The European Space Agency (ESA) today announced that the Herschel space observatory has run out of liquid helium coolant. The coolant is necessary to cool the telescope’s instruments to near absolute zero.

Herschel’s ground station in Western Australia this afternoon found that the temperature in all of the telescope’s instruments is rising, confirming that the helium has run out. The depletion of the coolant was expected, as the 2300 litres of liquid helium inside the observatory had been evaporating since Herschel’s launch in 2009.

“Herschel has offered us a new view of the hitherto hidden Universe, pointing us to a previously unseen process of star birth and galaxy formation, and allowing us to trace water through the Universe from molecular clouds to newborn stars and their planet-forming discs and belts of comets,” said Göran Pilbratt, a Herschel Project Scientist at the ESA.

The telescope has been gazing into space for over three years. In just the past few months data from Herschel has been used to find starburst galaxies, examine a near-earth asteroid, discover massive comet belts, and link the 1994 Shoemaker-Levy 9 impact to water on Jupiter.

“Herschel has exceeded all expectations, providing us with an incredible treasure trove of data that that will keep astronomers busy for many years to come,” said Alvaro Giménez Cañete, Director of Science and Robotic Exploration at the ESA.

(Image courtesy ESA)