Key Takeaways:
- Pluto reaches opposition on July 25th, appearing brightest and offering the best viewing opportunity for observers using large telescopes (11-inch or larger) and astrophotography techniques. Its magnitude is 14.4.
- On July 26th, Venus's close proximity to Zeta Tauri in the predawn sky offers a view similar to the supernova observation of 1054, with the Crab Nebula (M1) nearby.
- The Moon's movements are detailed for July 26th-31st, including close passes near Regulus, Mars, and Spica, providing opportunities for observation of these celestial pairings.
- Several deep-sky objects are highlighted for observation, including the open cluster NGC 6709 (July 27th), the globular cluster NGC 5634 (July 30th), and the Southern Delta Aquariid meteor shower's peak (July 31st).
Sky This Week is brought to you in part by Celestron.
Friday, July 25
Pluto reaches opposition at 3 A.M. EDT. Opposition is when objects typically appear at their best, and with no Moon in the sky, observers with large scopes and little light pollution may be able to visually snag the dwarf planet.
Pluto may be at its best, but it is still magnitude 14.4. According to Astronomy Associate Editor Michael Bakich, you’ll want an 11-inch scope — and preferably larger — to capture it visually. However, photography can boost your chances — many of today’s newer (and smaller) imaging smartscopes can also nab you Pluto, so give it a try!
Pluto rises around 8 P.M. local daylight time and is highest just after midnight. Late this evening you can find it about 20° high in the south from the Midwest, in far western Capricornus. It lies about 4.2° south of 5th-magnitude Sigma (σ) Capricorni and is just 10’ north of an 8th-magnitude field star, HD 193545. The dwarf planet sits roughly equidistant between two similarly bright field stars this evening, one magnitude 13.4 and the other magnitude 13.5. Remember, Pluto is still a full magnitude fainter than either of these.
Your best bet will be to use the go-to function on your scope, then look for the “star” that appears slightly “flat” and grayish in color between the two brighter pinpoints of light. At this distance, Pluto’s tiny disk spans less than 1”, so it may not appear circular to the eye.
One of the best ways to identify Pluto is to take a series of images over the course of three to four nights and look for the object that has moved. Pluto moves relative to the background stars at a rate of about 4” per day, so you’ll need a few days to spot the difference. It is currently moving west, so watch for the way the line of three lights north of Sigma Cap elongates into a triangle over time. The westward-moving dot pulling out of line is Pluto.
Check out the chart below for assistance locating Pluto once you’ve found HD 193545.
Sunrise: 5:53 A.M.
Sunset: 8:20 P.M.
Moonrise: 6:34 A.M.
Moonset: 9:16 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 12 P.M. local time from the same location.
Saturday, July 26
The Crab Nebula (M1) has one of the most famous origin stories around: The light from the supernova that created the nebula was recorded by ancient astronomers when it appeared as a “guest star” in July 1054. The new star, which sat near Zeta (ζ) Tauri, one of the horns of Taurus the Bull, was so bright it was visible during the day for a time.
Do you ever wonder what it was like to see a bright light appear in that spot in Taurus? Well, this morning is your chance, as magnitude –4 Venus sits just 45’ northwest of 3rd-magnitude Zeta Tau in the predawn sky. Look for the pair some 10° high in the east by 4 A.M. local daylight time. Half an hour later, they’ve gained another 5° in altitude. It’s a sight similar to the one those ancient astronomers got, but we also get a bonus: the mess of dust and gas left over by that exploding star, M1, which tonight sits just 0.5° north of Venus. They’re visible together in a telescope eyepiece.
The Crab shines at magnitude 8.7 and spans about 6’ by 4’, appearing as an oval-shaped smudge of light in most amateur scopes. At its center is a 16th-magnitude neutron star, the collapsed core of the star that died in the explosion. You’ll want to catch this target well before the sky starts growing light, as it’s faint and will be quickly washed out by the oncoming twilight.
Of course, you can also enjoy the sight of Venus through your scope, which isn’t a point of light but is instead a disk spanning a hefty 15”. The planet is now more than half-lit, showing off a 73-percent-illuminated gibbous phase this morning. It will be visible well into twilight, even after the stars have disappeared.
This afternoon, the Moon passes 1.3° north of Regulus at 4 P.M. EDT. You can view the pair for a little over an hour after sunset in the western sky, as they sink together toward the horizon. The Moon lies just to the upper left of Regulus; our satellite is now a delicate 6-percent-lit waxing crescent.
