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Herschel Space Observatory

Phase: Past

Launch Date: May 14, 2009

Mission Project Home Page -

Program(s):Cosmic Origins

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Herschel's infrared image of the Andromeda Galaxy shows rings of dust that trace gaseous reservoirs where new stars are forming and XMM-Newton's X-ray image shows stars approaching the ends of their lives. Both infrared and X-ray images convey information impossible to collect from the ground because these wavelengths are absorbed by Earth's atmosphere. Credits: ESA/Herschel/PACS/SPIRE/J.Fritz, U.Gent/XMM-Newton/EPIC/W. Pietsch, MPE

The Herschel Space Observatory was a space-based telescope that studied the light of the Universe in the far-infrared and submillimeter portions of the spectrum. It revealed new information about the earliest, most distant stars and galaxies, as well as those closer to home in space and time. It also provided a unique look at objects within our own Solar System.

Herschel was the fourth Cornerstone mission in the European Space Agency’s Horizon 2000 program. Ten countries, including the United States, participated in its design and implementation. Launched on May 14, 2009, the mission operated until the cryostat ran out of helium on April 26, 2013, a period of nearly four years after launch. Originally called “FIRST,” for “Far InfraRed and Submillimeter Telescope,” the spacecraft was renamed for Britain’s Sir William Herschel, who discovered in 1800 that the spectrum extends beyond visible light into the region we today call “infrared.”

Herschel’s namesake gave scientists their most complete look so far at the large portion of the Universe that radiates in far-infrared and submillimeter wavelengths. With a primary mirror 3.5 meters (approximately 11.5 feet) in diameter, Herschel was the largest infrared telescope sent into space as of the end of its mission. Using detectors cooled to temperatures very close to absolute zero (0 degree Kelvin), the three instruments called HIFI, SPIRE, and PACS enabled Herschel to be the first spacecraft to observe in the full 60-670 micron range.

The far-infrared and submillimeter wavelengths at which Herschel observed are considerably longer than the familiar rainbow of colors that the human eye can perceive. Yet, this is a critically important portion of the spectrum to scientists because it is the frequency range at which a large part of the universe radiates.

Much of the Universe consists of gas and dust that is far too cold to radiate in visible light or at shorter wavelengths such as x-rays. However, even at temperatures well below the most frigid spot on Earth, they do radiate at far-infrared and submillimeter wavelengths. Stars and other cosmic objects that are hot enough to shine at optical wavelengths are often hidden behind vast dust clouds that absorb the visible light and re-radiate it in the far-infrared and submillimeter range.

Science Highlights

Highlights of the Herschel mission include discoveries in the areas of planetary science, galactic astronomy, and extragalactic astronomy:

  • Within our solar system Herschel images and spectral data of Jupiter show that water is brought to the upper atmosphere (stratosphere) by comets, particularly the comet Shoemaker-Levy which struck Jupiter in 1994. Observations of Jupiter by Herschel show water to be in the southern hemisphere of Jupiter, high in its atmosphere, where the comet struck the planet.
  • Observations of Comet 103P/Hartley 2 showed that its water has the same D/H ratio (deuterium to hydrogen) as water on the earth, which is important for determining how the earth's oceans were formed, possibly by contributions from comets, and by extension, for bringing other molecules to the earth.
  • Herschel observed near-earth asteroids. The asteroid Apophis was shown to be bigger than previously thought (325 +/- 15 meters) and having a smaller albedo (less reflective). Study of this asteroid can lead to understanding of the Yarkovsky effect, how orbits of asteroids may change due to heating and radiation.
  • Studies of star formation in our Milky Way galaxy were particularly important. In the plane of the Milky Way, Herschel observed a filament structure to exist basically everywhere, and that stars tend to form along these relatively dense filaments of gas that may have been formed by magnetic fields in the galaxy.
  • Infrared images of the bright star Fomalhaut showed it to be surrounded by a disk of material, giving it the visual impression of the planet Saturn. The Fomalhaut ring may resemble the Kuiper belt of the solar system, which is comprised of comets that have not visited the inner portion of the solar system.
  • Herschel studied many stars for debris disks, to help us understand how planetary systems are formed and evolve.
  • Herschel detected heavy molecular hydrogen (HD) in the star TW Hydrae which then allowed for the determination of the mass of the disk. The disk is several times more massive than the disk thought to have formed the solar system.
  • Among research for galaxies, Herschel images of the Andromeda galaxy revealed star formations regions throughout its extensive spiral structure.
  • Galaxies active with star formation showed flows of molecular gas leaving the galaxy as it is pushed outward by radiation. This could diminish the amount of gas available to make stars and slow down the rate at which stars are being formed in a galaxy.
  • Herschel data allowed astronomers to measure the energy that was radiated by the dust where stars were forming at the earliest times of the universe, showing the stars formed at a tremendous rate (2000 times higher) compared with today.

Last updated: January 06, 2015

Related Links
  • ESA Herschel Website -
  • More about Herschel -
  • Science@ESA - ISO/Herschel video -