Friday, November 29
Pegasus the Winged Horse might be the most well-known horse-themed star pattern in the sky, but he is not alone. Once you find Pegasus, slowly sinking in the west this evening after sunset, next locate Enif, the star that typically is drawn marking Pegasus’ nose or mouth. Just below (west of) this star as the constellation sets is a small region of sky that is home to a lesser-known equine constellation: Equuleus the Foal.
The second-smallest constellation in the sky, Equuleus is larger only than Crux. It has just three stars that make up its shape: Alpha (α), Delta (δ), and Gamma (γ) Equulei. Only Alpha Equ cracks 4th magnitude, and even then, just barely (at magnitude 3.9). Delta is magnitude 4.5, while Gamma is magnitude 4.7. Altogether, the Foal looks a little like a backwards L or a hockey stick.
Equuleus is not devoid of deep-sky targets, however: Epsilon (ε) Equ, which lies just over 4° west of Alpha Equ, near the constellation’s southwestern border with Delphinus, is a double star with components that shine at magnitude 6.0 and 7.1. They are separated by nearly 11”.
Sunrise: 7:01 A.M.
Sunset: 4:35 P.M.
Moonrise: 5:35 A.M.
Moonset: 3:19 P.M.
Moon Phase: Waning crescent (2%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon’s illumination is given at 12 P.M. local time from the same location.
Saturday, November 30
One of the jewels of the constellation Cassiopeia is a the lovely open cluster NGC 7789, readily visible with binoculars or any telescope this evening as the Queen swings high overhead in the north.
Shining at magnitude 6.7, you’ll find this grouping of young stars 3° southwest of Caph (Beta [β] Cassiopeiae), which marks the westernmost end of the W-shaped asterism many observers recognize (the rightmost point on the W if the letter is drawn right-side up). Containing about 1,000 members, NGC 7789 spans 16’ and was discovered by Caroline Herschel in the late 1700s. Because of this, some call the cluster Caroline’s Rose.
Not far away, you’ll find another open cluster of similar brightness, though containing far fewer stars: magnitude 7.3 M52. You can reach it by skimming some 3.2° northwest of Caph. M52 spans about 13’ on the sky and houses a few hundred members.
Sunrise: 7:02 A.M.
Sunset: 4:35 P.M.
Moonrise: 6:39 A.M.
Moonset: 3:53 P.M.
Moon Phase: New
Sunday, December 1
December opens with no Moon in the sky, as New Moon occurs at 1:21 A.M. EST.
Now roughly 9th magnitude, Comet C/2023 A4 (Tsuchinshan-ATLAS) is a telescopic object — but it still has plenty in store for those willing and able to hunt it down. Currently in Aquila, it’s visible for a few hours after sunset and is passing near two open clusters tonight: NGC 6756 and NGC 6755.
You’ll find the trio about 4.5° northwest of 3rd-magnitude Delta Aquilae, near the center of the Eagle. Tsuchinshan-ATLAS lies just east of both clusters, with NGC 6756 to the comet’s northwest and NGC 6755 to its southwest. NGC 6755 is brighter and larger, glowing around magnitude 7.5 and spanning some 15’. NGC 6756, meanwhile, is roughly 11th magnitude and just 4’ across.
Neither of these open clusters will look much like a comet — but NGC 6760, a 9th-magnitude globular, is some 3.5° south-southeast of the trio. This one should look like a much better dupe for Tsuchinshan-ATLAS. What do you think?
Sunrise: 7:03 A.M.
Sunset: 4:35 P.M.
Moonrise: 7:44 A.M.
Moonset: 4:35 P.M.
Moon Phase: New
Monday, December 2
High in the east a few hours after sunset is the constellation Perseus the Hero. Standing directly above V-shaped Taurus, Perseus is often drawn holding the head of the gorgon Medusa. Representing that head in this pattern of stars is the 2nd-magnitude star Algol (Beta [β] Persei), also known as the Demon Star.
This “demonic” sun undergoes a transformation every 2.867 days, as Algol noticeably dims for a few hours, briefly flickering from its usual magnitude of 2.1 down to 3.4 and then back up again.
What’s going on? Algol is not one star but two, circling each other as an eclipsing binary. This means one star passes in front of the other from our point of view; each time that happens — every 2.867 days — the visible star we see from Earth appears to dim as its light is temporarily blocked.
Tonight, Algol is blazing at full strength, making it roughly as bright as Mirfak, Perseus’ alpha star. But in two days, on the 4th, it will go into eclipse, appearing much dimmer than Mirfak, even to the untrained eye. However, the eclipse on the 4th occurs during daylight hours in the U.S., as does the next, on the 7th. But the eclipse following that, on December 10, will take place early in the morning, at 4:19 A.M. EST. We’ll make sure to point you back toward Perseus then, so you can note the difference.
Sunrise: 7:04 A.M.
Sunset: 4:35 P.M.
Moonrise: 8:45 A.M.
Moonset: 5:28 P.M.
Moon Phase: Waxing crescent (2%)
Tuesday, December 3
Jupiter is shining brightly in the constellation Taurus, rising roughly at sunset and remaining visible until sunrise. The planet is fast approaching opposition and currently looks its best, particularly for those in the Northern Hemisphere.
The magnitude –2.8 gas giant far outshines Taurus’ brightest star, magnitude 0.9 Aldebaran, which sits to the planet’s upper right in the sky as they rise in the east. Through a telescope, Jupiter’s huge, 48”-wide disk shows off alternating dark and light cloud bands in most instruments. Also visible are the planet’s four largest satellites, the Galilean moons.