Sunrise: 5:53 A.M.
Sunset: 8:19 P.M.
Moonrise: 7:45 A.M.
Moonset: 9:42 P.M.
Moon Phase: Waxing crescent (4%)
Sunday, July 27
The Moon has moved away from the Lion’s heart and toward its haunches in the evening sky. It will pass close to the planet Mars tomorrow, while the Red Planet crosses from Leo into Virgo today. We’ll check out the pairing tomorrow after sunset.
This evening, look high in the southeast a few hours after sunset to find the stately constellation Aquila the Eagle, anchored by its brightest star, magnitude 0.8 Altair. In the northwestern regions of this constellation, near where it borders Ophiuchus, the bright open cluster NGC 6709 is our target for study tonight. Shining at magnitude 6.7, this cluster is visible in binoculars or any sized scope, making it a great target for beginners with any type of equipment. It lies just under 5° southwest of 3rd-magnitude 3.0 Zeta Aquilae.
Spanning about 13’, NGC 6709 is a rich cluster that will show off some three dozen stars through a 4-inch telescope. Larger telescopes will reveal even more stars. Astronomers estimate the cluster is quite young, around 140 million years old.
Sunrise: 5:54 A.M.
Sunset: 8:18 P.M.
Moonrise: 8:53 A.M.
Moonset: 10:04 P.M.
Moon Phase: Waxing crescent (10%)
Monday, July 28
The Moon passes 1.3° south of Mars at 4 P.M. EDT and sits horizontally in line with the Red Planet after sunset this evening. By 9 P.M. local daylight time, the pair is 15° high in the west, both now in Virgo the Maiden. They are visible for about two hours, setting shortly before 10:30 P.M. local daylight time.
Mars shines at magnitude 1.6, its disk spanning 4” through a telescope. Unfortunately, its small size precludes viewing much detail on the surface. But much closer and larger in the sky, the Moon is a nearly 20-percent-lit crescent tonight, with its eastern limb bathed in light as sunrise slowly crosses the lunar nearside. Look for the large, circular Mare Crisium in the lunar northeast, whose flat, dark floor stands out in stark contrast with the rougher, lighter surroundings. Its floor is pocked with a few smaller craters — there are three, standing roughly in a line near the mare’s western rim. These are (from largest to smallest and south to north) Picard, Pierce, and Swift.
While you’ve got your telescope out, glance to the upper left of the Moon and Mars as the sky grows dark. Third-magnitude Porrima, also cataloged as Gamma (γ) Virginis, is a lovely double star separated by some 3”. Although Porrima is sometimes occulted by the Moon, tomorrow our satellite will pass well below it in the sky, standing about 5.5° to Porrima’s lower left by evening.
Sunrise: 5:55 A.M.
Sunset: 8:17 P.M.
Moonrise: 9:57 A.M.
Moonset: 10:24 P.M.
Moon Phase: Waxing crescent (16%)
Tuesday, July 29
Saturn still stands out in the early-morning sky as a bright, 1st-magnitude point of light in southwestern Pisces. Two hours before sunrise, the ringed planet is roughly 50° high in the south and offers an easy stepping-stone to Neptune, which lies 1° north of Saturn — close enough to catch both worlds in a single field of view through your telescope. Neptune is invisible to the naked eye but will appear under magnification, shining at magnitude 7.7 and showing off a tiny, bluish-gray, 2”-wide disk.
Saturn is far more impressive, not only much brighter but also appearing much larger, with a disk 18” across and rings that stretch 42” from end to end. Its brightest moon, mid-8th-magnitude Titan, lies some 2.8’ east of the planet. Titan will reach its greatest eastern elongation tomorrow morning just after 7:30 A.M. EDT, when it will stand a bit more than 3’ due east of Saturn.
This morning several other fainter moons are visible as well, clustered much closer to the planet. Tenth-magnitude Tethys, Rhea, and Dione are all visible around 5 A.M. EDT; Rhea is about 1.3’ east of Saturn, while Tethys is just 30” west of the planet and Dione another 30” west of Tethys.
Sunrise: 5:56 A.M.
Sunset: 8:16 P.M.
Moonrise: 10:59 A.M.
Moonset: 10:44 P.M.
Moon Phase: Waxing crescent (24%)
Wednesday, July 30
Asteroid 4 Vesta remains an easy-to-spot target in western Libra, just 5° north of Zubenelgenubi, the Balance’s double alpha star. Tonight and tomorrow offer an excellent opportunity to see the 7th-magnitude space rock move relative to the background of stars, as it currently lies less than 0.5° from a slightly fainter 8th-magnitude background star (HD 130193).
