During October and early November, there are exceptionally beautiful gatherings of planets in the morning sky. A waning crescent moon graces the lineup of planets on Oct. 8-11. Oct. 22-29, three planets will converge into a compact group, and on Oct. 25 and 26, the brightest of these, Venus and Jupiter, will pair very closely.
With daylight saving time still in effect through October, a brief sky watch about an hour before sunrise would provide a wonderful, rewarding display of planets at a time not unreasonably early.
Thursday, Oct. 8, one hour before sunrise: Venus gleams brilliantly within 3 degrees to the lower left of the crescent moon. Bright Jupiter shines 13 degrees to the lower left of Venus. Faint reddish Mars glows 4 degrees above Jupiter and 9 degrees to the lower left of Venus. Mercury, just beginning a morning apparition, rises in the east, within 19 degrees to the lower left of Jupiter. On the near side of its orbit, Mercury brightens rapidly and climbs higher in the coming days, but not high enough to meet any of the other planets.
This morning and tomorrow, note blue-white Regulus, heart of Leo, about 2.5 degrees to the upper left of Venus. This morning, students can follow the moon and Venus until sunrise and well beyond to catch Venus in the daytime. A telescope and even a steadily held pair of binoculars will reveal Venus as a crescent. Look an hour before sunup the next three mornings and follow the moon as it slides down the lineup of four planets.
Friday, Oct. 9: The moon appears lower and closer to the sun this morning, so today’s crescent is thinner than yesterday’s. Brilliant Venus is now 9 degrees to the moon’s upper right. Bright Jupiter is about 4.5 degrees to the lower left of the moon. Faint Mars appears within 4 degrees to the upper right of Jupiter and about the same distance north (to the upper left) of the lunar crescent. Can you spot Mercury very low in the east?
Saturday, Oct. 10: An old moon, just 2.5 days before new, is a very striking sight with the sunlit crescent cradling the earthlit darker side within its horns. Look for Mercury 10 degrees to the lower left of the moon, and Jupiter 9 degrees above the moon. Still higher, in order, are dim red Mars, brilliant Venus, and Regulus, to Venus’ upper left.
Sunday, Oct. 11: This is the last chance to see this thin crescent old moon in the morning sky. Just 35 hours before new, it’s a few degrees above the horizon and a few degrees south of due east. Mercury is 2 degrees to the upper left of the moon, 29 degrees to the lower left of brilliant Venus, and 18 degrees to the lower left of Jupiter. Faint Mars is a few degrees above Jupiter, while Regulus is a few degrees to the upper left of Venus. This week, watch Mars close in on Jupiter, while Venus widens its distance from Regulus. Mercury climbs to its highest point in the morning sky for this year late this week, but gets no closer than 28 degrees to the lower left of Venus.
Thursday, Oct. 15, one hour after sunset: Look low in the southwest to west-southwest to find the three-day-old waxing crescent moon, with Saturn 7 degrees to its upper left. Look also for reddish twinkling Antares, heart of the Scorpion, 10 degrees to the lower left of Saturn. By Friday evening, the moon will appear 6 degrees to the upper left of Saturn.
Saturday, Oct. 17, one hour before sunrise: Look closely for faint Mars just 0.4 degrees (less than a moon’s width) to the north (upper left) of Jupiter.
Oct. 22-29: Three planets—in order of brightness Venus, Jupiter and Mars—form a trio, appearing within a 5-degree field of view. Binoculars magnifying up to about 10-power will fit the trio in on these eight mornings.
Sunday, Oct. 25, and Monday, Oct. 26: Venus and Jupiter will appear just more than a degree apart, providing striking views, all within a single telescope field: Jupiter, with its four bright moons discovered by Galileo, and Venus appearing as a “half moon.” This sight should not be missed! The next pairings of Venus-Jupiter—at dusk on Aug. 27, 2016, and at dawn on Nov. 13, 2017—will be tighter, but low in twilight and will catch Venus on the far side of its orbit, displaying a tiny, nearly full disk.
Beginning Tuesday, Oct. 27, in morning twilight: Follow the moon daily for 15 mornings, as it wanes from full, low in the west on Oct. 27, to a thin, old crescent, low in the east-southeast, only 28 hours before new on Tuesday, Nov. 10.
Wed. Oct. 28, 45 minutes before sunrise: Mercury, now on the far side of its orbit, passes within four degrees to the north of emerging Spica. Use binoculars to see the star to the lower right of Mercury. Each morning, Spica appears higher in the sky (resulting from Earth’s revolution around the sun), with Mercury lower (because the inner planet moves faster than Earth).
Thursday and Friday, Oct. 29 and 30, one hour before sunrise: Watch the waning gibbous moon leapfrog past Aldebaran, eye of Taurus, the Bull.
Refer to the October 2015 Sky Calendar for illustrations of the gatherings described in this article. To subscribe online, visit www.abramsplanetarium.org/skycalendar.
The Astronomical Society of the Desert will host a star party, on Saturday, Oct. 10, at dusk at Saw Mill Trailhead, elevation 4,000 feet in the Santa Rosa Mountains. The society will resume monthly star parties at the Visitor Center of the Santa Rosa and San Jacinto Mountains National Monument on Saturday, Oct. 24, from 7 to 10 p.m. Dates of future star parties, with directions and maps to the sites and info on lectures and special events, are available at www.astrorx.org.
Robert C. Victor was a staff astronomer at Abrams Planetarium at Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs. Robert D. Miller, who provided the twilight charts and the planet orbit charts, did graduate work in Planetarium Science and later astronomy and computer science at Michigan State University and remains active in research and public outreach in astronomy.