Several people have asked recently, “What is that brilliant object I see when I go outside at night?” The answer is Jupiter, which made its closest approach to Earth since 1963 on Sept. 20. It won’t be as close again until 2022. It takes the Earth roughly 365 days to orbit the sun. It takes Jupiter 4,332 Earth days to make the same journey. Thus, Earth periodically passes or “laps” Jupiter just as a fast runner laps a slower one on a circular racetrack. Because the orbits are not perfect circles, the planets are closer on some passes than others. The unusual closeness of the pass this year coupled with Jupiter’s huge size — its diameter is more than 11 times that of the Earth’s — makes for a spectacular view this fall. That we are a few days past the closest approach does not detract from the fact that Jupiter will be an outstanding sight in the fall sky for days to come.
Focus on the planets
The evening sky is fairly quiet in October, with Venus and Mars shining in the sun’s twilight glow, but soon disappearing from view. Jupiter, however, is a spectacular sight and remains in view throughout most of the night.
Mercury rises in the east about an hour before sunrise as the month begins but sinks in the sky each morning and disappears by the end of the first week of October.
Venus is low in the southwest shortly after sunset and is barely above the horizon when it is visited by a thin crescent moon on Oct. 9. Venus will disappear by midmonth as it prepares to make its appearance in the morning sky.
Mars opens the month to the upper right of Venus but is so distant and faint that it will appear only as a reddish point of light even with good binoculars.
Jupiter dominates the planetary scene in October, rising in the southeast at dusk and climbing higher each successive night. Jupiter remains in view until well after midnight. Bands and belts on the giant planet are readily visible, as are the four moons that continue their dance about and across the face of the planet.
Saturn makes its appearance very low in the east by mid-month. Saturn remains in view longer as the month progresses but little detail will be seen due to distortion by the Earth’s atmosphere.
Uranus is not as close to Jupiter as it was in September but spends the month in the same binocular field of vision just northeast of the gas giant where its blue-green disk can be spotted.
Neptune is high in the south shortly after darkness falls. Use powerful binoculars and the star chart in September’s Sky & Telescope to locate Neptune’s blue-gray disk.
1: Sunrise, 6:33 a.m.; sunset, 6:17 p.m. Moon in last quarter, 11:52 p.m. Saturn is at conjunction with the sun and passes into the morning sky.
4: Bright Regulus of Leo is to the lower left of the moon at dawn.
6: The moon is at perigee, or nearest approach to Earth. Look to the east just before dawn to see Mercury with a thin sliver of moon to its upper right.
7: New moon, 2:44 p.m.
8: Draconid meteor shower peaks tonight with very favorable viewing as the new moon is only a day past. The rate will likely be no more than 10 slow-moving meteors per hour.
10: Reddish-orange Mars is to the lower right of the moon as darkness falls.
14: Moon in first quarter, 5:25 p.m.
18: Moon at apogee, or greatest distance from Earth.
21: Orionid meteor shower peaks tonight but the full moon just under two days away will mask all but a handful of the brightest meteors of this normally impressive shower.
23: Full moon, 9:37 p.m. The full moon of October is the Hunter’s Moon. The sun enters the astrological sign of Scorpio but astronomically is still in Virgo.
30: Moon in last quarter, 8:46 a.m.
31: Halloween or All Saints’ Eve, a cross-quarter day marking the midpoint between the fall equinox and winter solstice. The sun is entering Libra on the ecliptic. Sunrise, 7:12 a.m.; sunset, 5:26 p.m.