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Large Magellanic Cloud: Nearby Satellite Dwarf Galaxy

Magellanic Clouds
This beautiful image of the Atacama Large Millimeter/submillimeter Array (ALMA), showing the telescope’s antennas under a breathtaking starry night sky, comes from Christoph Malin, an ESO Photo Ambassador. Image released April 15, 2013.
Credit: ESO/C. Malin

The Large Magellanic Cloud (LMC) is a satellite dwarf galaxy of the Milky Way that is among the closest galaxies to Earth. At about 163,000 light-years from Earth, the dwarf galaxy looks like a faint cloud in Southern Hemisphere skies. It lies on the border of the constellations Dorado and Mensa.

Both the LMC and its companion, the Small Magellanic Cloud, are named after Ferdinand Magellan. While astronomers in the Southern Hemisphere saw them before Magellan's round-the-world voyage in 1519, NASA said, the explorer and his crew were the first to bring that knowledge to the Western world.

Magellan died during that voyage in the Philippines, but his crew provided documentation of the discovery upon their return to Europe.

LMC location

Magellan's discovery of the LMC and SMC predated the use of the telescope for astronomical observations. Even after telescopes were used by Galileo and others in the early 17th century, it would take several hundred years before astronomers could accurately calculate how far away the LMC, the SMC and other nearby galaxies are to Earth.

Once cosmic distances were better understood through tools such as using "standard candles" (objects with known luminosities, such as certain types of variable stars), the LMC was considered the closest galactic object to Earth until 1994, when astronomers found the Sagittarius Dwarf Elliptical Galaxy, NASA said. Another discovery in 2003 — the Canis Major Dwarf Galaxy — turned out to be even closer.

The LMC is part of a collection of dozens of galaxies known as the Local Group, so named because they are fairly close to our own Milky Way galaxy. The most prominent member is the Andromeda Galaxy, a Northern Hemisphere object visible with the naked eye just north of the constellation with its name. Andromeda is 2.5 million light-years away and is moving closer to our galaxy for an eventual collision.

This image shows a young stellar grouping in one of the largest known star formation regions of the Large Magellanic Cloud, a dwarf satellite galaxy of the Milky Way. The picturesque view was captured by the Hubble Space Telescope's Wide Field Planetary C
This image shows a young stellar grouping in one of the largest known star formation regions of the Large Magellanic Cloud, a dwarf satellite galaxy of the Milky Way. The picturesque view was captured by the Hubble Space Telescope's Wide Field Planetary Camera 2.
Credit: ESA/Hubble, NASA and D. A Gouliermis. Acknowledgement: Flickr user Eedresha Sturdivant

Starbirth hotspot

Besides its proximity to Earth, the LMC is a location for starbirth. Within its borders, several observatories from NASA and others have captured vast amounts of gas coming together to create young stars.

A 2012 composite image of the Tarantula Nebula – more properly known as 30 Doradus – revealed violence and radiation through the eyes of the Hubble, Chandra and Spitzer space telescopes. "At the center of 30 Doradus, thousands of massive stars are blowing off material and producing intense radiation along with powerful winds," NASA wrote at the time.

"The Chandra X-ray Observatory detects gas that has been heated to millions of degrees by these stellar winds and also by supernova explosions. These X-rays ... come from shock fronts-similar to sonic booms-formed by this high-energy stellar activity." [Images: 50 Fabulous Deep-Space Nebula Photos]

A smaller star-forming region within the LMC is in a spot known as LHA 120-N 11. The LMC in general is an excellent spot to look for stars being born, NASA said in a statement accompanying an image of that region.

"It lies in a fortuitous location in the sky, far enough from the plane of the Milky Way that it is neither outshone by too many nearby stars, nor obscured by the dust in the Milky Way’s center," NASA stated. It is also close enough to study in detail (less than a 10th of the distance to the Andromeda Galaxy, the closest spiral galaxy), and lies almost face-on to us, giving us a bird’s eye view."

Stardate rotation

The LMC's relatively close location to Earth also affords astronomers the chance to study it in more detail, with the aim of using that understanding to extrapolate to how other galaxies behave. One example is through its rotation, which was picked up by the Hubble Space Telescope in results released in February 2014.

"Studying this nearby galaxy by tracking the stars' movements gives us a better understanding of the internal structure of disk galaxies," said Nitya Kallivayalil, a researcher at the University of Virginia who participated in the research, in a statement. "Knowing a galaxy's rotation rate offers insight into how a galaxy formed, and it can be used to calculate its mass."

The researchers discovered that the LMC makes a rotation every 250 million years. They found this by using Hubble to track the motion of stars in the galaxies sideways with respect to the plane of the sky. While this technique has been used for more nearby objects before, this effort represented the first time it was used for a galaxy.

The team next plans to turn its attention to the SMC to do the same sort of analysis. Since the SMC and the LMC also are close enough to gravitationally interact with each other, scientists said, looking at how they move in relation to each other could also give information on the movements of other galaxies in the Local Group.

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