The most detailed survey of the entire sky at infrared wavelengths has been made by the AKARI satellite. It will help astronomers produce a complete census of all nearby galaxies.
AKARI, a Japanese mission supported by the European Space Agency (ESA), uses a 0.7-metre-wide mirror and launched into space in February 2006. Now, it has made the first all-sky infrared survey since the IRAS (Infrared Astronomical Satellite) mission, a joint project of the US, UK and the Netherlands, made such a map more than 20 years ago.
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鈥淎KARI seeks to improve and extend the IRAS survey in many ways,鈥� says ESA鈥檚 Chris Pearson, an AKARI team member at the Japan Aerospace Exploration Agency (JAXA) in Sagamihara, Japan.
AKARI surveys the sky at six infrared wavebands compared to IRAS鈥檚 four. And it is the first survey to study wavelengths longer than 100 micrometres, allowing astronomers to detect very cool objects. 鈥淲e expect to detect objects that were too cold even for IRAS to see, such as populations of extremely cool galaxies,鈥� Pearson told 快猫短视频.
Perhaps most importantly, AKARI can resolve objects in much finer detail than IRAS (see image at right, below). 鈥淪ince the sensitivity of such surveys is limited by a telescope鈥檚 ability to distinguish between confusing clumps of interstellar dust, small groupings of stars, and nearby versus distant galaxies, the advance in angular resolution is particularly important,鈥� agrees Chas Beichman, an infrared astronomer at Caltech and NASA鈥檚 Jet Propulsion Laboratory in Pasadena, California, US.
The survey should turn up all of the galaxies within about 1 billion light years of Earth, and bright galaxies within a distance of about 6 billion light years, Pearson says. 鈥淒ue to the wide coverage of the sky, there also exists the potential for the discovery of extremely rare and unusual objects, such as primeval galaxies . . . [This] will provide important clues to the formation of the very first galaxies in the universe.鈥�
AKARI will continue to survey the sky until it loses its 170 litres of liquid helium, which it uses to keep its infrared detectors cold. The helium is expected to last until 9 September 2007, and then mission controllers expect to use mechanical coolers to observe objects at near-infrared wavelengths for another year.
The survey was presented on Wednesday at a cosmology conference called 鈥淔rom IRAS to Herschel and Planck鈥� in London, UK.
