Friday, September 11
Already high in the north after sunset, the planetary nebula NGC 6543 in Draco is famously called the Cat’s Eye Nebula. It’s best seen with a large telescope, but even a small scope will pick it up and show it off in tonight’s moonless sky.
Two hours after sunset, you’ll find the Cat’s Eye 60° high in the north. It lies just over 5° northeast of magnitude 3.2 Zeta (ζ) Draconis, to the upper left of the Little Dipper and the famous star at the end of its handle, Polaris. Glowing at magnitude 8.1, the Cat’s Eye is quite bright and will show up even in small scopes as a circular glow. Some observers see it as blue, some as green, and some as a mix of the two — what do you see?
Through large instruments under higher magnification, some of its intricate detail begins to emerge: a spiral-shaped structure twirling around the brighter, compact central core, which helps give the object its common name. Overall, NGC 6543 stretches about 6’ measures only about 20” across.
Sunrise: 6:37 A.M.
Sunset: 7:15 P.M.
Moonrise: 7:09 A.M.
Moonset: 7:24 P.M.
Moon Phase: Waxing crescent (1%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon’s illumination is given at 10 P.M. local time from the same location.
Saturday, September 12
Saturn dominates the southern sky in the early hours after midnight. It’s the brightest point of light here, standing some 50° high around 2 A.M. local daylight time. In addition to its biggest and brightest moon, mid-8th-magnitude Titan, 10th-magnitude Rhea, Tethys, and Dione are also often visible through a telescope, hugging the planet as they orbit closer in than Titan.
Dione skims Saturn’s north pole early this morning starting around 2:55 A.M. EDT (the 12th in all U.S. time zones except Pacific, where it is just before midnight, late on the 11th). The moon is preceded by its small shadow, which appears on Saturn’s northeastern limb just after 2 A.M. EDT. Dione itself tracks over the north pole for about 40 minutes, before moving off to the west around 3:35 A.M. EDT.
Shortly before Dione’s transit starts, look near the southwestern limb of Saturn to find Tethys approaching from the west. It disappears before it ever meets the limb around 2:10 A.M. EDT, when it passes into Saturn’s long, dark shadow, which extends beyond the planet to the southwest.
During this series of events, Rhea is visible to the planet’s west with Titan beyond it, far to the west.
Sunrise: 6:38 A.M.
Sunset: 7:14 P.M.
Moonrise: 8:17 A.M.
Moonset: 7:47 P.M.
Moon Phase: Waxing crescent (5%)
Sunday, September 13
Blazing at magnitude –4.8, Venus is nearing its greatest illuminated extent and stands out as an unmissable evening star after sunset. This evening it is joined by a lovely thin crescent Moon as the pair hangs together in Virgo the Maiden, near its bright alpha star, Spica.
Venus should be visible shortly after sunset — a good thing, as it’s not particularly high, only 8° above the western horizon 20 minutes after the Sun disappears. The Moon lies just to its lower right, now nearly three days past New. If you have a particularly clear, flat horizon or an elevated observing site, you may also spot magnitude –0.6 Mercury, but it’s only 2° high 20 minutes after the Sun sets. It disappears within another 10 minutes.
Just to the Moon’s upper right is magnitude 1.0 Spica. Some 250 light-years away, this relatively nearby star is nearly 2,000 times as bright as our own Sun. Together with Venus, the three objects form a nice triangle in the west as they set, offering a great astrophoto target — especially for a wide-view nightscape shot.
Sunrise: 6:39 A.M.
Sunset: 7:12 P.M.
Moonrise: 9:24 A.M.
Moonset: 8:10 P.M.
Moon Phase: Waxing crescent (10%)
Monday, September 14
Asteroid 3 Juno stands stationary at 1 A.M. EDT among the stars of Aquila the Eagle. The best time to catch this main-belt world will be next week, when its motion through a gaggle of background stars makes it easier to pick up. So stay tuned — we’ll come back in just a couple of days to observe it.
