Following the spectacular conjunction of Jupiter and Saturn on December 21, the pair of planets continues to separate slowly night by night. In early January, we get the added benefit of Mercury, producing a fascinating trio of planets visible in the southwest 30 minutes after sunset.
During the first week of the new year, Jupiter and Saturn start out 1.3° apart and extend to 2° by January 7, when magnitude –0.9 Mercury joins the twilight scene 3.7° below magnitude 0.6 Saturn. Jupiter shines brightest at magnitude –2.
Mercury slides up to 1.9° due south of Saturn January 9, and the next evening forms a nice equilateral triangle with the gas giants. All three planets lie within a 2.3°-wide circle. On January 11, Mercury moves next to Jupiter and stands 1.4° to its south (lower right). Catch these events 30 minutes after sunset and for about the next 30 minutes before the last of the three planets sets around 6 P.M. local time.
There’s a challenging young Moon in this region January 13 — attempts to view it will require a very clear southwestern horizon. New Moon occurs at 12 A.M. EST on January 13, and that evening at sunset will show a less-than-1-percent-lit crescent. Search for it between 20 and 25 minutes after sunset, when our satellite stands about 1° above the horizon. It’s a very difficult observation unless conditions are perfect.