Eta Carinae

Eta carinae supernova

Eta Carinae 1

 Eta Carinae:The most beautiful regions of the Milky Way

A magical stretch

Eta Carinae lies at the midpoint of one of the most beautiful regions of the Milky Way. Here, turbulent eddies of milky starlight stretch from Centaurus to Carina. This includes about two dozen open star clusters (including the Southern Pleiades), a dozen nebulae (including Eta Carinae), dense star clouds, and dust-filled voids (including the Coalsack).

The Southern Cross is the most obvious asterism of stars in this Van Goghian celestial landscape. But here’s an aside. When I first saw the Southern Cross, it didn’t strike me as the mystical symbol Crosby, Stills & Nash sang about; seeing it didn’t make me understand anything except that this little constellation (6[degrees] across, or only slightly larger than the handle of Sagittarius’ Teapot asterism) looks more like a tail-less kite than a cross.

Don’t get me wrong. I do think that the Southern Cross is beautiful, but largely because of its placement next to Alpha and Beta (P) Centauri, which point almost directly at it. Adding to this celestial advertising is the fortunate positioning of the Coalsack, which looks like a bleak shadow just to the Cross’ southeast. It’s the union of these celestial bodies that creates an atmosphere of visual magic in this region of the Milky Way. Remove those two bright stars and that web of darkness from the scene, and the Southern Cross would lose much of its visual impact.

The Southern Cross also harbors one of the southern sky’s most popular open star clusters: the Kappa (k) Crucis Cluster, better known as the Jewel Box. I find its reputation a bit overhyped, perhaps a product of its placement (near Beta Crucis and the Coalsack) and 19th-century hyperbole–a creation of John Herschel, who, after observing it through his 18-inch reflector, noted that the cluster’s stars shine with different colors, like the “effect of a superb piece of fancy jewelry.”

That’s fine and appropriate, and the Jewel Box remains one of the most popular southern treasures. There is, however, a lesser-known, yet in my opinion much more visually stunning open star cluster nearby: NGC 3293 in Carina. I call it the “Little Jewel Box” because the cluster is just as bright as the Kappa Crucis Cluster but only half its apparent size. And although NGC 3293 has about one-third the number of stars as the Jewel Box, the brightest ones pack a powerful visual punch that makes a much more attractive sight through small telescopes.

Others have similar opinions about the Jewel Box. German astrophotographer Dieter Willasch, for instance, believes that yet another open cluster in Carina, NGC 3766, deserves to be called the Jewel Box more than the Kappa Crucis Cluster. He suggested the “Rich Man’s Jewel Box” as an alternative name. NGC 3766 lies midway between the Eta Carinae Nebula and Acrux (Alpha Crucis) and appears as a fine scattering of scintillating jewels seen against the carpet of the Milky Way. It is a stunning cluster, but mainly for larger instruments.

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The flip side

As we have seen, the southern sky is the domain of many superlative wonders, some of which have counterparts in the north: There’s a Southern Pleiades Cluster, a Southern Beehive Cluster (NGC 2516), a Southern Ring Nebula (NGC 3132), and a Southern Pinwheel Galaxy (M83). All are just as bright and wonderful as the objects in the north that they mirror.

Add to this list the south’s two extragalactic naked-eye marvels, the Large and Small Magellanic Clouds; Omega Centauri and 47 Tucanae, the two greatest globular star clusters in the heavens; the enigmatic galaxy Centaurus A (NGC 5128), a superlative in virtually every region of the electromagnetic spectrum; and Eta Carinae, which had the largest explosion that any star is known to have survived, and you can begin to understand the visual impact the southern celestial sky can have on a transplant from the north.

One sight that always amazes me from the Southern Hemisphere is the hub of the Milky Way flipped with respect to my normal northern perspective with its attendant arms parallel to the horizon. For some reason, whenever I look at the Milky Way in this position, I find the dark nebulae standing out more dramatically than their bright background.

