Solar system showing relative size of (but not distance between) planets.

Planet Watch is the Morrison Planetarium's guide to planetary activity for January through March 2018.


The planet Mercury, image by NASA/JPL

All of the naked-eye planets start the year as predawn objects, at least three of them far enough away from the Sun's glow to be visible. This includes Mercury, which is located in Ophiuchus the Serpent-Bearer, rising a little more than an hour before the Sun, but already in the process of retreating into the twilight. In conjunction with Saturn on the morning of January 13, Mercury is then joined by the waning crescent Moon on the mornings of the 14th and 15th, although all objects will be very low in the southeast, rising only an hour before dawn. Mercury's predawn visibility quickly diminishes as the littlest planet reaches superior conjunction on February 17, reemerging into the evening sky by mid-March. Its close encounter with Venus will be too close to the Sun to see, but the day-old crescent Moon's meeting with both objects in the twilight on March 18th make a pretty sight very low in the west just after sunset.



The planet venus, image by NASA/Caltech/JPL

Reaching superior conjunction on January 8, Venus passes behind the Sun and enters the evening sky, but it doesn't become visible after sunset until early March. On March 3rd, it might still be too close to the Sun to see it with Mercury only a degree away, very low in the west just after sunset. The day-old crescent Moon joins them on the 18th, but they'll all be very low in the west just after sunset.



The planet Mars, image by NASA

The Red Planet begins the year in the process of passing Jupiter as it moves eastward against the stars. Only two degrees apart on January 1, the two are a quarter of a degree apart (half the apparent width of the full Moon) on the 6th, after which Mars moves eastward into Scorpius and Ophiuchus as Jupiter continues loitering in Libra and gradually moving westward. The Moon passes near the two on the morning of January 11th. It passes Mars again on February 9 (when Mars is conveniently close to Antares, the bright star in Scorpius the Scorpion that is named after it ("Rival of Mars"). During March, keep watching Mars as it moves closer to Saturn in the morning sky, with the Moon passing by once more on the 9th & 10th.



The planet Jupiter, by NASA

At the beginning of January, the largest planet is already rising around 3 am and is easily visible in the south-southeast just before dawn. Moving very little against the backdrop of stars behind it, Jupiter rises around 1:30 am at the end of January, around midnight at the end of February, and at about 10:45 pm at the end of March. Look for the Moon passing nearby on the mornings of January 11, February 8, and March 7.



The planet Saturn, by NASA/JPL/Saturn institute

The most distant and slowest-moving of the naked-eye planets is just climbing out of the twilight in early January and isn't easily visible until after mid-month, located against the stars of Sagittarius the Archer. On the morning of January 13th, it's located less than a degree from Mercury, and the waning crescent Moon sweeps by on the 14-15th. The Moon's next encounters are separated further from the Sun and are thus easier to see on the mornings of February 11 and March 10-11. By the end of March, Saturn is drawing very close to Mars, both located in the south-southeast at dawn.


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Planetarium by Night

Planetarium by Night

Morrison Planetarium is open for Thursday NightLife events, featuring special shows and presentations.