Back at the end of April, the European Space Agency's Herschel space observatory ran out of its liquid helium coolant. The coolant was used to cool the telescope's instruments to near absolute zero, enabling it to observe infrared light coming in from deep space. With the coolant gone, the telescope's science mission has now ended, though researchers still used the satellite's final days to stress test some of its hardware components. Finally, on June 17 Herschel was given its final command and moved into a heliocentric "disposal orbit."
Today, the ESA released what is likely to be the last ground-based photo of the Herschel observatory. The picture shows Herschel, pointed out by the two black lines, flying away from Earth against the backdrop of a star field (the black streaks). The satellite is now in a heliocentric orbit, and will not pass by Earth again for another 13 years.
It's a poignant goodbye for one of the most advanced tools in modern astronomy, as well as a glimpse into the sentimental nature of astronomers. The picture was taken using the Faulkes Telescope North at the Remanzacco Observatory in Hawaii. Since Herschel's orbit was altered by the ESA's final commands, astronomers at the observatory used precious time to search the sky for the now-doomed infrared telescope.
(Image courtesy ESA)