Early this evening, Callisto stands alone to Jupiter’s east, while Io, Europa, and Ganymede line up to the west, in that order from closest to farthest. The orbits of these satellites are aligned with the planet’s equator, meaning that we often see them transit in front of the disk or become occulted behind it. The exception, however, is Callisto, whose orbit carries it far enough from the planet that, because of Jupiter’s tilt, the icy moon instead appears to completely “miss” the disk, passing above or below it.
Just such an event happens tonight, as Callisto passes south of Jupiter. As the night stretches on, the moon travels from east to west, standing due south of its central meridian around 2 A.M. EST (early on the 4th for most of the U.S., though still late on the 3rd for those in the Pacific time zone).
You might also notice Europa drawing closer to the planet, moving west to east, at the same time. If you keep watching well into the early-morning hours of the 4th, you’ll see Europa undergo an occultation, but it’s a bit of a strange one. Sharp-eyed observers will see the moon “disappear” at 3:02 A.M. EST, when it is still a few scant arcseconds from the planet’s northwestern limb. This occurs because the moon passes into the planet’s dark shadow, which stretches nearly —but not quite — directly behind the world as it approaches opposition.
Sunrise: 7:05 A.M.
Sunset: 4:35 P.M.
Moonrise: 9:41 A.M.
Moonset: 6:28 P.M.
Moon Phase: Waxing crescent (7%)
Wednesday, December 4
The Moon passes 2° south of Venus at 6 P.M. EST. You can catch the pair hanging together in the evening sky some 16° high an hour after sunset, brightening eastern Sagittarius. Blazing Venus stands to the Moon’s upper right. It’s a picturesque pairing that any astrophotographer will want to capture.
At magnitude –4.2, Venus is a stunning evening star that you can’t miss. Through a telescope, its disk appears 18” across and some 66 percent lit. Compare that gibbous phase to the Moon’s thinner crescent: Our nearly four-day-old satellite is just 14 percent lit as the Sun slowly peeks over the eastern limb. See if you can spot any earthshine on the western portion of the Moon — this occurs when sunlight bounces off Earth and lights up regions that are still hidden in Earth’s shadow.
The pair is visible for nearly three hours after sunset, offering a great evening view whether you’re able to get out right at sunset or opt to step outside once darkness has fully fallen.
Sunrise: 7:06 A.M.
Sunset: 4:34 P.M.
Moonrise: 10:27 A.M.
Moonset: 7:37 P.M.
Moon Phase: Waxing crescent (13%)
Thursday, December 5
Mercury reaches inferior conjunction at 9 P.M. EST. It won’t be gone for long, though — it should quickly reappear in the morning sky, readily visible by midmonth.
Clearly visible in the early-morning sky these days is Mars. Now headed toward opposition early next month, the Red Planet stands high in the south around 3:30 A.M. local time and remains well above the horizon in the several hours before dawn, offering plenty of time for observation. At magnitude –0.6, it’s the brightest point of light in Cancer the Crab, where it sits just 2° from the constellation’s showpiece open cluster, M44. Also known as the Beehive Cluster, this bright grouping of young stars shines at magnitude 3.7 and spans nearly 100’ — it’s visible to the naked eye under good conditions and easy to capture together with Mars in binoculars.
If your skies are steady and clear, consider pulling out your telescope to zoom in further on Mars’ 12”-wide disk. Around local midnight in the central U.S., Valles Marineris and Solis Lacus will appear central on the disk. A few hours later, Olympus Mons and the Tharsis region dominate the view.
Sunrise: 7:07 A.M.
Sunset: 4:34 P.M.
Moonrise: 11:05 A.M.
Moonset: 8:48 P.M.
Moon Phase: Waxing crescent (20%)
Friday, December 6
As if slowly chasing the Moon, Venus moves out of Sagittarius and enters Capricornus this evening, standing just over the border of the latter in the western sky as dusk falls. Now nearly 25° high at sunset, Venus lingers long into the evening hours, setting roughly three hours after the Sun. You’ll easily find it to the far lower right of the crescent Moon, which is now at the other (eastern) end of Capricornus, appearing to mov much faster across the sky due to its proximity to Earth.
Once darkness has fully fallen, turn east to look for Auriga, which is rising beneath its brightest star, magnitude 0.1 Capella. Asteroid 15 Eunomia hangs some 12° below this luminary, climbing as the hours pass and reaching 60° in altitude by 10 P.M. local time. The 8th-magnitude main-belt world is just passing NGC 1931, a nebula sometimes referred to as a “miniature” version of the famous Orion Nebula (M42) in the Hunter.
You’ll find Eunomia just 0.8° due east of magnitude 5.1 Phi (φ) Aurigae. NGC 1931 is just 0.3° from Eunomia, to the asteroid’s southwest. It contains a 10th-magnitude open cluster with a handful of bright stars surrounded by a 4’-wide nebula. A larger scope will show it best.
For easier viewing in smaller instruments, a full degree in the other direction, to Eunomia’s southeast, is the 6th-magnitude open cluster M36. This relatively nearby (4,000 light-years) grouping of young stars spans 12’ and has some 60 members.
Sunrise: 7:08 A.M.
Sunset: 4:34 P.M.
Moonrise: 11:37 A.M.
Moonset: 10:00 P.M.
Moon Phase: Waxing crescent (30%)
Sky This Week is brought to you in part by Celestron.
