The astronomical guard is changing as one pioneering space telescope begins to yield to a more-capable successor.
The European Space Agency (ESA) today released a "first light" image from its Herschel Space Observatory, shown above. The target is the Whirlpool Galaxy, some 31 million light years away in the constellation Canes Venatici. ESA launched Herschel (along with the agency's Planck spacecraft) May 14.
A quick scan of the two images shows why astronomers are excited about this new observatory. Herschel's vision is much sharper, thanks to a light-gathering mirror that's 3.5 meters (11.5 feet) cross.
Spitzer, launched in 2003, has been no slouch of an observatory, however. It's one of NASA's so-called "great observatories" on orbit, a roster that includes the Hubble Space Telescope, the Chandra X-Ray Observatory, and the Compton Gamma Ray Observatory.
For instance, Spitzer has helped astronomers study brown dwarfs -- stellar wannabies that never gained enough mass to trigger the powerful fusion reactions that ignite larger stars.
It's plumbed galaxies that give off most of their light in the infrared, a feature thought to be triggered by high rates of star formation within galaxies loaded with the cold gas and dust that form the basic building blocks for stars and planets.
It's conducted a survey of galaxies reaching back billions of years to help astronomers understand how galaxies have evolved.
And it has spotted nascent solar systems in the Milky Way, testing ideas astronomers have developed about how solar systems, including our own, form. In fact, it was the first telescope to detect light from a planet orbiting another star and gather rudimentary information about the planet's atmosphere.
As the Spitzer science team has put it, they're after the old, cold, and dirty.
As it was getting ready to hand off some of these tasks to Herschel, Spitzer ran out of liquid helium the day after Herschel was launched. The liquid helium cools the telescope's mirror to ensure it remains sensitive to the very low-temperature emissions from the old, cold, and dirty.
These days, Spitzer engineers are reconfiguring the telescope to continue its work. Without the liquid helium, it won't be quite as sensitive as it once was. But it will still be capable of studying planets around other stars as well as asteroids in our own solar system. Among other tasks, astronomers plan to used Spitzer to take an asteroid census, with an eye toward refining estimates of the sizes and distribution of these objects.
Enter Herschel, which boasts the largest light-gathering mirror yet placed on orbit. In addition to gathering images, Herschel also has a spectrometer that will be able to tease out detailed information about the chemical elements present in the objects it observes.
In addition to continuing the quest to understand the old, cold, and dirty at infrared wavelengths, Herschel's detectors also are sensitive to even longer wavelengths of radiation at so-called submillimeter level.
Submillimeter wavelengths are a prime location along the electromagnetic spectrum for identifying the kinds of molecules present in the clouds of cold dust and gas Herschel observes at infrared wavelengths.
Undoubtedly, astronomers will point Herschel at intriguing infrared sources Spitzer could only see as fuzzy patches. And with new capabilities come discoveries no one anticipated.
Then it will be time for another hand-off. In 2014, NASA aims to launch the James Webb Space Telescope, an infrared scope with a 6.5-meter mirror. What stories these two observatories will help astronomers tell!