Herschel Space Observatory Mission Science Objectives
The Herschel Space Observatory's principal objectives were to help scientists study and understand:
- How galaxies formed and evolved in the early universe, and the nature of enormously powerful galactic energy sources.
- The formation, evolution, and interrelationship of stars and the interstellar medium in the Milky Way and other galaxies.
- Chemistry in our galaxy.
- Molecular chemistry in the atmospheres of Mars and our solar system's comets and giant planets, and the nature of comet-like objects in the Kuiper belt beyond Neptune.
With its unique ability to detect light in the full 60-670 micron range, Herschel was able to gather information that has previously been unavailable.
Much of the universe is extremely cold, and shines only at far-infrared and submillimeter wavelengths beyond the reach not only of the human eye, but of most telescopes to date.
Most wavelengths in that range are readily absorbed by moisture in Earth's atmosphere, and so are inaccessible to earthbound telescopes. No previous space-based telescope was designed to detect the full range of light frequencies in that portion of the spectrum.
Herschel's large mirror and new generation of detector instruments enabled it to unveil new information about how galaxies first came into being; the symbiotic relationships among galaxies, stars, and the interstellar medium; the origins and evolution of chemicals; the mechanisms by which dense molecular clouds begin to collapse into stars; the engines behind the powerhouses at galactic cores; and the origins of planetary systems, including our own.
And much of this knowledge about the cosmos comes from observing dust and water.
Discoveries in the Dust
Vast, cold clouds of smokelike dust and gas lie between us and many of the objects we'd most like to observe, like the early stages of star formation and the hearts of galaxies. And these clouds have a real penchant for infrared light.
They allow only infrared and longer wavelengths of light to pass through them. Visible light from stars and other luminous sources behind them is absorbed and reradiated at far-infrared and submillimeter wavelengths. And the dust and gas themselves radiate in that same range of long wavelengths.
But Herschel enabled scientists to measure the dust's temperature, analyze its composition, calculate its density, determine its motion - and deduce information about what lies around and behind it, whether it's the birth of a new star or the formation of a primordial galaxy.
Water, water everywhere
Water, too, radiates in the far-infrared and submillimeter wavelengths that Herschel is designed to detect. And water has two features that make it very valuable to astronomers: it appears to be fairly commonplace in the cosmos, and its spectral signature can be interpreted to provide information about its environment.
By analyzing the emission and absorption lines in spectrographs of water, which vary in distinctive ways with density and temperature, scientists will be able to deduce information about interstellar clouds and other environments in which they detect water.
Herschel contributed to obtaining a complete inventory of water in its various manifestations in space.
Light from the Dark Age
One of Herschel's prime objectives was to study the "Dark Age" of the universe, when the first galaxies began to form. Light from this early epoch has traveled for as much as 8.5 billion years before reaching us, and has been redshifted into Herschel's range by the expansion of the universe.
Chemistry in Space
Herschel's ultra-high resolution spectrometer, HIFI, was uniquely suited to identify the chemical composition of the interstellar medium and the atmospheres of comets and planets in our solar system. It helped scientists understand the chemical history of the Galaxy and our solar system.
The Great Unknown
The universe reveals different things by the light of different wavelengths. Herschel provided the opportunity to see things in the far-infrared and submillimeter portions of the spectrum that have never been seen before.
Herschel's final objective is to achieve its discovery potential. The unexpected may be the most important finding of all.