Sagittarius in detail | Astronomy.com (2024)

In the August 2013 issue of Astronomy, we printed a two-page chart of the constellation Sagittarius the Archer. On that chart, I included the locations and basics for 40 deep-sky objects. Unfortunately, I didn’t have room to go into detail about any of them. Here online, however, I have all the space I need. What follows, then, is a beefier write-up of each of the objects, in order of their right ascensions. So, print out these descriptions, and take them and the chart out to your favorite observing site this summer.

Editor’s Note: In the August issue, the declination lines in “40 deep-sky targets in Sagittarius“ were labeled incorrectly. We apologize for the error, and please find a corrected version of the story for you to download below.

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NGC 6445 // Lisa Dombrow/Phil Terry/Adam Block/NOAO/AURA/NSF

NGC 6440
17h49m, –20°22′
This target lies 5.9° west of magnitude 3.8 Mu (μ) Sagittarii. NGC 6440 is small and reasonably faint. Its main claim to fame is that it sits less than 0.4° south-southwest of NGC 6445. Insert your highest-power eyepiece that gives at least a half-degree field of view. The globular itself shows a wide, concentrated core surrounded by a thin halo of unresolved stars.

NGC 6445
17h49m, –20°01′
Our next target lies 5.8° west of magnitude 3.8 Mu Sagittarii and less than 0.4° north-northeast of NGC 6440. NGC 6445 is the second “Box Nebula” amateur astronomers talk about. The other is NGC 6309 in Ophiuchus.

Astronomers classify NGC 6445 as a bipolar planetary nebula, and, as its name implies, it does have a distinct rectangular shape. Through a 12-inch telescope at 250x, you’ll see the two relatively bright lobes, one to the northwest and the other to the southeast, separated by a dark central region. Larger telescopes show this planetary as a thin rectangle with a large, dark central void.

M23 (NGC 6494)
17h57m, –19°01′
M23 is a small-telescope target and one of Charles Messier’s least-observed objects. That’s a shame because it’s gorgeous. To locate this fine sight, point your telescope, or even binoculars, 4.4° west-northwest of magnitude 3.8 Mu Sagittarii, toward the thickest part of the Milky Way.

This open cluster shines at magnitude 5.5 and measures 27′ across, a size equal to the Full Moon. It shows up clearly through a finder scope, and you might even catch its faint glow without optical aid from a dark site.

Through a 4-inch telescope at 100x, you’ll see a gorgeous cluster with 50 stars spreading out into several curving rows of stars. (I can make five distinct chains.) Although the surrounding star field is rich, you’ll have no trouble identifying where M23 ends. The brightest non-cluster star in the area is magnitude 6.5 SAO 160909, which lies 20′ northwest of M23’s center. If you have access to larger telescopes, you’ll see more stars up to a limit of about 100 cluster members.

M20 (NGC 6514)
18h02m, –23°02′
Our next treat is the magnificent Trifid Nebula, an object French comet hunter Charles Messier discovered June 5, 1764. This object owes its common name to three dark dust lanes that converge in front of the brighter emission nebulosity. Look for a nice triple-star system just west of center. These three stars, and two more, provide the ultraviolet radiation that causes M20 to glow. On the Trifid’s northern edge sits a reflection nebula, shown as blue in photos. This region reflects the light of the 9th-magnitude star that sits at its center. You’ll want to set a lot of time aside to observe this object.

You’ll find M20 3.3° southwest of magnitude 3.8 Mu Sagittarii.

NGC 6520
18h03m, –27°53′
This open cluster lies 2.6° north-northwest of magnitude 3.0 Al Nasl (Gamma² [γ²] Sagittarii). Through a small telescope, you’ll see a well-defined cluster against a bright background of distant stars. Through an 8-inch telescope, 30 stars of magnitudes 10 and 11 sit in the central one-third of the cluster. Scan the region to the west and south at about 150x, and you’ll see far fewer stars. What you’re looking at is the dark nebula Barnard 86.

