Southern Sky Notes

Notes · Deep sky

A Guide to the Magellanic Clouds

The Large and Small Magellanic Clouds are the great consolation prize of southern astronomy. Northern observers get the Pole Star and the Andromeda Galaxy high overhead; we get two whole neighbouring galaxies visible to the naked eye, and from New Zealand they never set.

What they are

Both are dwarf galaxies orbiting, or perhaps just passing, our own Milky Way. The Large Magellanic Cloud (LMC) is roughly 160,000 light years away and the Small Magellanic Cloud (SMC) about 200,000. Between them they hold billions of stars, plus clusters and nebulae that would be famous in their own right if they sat in our own galaxy.

The LMC was home to Supernova 1987A, the closest supernova seen since the invention of the telescope. It was a southern-hemisphere event, and observers in New Zealand were among those who followed it night after night.

Always above the horizon

From New Zealand both clouds are circumpolar. The LMC sits at a declination of roughly 69° south and the SMC at about 73° south, and from Cape Reinga southward anything further south than about 56° never sets (the limit is lower still the further south you live). They circle the south celestial pole once a day, high in some seasons and skimming the southern horizon in others.

  • The SMC rides highest in the evening sky in late spring and early summer, from about October to December.
  • The LMC is highest in the evening from about December to February.
  • In winter evenings, both sit low in the south, and haze or a southern hill can hide them. They climb again before dawn.

Our guide to finding south with the Southern Cross will help you get your bearings; the clouds lie on the far side of the south celestial pole from the Cross, and on summer evenings the Cross is low while the clouds are high.

Finding them

The clouds are obvious from a dark site but easily lost under city skies or with a bright Moon. Look for two pale patches of light, like detached pieces of the Milky Way. The LMC is larger and brighter, stretching about 20 full-Moon widths along its long axis. The SMC is smaller and fainter, about 21° away, or roughly two outstretched hand-widths.

Between and slightly toward the pole, the stretch of sky has very few bright stars, which is part of why the clouds stand out. Achernar, the bright star at the end of Eridanus, lies not far from the SMC and is a helpful signpost. Canopus, the second-brightest star in the sky, is a fair way from the LMC in the direction of the Milky Way.

With binoculars

Binoculars transform both clouds. The LMC dissolves into a mottled bar with knots, clusters and nebulae scattered across it. The SMC shows a soft, elongated glow with a brighter core. Our post on binocular astronomy under the southern sky covers choosing and steadying a pair.

The Tarantula Nebula

The standout object in the LMC is the Tarantula Nebula (NGC 2070, also called 30 Doradus). From a dark site it can be picked out with the naked eye as a slightly fuzzy "star" near the eastern end of the LMC's bar. In binoculars it is a distinct glowing knot; in a telescope of 150 mm or more, loops and filaments of gas reach out from the bright centre like legs, which gives it its name.

The Tarantula is the largest and brightest star-forming region in the Local Group of galaxies, more than a thousand light years across, energised by the dense young cluster R136 at its heart. The Orion Nebula would fit inside it many times over.

Sweep the rest of the LMC with a telescope at low power and you will find dozens of clusters and small nebulae. A good star atlas or planetarium program such as Stellarium makes it easier to put names to them.

47 Tucanae

Right beside the SMC, but much closer to us and actually part of our own Milky Way, sits 47 Tucanae (NGC 104). At around 15,000 light years, it is one of the finest globular clusters in the sky, second only to Omega Centauri.

To the naked eye 47 Tuc is a fuzzy star of about fourth magnitude. Binoculars show a bright, round glow with a strongly concentrated core. A small telescope starts to resolve the edges into stars, and a 200 mm telescope on a steady night shows a dense ball of thousands of points piling up toward a blazing centre.

NGC 362

Just north of the SMC is a smaller globular cluster, NGC 362. Like 47 Tuc, it belongs to our galaxy and simply lies in the same direction as the SMC. It is fainter and more compact, a nice comparison object, and a moderate telescope will resolve its outer stars.

Getting the most from the clouds

  • Go dark. The clouds are low surface brightness objects, and light pollution hits them hard.
  • Watch the Moon. A first-quarter or brighter Moon will wash them out.
  • Use low power. Start with your widest eyepiece and sweep slowly.
  • Be patient with your eyes. Twenty minutes of dark adaptation makes an enormous difference.
  • Pick the season. Late spring for the SMC and 47 Tuc, midsummer for the LMC and the Tarantula.

People who move to New Zealand from the north often say the Magellanic Clouds are what first made them feel the southern sky was truly different. They are worth getting to know on every clear night they are high.