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| Clusters Nebulae Galaxies on May 04, 2010

Small Magellanic Cloud: a nearby dwarf galaxy

If you could view it with your eye alone – in the sky visible from Earth’s southern hemisphere – you would say it does resemble a luminous cloud. Really, though, it is a nearby dwarf galaxy, orbiting our Milky Way.

How to see it

You’ll see the Small Magellanic Cloud (SMC) from Earth’s southern hemisphere. It’s even farther to the south than its larger cousin, the the Large Magellanic Cloud (LMC). Never seen north of about 17 degrees North latitude, the SMC not visible from North America (except far southern Mexico), northern Africa, and all of Europe and Asia (except the southern regions of India and Southeast Asia).

From more northerly latitudes where it still can be observed, the SMC is best seen in the evening in late autumn and early winter (late night in October, mid-evening in November and December, and early evening in January). Whenever the W or M-shaped constellation Cassiopeia the Queen climbs to her highest point in the northern sky, look for the Small Magellanic Cloud to soar to its highest point in the southern sky.

The Small Magellanic Cloud is located about 20 degrees from the South Celestial Pole, in the southeast corner of the constellation Tucana. To find where the SMC lies, look about 15 degrees below the bright far southern star Achernar in the constellation Eridanus the River. For reference, a fist-width at an arm length equals about 10 degrees. Eridanus the River meanders all the way from the Orion star Rigel to Achernar, the end of the River.

The SMC is distinctly smaller and fainter than the LMC, and covers an area roughly 2.5 by 5 degrees in dimension. The overall magnitude is about +2. Since its brightness is spread over about 13 square degrees, it is somewhat harder to find than the LMC, and requires darker skies.

History and Myth

Given its faintness and location far to the South, the SMC was not known in Europe and has no classical mythology associated with it. It does share in the Australian aboriginal tale of Jukara, the old couple who are fed fish from the sky river (Milky Way) by star people. The SMC is the camp of the old woman.

Although the myths are sparse, the SMC holds a very important role in 20th Century astronomy. It was from stars in this galaxy that Henrietta Leavitt deduced the famous “period luminosity” relationship that allowed astronomers for the first time to gauge the distance to star clusters and nearby galaxies.

Science

After the LMC, this galaxy is the fourth closest galaxy to the Milky Way. The best current estimate of its distance is about 210,000 light years, or about 30 percent farther than the LMC. Classified as a dwarf irregular galaxy, it appears to some as showing indication of a distorted barred spiral structure, likely deformed by the gravitational influence of the Milky Way. Some 15,000 to 17,000 light-years across in the longest dimension, the SMC spans nearly 5 degrees of the sky, the equivalent of 9 or 10 full moons. It may contain as many as a few hundred million stars, significantly less than the LMC and much less than the Milky Way.

The center of the LMC is approximately RA: 0h 52m 45s, dec: -72°49’43″

Large Magellanic Cloud: Spectacular from Earth’s Southern Hemisphere