Fri. Oct. 2:
one hour before sunrise: The waning gibbous Moon, about three-quarters full, is high in southwest. Just 1.5° (three moon-widths) to upper left of the Moon's bright limb is the star Aldebaran, marking the eye of Taurus, the Bull. The Moon is creeping slowly eastward toward the star, and will occult or cover it shortly before 10 a.m. EDT from Michigan. Shortly before 11 a.m., the star reappears near the midpoint of the Moon's dark limb. In clear skies, both daytime events are observable through a telescope.
Ranking next in brilliance after the Moon are two planets in the eastern sky: An hour before sunup on Oct. 2, find Venus with Jupiter 16° to its lower left. Next in brightness after Jupiter is Sirius, the “Dog Star” in SSE. Between Sirius and the Moon that morning, lies Orion the Hunter, halfway up the southern sky. Return to Venus and Jupiter in the east and look for two lesser objects of contrasting color between them: Blue-white Regulus 6° lower left of Venus, and reddish Mars about the same distance upper right of Jupiter. Keep your eyes on the eastern morning sky for the next 5 weeks for some spectacular changes.
Thurs. Oct. 8:
one hour before sunrise: Venus gleams brilliantly within 4° lower left of the crescent Moon. Bright Jupiter shines 13° lower left of Venus. Faint reddish Mars glows 4° above Jupiter and 9° lower left of Venus. Mercury, just beginning a morning apparition, rises in east within 19° lower left of Jupiter. Mercury brightens rapidly and climbs higher in coming days, but not high enough to meet any of the other planets. This morning and tomorrow, note the blue-white star Regulus, heart of Leo, about 2.5° north (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 each of the next three mornings and follow the Moon as it slides down the lineup of four planets.
Fri. 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 within 8° to the Moon's upper right. Bright Jupiter is about 5.5° lower left of the Moon. Faint Mars appears less than 4° upper right of Jupiter and about the same distance north (upper left) of the lunar crescent. Can you spot Mercury very low in east?
Sat. Oct. 10:
The old Moon, just 2.5 days before New, is a striking sight with the sunlit crescent cradling the earth-illuminated darker side within its horns. Look for Mercury 11° lower left of Moon, and Jupiter within 8° above the Moon. Higher yet, in order: dim red Mars, brilliant Venus, and Regulus to Venus' upper left.
Sun. Oct. 11:
Last chance to see the thin crescent Moon in the morning sky in this cycle of phases. Just 37 hours before New, it's a few degrees above the horizon and a few degrees south of due east. Mercury is just over 1° upper left of the Moon' northern cusp (upper point of the crescent), 29° lower left of brilliant Venus and 18° lower left of Jupiter. Faint Mars is 2.8° above Jupiter, while Regulus is 3.1° 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 in the morning sky for this year late this week, but gets no closer than 28° to the lower left of Venus.
Thurs. Oct. 15:
one hour after sunset: Look low in SW to WSW to find the 3-day old waxing crescent Moon with Saturn 8° to its upper left. Look also for reddish twinkling Antares, heart of the Scorpion, 10° lower left of Saturn. By Friday evening, the Moon will appear 5° upper left of Saturn.
Sat. Oct. 17:
one hour before sunrise: Look closely for faint Mars just 0.4° (less than a Moon's width) to the north (upper left) of Jupiter.
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. Binoculars of lower magnification, such as 7X, will fit them in for a longer interval, Oct. 17-Nov. 2 if they provide a 7-degree field. Most trios of naked-eye planets involve Mercury (always low in twilight) or Venus (usually low), but on this occasion we catch Venus at its greatest apparent distance from the Sun and near peak altitude of a very favorable apparition high in the eastern morning sky. Not until November 2039 will we witness another compact trio of planets so high in a dark sky.
Sun. Oct. 25 and Mon. Oct. 26:
Venus and Jupiter will appear just over 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 is not to be missed! The next pairings of Venus-Jupiter, at dusk on August 27, 2016 and at dawn on November 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. We must wait until the year 2036 for a pairing of Jupiter with Venus in crescent phase.
Beginning Tues. 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 ESE only 30 hours before New on Tues. Nov. 10. Watch also for these events:
Thurs. and Fri., Oct. 29 and 30,
one hour before sunrise: Watch the waning gibbous Moon leapfrog past Aldebaran, eye of Taurus, the Bull. (Moon will appear widely S (lower left) of Pollux Nov. 2, and 7° from Regulus Nov. 4 and 5.) On Oct. 29 and 30, 45 min. before sunrise, Mercury passes within 4° N of emerging Spica. Use binoculars to see this star to the lower right of Mercury. Each morning, Spica appears higher in the sky (resulting from Earth's revolution around the Sun), and Mercury lower (because the inner planet is faster).
Tues. Nov. 3:
Venus passes Mars in the last of three close predawn pairings of planets in October-November 2015. Look for the faint red planet just 0.7° N (upper left) of brilliant Venus. This morning the Moon is at Last Quarter phase, appearing half full and 90° or one-quarter circle west of the Sun. First activity of the morning in the schoolyard: In your right hand with arm fully extended, hold a ball up to the Moon and note how the lighting on the ball matches the lighting on the Moon! Use a telescope with a low-power eyepiece fitted with a polarizing filter to view the Moon Nov. 2-4. Rotate the eyepiece in its tube until the blue sky is darkest, and there'll be plenty of contrast for seeing details on the Moon, even in the daytime!
Fri. Nov. 6:
Jupiter within 3° N (upper left) of Moon. Venus 11° to Moon's lower left. Mars 1.6° upper right of Venus.
Sat. Nov. 7:
Venus 1.6°, Mars 2.8°, to upper left of Moon. Venus-Mars 2.0° apart.
Mon. Nov. 9:
Spica within 4° S (lower right) of Moon.
And finally, on Tues. Nov. 10,
about 45 minutes before sunrise: Look for a thin, old crescent Moon, about 30 hours before New, rising in E to ESE 11° lower left of Spica.
In mid-December 2015, Saturn will emerge into the morning sky. When Mercury returns from late January through most of February 2016, all five naked-eye planets will be fine display in a long arc from ESE to W across the southern morning sky. Stay tuned!
For illustrations of most of the events listed above, we are providing the October 2015 Sky Calendar. To subscribe, visit www.abramsplanetarium.org/skycalendar/
For a selection of Robert Miller's monthly charts depicting positions of bright planets and first-magnitude stars at mid-twilight, visit www.abramsplanetarium.org/msta/
An activity, Modeling seasonal visibility of stars and visibility of the planets, to help students investigate visibility of bright planets and first magnitude stars, is also available at that link. As stars and planets come and go in morning and evening skies and display beautiful pairings and groupings, students can model these changes and explain their observations with the aid of items provided: Two planet orbit charts, Mercury through Mars and Mercury through Saturn; a table of data for plotting planets on orbit charts; and a sheet with questions on star and planet visibility in 2015-2016.
Robert C. Victor was Staff Astronomer at Abrams Planetarium, 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.