After four years of helping scientists understand how stars and planets form, the Herschel space telescope has stopped working.
NASA announced Monday afternoon that the space telescope, launched and maintained by the European Space Agency (ESA), has stopped making observations after running out of liquid coolant.
The cessation of the telescope's operations was expected.
NASA had a hand in building the telescope by creating components for two of Herschel's three scientific instruments, as well as by processing the data it compiled.
"Herschel gave us the opportunity to peer into the dark and cold regions of the universe that are invisible to other telescopes," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate, in a statement. "This successful mission demonstrates how NASA and ESA can work together to tackle unsolved mysteries in astronomy."
Herschel made several major discoveries, such as: finding the first oxygen molecules in space; discovering high-speed outflows around black holes in active galaxies; and finding evidence that comets could have brought a substantial fraction of water to Earth.
The space agencies received confirmation earlier Monday that Herschel's supply of helium, which acts as a coolant, had run out. A marked rise in temperatures has been measured in all of the telescope's instruments.
Herschel was launched in May of 2009 aboard an Ariane 5 rocket from French Guiana.
The telescope's instruments were designed to pick up the glow from celestial objects with infrared wavelengths as long as 625 micrometers, or 1,000 times longer than what can be seen with the naked eye. Because heat interferes with these devices, they were chilled to temperatures as low as minus 456 degrees Fahrenheit.
According to NASA, the detectors also were kept cold by the spacecraft's orbit, which is about 930,000 miles from Earth.
"Herschel has improved our understanding of how new stars and planets form, but has also raised many new questions," said Paul Goldsmith, NASA's Herschel project scientist. "Astronomers will be following up on Herschel's discoveries with ground-based and future space-based observatories for years to come."
The final batch of Herschel's data will be made public in six months, NASA noted.
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