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Subaru Telescope Captures Visible-Light Images of the Comets ISON and Lovejoy

November 14, 2013

During the early morning of October 31, 2013, the Faint Object Camera and Spectrograph (FOCAS), mounted on the Subaru Telescope, captured images of the detailed structures of the envelopes of dust and gas (i.e., the comae) surrounding the nuclei of the comets ISON (C/2012 S1) and Lovejoy (C/2013 R1).


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Figure 1: Optical image of the structures surrounding the nucleus of the Comet ISON, captured by FOCAS mounted on the Subaru Telescope. This image was taken in the early morning of Oct 31, 2013 (Hawaii time) in V-band (550 nm) with an exposure time of 5 seconds. The field of view is about 6 x 3 arcminutes. (Credit: NAOJ/Observation and data reduction by Dr. Masafumi Yagi [NAOJ])


The optical image of the Comet ISON (Figure 1) follows Subaru's successful mid-infrared imaging of it with the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on October 19th and 21st (Hawaii time, 2013) (Subaru Telescope Captures Clear Image of Comet ISON in the Mid-Infrared Range). The current image, taken with an exposure time of 5 seconds, shows the structure of the coma (i.e., the atmosphere around the nucleus) as well as a tail extending from the nucleus. Named for the robotic telescope that spotted it, the International Scientific Optical Network (ISON), the comet was 190 million kilometers away from the Earth (and 150 million kilometers from the Sun) at the time of observation conducted by Dr. Masafumi Yagi (NAOJ). As it continues to head for its close encounter with the Sun, Comet ISON is expected to become very bright.

During the same night of Dr. Yagi's observations (October 31, 2013), FOCAS also captured an image showing the detailed features around the nucleus of the Comet Lovejoy (Figure 2), which was only recently discovered in September, 2013 by the Australian observer Terry Lovejoy. The most notable aspect of this image is the x-shaped, complex structure surrounding the nucleus, which is probably a dust jet flowing from it. It can be seen around midnight from Japan and Hawaii.


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Figure 2: Optical image of the structures surrounding the nucleus of the Comet Lovejoy, captured by FOCAS mounted on the Subaru Telescope. This image was taken in the early morning of Oct 31, 2013 in V-band (550 nm) with an exposure time of 5 seconds. The field of view is about 6 x 3 arcminutes. The lower-left inset shows the structures around the nucleus after adjusting the contrast in the image. (Credit: NAOJ/Observation and data reduction by Dr. Masafumi Yagi [NAOJ])


Dr. Masafumi Yagi, who carried out the observations and data analyses of both comets, commented, "The observation of the night was hard, because the weather conditions changed often. We needed to open and close the dome several times. We were fortunate to capture clear images of the comets, and share these images with so many people."





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