Astronomy magazine Contributing Editor Stephen James O’Meara calls this object the Castaway Cluster in honor of Robinson Crusoe because, to him, the view around NGC 6520 is so grand that the cluster looks like some lonely, uncharted isle in a tempestuous sea.

NGC 6522
18h04m, –30°02′
For our next treat, head 0.6° northwest of magnitude 3.0 Al Nasl (Gamma² Sagittarii). A region of low obscuration known as Baade’s Window, named for German astronomer Walter Baade, enables us to see this cluster, which lies 90 percent of the way to our galaxy’s center.

A 12-inch telescope will resolve several dozen stars around a strongly concentrated core you won’t resolve. You’ll also spot a magnitude 11.4 foreground star less than 2′ from the cluster’s eastern edge.

Finally, look 16′ to the east of NGC 6522 for another globular cluster, magnitude 9.6 NGC 6528.

M8 (NGC 6523)
18h04m, –24°23′
Look 5.5° west of magnitude Lambda (λ) Sagittarii for the magnificent Lagoon Nebula. Around 1680, English astronomer John Flamsteed discovered what became the eighth object on Messier’s list.

You’ll spot this object with your naked eyes from a dark site. It measures three times as wide as the Full Moon, and you’ll be able to follow most of the nebulosity through your telescope. A dark lane (the lagoon) cuts the object in half. On the eastern side of the rift, you’ll see three dozen stars of open cluster NGC 6530 embedded in the gas.

The brightest star west of the lane is the magnitude 5.9 star 9 Sagittarii, which is responsible for the nebula’s glow. A bit more to the west is M8’s core, a region of intense brightness. Look for the Hourglass Nebula, a star-forming region with lots of young stars.

M21 (NGC 6531)
18h04m, –22°29′
You’ll find this relatively unobserved Messier object 2.6° southwest of magnitude 3.8 Mu Sagittarii. I’m pretty certain you’ll sweep up the Trifid Nebula (M20) first, so when you do, move 42′ northeast for M21.

Father Pietro Angelo Secchi (1818¬–1878) called the Sagittarius Star Cloud “Delle Caustiche,” as he said, “from the peculiar arrangement of its stars in rays, arches, caustic curves, and intertwined spirals.”

Barnard 92
18h18m, –18°04′
Less than 1° west-northwest of NGC 6603 lies Barnard 92, a prominent, small, dark nebula shaped like a fingerprint. The only break in its darkness is the magnitude 11.4 star GSC 6268:517. It is one of the first dark nebulae known, discovered in 1913 by Edward Emerson Barnard.

M18 (NGC 6613)
18h20m, –17°06′
You’ll find another of Charles Messier’s lesser-known objects 4.2° north-northeast of magnitude 3.8 Mu Sagittarii. A 4-inch telescope reveals about a dozen stars. Larger telescopes don’t show many more, and higher magnifications spread the cluster out so much that, in effect, it gets lost among the background stars.

M17 (NGC 6618)
18h21m, –16°11′
The Omega Nebula (also known as the Swan Nebula, the Checkmark Nebula, and the Horseshoe Nebula) lies 2.6° southwest of magnitude 4.7 Gamma Scuti. Swiss astronomer Jean-Phillippe Loys de Chéseaux (1718–1751) discovered M17 (and M16) about 1746. Through a 6-inch telescope, the Omega Nebula appears as a bright bar 7′ long with a short extension from the west end to the south. Increase the magnification past 150x, and the extension reveals itself as a hook-shaped feature with dark material obscuring light from its central region. Through a 12-inch or larger scope, you’ll see much more nebulosity — and the brightest regions will show fine striations.

NGC 6624
18h24m, –30°22′
This globular cluster lies 0.8° southeast of magnitude 2.7 Kaus Media (Delta [δ] Sagittarii). Through a 4-inch telescope, you’ll spot this cluster easily as round and evenly bright. A 10-inch scope at 250x reveals the outer edge as irregular and the tiny center brighter than the halo.

