(Cooled Mid-Infrared Camera and Spectrometer)

Observing the Universe's Dusty Veil

Because the air on Mauna Kea is thin and dry, Subaru is able to detect mid-infrared light from astronomical objects. At most places on Earth, mid-infrared light is almost completely absorbed by the Earth’s atmosphere before it can reach sea level. COMICS is a camera and spectrograph for taking advantage of this rare observing window on Mauna Kea It can be used to study the formation of individual stars in our own Galaxy and large-scale star formation in other galaxies. It can also be used to study the formation of interstellar dust, the raw material for planets.

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The Galactic Center

The center of our Galaxy is populated not only by stars but by a large amount of gas and dust. Although the Galactic center is invisible in the optical because of the dust obscuration of stellar light, COMICS clearly reveals the complex dust structures in the mid-infrared. Some bright spots are emission from dust heated by embedded stars. The very center of the Galaxy is the dark part slightly to the right of the center of this image, where astronomers believe a super-massive black hole 2-3 million times more massive than the Sun is present.

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Debris disk around a young star

The pictures above show a star named HD 130948 taken with a combination of AO and IRCS. HD 130948 is a 6th magnitude normal star in the constellation Bootes and is located 60 light years away from us. In the top left panel, you may see two faint dots to the left of the bright primary. Their presence is difficult to recognize in the image taken without AO (top right panel). Spectroscopic observation with AO ( bottom right panel) revealed that the binary companions are a brown dwarf pair. A brown dwarf is a very light star weighing as little as just one hundredth of the mass of the Sun. Since it cannot continue to shine like normal stars by nuclear fusion of hydrogen atoms, it is often called "a failed star". The separation between the two companions is as small as 0.13 arcseconds, which is comparable to seeing the Eiffel tower from the Moon.

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Ejected gas from an evolved star

Once the hydrogen in its core is fused into helium, a star begins to repeatedly expand and collapse.
These observations by COMICS in three wavelengths show that the mass loss that accompanies these oscillations is not symmetric.

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COMICS explores the Universe at room temperature. Between the extreme of cold and hot in the Universe, there are places with dust grains like sand of the beach that have temperature just like sand on the beach This is what COMICS sees.

What is most exciting about COMICS is that pretty much every thing we observe with COMICS will be a new discovery. Mid-infrared observational astronomy is a very new field. The technology to take images in the mid-infrared didn’t come into existence until the 1990’s. COMICS is the first of the second gee ration mid-infrared instruments equipped with large-format mid-infrared detectors to go into operation in the whole world.

Because of the large aperture of Subaru telescope, we will be able to take images with a very fine spatial resolution. One of the reasons why mid-infrared astronomy was slow to develop is that you need an observational site at high altitude like Mauna Kea to detect mid-infrared radiation. The combination of Subaru, Mauna Kea, and COMICS is ideal.

Most researchers use COMICS to study either newly born stars of dying stars within our Galaxy. On the one hand, dust gathers together to form new stars. On the other hand, stars end their lives by ejecting dust. The ejected dust will gather together to form new stars again. I hope to see many exciting results in the field of not only our Galaxy but also external galaxies.

(From an January 2003 interview with COMICS support astronomer Takuya Fujiyoshi and research intern Shigeyuki Sako.)






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