An Unexpectedly Calm Hot Gas in the Center of the Perseus Cluster
An international team observed the hot gas in the Perseus cluster with the Soft X-ray Spectrometer (SXS) on board the X-ray Astronomy Satellite ASTRO-H ("Hitomi") during its initial operation phase, which started one week after liftoff. The total integration time was 230,000 s. The energy resolution of the SXS data was high, equaling the best resolution estimated during ground testing. The observation data demonstrated the good in-orbit performance of the SXS and its ability to measure the vel...
About X-ray Astronomy Satellite "Hitomi" (ASTRO-H)
Insight into the Hot Universe—The new generation X-ray astronomy satellite
The universe appears to be cold and peaceful, but seen in X-ray, outer space is filled with turbulence in the form of explosions, collisions, and outbursts. For the purpose of advancing astronomical observations in X-rays, the next generation X-ray observatory "Hitomi" (ASTRO-H) was developed from an international collaboration including Japan and NASA. The cutting edge instrument on board is the “X-ray micro-calorimeter,” which observes X-rays from space with the world’s greatest spectral capability. The other 3 detectors on board allow high sensitivity observations in a wide bandwidth spanning soft X-ray to the softest Gamma-ray. "Hitomi" (ASTRO-H) will apply these new functions to investigate the mechanisms of how galaxy clusters—the largest objects in space made of “visible matter”—formed and influenced by dark energy and dark matter, to reveal the formation and evolution of supermassive black holes at the center of galaxies, and to unearth the physical laws governing extreme conditions in neutron stars and black holes.
Characteristics of X-ray Astronomy Satellite "Hitomi" (ASTRO-H)
Scientific objectives of "Hitomi" (ASTRO-H)
"Hitomi" (ASTRO-H) enables high sensitivity observations of celestial sources across a wide energy range, from X-rays to gamma-rays, bands presenting considerable technical challenges. Thesatellite features cutting-edge instruments; SXS, operated at only 50 mK, is capable of measuring, with unprecedented accuracy, the energy of incoming X-rays. It measures temperature changes in a sensor resulting from absorption of X-ray photons. HXI, operating in the focusing of a Hard X-ray Telescope, will produce the first ever images of the high-energy X-ray universe. SXI, featuring domestically produced X-ray CCDs, will enable us to make wide field X-ray images of the sky with ultra-low noise. The narrowview semi-conductor Compton camera, SGD, revitalizes the field of gamma-ray observations by featuring the greatest sensitivity in this band. The Japanese heritage of successful previous satellites will provide a basis for meeting these challenges.
There are four focusing telescopes mounted on the top of a fixed optical bench (FOB). Two of the four telescopes are Soft X-ray Telescopes (SXTs) and they have a 5.6 m focal length. One SXT will point to a soft X-ray spectrometer (SXS) and the other SXT will point to a soft X-ray imager (SXI). The other two telescopes are Hard X-ray Telescopes (HXTs), which focal length is 12 m. The Hard X-ray Imaging detectors (HXIs) are mounted on the HXI plate, at the end of a 6 m extendable optical bench (EOB) that is stowed to fit in the launch fairing and deployed once in orbit. In order to extend the energy coverage to the soft γ-ray region up to 600 keV, the Soft Gamma-ray Detector (SGD) will be implemented as a non-focusing detector. Two SGD detectors, each consisting of three units will be mounted separately on two sides of the satellite.
Type of Orbit
about 96 min.
Scientific Instruments (Planned)
Hard X-ray Telescope (HXT)
Soft X-ray Telescope (SXT-S, SXT-I)
Hard X-ray Imager (HXI)
Soft X-ray Spectrometer (SXS)
Soft X-ray Imager (SXI)
Soft Gamma-ray Detector (SGD)
Moving Beyond the Loss of X-Ray Astronomy Satellite ASTRO-H ("Hitomi")
Saku Tsuneta, Director General, ISAS (2016.7)