The Moon passes 0.5° due north of Venus at 7 A.M. EDT. In the evening sky, the pair is now standing in line with the tiny planet Mercury and the bright star Spica. If you caught the view last night, when Venus, the Moon, and Spica formed a triangle after sunset, compare that sight with the one that greets you tonight.
Mercury is now magnitude –0.5 — relatively bright, but still very low, setting less than 40 minutes after the Sun. About 20 minutes after sunset, you might catch the tiny planet hugging the western horizon if you’ve got a clear view free of obscuring trees or buildings. Getting up on a hill or other tall structure might help as well. You may need binoculars to locate it, only 2° high.
Venus won’t be hard to find — at magnitude –4.8, Earth’s sister planet will pop out of the twilight relatively early, and it’s still more than 5° high in the west 20 minutes after sunset. Tonight it lies just over 6° to the lower right of the crescent Moon, which now sits near the border of Virgo and Libra, where our satellite will be tomorrow.
Spica is another 9.1° to Venus’ lower right; at magnitude 1.0, the star may need a bit more time for the sky to darken enough for it to appear. But if you can catch it just before Mercury sets, you’ll be able to see all four objects in a line from upper left to lower right, bounded by the Moon at the top and Mercury at the bottom. Even once Mercury sets, you’ll have a bit of time to see the Moon, Venus, and Spica lined up, until Spica and then Venus sets around 8:15 P.M. local daylight time.
Sunrise: 6:40 A.M.
Sunset: 7:10 P.M.
Moonrise: 10:30 A.M.
Moonset: 8:37 P.M.
Moon Phase: Waxing crescent (17%)
Tuesday, September 15
The time around the equinox is one of the best opportunities to catch sight of the ethereal zodiacal light, the soft glow generated by dust that orbits the Sun along the plane of the solar system, the ecliptic. That dust has been left by countless comets as they circle the Sun, losing material as they heat up when near our star. Over time, it settles into orbit along the ecliptic, and sunlight scattering off these fine grains creates a pyramid-shaped glow rising up from our horizon either before sunrise or after sunset, depending on the time of year.
Related: Does a comet’s period change because it loses mass every time it nears the Sun?
As we near the autumn equinox, the zodiacal light is visible in the east before the sky begins to brighten with the oncoming dawn. So, the best time to look is in the few hours before sunrise from a dark location with little to no artificial lighting. It’s also best to wait until the Moon is out of the predawn sky — so again, now is your chance.
About two hours before sunrise, the head of Leo the Lion is just starting to peek above the eastern horizon, led higher up by Cancer, Gemini, and Taurus. Look for the zodiacal light along a line connecting these constellations — that’s where the ecliptic lies, so swing your gaze from lower left to upper right as you get higher above the horizon. The zodiacal light will be wider at its base and narrow higher in the sky as it comes to a point in Gemini or Taurus.
Sunrise: 6:41 A.M.
Sunset: 7:09 P.M.
Moonrise: 11:37 A.M.
Moonset: 9:09 P.M.
Moon Phase: Waxing crescent (25%)
Wednesday, September 16
Rising around sunset and highest in the early-morning hours before sunrise is the constellation Triangulum. This tiny triangular star pattern is perfect for evening or morning observers: Around 10 P.M. local daylight time, it’s high enough (25°) in the east to observe easily, and is also still high in the west (60° or more) in the hour or two before sunrise, so early birds can catch it, too.
In the evening sky, you’ll find it sandwiched between the constellations Perseus and Pisces as they rise. Triangulum is very small, just 78th (out of 88) in size among the official constellations astronomers use to chart the sky. In total, it covers an area of about 132 square degrees.
It (predictably) has three bright stars that make up its namesake shape: Alpha (α), Beta (β), and Gamma (γ) Trianguli. These shine at magnitude 3.4, 3.0, and 4.0, respectively, making Beta the brightest star despite its secondary designation. A fourth relatively bright star, Delta (δ) Tri, shines at magnitude 4.8 just northwest of Gamma. Only eight other stars in this constellation shine brighter than magnitude 5.5, and all are fainter than these, so the shape of the constellation is pretty easy to pick out by eye.