The constellation Sagittarius also dissolves from view, and several smaller unfamiliar and disconnected stellar groupings replace it. Suddenly I’m lost in familiar territory, and a spark of childlike wonder ignites. When you’ve looked at the sky for as long as I have, it’s hard to lose your place, which also means it’s hard to see things from a fresh perspective. But with the topsy-turvy southern skies, I now can look into the luminous folds of the Milky Way and get lost in their glory once more.

And that is the true beauty of the southern skies to this northern observer–that they can transport me back to a time when the night skies were vast and foreign and beckoned me to explore them. As Judith Thurman, a contributing writer for The New Yorker, says, “Every dreamer knows that it is entirely possible to be homesick for a place you’ve never been to, perhaps more homesick than for familiar ground.”

Caption: The southern Milky Way above the Atacama Desert’ competes herewith a storm cloud and city lights, yet it still emerges victorious, Note the Large Magellanic Cloud to-the lower right of center. YURI BELETSKY

Caption: The Tarantula Nebula (NGC 2070) is bright despite the fact that it lies not within the Milky Way, but in the Large Magellanic Cloud. KEN CRAWFORD

Caption: The Southern Pleiades (IC 2602) is a gorgeous open cluster in the constellation Carina the Keel. MARCO LORENZI

Eta Carinae

Caption: Omega Centauri (NGC 5139) is the brightest globular cluster in the sky. It may contain as many as 10 million stars. TONY HALLAS

Caption: The Pipe Nebula (Barnard 59/65-67/78), shown in this image of the Milky Way above Delinha Observatory in the Qinghai Province of China, is the dark extension at the lower right of center. JEFF DAI

Caption: The Southern Beehive Cluster (NGC 2516) lies in Carina near the 2ndmagnitude star Avior (Epsilon [[epsilon]] Carinae). YURI BELETSKY

Caption: NGC 104 is the sky’s second-brightest globular cluster. Its common name, 47 Tucanae, comes from a time when celestial cartographers thought it was a star. THOMAS V. DAVIS

Caption: The Coalsack is a dark nebula within the sky’s smallest constellation, Crux the Southern Cross. LUKE DODD

Caption: The sky’s brightest emission nebula is the fabulous Eta Carinae Nebula (NGC 3372). It’s a favorite target for southern-sky imagers. GERALD RHEMANN

Caption: The Jewel Box (NGC 4755), also known as the Kappa ([kappa]) Crucis Cluster, is a beautiful sight through any size telescope. DON GOLDMAN

Caption: The Sagittarius region near our galaxy’s center contains many nebulae, but few rise to the splendor of the Lagoon Nebula (M8, right of center) and the Trifid Nebula (M20, upper left of center). TERRY HANCOCK/FRED HERRMANN

Caption: The Southern Ring Nebula (NGC 3132) in Vela lies nearly halfway between the celestial equator and the South Celestial Pole. DON GOLDMAN

Caption: The Southern Pinwheel Galaxy (M83) is a spectacular sight through medium-sized telescopes. It lies in the constellation Hydra some 15 million light-years away. ADAM BLOCK/MOUNT LEMMON SKYCENTER/UNIVERSITY OF ARIZONA

 

Stephen James O’Meara is a contributing editor and “Secret Sky” columnist for Astronomy.

Star-hop through a patch of your southern sky tonight to find 14 selected sights for binoculars.

Of all the summer constellations, Scorpius holds a special place. It has lots of bright stars and a distinctive shape. It has Antares, one of the three most strongly colored 1st-magnitude stars in the sky (the others are Betelgeuse and Aldebaran). But for skywatchers at midnorthern latitudes, Scorpius is so low in the south that it’s gone before you know it. It puts on a good evening appearance over the treetops only in June and July. You can find it on the all-sky constellation map in the special pull-out section.

Because Scorpius is so low, telescope users who can’t tote their gear to a site with a good southern exposure miss out entirely. Binoculars, however, are utterly portable. And the Scorpius area is swarming with fine binocular targets.

