 6. Full moon on Jan. 9 is in Gemini, and the two stars above it are Pollux (the brightest) and Castor. From the 15th through the 17th, the waning moon passes below the three bright morning planets (Mars, Saturn, and Jupiter), going through last quarter on the 16th. New moon is on Jan. 25, and the crescent of the next cycle will be visible on the last few evenings of the month.
Stars and planets: It started out as a poor winter for evening planets, and it is getting worse! Venus, however, could be seen in December, and maybe for the first week in January, but forget it after that. When it shifts into the morning sky on Jan. 21, it leaves Mercury alone in the evening sky, and poorly placed. For the last 10 days of January, all seven of the other planets are morning stars. Three of them, Mars, Saturn, and Jupiter, are exceptionally well placed in Virgo, however, near its brightest star, Spica. You will see them every clear morning, from shortly after midnight until dawn. Mars rises first, before midnight, then Saturn and Spica close to each other (Saturn above), and lastly Jupiter about an hour or so after midnight. By 3 a.m. or later, they will be well up in the east, stretched out in a line across the sky, drifting slowly westward. Jupiter, the trailing (lowest) planet, is brightest by far. Mars, the reddish-colored leader, Saturn and Spica in the middle, are all about the same brightness early in the month, but by the end of January the quickly brightening Mars will easily outshine the two others. The alignment of the three planets (and the moon when it joins them at mid-month) will show you where the ecliptic (the earth's orbital plane and the general plane of the solar system) extends across the sky. Jan. 4: Earth is at perihelion, the position in its orbit where it is nearest to the sun (about 147,102,000 kilometers, or 91,405,000 miles, distant). Perihelion, coming in the northern winter, and aphelion (in the northern summer) moderate our seasons. But they cycle through the seasons over a long period of time. This change probably influenced the cycle of the Ice Ages.
Jan. 4: The latest sunrise of the year occurs. Note that the late darkness of winter mornings persists well into January, but the early darkness of winter evenings moderates very rapidly.
Jan. 8: Saturn is in conjunction with Spica. The planet has been slowly approaching the star from the right, and now moves to its left (east). But keep your eye on these two objects this year. Saturn is approaching opposition with the sun (April 18), and it will soon begin the retrograde (westerly) motion that always takes place for some months before and after opposition. This will take it to the right again to pass Spica in late February, and then to the left again (in June) to pass Spica in September. Another triple conjunction! After that, Saturn will not pass Spica again for 30 more years.
Jan. 9: Mercury and Venus, both poorly placed evening stars, are in conjunction.
Jan. 9: Full moon, in Gemini. A total lunar eclipse occurs today while the moon is below our horizon. It is visible in Asia, Africa, and Europe, but not in the Americas.
Jan. 15-18: The waning moon passes by the gathering of planets in the morning sky (Mars, Saturn, and Jupiter, with the star Spica). Watch it daily (from 4 a.m. till dawn) to see its changes relative to the other objects. On the 15th, it is to the right of all; on the 16th, nearest Mars; on the 17th, closest to Saturn and Spica; on the 17th, near Jupiter; and on the 18th, to the left of all.
Jan. 16: Mercury is at greatest easterly (evening) elongation but poorly placed for viewing. The planet is too low at sundown, setting during early twilight before it can become visible.
Jan. 21: Venus, poorly placed as an evening star since last summer, is in inferior conjunction, passing between earth and sun from left to right. It now becomes a morning star, but again the circumstances of its position relative to the sun are not favorable.
Jan. 22: Mercury is stationary among the stars and begins its retrograde (westerly) motion.
Jan. 25: A partial solar eclipse occurs in the southern Pacific Ocean and Antarctica.
Jan. 28: The early crescent moon should be visible tonight and on the remaining evenings in January. The new crescent moon of midwinter is very favorably placed. It appears quite high in the twilight and sets late, relative to other times of the year. For this reason, because we see it high in the dark skies after twilight, it appears to be particularly bright.