Mission accomplished: Herschel Space Observatory shuts down forever

The Herschel Space Observatory, ranked as the world's largest infrared space telescope since it was launched into orbit in 2009, took its final bow yesterday, after having depleted the supply of liquid helium coolant that was crucial for the operation of its sensitive instruments.

This joint mission between NASA and the European Space Agency scanned the universe in the infrared spectrum, picking up the 'invisible' glow from objects that optical telescopes can't see. Since any heat from the spacecraft or its surroundings would interfere with its observations, Herschel was equipped with a liquid helium coolant system. This kept its instruments at a frigid -271 degrees Celsius, which is only 2° above absolute zero — the lowest temperature possible.

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By looking at objects in the universe at longer infrared wavelengths, as opposed to the shorter-wavelength visible spectrum we see in, astronomers were able to use Herschel to reveal much more about the objects we could already see with visible telescopes. However, what was truly remarkable was how it could effectively 'see through' space dust to reveal the universe like we'd never seen it before.

"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, the ESA’s project scientist for the Herschel Observatory, in an ESA statement.

During its time in orbit, Herschel's observations definitively confirmed the presence of oxygen molecules in space, unmasked spectacular regions of star-birth previously obscured by dust, showed us incredible new views of extremely distant galaxies, and tracked down water molecules in galaxies, gas clouds and in distant planet-forming star systems. Astronomers even used Herschel to confirm their ideas that Earth's oceans may have come from the comets that streak through our solar system.

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Now that Herschel's mission is completed, astronomers will continue to work on its last observations for the next six months. The observatory itself will remain in contact with ground stations, and will be moved into a permanent parking orbit around the Sun sometime in May.

"Although this is the end of Herschel observing, it is certainly not the end of the mission – there are plenty more discoveries to come," said Dr. Pilbratt in the statement.

"We will now spend the next few years making our data accessible in the form of the best possible maps, spectra and various catalogues to support the work of present and future astronomers. Nevertheless, we’re sad to see the end of this phase: thank you, Herschel!"

(Images courtesy: ESA/C. Carreau and Wikimedia Commons)

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