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Date: 12/05 (Thu)
Time: 14:45-16:30
Place: 8-1-03
Speaker: Yuki Sato
Title : Observation of Neptune’s storms with Pirka telescope

Abstract:
　Neptune is the eighth planet of the solar system. It’s mainly composed of hydrogen and helium. Previous study shows that storms occur at both northernand southern mid latitude. (15－60°N, 15－60°S)[Imke de Pater et al., 2014]. Storms rotate at a certain speed in the longitude direction. The speed of storms is correlated with the zonal winds measured by Voyager 2.
　On June 26 and July 2 2017, a large-scale storm(the diameter is 9,000 km) was observed by the Keck Observatory. Storms occur at mid latitude, but this huge storm occurred at Neptune’ equator. Some scientists say that this is probably because of seasonal change.
　In this study, I developed the technique to estimate the drift rate and intensity of storms by observing a whole spectrum of Neptune. By using this technique, when seeing is bad, it’s possible to observe Neptune in short time span for a long term. In this seminar, I estimated the lifetime, intensity, drift rate of storms in 2017, 2018, 2019.
   I use methane absorption band in this study. Methane absorbs an 890 nm flux strongly. When I observe the aspect with a storm at 890 nm, an 890 nm flux becomes stronger compared to the aspect without a storm. This is because the altitude of storms is higher than that of other areas. And the apparent area of storms changes by the rotation of Neptune, so 890 nm flux changes. I calculate the theoretical value of an 890 nm flux changing by the rotation. I take the ratio of an 890nm flux and an flux of 855 nm to correct the effect of the Earth atmosphere, and compare the theoretical line with the observed values.
　In this presentation, I’ll show the results of my observation.
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