Of course, you need a . The map on the facing page isadapted from Wil Tirion’s Sky Atlas 2000.0, which shows stars as faint as magnitude 8.0. Plotted on it are selected sights for a binocular nature tour. The black circles are 6 [degrees] across, about as wide as the field of view that you see in typical 8-power glasses. If your binoculars have a lower magnification, they’ll probably show a slightly larger field. With higher power, the view will be smaller.

I scouted the area with hand-held 7×50 binoculars, typical of what many amateurs use, then with tripod-mounted 10x50s. My light pollution was fairly severe so low in the sky; no stars fainter than magnitude 4.5 were visible to the naked eye.

So where I saw something, you almost surely can too.

  1. Antares, the brightest star of Scorpius, is a red supergiant, spectral type M2 lab. In binoculars it’s a brilliant orange firespark, like a bonfire miles away. Antares is about 500 light-years from us and 600 times larger than the Sun, easily big enough to encompass the orbit of Mars. Like other red supergiants, it has shown evidence of being oblong rather than round. Antares is the brightest member of the vast Scorpius-Centaurus Association of highly luminous young stars, which spills across several constellations and gives them their brilliance.Bracketing Antares in the same binocular field are two other association members: silvery bluish Tau ([Tau]) and Sigma ([Sigma]) Scorpii, types B0 and B1. They’re both 3rd magnitude and located 2 [degrees] from the central fire of Antares. What a fine color contrast the trio makes! Tau is bluer than Sigma by just a trace. When seen low through summer haze, however, they can both appear yellow.Just 1/2 [degree] east (left) of Antares is a 6th-magnitude neighboring star that I’ve never seen mentioned in descriptions of this famous field. So strong is the effect of color contrast from bright Antares that the little star looks blue to me by comparison. In fact it is an orange giant, spectral type K1. It’s such a significant part of the binocular scenery here that it ought to have a better name than just SAO 184437. Suggestions, anyone?
  1. M4 is a globular star cluster tucked conveniently under the line from Antares to Sigma. In my old hand-held 7x50s I can detect M4 almost at first look – a very dim, gray fuzzball with almost no concentration toward its center. In the tripod-mounted 10x50s it is much more obvious, even displaying a hint of stellar mottling. Aside from the benefit of the 10x50s’ higher magnification, you can see much more in abinocularview that remains truly rock-steady.At a distance of 7,000 light-years, M4 may be the nearest of all the globular clusters. But it’s less densely packed with stars than most. And, unfortunately, it’s somewhat obscured by the clouds of interstellar dust that riddle this entire area.Just south and east of M4 is a row of three faint stars, 7th and 8th magnitude, almost 1 [degree] long. To me it’s a miniature duplicate of the familiar row of three bright stars forming the head of Scorpius off to the west. The little miniature is barely visible in the 7x50s but plainer in the 10x50s.
  1. Rho ([Rho]) Ophiuchi, to the north in the same field, is a lovely triple star for binoculars. The 5th-magnitude primary is flanked on its north and west-southwest by two 7th-magnitude stars at nearly equal distances from it, 150 and 170 arcseconds. This is a very nice object in 7x50s and much more so in the 10x50s.

If you have a pitch-black sky, look for traces of large, dim nebulosity near Rho. In a telescope, Rho itself is a fine double star with a separation of only 3″.

