Artist's concept of Planck in space, with Earth in the background. Image credit: ESA
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A JPL-developed and -built cooler on the Planck spacecraft has chilled the mission's low-frequency instrument down to its operating temperature of a frosty 20 Kelvin (minus 424 degrees Fahrenheit). The so-called hydrogen sorption cooler was turned on June 4 and achieved the target temperature of 20 Kelvin eight days later. The cooler is part of a chain of coolers that works together to ultimately chill the high-frequency instrument down to 0.1 Kelvin -- an event scheduled to take place in a few weeks.

Planck is currently on its way to its final orbit at the second Lagrange point, which is located about 1.5 million kilometers (930,000 miles) from Earth, on the opposite side of our planet from the sun. Once there, it will look back to the dawn of time to study the birth of our universe.