M28 // Harel Boren

M28 (NGC 6626)
18h25m, –24°52′
This bright globular cluster lies 1° northwest of magnitude 2.8 Lambda Sagittarii. Through an 8-inch telescope at 150x, you’ll resolve several dozen stars in the wide halo. Through a 14-inch scope, your star count will climb past 150. Viewing the core at 250x or above gives a three-dimensional effect. A relatively bright chain of stars extends to the north. Another fainter one heads to the north-northwest.

M69 (NGC 6637)
18h31m, –32°21′
To find our next target, another globular cluster that Charles Messier put in the middle of his list, look 2.5° northeast of magnitude 1.8 Kaus Australis (Epsilon Sagittarii). M69 sits near the southwest corner of the Teapot asterism.

M69 lies 30,000 light-years from us and only 6,000 light-years from the center of the Milky Way. Astronomers classify it as one of the most metal-rich globulars, which means its stars have relatively high concentrations of elements heavier than helium. That amount is much less than that of our Sun, however, dating M69’s stars to be much older than the one we orbit.

Through an 8-inch telescope, you may have a bit of trouble resolving this globular’s stars. Its core appears broad but concentrated, and a thin halo surrounds it. The cluster lies within a rich star field, so crank up the magnification — it can take it.

Through a 14-inch scope, you’ll be able to resolve about a dozen of M69’s stars, but even with that size instrument, it won’t be easy. Look for three clumps of faint stars that form a triangle close to and surrounding the cluster’s center, one to the northwest, one southwest, and the third one to the east. Oh, and the magnitude 8.0 star that sits a bit more than 4′ northwest of M69’s center is SAO 210259.

NGC 6638
18h31m, –25°30′
Our next target — another globular cluster — lies 0.7° east of magnitude 2.8 Kaus Borealis (Lambda Sagittarii). Through an 8-inch telescope at 150x, this conglomeration appears round with a small, condensed core and a thin halo. Magnitude 9.9 SAO 186904 lies a bit more than 3′ to the south-southwest of the cluster’s center.

NGC 6642
18h32m, –23°29′
This globular cluster sits 2.1° north-northeast of magnitude 2.8 Kaus Borealis (Lambda Sagittarii). Through a 10-inch telescope at 250x, you might notice a slight widening of the central area in a northwest to southeast orientation. That core region remains unresolvable through much larger scopes, although it somewhat resembles a dumbbell. A wide double star lies 2′ north-northwest. The components shine at magnitudes 10.7 and 12.4 and lie 30″ apart. Another, with orange magnitude 7.7 SAO 186912 as the primary and a magnitude 10.9 secondary, lies 12′ northwest. That pair’s separation also measures 30″.

M25 (IC 4725)
18h32m, –19°07′
This open cluster lies 4.4° east-northeast of magnitude 3.8 Mu Sagittarii. It’s visible to the naked eye from a dark site, but not easily because of the richness of the Milky Way background.

A 6-inch telescope at 125x reveals 50 member stars. Two chains of stars stretching east to west lie near the center. A starless gap divides them. Many of M25’s stars exceed 11th magnitude, making this a nice sight through small telescopes. Yellow magnitude 6.8 SAO 161557 sits at the northwest edge.

NGC 6645
18h33m, –16°53′
Move your telescope 2.4° north of our previous treat, M25, to discover NGC 6645, another fine open cluster. Through an 8-inch telescope, you’ll count 50 stars. The feature you want to see lies near the center of the cluster. It’s a circlet of 15 stars whose center is empty. A line of a half-dozen stars protrudes from the eastern side and heads toward the east-northeast for nearly 10′.

NGC 6652
18h36m, –32°59′
This relatively bright globular cluster sits 2.8° east-northeast of magnitude 1.8 Kaus Australis (Epsilon Sagittarii). Through a 6-inch telescope at 125x, this object has a compact core with an irregular halo around it. A 14-inch scope at 300x won’t resolve any of its stars, but it will expand the core enough to make it appear wedge-shaped, pointed toward the east-southeast. Magnitude 6.9 SAO 210344 lies 7′ northwest of the cluster’s center.