  1. The Antares Dipper. Coming to this familiar field with fresh eyes, I noticed something new. A small, dipperlike star pattern fills the binocularfield around Antares. Its lip is Rho Ophiuchi, and the bottom of its bowl is formed by Omicron (o) and Sigma Scorpii. Antares is at the joint of the bowl to the handle, which consists of Tau (and, if you want to extend the handle, Epsilon Scorpii 7 [degrees] to the southeast).
  2. The Floating Fan. Between Antares and Rho Ophiuchi, floating as if on water filling the dipper’s bowl, is a big-gish asterism around 5th-magnitude 22 Scorpii. This star is a wide triple, like a looser, more straggly version of Rho. Its two outliers point north-northwest and west-southwest toward the ends of the asterism, like arms flung wide to the ends of an opened fan. It’s marked on the map. All of the fan’s stars except 22 Scorpii are 7th or 8th magnitude.
  3. The Crown of the Scorpion. Shift now about a binocular field north and west to 3rd-magnitude Beta ([Beta]), Delta ([Delta]), and Pi ([Pi]), the row marking Scorpius’s traditional head. Some turn-of-the-century guidebooks call it the Crown of the Scorpion. This is another grand and best hunting binocular field.But just west of the line between Delta and Pi is a virtually unknown asterism – a north-pointing arrow, just over 1 [degree] long, made of 5th- and 6th-magnitude stars like a miniature of the constellation Sagitta. Once you notice it, it will catch your attention whenever you return here.The northern part of the Crown, however, holds the most interest.
  1. Nu ([Nu]) Scorpii. The Crown’s northern bright star is Beta Scorpii, a famous telescopic double. East-northeast of it by 1.6 [degrees] is Nu, a lively little double for binoculars. The magnitudes are 4.2 and 6.4, and the separation is 41[feet], with the faint star north-northwest of the brighter. I can’t definitely resolve it in hand-held 7x50s, but the 10x50s do the trick when firmly mounted or even braced against a railing.
  2. Omega(1) and Omega(2) ([Omega](1)) and ([Omega](2)) Scorpii. This pair of naked-eye gems, magnitudes 4.0 and 4.3, respectively, reminds me of a pair of eyes set akilter and peering through Scorpius’s head. With spectral types B1 and G3, respectively, they show subtly but unmistakably different colors in binoculars: bluish white and very pale yellow.
  3. M80. Backtracking partway to Antares, try hunting binoculars for this 7th-magnitude globular duster. It’s very different from M4, our first globular of the night. M80 is tiny and concentrated, almost starlike in binoculars. I found it a challenge just to identify. Find the faint “star” at the correct point on the map, then look for signs of its nonstellar fuzziness. An 8.4-magnitude star lies just off M80’s northeastern edge.
  4. RR Scorpii. Now we move farther afield to the southeast. Using the map, memorize the shape of the triangle that Tau and Epsilon Scorpii form with the “Trowel” asterism that’s plotted east of them. It’s 1.3 [degrees] tall and made of 6th- to 8th-magnitude stars. Just 1/2 [degrees] east of its brightest member is RR Scorpii.This red, Mira-type variable usually ranges from magnitude 6 to 12 in a period of nine months. Its next maximum is due around September 20th, so you can watch it swelling into view this summer.
  1. M62 begins our final trio of globular dusters for the night. It’s 1 [degree] eastnortheast of RR Scorpii, just over the border in Ophiuchus. I spotted it almost right away in both binoculars as a little cottony fuzzball. It’s just south of a pair of 8th-magnitude stars, with which it can be confused at first glance.
  2. M19, 4 [degrees] north, looks similar but just a bit fainter. (The two globulars are cataloged as magnitudes 6.6 and 7.2, respectively.) M19 is nestled to the lower right of an arc of three widebinocularstar pairs that include 26, 28, 31, and BF Ophiuchi. These three pairs quickly become M19’s distinctive landmark.
  3. BF Ophiuchi is a Cepheid variable that ranges from magnitude 6.9 to 7.6 and back every 4.068 days. The star that appears paired with it 1/5 [degrees] to its east is magnitude 6.2. Watch the brightness difference between them change from night to night.
  4. M9 is much farther north. I spotted this globular cluster too almost at first glance, once I had the right point. But it’s fainter (at magnitude 7.6) and smaller than the previous two.

 

Each of these last three clusters has a dimmer, 8.2- to 8.4-magnitude globular roughly 2 [degrees] to its east. Try as I might, I saw no definite sign of NGC 6304, 6293, or 6356. Nor did I get the three, 9th-magnitude globulars we’ve plotted on the map. With a darker sky, maybe you can.

We’re now in the edge of the richest zone of the summer Milky Way. In a dark, natural sky this whole area is mottled with spooky dark nebulae. Off to the southeast is the tail of Scorpius with its great spangled open clusters, including M6 and M7, which are pictured for  observers on page 84 of this issue. To the east lurk the great Messier nebulae and clusters of Sagittarius. But that’s another story.