ALMA makes the worldò??s first interferometric map of carbon atoms

ALMA opens another window to the universe in the 500 GHz frequency band. Astronomers successfully synthesized the distribution of atomic carbon around planetary nebula NGC 6302 in test observations with the ALMA Band 8 receiver, developed by the National Astronomical Observatory of Japan (NAOJ). This is the first 500 GHz-band astronomical image captured by a radio interferometer with unprecedentedly high resolution.

NGC 6302 is a planetary nebula, which is in the final stage of the life of a star with a mass several times that of the Sun. Visible light images show a bipolar shape of gas ejected from the dying star. ALMA targeted the center of the nebula, revealing that the distribution of carbon atoms is concentrated in a small part. This region is similar to a dust and gas disk around the central star that previous observations with other telescopes have shown. Further observations of carbon atoms with better resolution will give us a more detailed view of the chemical environment in the nebula.

So far, observations in the 500 GHz band, including emission lines from cosmic carbon atoms, have been made only with single-dish radio telescopes. The typical spatial resolution of those observations is 15 arcseconds or larger (1 arcsecond corresponds to 1/3600 of 1°). However, ALMA achieved a high resolution of 3.5 arcseconds in this test observation. By installing the Band 8 receiver into all the ALMA antennas, the resolution becomes 400 times better. Astronomers around the world have high expectations for observations with Band 8.

“I deeply appreciate long and hard efforts of all staff to realize ALMA observation of carbon atom,” said Yutaro Sekimoto from NAOJ. “I expect further ALMA observations will unveil the evolution process of interstellar matter.”