Astronomy in the Atacama

Chilean telescope unlocks secrets of planet birth

The ALMA telescope in Chile’s Atacama Desert has observed for the first time a crucial and spectacular stage in the formation of gas giants. 

Monday, January 21, 2013 Category: Education
An artist’s impression of the disc and gas streams around HD 142527. Photo courtesy of the European An artist’s impression of the disc and gas streams around HD 142527. Photo courtesy of the European Southern Observatory (ESO).


More than 450 light-years from earth and surrounded by a swirling disc of gas and dust, the young star HD 142527 has unveiled to astronomers a planetary nursery, where the birth and growth of gas giants similar to Saturn and Jupiter can be seen in action for the first time.


The disc surrounding the star is punctuated by a vast gap, thought to be created by the orbits of newly forming gas giants. A long standing theory has predicted growing planets suck in material from the outer disc via vast gas streams, though only now have scientists been able to confirm this theory with empirical evidence.


A team of international scientists working with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in northern Chile were able to view gigantic gas streams bridging the gap between the inner and outer disc, and acting as vast cosmic umbilical cords from which new planets guzzle up material.


“Astronomers have been predicting that these streams must exist, but this is the first time we’ve been able to see them directly,” astronomer Simon Casassus of the Universidad de Chile and leader of the new study, said. “Thanks to the new ALMA telescope, we’ve been able to get direct observations to illuminate current theories of how planets are formed.”


According to Casassus, the gap in the young star’s disc was already known, however close inspection of the gap had not been possible using infrared or visible light telescopes due to the glare from the star. As the ALMA telescope observes submillimeter wavelengths (between far infrared and microwave wavebands), viewing is unaffected by such a glare, allowing astronomers to capture images in never before seen detail.


Another theory that was confirmed by the study was the existence of diffuse gas within the gap in the disc. The existence of such gas is further confirmation that the gap is created by newly forming planets rather than a larger body such as a nearby star.


"A second star would have cleared out the gap more, leaving no residual gas. By studying the amount of gas left, we may be able to pin down the masses of the objects doing the clearing,” Gerrit van der Plas, a team member from Universidad de Chile, said. "Astronomers have been looking for this gas for a long time, but so far we only had indirect evidence for it. Now, with ALMA, we can see it directly."


Due to its almost non-existent humidity and clear skies, the Atacama is the world’s premier location for astronomy. Chile is home to almost half the world’s telescope infrastructure, and this is set to increase to over two thirds in the next decade.


For an in depth look at the work of ALMA and astronomy in Chile, be sure to read our Turning the Telescope series

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