Saturday, September 4
Getting up early on the weekend isn’t always fun, but it can be worth it: This month, the hours before sunrise are when Orion the Hunter is climbing above the horizon, with one of the northern sky’s best sights tucked into his belt. Hanging below the three familiar stars of Orion’s Belt is the soft glow of his sword, formed by the famous Orion Nebula (M42). Although its light can be seen with the naked eye, the nebula itself was not truly discovered until the early 1600s, when several people independently turned telescopes its way.
The nebula spans more than a full degree and is roughly magnitude 4. Binoculars and telescopes both will draw out some of its features, with larger apertures providing ever-more-intricate detail. Nestled within the nebula’s glowing gas are numerous forming stars, some of the oldest of which are the blazingly bright stars of the Trapezium cluster, whose energetic photons are still shaping the nebula today. At least four of these stars are visible under good conditions, but a 6-inch or larger scope should bring out six stellar younglings.
Sunrise: 6:31 A.M.
Sunset: 7:26 P.M.
Moonrise: 3:36 A.M.
Moonset: 6:38 P.M.
Moon Phase: Waning crescent (6%)
Sunday, September 5
Venus passes 1.7° north of Spica at 2 A.M. EDT; however, both are below the horizon at the time. Instead, you can catch them just after sunset. Venus is still 11° high 30 minutes after the Sun disappears, and is now about 1.5° northeast of Spica, whose bright magnitude 1 glow should pop out quickly against the darkening sky. Venus, at magnitude –4, far outshines the star. And if you’re quick, you may also catch fainter, magnitude 0.1 Mercury as well. It’s just 3° above the horizon 30 minutes after sunset and about 15° east of Venus.
But this isn’t the only planetary show tonight. Observers will also want to swing a telescope back toward Jupiter, where — by 30 minutes after sunset in the Midwest, at 8:54 P.M. EDT — Europa and its shadow are transiting the disk, with Ganymede poised just off Jupiter’s eastern limb. By 8:59 P.M. EDT, the large moon has also slipped onto the planet’s face, sharing it with Europa for a mere minute until the latter ends its transit at 9:00 P.M. EDT.
Keep watching, and you’ll see Ganymede’s large shadow cross onto the jovian cloud tops at 10:45 P.M. EDT, while the moon itself is only halfway across the disk. The pair will progress from east to west, with Ganymede’s transit ending just after 12:30 A.M. EDT on the 6th (late on the 5th for the rest of the U.S.) and its shadow disappearing a little less than two hours later.
Sunrise: 6:32 A.M.
Sunset: 7:25 P.M.
Moonrise: 4:42 A.M.
Moonset: 7:12 P.M.
Moon Phase: Waning crescent (2%)
Monday, September 6
New Moon occurs at 8:52 P.M. EDT. With the promise of a dark, moonless sky, it’s the perfect night to search for our solar system’s most distant planet, Neptune, which will reach opposition in about a week. That means it’s visible all night long and well placed for observation.
Neptune currently sits about 2.7 billion miles (4.3 billion kilometers) from Earth. At that vast distance, even its large size (nearly 4 times that of Earth) is reduced to a 2"-wide disk that glows a soft magnitude 7.7. But that’s visible through binoculars, bringing the ice giant within reach of most observers. If you do have a telescope, you may be able to discern its blue-green color, which differentiates it from nearby field stars.
To find Neptune, look for 4th-magnitude Phi (ϕ) Aquarii, which is south-southwest of the Circlet in Pisces. From Phi, scan 4.5° east to locate Neptune, which sits within a triangle of 6th-magnitude field stars (HIP 116266, HIP 116106, and HIP 115953) roughly 6.5° due south of the Circlet.
Sunrise: 6:33 A.M.
Sunset: 7:23 P.M.
Moonrise: 5:52 A.M.
Moonset: 7:41 P.M.
Moon Phase: New