M22 // Bernhard Hubl

M22 (NGC 6656)
18h36m, –23°54′
One of the most spectacular objects in Sagittarius is globular cluster M22. This easy naked-eye object ranks as the sky’s third-brightest globular, exceeded only by Omega Centauri (NGC 5139) and 47 Tucanae (NGC 104).

When you observe M22, altitude — how high it appears in the sky — is everything. Many amateur astronomers in Northern Europe, Canada, and the northern United States are unaware of this cluster’s magnificence because, for them, it hugs the southern horizon. See it high in the sky, however, and you’ll understand the hype.

Through even a 4-inch telescope, you’ll see several dozen stars. Pay attention to the bright starry background, which adds character to the scene. Try to discern exactly where the outer boundary of M22 ends and the background begins.

Move up to a 10-inch scope, and you’ll be overwhelmed by hundreds of member stars. You can try counting them by dividing M22 into eight wedge-shaped pieces. Count the stars in just one wedge, then multiply by 8.

M22 lies 2.4° northeast of magnitude 2.8 Kaus Borealis (Lambda Sagittarii).

M70 (NGC 6681)
18h43m, –32°17′
This southerly Messier object lies midway between magnitude 2.6 Ascella (Zeta [ζ] Sagittarii) and magnitude 1.8 Kaus Australis (Epsilon Sagittarii). M70 is similar in brightness to M69 but has a more sharply concentrated center. Through an 8-inch telescope at 200x, you’ll see a bright core and a thin halo in which you can resolve half a dozen stars. A short line of relatively bright stars shoots northward from the cluster’s eastern side.

M70 has an association with Comet Hale-Bopp (C/1995 O1). Neither discoverers Alan Hale nor Thomas Bopp was actively comet hunting when they made their discoveries July 23, 1995. They merely pointed telescopes at M70 and spotted a foreign object in the field of view.

M54 (NGC 6715)
18h55m, –30°29′
Our next treat lies 1.7° west-southwest of magnitude 2.6 Ascella (Zeta Sagittarii). Although its total magnitude is bright, M54’s stars only resolve through the largest amateur telescopes. That’s because it lies 87,000 light-years away, making it the most distant globular cluster in Charles Messier’s catalog. Its brightest stars shine at only magnitude 15.5.

Through a 12-inch telescope, M54’s center appears broad and bright. A razor-thin halo surrounds it, but you’ll need to crank up the magnification past 350x to see it.

NGC 6716
18h55m, –19°54′
This object sits 1° northwest of magnitude 5.0 Xi¹ (ξ¹) Sagittarii, and it’s one I put into the class I call the “great equalizer” clusters. That means NGC 6716 looks as good through a 4-inch telescope as it does through a 12-inch one. Sure, you may see more ultra-faint stars when you use a larger aperture, but the essence of the cluster will be the same.

So, through a 4-inch or larger scope, you’ll see two distinct groupings of stars with a gap between them. A curved arc of half a dozen 9th- and 10th-magnitude stars sits to the north, and a second group whose shape reminds me of the Coathanger cluster (Collinder 399) lies to the southwest. Adding a splash of color is the orange magnitude 7.0 star SAO 161947, which lies 12′ to the west-northwest of NGC 6716’s center.

NGC 6717
18h55m, –22°42′
Our next object is a globular cluster you’ll find 1.7° south-southwest of magnitude 3.5 Xi2 Sagittarii. When you arrive at that location, however, you’ll encounter a problem: Magnitude 5.0 Nu² (ν²) Sagittarii lies less than 2′ north of our target. Through small telescopes, the globular appears as a hazy patch near the star. Be sure to crank the power up to at least 200x to put some separation between the two objects.

At that magnification, or through a larger scope like the 12-inch with which I last observed NGC 6717, you’ll first spot several foreground stars, the brightest of which shines at magnitude 11.7. Those stars seem superimposed on a nebulous background glow, and that’s what you’re trying to see. I think of Bruce Lee’s instruction to his student in the 1973 movie Enter the Dragon: “It’s like a finger pointing the way to the Moon. Don’t concentrate on the finger, or you’ll miss all that heavenly glory.”