Tonight, Vesta is 10.5’ northwest of that star. Tomorrow, it is a little less than that distance roughly due east of it. Vesta is also drawing closer to 6th-magnitude Xi1 (ξ1) Librae and will sit due south of this star on August 6, offering another chance to easily catch the asteroid moving against the stationary background for a few days before and after this date.
While you’ve got your scope out, swing up 6.7° northwest into Virgo to enjoy NGC 5634, a lovely compact globular cluster that shines at magnitude 9.6. Astronomers believe this cluster was once part of one of the Milky Way’s smaller satellite galaxies, likely the the Sagittarius Dwarf Elliptical Galaxy or the Sagittarius Dwarf Spheroidal Galaxy. Its brightest star, 8th-magnitude SAO 139967, is just southeast of the cluster’s center. The markedly orange-hued sun stands out distinctly against the fuzzy background created by the compact structure of the grouping.
Sunrise: 5:57 A.M.
Sunset: 8:15 P.M.
Moonrise: 12:00 P.M.
Moonset: 11:05 P.M.
Moon Phase: Waxing crescent (33%)
Thursday, July 31
The Moon passes 1.0° south of Spica at 2 A.M. EDT, though both are below the horizon at that time. That’s good news, because it means the Southern Delta Aquariid meteor shower peaks this morning with no moonlight to interfere with your view of shower meteors.
These meteors appear to radiate from a point in the sky to the lower right of the star Skat (magnitude 3.3) in Aquarius as the constellation sets in the early-morning sky. An hour before sunrise, the radiant is 25° high in the southwestern sky.
You can expect to see around a dozen shower meteors per hour. Your best chance for the most impressive sights will be to look some 40° to 60° away from Skat, to either side of this star. The Southern Delta Aquariids are medium-fast meteors, streaking through the sky at around 25 miles (40 kilometers) per second. They likely originate from Comet 96P/Machholz 1, which loops around the Sun every 5.3 years.
The peak of the Southern Delta Aquariids overlaps with the ramp-up period for next month’s meteor shower, the Perseids, which peak August 12. So, although most of the meteors you’ll see this morning will be Southern Delta Aquariids, you might also catch some stray Perseids, which will originate in the northeast. That’s a very different direction — see if you can identify which shower the shooting stars you see belong to!
Night owls might still be able to catch the tail end of the shower’s peak as well. The radiant rises around 9:30 P.M. local daylight time and reaches some 20° high in the southeast by local midnight.
Mercury reaches inferior conjunction at 8 P.M. EDT. It will become visible in the morning by the second week of August.
Sunrise: 5:58 A.M.
Sunset: 8:15 P.M.
Moonrise: 1:01 P.M.
Moonset: 11:28 P.M.
Moon Phase: Waxing crescent (42%)
Friday, August 1
First Quarter Moon occurs at 8:41 A.M. EDT. Rising early in the afternoon, the Moon then reaches apogee — the farthest point from Earth in its orbit — at 4:36 P.M. EDT, when it will be 251,134 miles (4041,61 km) away. Readily visible in the south at sunset, our satellite is now half-lit and shows off its terminator, which separates night from day, running roughly down the middle of the visible lunar face.
Mare Crisium is still apparent in the lunar northeast; now in the southeast you’ll find the large crater Stevinus, surrounded by a mass of bright rays, also easy to spot. These rays are composed of material that was excavated and thrown outward by the force of the impact that created the 47-mile-wide (74 km) crater. Note how some of those rays fall across the dark floors of the neighboring Maria, the Seas of Nectar and Fertility. The way these features are layered shows clearly that the seas are older, with the ejecta from Stevinus strewn overtop them, signaling it came later in time.
Along the terminator, you may also be able to pick out the craters Alphonsus, Ptolemaeus, and Arzachel. Ptolemaeus is northernmost of the trio, located just south of the Moon’s equator. Below it is Alphonsus, and below that is Arzachel. This lunar phase is one of the best times to observe this trio, as their proximity to the terminator creates shadows that help highlight their striking features.
Sunrise: 5:59 A.M.
Sunset: 8:13 P.M.
Moonrise: 2:03 P.M.
Moonset: 11:54 P.M.
Moon Phase: Waxing gibbous (52%)
