Space Observatory's Mission Ends
April 29, 2013

Herschel Runs Out Of Liquid Coolant, Ends Mission

Lee Rannals for - Your Universe Online

The European Space Agency's (ESA) Herschel observatory has officially run out of liquid coolant, ending its mission.

The space observatory launched nearly four years ago with a goal to help reveal some of the cooler sides of the universe, including planet, star and galaxy formation.

"Herschel gave us the opportunity to peer into the dark and cold regions of the universe that are invisible to other telescopes," said John Grunsfel, associate administrator for NASA's Science Mission Directorate at NASA headquarters in Washington. "This successful mission demonstrates how NASA and ESA can work together to tackle unsolved mysteries in astronomy."

Scientists confirmed today that the helium inside Herschel was exhausted after ground controllers saw a rise in temperatures in all of the space observatory's instruments. Herschel first launched aboard an Ariane 5 rocket from French Guiana in May 2009.

The observatory's detectors were designed to pick up the glow from celestial objects with infrared wavelengths as long as 625 micrometers, which is 1,000 times longer than we are able to see with our eyes. Heat interferes with instruments trying to pick up these objects, so they were chilled to temperatures as low as negative 456 degrees Fahrenheit using liquid helium. The spacecraft was also kept cool because it was orbiting 930,000 miles away from Earth.

Herschel will not be making any more observations, but discoveries can still continue with all the data the observatory helped to collect.

"Herschel has improved our understanding of how new stars and planets form, but has also raised many new questions," said Paul Goldsmith, NASA Herschel project scientist at JPL. "Astronomers will be following up on Herschel's discoveries with ground-based and future space-based observatories for years to come."

ESA's telescope helped astronomers discover some of the youngest stars ever seen. Herschel assisted NASA´s Spitzer Space Telescope and the Atacama Pathfinder Experiment (APEX) telescope in discovering dense envelopers of gas and dust around the fledging stars known as protostars.

“Herschel has revealed the largest ensemble of such young stars in a single star-forming region,” said Amelia Stutz, lead author of a paper to be published in The Astrophysical Journal and a postdoctoral researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany. “With these results, we are getting closer to witnessing the moment when a star begins to form.”

Herschel has helped discover everything from starburst galaxies to newly forming planetary systems. ESA engineers performed a few last-minute observations with the telescope while they could to try and get the most out of every drop of liquid helium that remained. In all, Herschel was able to perform over 22,000 hours of science observations, which was 10 percent more than ESA originally planned.