Herschel: Running on Empty
Herschel To Finish Observing Soon
The European Space Agency’s (ESA) Herschel Space Observatory is expected to soon exhaust its supply of liquid helium coolant after spending more than three very exciting years studying the cool Universe. Launched in May of 2009, with a main mirror 3.5 m across, Herschel is the largest, most powerful infrared telescope ever flown in space and was named after the astronomer William Herschel who discovered the existence of infrared radiation while studying the Sun in 1800.
Herschel’s mission, the first to cover the entire wavelength range from the far-infrared to submillimetre, made it possible to study previously invisible cool regions of gas and dust in the cosmos, and provided new insights into the origin and evolution of stars and galaxies. In order to make such sensitive far-infrared observations, the detectors of the three science instruments, two cameras/imaging spectrometers and a very high-resolution spectrometer, must be cooled to an extremely frigid –271°C, close to absolute zero, and as such, sit atop a tank filled with superfluid liquid helium, inside a giant thermos flask known as a cryostat.
Part of the Multi-tiered Extragalactic Survey (HerMES) Key Project, studying the evolution of galaxies in the distant, ancient Universe, this Herschel image, taken in the Lockman Hole region of space, shows thousands of galaxies packing themselves closely together, forming large clusters of galaxies by the force of their mutual gravity. Indications are that these galaxies are busy crashing into one another, forming large quantities of stars as a result of these violent encounters. Each dot is an entire galaxy containing billions of stars.
Herschel has made extraordinary discoveries across a wide range of topics, from starburst galaxies in the distant Universe to newly forming planetary systems orbiting nearby young stars. However, as all good things must come to an end, engineers believe that nearly all of Herschel’s liquid helium, more than 2,000 liters at launch, has now gone.
“It is no surprise that this will happen, and when it does we will see the temperatures of all the instruments rise by several degrees within just a few hours,” says Micha Schmidt, the Herschel Mission Operations Manager at ESA’s European Space Operations Centre in Darmstadt, Germany.
Once the detectors start to warm from their ultra-frigid state, they will stop working. The end, when it happens, will be sudden. The science observing program was carefully planned to take full advantage of the lifetime of the mission, and all of the highest-priority observations have already been completed. Herschel is also performing numerous other observations specifically chosen to exploit every last drop of its helium.
“We will finish observing soon, but Herschel data will enable a vast amount of exciting science to be done for many years to come,” says Göran Pilbratt, ESA’s Herschel Project Scientist at ESA’s European Space Research and Technology Centre in Noordwijk, the Netherlands. “In fact, the peak of scientific productivity is still ahead of us, and the task now is to make the treasure trove of Herschel data as valuable as possible for now and for the future.”
Herschel will continue communicating with its ground stations for some time after the helium is exhausted. Finally, in early May, it will be propelled into its long-term stable parking orbit around the Sun.
The Rosette Nebula, a stellar nursery about 5,000 light-years from Earth in the Monoceros constellation. This image is a three-color composite showing infrared wavelengths of 70 microns (blue), 160 microns (green), and 250 microns (red). In this image from Herschel the bright smudges are dusty cocoons containing massive embryonic stars, which will grow to 10 times the mass of our Sun. The small spots near the center of the image are lower mass stellar embryos. The Rosette Nebula itself, and its massive cluster of stars, is located to the right of the picture.
Because Herschel can obtain data at a wide range of infrared light and reveal a more complete picture of star birth than ever seen before scientists discovered that galaxies do not always need to collide with each other in order to drive vigorous star birth, overturning a long-held assumption and painting a more complete picture of how galaxies evolve. These results were based on Herschel’s observations of two patches of sky, each about one-third the size of the full moon. In this artist’s conception, a galaxy accretes mass from rapid, narrow streams of cold gas. These filaments provide the galaxy with continuous flows of raw material to feed its star-forming.
In this, the most detailed image of the Andromeda Galaxy ever taken at infrared wavelengths, two ESA observatories combine forces to show the galaxy in an entirely new light. Herschel shows us rings of star formation, while ESA’s X-ray space observatory, XMM-Newton, shows us dying stars shining X-rays into space. This image of our nearest large spiral galaxy neighbor clearly shows that more stars are on their way. Infrared and X-ray images convey information impossible to collect from the ground because these wavelengths are absorbed by Earth’s atmosphere.
All images credited to the European Space Agency.
For more Herschel images visit OSHI – Online Showcase of Herschel Images.