NGC 6717 carries another astronomical designation — Palomar 9. In fact, it’s the brightest (by more than a magnitude) of any from that relatively obscure list of 15 deep-sky targets.

NGC 6723
19h00m, –36°38′
The gorgeous Chandelier Cluster (NGC 6723) sits 0.5° north-northeast of magnitude 4.8 Epsilon Coronae Australis, within a region rich in reflection nebulosity.

Through an 8-inch telescope at 200x, you’ll see a large, concentrated core that exhibits mottling (alternating bright and dark regions). Two dark gaps lie at the cluster’s southwestern edge.

Through a 14-inch scope, crank the magnification up to 300x, and you’ll see NGC 6723’s irregular shape plus many more individual stars. Do you see the draping arcs of stars for which this globular got its popular name the Chandelier Cluster? A 16-inch scope will reveal more than 100 faint points of light. The brightest star in view glows at magnitude 10.4 and lies 3′ from the cluster’s center.

M55 (NGC 6809)
19h40m, –30°58′
Our next treat is another globular cluster from Charles Messier’s catalog. M55 is a superb object you may just spot with your naked eye from an ultra-dark site. Observers describe this cluster as “highly resolved.” That means its core doesn’t appear packed with stars, which often gives a “burned out” effect.

A 12-inch telescope at 300x will break it into hundreds of 11th- and 12th-magnitude stars. Through an eyepiece with a small field of view, M55 may appear more like a rich, open cluster.

You’ll find M55 8° east of magnitude 2.6 Ascella (Zeta Sagittarii).

NGC 6818
19h44m, –14°09′
The treat amateur astronomers call the Little Gem (NGC 6818) sits in a no man’s land bereft of bright stars near the Archer’s northern border with Aquila. Look for this small planetary nebula 9° due west of 3rd-magnitude Beta (β) Capricorni. Although stellar luminaries in this part of the sky are scarce, this is a great area for deep-sky treats. The Little Gem lies only 0.7° north-northwest of Barnard’s Galaxy (NGC 6822). Talk about two objects that are on the opposite ends of the surface brightness spectrum!

As luck would have it, the Little Gem is the bright one. It shines at magnitude 9.3 and measures roughly 0.8′ across from north to south and a bit less from east to west. The combination of brightness and size means NGC 6818’s surface brightness is high, and you can really crank up the magnification. The greenish-blue color most observers see appears best at around 100x. Above that power, look for this object’s ever-so-slightly darker inner half.

Observers began to refer to this planetary as the Green Mars Nebula when they noticed its size through a small telescope (22″, less than half its listed diameter) equaled that of Mars when the Red Planet approaches closest to the Sun.

NGC 6822
19h45m, –14°48′
If you use an 8-inch or larger telescope, insert the eyepiece that gives you the widest field of view, and look for Barnard’s Galaxy, also known as NGC 6822. This object lies in Sagittarius 1.5° north-northeast of 5th-magnitude 55 Sagittarii. In 1881, American astronomer Edward Emerson Barnard discovered this object through a 6-inch refractor.

Barnard’s Galaxy shines at magnitude 9.3 — pretty bright for a galaxy. Unfortunately, its light spreads out over an area 16′ by 14′, so its overall surface brightness is low.

Look for a dim haze roughly twice as long as it is wide. Note the slightly brighter streak that spans NGC 6822’s long axis.

Larger scopes show several star-forming regions along the galaxy’s northern end. To see just these, use a nebula filter. Without a filter, and through a 12-inch or larger scope, look for individual supergiant stars. They’re faint — the brightest glow at only 14th magnitude — but they reveal themselves by lending a granular appearance to the galaxy.

