Planck was launched in May 2009. The missions ultimate goal is to learn more about the evolution of the universe by mapping the cosmic background radiationthe faint afterglow of the big bang. That could take another year or two, says Charles Lawrence of NASAs Jet Propulsion Laboratory, one of Plancks project scientists. Meanwhile, Lawrence says, the space observatory is revealing a lot about everything else in the universe.
The stellar wombs are a case in point. These are the coldest objects known in the universe, says Lawrence; some are just 7 above absolute zero. Such cold objects give off faint radiation at wavelengths shorter than 1 millimeter, and Plancks sensitive detectors are great at finding them, says Helou.
Using the sharper view of another European space observatory called Herschel, astronomers have studied 10 of the cold cores discovered by Planck in more detail. They turn out to be elongated and grouped into filaments. Moreover, they show a wide variety of shapes, sizes, and substructure. Some of these smaller clumps are no larger than 1 light-year acrossabout the size of the giant cloud of comets surrounding our own solar system.
Helou is confident that the Planck observations will eventually lead to a much better understanding of the critical last steps leading up to stellar birth. Specifically, astronomers want to know how and how fast a collapsing cloud of gas fragments into different stars. Theres a lot of follow-up work to be done, however. The Planck team believes the large variety of cold cores corresponds to different stages in the prenatal evolution of stars, from cold, starless clumps to young protostellar objects still embedded in their surrounding cloud. Says Helou: We have to place these objects in the right sequence.
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