The Small Magellanic Cloud

magellanic clouds
The Large Magellanic Cloud (middle left) and Small Magellanic Cloud (upper center) over Paranal Observatory in Chile. European Southern Observatory

The Small Magellanic Cloud is a favorite stargazing targetfor southern hemisphere observers. It's actually a galaxy. Astronomers classify it as a dwarf irregular type galaxy that is roughly 200,000 light-years from our Milky Way galaxy. It is part of the Local Group of more than 50 galaxies that are gravitationally bound together in this region of the universe.

Formation of the Small Magellanic Cloud

Close study of the Small and Large Magellanic Clouds indicates that they were both once barred spiral galaxies.Over time, however, gravitational interactions with the Milky Way distorted their shapes, tearing them apart.

The result is a pair of irregularly shaped galaxies that are still interacting with each other and with the Milky Way.

Properties of the Small Magellanic Cloud

The Small Magellanic Cloud (SMC) is roughly 7,000 light-years in diameter (about 7% of the Milky Way's diameter) and contains about 7 billion solar masses (less than one percent of the mass of the Milky Way). While it is about half the size of its companion, the Large Magellanic Cloud, the SMC contains nearly as many stars (about 7 billion versus 10 billion), meaning it has a higher stellar density.

However, the star formation rate is currently lower for the Small Magellanic Cloud. This is probably because it has less free gas than its larger sibling, and, therefore, had periods of more rapid formation in the past. It has used up most of its gas and that has now slowed down starbirth in that galaxy.

The Small Magellanic Cloud is also the more distant of the two.

Despite this, it is still visible from the southern hemisphere. To see it well, you should search it out in clear, dark skies from any southern hemisphere location. It's visible in the evening skies beginning in late October through January. Most people mistake the Magellanic Clouds for storm clouds in the distance.


Discovery of the Large Magellanic Cloud

Both the Large and Small Magellanic Clouds are prominent in the night sky. The first recorded word of its position in the sky was noted by the Persian astronomer Abd al-Rahman al-Sufi, who lived and observed in the middle of the 10th century. 

It wasn't until the early 1500s that various writers began recording the presence of the clouds during their voyages across the ocean. In 1519, Ferdinand Magellan brought it into popularity through his writings. His contribution to their discovery eventually led to their naming in his honor. 

However, it really wasn't until the 20th century that astronomers realized the Magellanic Clouds were actually whole other galaxies separate from our own. Before that, these objects, along with other fuzzy patches in the sky, were assumed to be individual nebulae in the Milky Way galaxy. Close studies of the light from variable stars in the Magellanic Clouds allowed astronomers to determine accurate distances to these two satellites. Today, astronomers study them for evidence of star formation, star death, and interactions with the Milky Way Galaxy.

Will the Small Magellanic Cloud Merge with the Milky Way Galaxy?

Research suggests that both the Magellanic Clouds have orbited the Milky Way galaxy at roughly the same distance for a significant portion of their existence.

However, it is not likely that they have ventured as close as their current position very often.

This has led some scientists to suggest that the Milky Way will eventually consume the much smaller galaxies. They do have trailers of hydrogen gas streaming between them, and to the Milky Way. This gives some evidence of interactions between the three galaxies. However, recent studies with such observatories as the Hubble Space Telescope seem to show that these galaxies are moving too fast in their orbits. This could keep them from colliding with our galaxy. That doesn't rule out closer interactions in the future, as Andromeda Galaxy closes in on an long-term interaction with the Milky Way. That "dance of the galaxies" will change the shapes of all the galaxies involved in drastic ways. 

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Millis, John P., Ph.D. "The Small Magellanic Cloud." ThoughtCo, Jul. 1, 2017, Millis, John P., Ph.D. (2017, July 1). The Small Magellanic Cloud. Retrieved from Millis, John P., Ph.D. "The Small Magellanic Cloud." ThoughtCo. (accessed November 22, 2017).