The Tarantula Nebula has an apparent magnitude of 8. Considering its distance of about 160,000 light years, this is an extremely luminous non-stellar object. Its luminosity is so great that if it were as close to Earth as the Orion Nebula, the Tarantula Nebula would cast shadows. In fact, it is the most active starburst region known in the Local Group of galaxies. It is also the largest such region in the Local Group with an estimated diameter of 200 parsecs. This spiderweb-like tangle of gas and dust is a star-forming region called 30 Doradus. It is one of the largest such regions located close to the Milky Way galaxy, and is found in the neighboring galaxy Large Magellanic Cloud. About 2,400 massive stars in the center of 30 Doradus, also known as the Tarantula nebula, are producing intense radiation and powerful winds as they blow off material. Multimillion-degree gas detected in X-rays (blue) by NASA's Chandra X-ray Observatory comes from shock fronts -- similar to sonic booms -- formed by these stellar winds and by supernova explosions. This hot gas carves out gigantic bubbles in the surrounding cooler gas and dust shown here in infrared light from NASA's Spitzer Space Telescope (orange).
The Tarantula Nebula is expanding, and researchers have recently published two studies that attempt to determine what drives this growth. The most recent study concluded that the evolution and the large-scale structure of 30 Doradus is determined by the bubbles of hot, X-ray bright gas confined by surrounding gas, and that pressure from radiation generated by massive stars does not currently play an important role in shaping the overall structure. A study published earlier in 2011 came to the opposite conclusion and argued that radiation pressure is more important than pressure from hot gas in driving the evolution of 30 Doradus, especially in the central regions near the massive stars. More detailed analysis and deeper Chandra observations of 30 Doradus may help decide between these different ideas.
The Tarantula is the largest and brightest emission nebula in the Large Magellanic Cloud (LMC) and one of the largest emission nebulae known. The Tarantula Nebula lies at the eastern end of the LMC. It was first cataloged as a star, 30 Doradus, then discovered to be a nebula by Nicolas Lacaille in 1751-52.
Also known as the Looped Nebula (a name that goes back to John Herschel), the Tarantula is roughly 100 times larger than the famous Orion Nebula but is illuminated in the same way: by the ultraviolet radiation from a collection of hot, young, massive stars embedded within it. Several OB associations have been observed inside the Tarantula, including the extremely luminous and compact cluster R136 near its center; it is a hotbed of Wolf-Rayet stars. Supernova 1987A occurred in an outlying part of the Tarantula â€“ a harbinger of what lies in store for many of the Nebula's stars.
For further information: http://www.jpl.nasa.gov/news/news.cfm?release=2011-350&rn=news.xml&rst=3197