Herschel Space Observatory Mission Science Objectives
The Herschel Space Observatory's principal objectives are to help scientists
study and understand:
With its unique ability to detect light in the full 60-670 micron
range, Herschel has been able to gather information that has
previously been unavailable.
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.
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
Herschel's large mirror and new generation of detector
instruments have 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 will come 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
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 has 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 have been able to deduce information about
interstellar clouds and other environments in which they detect
Herschel has been working to obtain a complete inventory of water in
its various manifestations in space.
Light from the Dark Age
One of Herschel's
prime objectives is 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
Chemistry in Space
resolution spectrometer, HIFI, is uniquely suited to identify the
chemical composition of the interstellar medium and the atmospheres
of comets and planets in our solar system. It has dramatically helped
scientists understand the chemical history of the Galaxy and our solar
The Great Unknown
The universe reveals
different things by the light of different wavelengths. Herschel
has the opportunity to see things in the far-infrared and
submillimeter portions of the spectrum that have never been seen
Herschel's final objective is to achieve its discovery potential.
The unexpected may be the most important finding of all.