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  • IR ‘Eyes’ to See Back in Time
Dec 2009
GREENBELT, Md., Dec. 30, 2009 – When it is sent into orbit in 2014, NASA’s James Webb Space Telescope’s Mid-Infrared Instrument (MIRI) will see even further back in time than its predecessor, the Hubble Space Telescope.

The Webb telescope is the largest space observatory ever constructed. As a result, MIRI will have a huge discovery potential and will enable the Webb telescope to achieve more than 100 times the sensitivity of any previous observatory at these wavelengths.

To see the very first stars and galaxies, astronomers have to look deep into space and far back in time. Starlight travels through space at a finite speed (300,000 km/s). So if we observe with the Webb telescope an object that is 300,000 kilometers away, we see it as it was one second in the past. Astronomical distances are measured in light-years – the distance that light travels in a year. Galaxies can be billions of light-years away. As a result of this transmission delay, astronomical telescopes such as the Webb allow astronomers literally to look back in time and see the universe as it was billions of years in the past.

The space that fills the universe has been expanding since the Big Bang. As a consequence of this expansion, the wavelength of ultraviolet and visible light emitted by the first galaxies to form after the Big Bang has been stretched into the infrared portion of the spectrum and can be observed only by telescopes, such as the MIRI, that are equipped with infrared cameras.

Computer-rendered model of the MIRI Instrument. (Images: University of Leicester, European Consortium Institutes and JPL)

“The MIRI is one of four science instruments aboard the Webb telescope that is designed to record images and spectra at the longest wavelengths that the Webb telescope can observe,” said Matt Greenhouse, project scientist for the science instrument payload. “The mid-infrared spectrum covers wavelengths in the range of 5 to 28 micrometers, or microns (about 10 to 50 times longer than our eyes can see). Light in this portion of the spectrum is invisible to our eyes but is produced by all room-temperature objects and carries key information about the local and early universe.”

Light at these wavelengths is blocked by water vapor in the earth’s atmosphere and can be efficiently observed using only a telescope in space.

The MIRI optics module is labeled here to show the various components.

“The Webb observatory design has been optimized to enable infrared observations that will, for the first time, enable astronomers to see the period in the evolution of the universe in which the first galaxies formed,” Greenhouse added. “The MIRI will play a key role in enabling the very first observations of the galaxy formation epoch.”

A new video about the MIRI detectors is part of an ongoing series called “Behind the Webb,” about the James Webb Space Telescope. It was produced and created by the Space Telescope Science Institute (STScI) of Baltimore and is available at Part of the video was shot at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., in January 2009.

The video runs exactly three minutes and explains how the three detectors on the MIRI work and how the tests they endure prepare them for the Webb telescope’s launch and flight in space. The video is hosted by Mary Estacion, news video producer at STScI, who interviewed Dr. Michael Ressler, the MIRI project scientist at NASA JPL. 

Besides the huge discovery potential, MIRI will provide valuable information in the four areas of the Webb’s science objectives – discovery of the “first light” emitting objects after the Big Bang; assembly of galaxies: history of star formation, growth of black holes, prediction of heavy elements; determination of how stars and planetary systems form; and evolution of planetary systems and conditions for life.

MIRI is an international partnership between NASA and the European Space Agency (ESA) combining the talents of NASA JPL, a consortium of European partners and an international science team. The MIRI is designed around performance requirements that were established by a succession of international science working groups that developed the science objectives for the Webb telescope mission.

The James Webb Space Telescope is the next-generation premier space observatory, exploring deep-space phenomena ranging from distant galaxies to nearby planets and stars. The Webb telescope will enable scientists to observe the formation and evolution of the first galaxies and the evolution of our own solar system, from the first light after the Big Bang to the formation of planetary systems capable of supporting life. The Webb mission is a joint project of NASA, the European Space Agency and the Canadian Space Agency.

For more information and to view the video, visit:

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