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R136

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R136 is a massive concentration of stars located at the heart of the NGC 2070 star cluster. This cluster sits within the center of the Tarantula Nebula. The nebula itself is part of the Large Magellanic Cloud. R136 is classified as a starburst region. This term describes a place with a very high number of young, massive stars. These stars produce most of the energy that makes the Tarantula Nebula visible.

Grand star-forming region R136 in NGC 2070 (captured by the Hubble Space Telescope)
Grand star-forming region R136 in NGC 2070 (captured by the Hubble Space Telescope)

The structure of R136 is incredibly dense. The central concentration of the cluster spans about 2 parsecs across. This is a very small area for so many stars. Within just 5 parsecs of the center, there are 72 class O and Wolf-Rayet stars. The stellar density here is roughly 200 times higher than a typical OB association like Cygnus OB2. This extreme crowding creates a very energetic environment. The massive stars act like engines for the surrounding nebula.

Scientists have identified several distinct components within this region. R136 was originally resolved into three main parts: R136a, R136b, and R136c. R136a is the brightest knot at the very center. Using a technique called speckle interferometry, researchers found even more detail. They discovered that R136a may contain as many as 24 separate components. These components are dominated by three extremely massive stars named R136a1, R136a2, and R136a3. All three are WNh stars, which are a type of extremely luminous Wolf-Rayet star.

The stars in R136 represent some of the most extreme objects in the universe. Within the central 5 parsecs, there are 32 of the hottest type O stars, specifically types O2.0 through O3.5. There are also 40 other O stars and 12 Wolf-Rayet stars. Most of these Wolf-Rayet stars are the extremely luminous WNh type. Looking further out, within 150 parsecs, there are an additional 19 Wolf-Rayet stars. Some stars, such as VFTS 682, are considered runaway stars associated with this cluster.

History shows how our understanding of R136 has changed. It was once known as RMC 136 from the Radcliffe Observatory Magellanic Clouds catalogue. It was also catalogued as HD 38268 and the Wolf-Rayet star Brey 82. Originally, astronomers saw it as a single, unresolved stellar object. It was only through better technology and observations that we could see the individual stars. Space-based observations helped reveal the complex nature of the R136a knot.

The numbers associated with R136 are truly enormous. The estimated mass of the entire cluster is 450,000 solar masses. This means the cluster weighs as much as 450,000 suns. R136 is also quite young, estimated to be less than 2 million years old. Because it is so young, none of the member stars have exploded as a supernova yet. This means the cluster lacks red supergiants, blue hypergiants, or luminous blue variables. The brightest stars present are WNh stars and various O-class supergiants.

Individual stars within the cluster show incredible scale. For example, R136a1 is an extremely massive WNh star. It has a mass of 291 times that of our sun. Its luminosity, or brightness, is 7,244,000 times greater than the sun. Other stars like R136a2 and R136a3 are also millions of times more luminous than the sun. These stars are described as fully convective, meaning their material moves in a specific way throughout the star. These massive stars dominate the light and energy of the entire region.

Because of its size and density, R136 is a significant object for studying stellar evolution. Scientists believe the cluster may eventually become a globular cluster. Globular clusters are large, dense, and round groups of stars. R136 provides a rare look at a starburst region in its early stages. It shows how massive stars form and interact in a very crowded space. Studying this cluster helps us understand how the most massive stars in the universe behave.

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File:Grand star-forming region R136 in NGC 2070 (captured by the Hubble Space Telescope).jpg
Grand star-forming region R136 in NGC...
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