CIAO which has seen first-light in the same February as FOCAS (Subaru This Month) is featured this month. CIAO is a Coronagraphic Imager with Adaptic Optics and installs at the Cassegrain focus of the Subaru Telescope as well as COMICS (January's Subaru This Month) and FOCAS. The outward looks like COMICS well, and the main device is in a silver vacuum container (like a thermos). The size of CIAO is about 2-2-2 meters and the weight is about two ton.

CIAO examining at the simulator at the base facility

FOCAS and COMICS is instruments which observe visible light and middle-infrared radiation, respectively. CIAO observes near-infrared radiation of wavelength 0.9- 5.5 micron (micron is 0.001mm) which is between visible light and middle-infrared radiation. If a device is warm, it radiates infrared radiation itself and disturbs infrared observation. Therefore, we put the device of CIAO into the vacuum container and cool it under about - 364 degrees F (about - 220 degrees C).

There are three instruments, CIAO, IRCS, and OHS, which can observe near-infrared radiation among the first stage instruments of the Subaru Telescope. The point where CIAO is different from other instruments is that CIAO has a mechanism called a coronagraph; it is able to hide a star under a circular black mask. As a result, it is effective in observing surrounding faint structure of a star or discovering an object near a star; they have been difficult because of bright starlight.

Coronagraph

Sample images

When the CIAO system passed an examination at the base facility, CIAO left for the Subaru Telescope on the top of Mauna Kea on January 19. After the final inspection, CIAO was installed in the Cassegrain focus and waited for observation.

CIAO attached at the Subaru Telescope

CIAO could obtain a star as an imaging mode on February 9; this was the moment of "First Light." Furthermore, CIAO could observe a bright star hidden with a mask on 10th (AO did not use.).

Staff conducting observations at the control building beside the Subaru Telescope

A star hidden with a mask

The mask does not hide all light from a star, and we can see some light which shows through the mask. It makes us adjust the position of the mask easily.

CIAO is a unique instrument in a cooled infrared coronagraph. The aims in CIAO are to observe star-formation regions and to discover a planet around a star directly. The result of CIAO will be reported on the web pages.