M75 (NGC 6864)
20h06m, –21°55′
Our next object is globular cluster M75, which lies 60,000 light-years away. Because of its vast distance, you’ll have trouble resolving even its brightest stars through a 12-inch telescope. The core appears bright and stellar at low magnification. Although M75 is in Sagittarius, it’s outside the Milky Way’s band, so the field is bereft of foreground stars. You’ll find it 5° north-northeast of magnitude 4.7 Omega (ω) Sagittarii, next to that constellation’s border with Capricornus.

Sagittarius in detail | Astronomy.com (2024)

FAQs

What is special about Sagittarius A? ›

At just 26,000 light years from Earth, Sgr A* is one of very few black holes in the universe where we can actually witness the flow of matter nearby.

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Why is the Milky Way black hole called Sagittarius A? ›

Sagittarius A* is more than 25,000 light years from Earth – our nearest supermassive black hole, with an estimated mass millions of times that of our Sun. Often abbreviated by researchers to Sgr A* (pronounced “Sagittarius A star”), it sits in the constellation of Sagittarius at the very heart of the Milky Way.

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How was Sagittarius formed? ›

Sagittarius A* did not come from a star. And neither did any supermassive black hole. The most likely possibility is that it, and others like it, formed from the spontaneous collapse of massive clouds of interstellar molecular hydrogen and dust.

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What is the asterisk in Sagittarius? ›

The name Sgr A* was coined by Brown in a 1982 paper because the radio source was "exciting", and excited states of atoms are denoted with asterisks. Since the 1980s, it has been evident that the central component of Sgr A* is likely a black hole.

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Why is Sagittarius so powerful? ›

As the ninth sign of the zodiac, fiery and mutable Sagittarius (whose planetary ruler Jupiter represents intellect, expansion, and wisdom) is known to be the “spiritual warrior” because they fight for what is right and just in the world.

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What is rare about Sagittarius? ›

As a professional astrologer with almost 10 years of experience, I can honestly say that there is no zodiac sign like Sagittarius. What makes Sagittarius so unique is its dynamic blend of passion, curiosity, intensity, and adaptability.

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What kind of body is Sagittarius A? ›

Our local galactic center's black hole, Sagittarius A*, is a supermassive black hole with a mass of about four million suns, which is fairly small for a supermassive black hole. NASA's Hubble Space Telescope and other telescopes have determined that many galaxies have supermassive black holes at their center.

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What is the bigger black hole than Sagittarius? ›

While Sgr A*, 27 000 light-years away, has a mass roughly four million times the Sun's mass, M87* is more than 1000 times more massive. Because of their relative distances from Earth, both black holes appear the same size in the sky.

What God is associated with Sagittarius? ›

Sagittarius is ruled by Jupiter and hence, shares a direct connection with the blessings of Lord Vishnu and Lord Hanuman. Sagittarians are the thriver of wealth and accomplishments and hence, they must always pray to Lord Hanuman and keep fasts on either Tuesdays or Saturdays.

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What is the myth of Sagittarius? ›

Greek mythology

Some identify Sagittarius as the centaur Chiron, the son of Philyra and Cronus, who was said to have changed himself into a horse to escape his jealous wife, Rhea, and tutor to Jason. As there are two centaurs in the sky, some identify Chiron with the other constellation, known as Centaurus.

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What is Sagittarius' weakness? ›

Strengths: Sagittarians are extremely adventurous and fun-loving. They're amusing and always in good spirits. Very ambitious and admirable. Weaknesses: Sagittarians can be very impatient and need instant results. Initially, they may boast of great things, however may fail to follow up on time.

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What is the lucky alphabet for Sagittarius? ›

Lucky Alphabet For Sagittarius

Sagittarius can attract fortune and good wealth by using letters like A, Y, and M. These letters are the most advantageous for Saggitarius natives. They can also go a long way in industries like publishing, banking, advertising, marketing, and more. But their unlucky letters are V and K.

What are the lucky days for Sagittarius? ›

Thursday and Friday are the lucky days of this zodiac. 6, 3, and 8 are the lucky numbers of this zodiac. 15th, 21st, and 28th are the lucky dates for Sagittarius. Iron and Gold are the lucky metals of the Sagittarius.