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The Mysterious Origin Of Ancient Stardust

The origin of the abundant stardust, floating around within the multitude of galaxies inhabiting the ancient Universe, is a mystery. For decades, however, many astronomers have suspected that stellar explosions, heralding the fiery demise of massive stars, may be the culprits! Stardust is crucial for both star birth and the formation of rocky planets like our own Earth, and it provides the ingredients for that wonderful brew called “life”–but no one has been able to definitely determine where all that crucial cosmic dust came from. In fact, observations of supernovae near our own barred-spiral Milky Way Galaxy indicate that they create too little material to account for the copious quantities of dust floating around in the early Universe. In July 2014, a team of astronomers reported that they have been able to follow stardust being churned out by supernova blasts in real-time–showing that these Cosmic dust factories produce their grains of dust in a two-step process, starting soon after the stellar blast, but also continuing for years afterwards.

The international team of astronomers used the X-shooter spectrograph on the European Southern Observatory’s (ESO’s) Very Large Telescope (VLT) on Cerro Paranal in Chile, to measure the amount of visible light absorbed by the dust grains, as well as the infrared radiation that the grains themselves emitted. The astronomers analyzed the light being shot out from the supernova SN2010jl as it slowly dimmed over time, observing the supernova nine times in the months following the explosion– and for a tenth time 2.5 years after the blast. This unusually brilliant supernova, the sad result of the death of a massive star, exploded in the small galaxy UGC 5189A. The results of the new study are published online in the July 9, 2014 issue of the journal Nature.

“By combining the data from the nine early sets of observations we were able to make the first direct measurements of how the dust around a supernova absorbs the different colors of light. This allowed us to find out more about the dust than had been possible before,” explained lead author Dr. Christa Gall in a July 9, 2014 ESO Press Release. Dr. Gall is of Aarhus University in Denmark.

Even though astronomers have long suspected that supernovae may be the main source of dust, especially in the young Universe, its origin in galaxies remains mysterious–it is still unclear how and where the dust grains condense and grow. It is also unclear how they manage to avoid being destroyed in the hostile environment of a star-birthing galaxy. However, the new study offers to lift this obscuring veil for the first time, documenting the formation of dust emitted from SN2010jl only a few weeks following its blast, and continuing for almost 2.5 years afterwards. The study also shows the formation of large dust grains that were able to survive the violent, harsh shocks of the supernova. It also reveals that dust production starts off slow, at first–but eventually speeds up.

Stellar Life

Stars are born in dense, cold blobs that form within enormous, frigid, dark molecular clouds that haunt our Universe like billowing phantoms. There are many such dark, cold, giant clouds floating through interstellar Space, and they serve as strange, secretive nurseries for the multitude of sparkling baby stars that set our Galaxy ablaze with their dancing light. At long last, within a dense star-forming blob, hidden within the cold flowing folds of the enormous cloud, delicate, fragile threads of material twirl around together, thus combining to create clumps that continue to increase in size for hundreds of thousands of years. The growing blob eventually acquires sufficient mass to collapse under the heavy weight of its own gravity–and a brilliant baby star is born.

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