The Cosmic Web - NGC 2070

The Cosmic Web - NGC 2070 by Joseph Brimacombe

Thursday, November 06, 2008

Just one glance at this incredible visage is enough to make you do a double take. This intricate net of nebular mists is known as 30 Doradus, or even more commonly as the "Tarantula", but no space spider created this web. No, sir. What spun out these gossamer strands of HII silk is one of the largest and most active star forming regions known to our local galaxy group…

When Nicolas Louis de Lacaille first saw it in 1751 through his half-inch spyglass, he knew it was something different. He wrote down that it was nebular in nature, without stars and said; "It resembles the nucleus of a small comet." Too bad he didn't realize what he was really looking at, for Lacaille was a huge fan of all things science. What he couldn't see with his primitive telescope is there really is a cluster of stars at the heart of this web… A very compact cluster stars known as R136a. And in its midst? Twelve stars… twelve very massive and luminous stars almost exclusively of spectral type O3. Even at a distance of 180,000 light years these stars light up this nebula so brightly that if it were as close to Earth as the Orion Nebula, it would cast shadows on the night.

So what else lay hidden in the 1000 light year expanse of the cosmic web? Look beyond what you can see in visible light and think like a spider… Try infra-red. With the eyes of the Spitzer Space Telescope aimed towards NGC 2070, scientists could penetrate the dust clouds throughout the Tarantula to reveal previously hidden sites of star formation. Within the luminescent nebula, holes began to appear. These voids are created by highly energetic winds spewing out from the massive stars in the central star cluster. Like the intricate designs woven by the spider, the structures at the edges of these voids are particularly interesting. Dense pillars of gas and dust, sculpted by the stellar radiation, will be the birthplace of future generations of stars!
But like the spider web… It's a place of death, too.

In 1987 one of the closest supernova events ever to occur near Earth happened in the outskirts of the Tarantula Nebula. The light from the supernova reached Earth on February 23, 1987 and not.since 1604 had humankind been witness to such an event. Even though we were witnessing something that occurred 168,000 years in the past, those X-ray and radio emission were still just as bright as the day the highly energetic electrons and particles spewed into the interstellar medium upon the explosive death of the progenitor star. Oh, there is skeletons in the web, too. Older and weaker supernovae remnants are scattered about, their signatures as faint as the imprint of a fallen leaf that has long blown away. This "Cosmic Web" is home to many supergiant stars. At any moment, a snapshot of any dense region of supergiant stars will show a mixture of newborn stars and supernovae, the signature of stars who those that have lived fast and died young.