The most famous deep-sky object in Triangulum is M33, also called the Triangulum Galaxy. This 6th-magnitude spiral lies in far western Triangulum, about 4.3° west-northwest of Alpha Tri, and should be readily visible with any telescope tonight, especially with no Moon for most of the dark hours overnight.
Sunrise: 6:42 A.M.
Sunset: 7:07 P.M.
Moonrise: 12:40 P.M.
Moonset: 9:46 P.M.
Moon Phase: Waxing crescent (34%)
Thursday, September 17
The Moon passes 0.6° south of the bright star Antares at 9 A.M. EDT. By evening, our satellite sits near the border of Scorpius and Ophiuchus, some 6° east (to the upper left) of Antares. They make a lovely pair: a bright red giant star and the waxing crescent Moon, some 15° high in the south an hour after sunset. Once it’s fully dark, see if you’re able to make out the entire long, curving form of Scorpius, with its claws to the right of Antares and its tail to the lower left, closer to the horizon. Antares, Scorpius’ alpha star, is often envisioned as the Scorpion’s heart.
Antares and the Moon remain visible for roughly three hours after sunset, setting around 10:15 P.M. local daylight time. Red giant Antares glows visibly orange-red and is often mistaken for the planet Mars. The Red Planet, however, is currently a morning object, rising around 1:30 A.M. local daylight time and visible in the hours before sunrise.
By the hour, the Moon is moving east, crossing southern Ophiuchus and pulling away from Scorpius and its heart. Our satellite covers an average of 13° per day on the sky as it orbits Earth, appearing to track quickly across the constellations over the course of a little more than a month. It is heading for Sagittarius next, and will sit just off the spout of that constellation’s Teapot asterism tomorrow night.
Sunrise: 6:43 A.M.
Sunset: 7:05 P.M.
Moonrise: 1:41 P.M.
Moonset: 10:29 P.M.
Moon Phase: Waxing crescent (43%)
Friday, September 18
First Quarter Moon occurs at 4:44 P.M. EDT. The Moon reaches apogee, the farthest point from Earth in its orbit, later tonight at 11 P.M. EDT. At that time, our satellite will be 251,171 miles (404,221 kilometers) away.
Venus reaches greatest brilliancy this evening at 9 P.M. EDT, shining at magnitude –4.8 and visible in the west for about 70 minutes after sunset.
Later this evening, high in the eastern sky you’ll find the zig-zagging constellation Lacerta, home to several lovely and relatively bright open star clusters. Tonight, let’s check out the brightest of those: magnitude 6.4 NGC 7243, also known as Caldwell 16.
A great small-telescope target, NGC 7243 is located about 2.6° west of magnitude 3.8 Alpha (α) Lacertae. It’s visible to the naked eye under dark conditions as a hazy patch of light, so once the Moon sets, see if you can spot it first without optical aid before swinging your telescope up for a better view. Stretching 21′ across, NGC 7243 will show several dozen stars in a small scope, with more becoming visible the larger your aperture. Its brightest star happens to sit right in the center of the cluster, shining at 8th magnitude.
This young group of stars lies nearly 2,900 light-years from Earth and is an estimated 250 million years old.
Mars passes 6° south of Pollux in Gemini at midnight EDT, and both are visible in the early-morning sky of the 19th. We’ll cover that view in next week’s column.
Sunrise: 6:44 A.M.
Sunset: 7:04 P.M.
Moonrise: 2:35 P.M.
Moonset: 11:20 P.M.
Moon Phase: Waxing gibbous (53%)
Alison Klesman is senior editor of Astronomy magazine. She holds a Ph.D. in astronomy and has studied a variety of topics, from minor planets to supermassive black holes.
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