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Realm of the nebulae

Map 13: Equatorial Region 4
Virgo to Ophiuchus
ngc_4361_250
Planetary nebula NGC 4361 is located in the constellation Corvus.
Elliot Gellman and Duke Creighton/Adam Block/NOAO/AURA/NSF

Nineteenth-century observers called the area covered by Map 13 the "realm of the nebulae." They weren't describing nebulae in the current sense, however. Their nebulae were galaxies, which looked nebulous through the small telescopes most observers used. Luckily, amateur scopes today are bigger, better, and easier to acquire. Unfortunately, our sky is brighter due to light pollution.

Roughly 9° east-southeast of Epsilon Virginis, you'll find NGC 5248. This magnitude 10.3 spiral galaxy actually resides in the southwest corner of Boötes and is that constellation's brightest galaxy. NGC 5248's bright core and outer regions show up even through small telescopes. A 12-inch scope shows a barely elongated oval 3.5' by 3' with a stellar nucleus slightly offset to the north. You'll also see a prominent dark patch south of the core and some of the structure making up the spiral arms. If you're observing with an even larger scope, look for two of NGC 5248's 15th-magnitude companion galaxies: UGC 8575 lies 27' to the west, and UGC 8629 is 30' to the southeast.

Of the 88 constellations, Serpens the Serpent is the only one that's not contiguous. Stellar cartographers call its western part, or head, Serpens Caput and its eastern part, or tail, Serpens Cauda. Map 13 contains most of Serpens Caput. Find Serpens Cauda on Map 14.

The brightest deep-sky object in Serpens Caput is globular cluster M5. You'll see M5 without optical aid from a dark site — it shines at magnitude 5.7. The almost equally bright star 5 Serpentis lies 22' to the southeast; M5 looks fuzzier. Through a telescope, however, M5 really stands out. Through a 6-inch scope, the cluster appears 10' in diameter with a densely packed center about one-quarter its diameter. Through a 10-inch telescope, individual stars appear to form streamers that cross the cluster and radiate from it.

The northern part of Libra is bereft of deep-sky objects within the reach of small scopes. If your telescope measures 12 inches or larger, however, many galaxies lie beyond the magnitude 11 threshold. Among them are NGC 5728, NGC 5812, and NGC 5878.

Approximately 2° southeast of Eta Crateris, you'll find the Antennae (NGC 4038 and NGC 4039). The bright tails of these interacting galaxies are huge plumes of material thrown out by tidal interactions. This pair is visible, although indistinct, through a 6-inch telescope. Move up to a 12-inch scope, and you'll notice NGC 4038 is the brighter of the two. Both cores will be visible at 100x through a 12-inch scope. If you increase the magnification to 200x, you'll see bright knots, mainly in NGC 4038. If you want to see the tails, attend a spring star party and hope someone there has a 24-inch telescope.

Below, and nearly equidistant from Delta and Gamma Corvi, lies planetary nebula NGC 4361. This magnitude 10.9 object shows up well even through a 6-inch scope because its light is concentrated in an area only about 1' across. Increase the magnification, and you'll see NGC 4361's irregular edge and relatively bright central star.

Moving to Coma Berenices, it's hard to believe it holds so many deep-sky treasures. Map 13 contains only the southern half of the constellation, but even that small area holds seven Messier objects.

Two globular clusters populate Coma's southeastern corner. M53 lies 1° northeast of Alpha Comae Berenices, and you'll find NGC 5053 1.5° east of the star. M53 shines at magnitude 7.7 and measures about 12' across. A 6-inch telescope will resolve its outer stars well and show the core as broad and dense. In contrast, magnitude 9.9 NGC 5053 is one of the least-concentrated globulars, looking somewhat like a tight open cluster. Even a 12-inch scope shows only about 30 stars in a 5'-wide area.

Just 2° east-southeast of 11 Comae lies spiral galaxy NGC 4450. Through a 10-inch scope, this magnitude 10.1 object covers roughly 4' by 3'. You'll see a 9th-magnitude star 4' to the southwest. NGC 4450's core appears lumpy with a starlike nucleus slightly off-center to the east.

Finally, we come to Virgo. If you're a galaxy-hunter, you can spend a whole season in this one constellation. Virgo holds more bright galaxies than any other constellation.

Start about 4.5° south-southeast of Gamma Virginis at elliptical galaxy NGC 4697. At magnitude 9.3, this is a bright object, but detail is lacking because of its distance. Through a 10-inch telescope, NGC 4697 appears 2' by 1' with a large, bright core and a faint halo.

Move 3° south from NGC 4697 to find NGC 4699. At first glance through a 6-inch scope, this object looks like an elliptical galaxy similar to NGC 4697. In fact, it's a tightly wound spiral galaxy. Use a 12-inch or larger telescope and high power to see its arms. NGC 4699 measures 3.5' by 2.5' and glows brightly (for a galaxy) at magnitude 9.6.

Only one non-galaxy deep-sky object brighter than magnitude 12 resides in Virgo, and it's a worthwhile target — globular cluster NGC 5634. To find it, point your scope midway between Mu and Iota Virginis. In addition to the cluster, a magnitude 8.5 foreground star lurks only 1.3' east-southeast of NGC 5634's center. NGC 5634 shines at magnitude 9.4 and measures about 5' across.

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