Collaborative Research: A Multi-Frequency Campaign to Probe Neptune's Dynamics and Deep Atmospheric Structure

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The circulation of the planet Neptune's atmosphere has been modeled based on observations made from ground and space-based telescopes. Scientists now see Neptune as having an atmosphere with gases that sink at Neptune's equator and south pole, and rise at its mid-latitudes. But scientists have also seen clouds where air was expected to be sinking, and thinner atmosphere where air was expected to be rising. To study this contradiction, the investigators will use radio and optical telescopes to observe Neptune at the same time. They aim to understand the cloud formation and motions of gases, in order to understand the composition of Neptune's atmosphere at many different depths, the circulation of the atmosphere across the whole planet, storms, and unusual but local changes across all of Neptune. Students and amateur astronomers will also work on this project. This research serves the national interest by detailing the structure and composition of Neptune, one of four gas giant planets in the Solar System, and similar to many planets discovered around other stars. The investigators also regularly give talks to the public about their research, and will present the story of Neptune and how it relates to planet formation in general. A global circulation model of the planet Neptune has been derived, with gas rising at mid-latitudes and descending over the equator and the south pole. This circulation model extends from the stratosphere (0.1 mbar pressure levels) down to tens of bars into the deep troposphere. Many puzzles remain, however, such as the presence of clouds in regions of subsiding air (e.g., South pole, equator), and a relatively low radio opacity at mid-southern latitudes contrary to expectations of rising air. The principal investigators will use the combination of Very Large Array (1-13 cm), Atacama Large Millimeter/submillimeter Array (1-3 mm), Hubble Space Telescope (visible) and W. M. Keck Observatory (NIR) telescopes to observe Neptune often simultaneously to couple cloud formation to gas dynamics and condensation. These data are critical for understanding the composition of the deep atmosphere, the global circulation pattern, localized storm systems and turbulent motions in Neptune's atmosphere. The combined datasets cover Neptune's entire altitude range from the stratosphere down to ~100 bar. Maps of the planet will be produced at different frequencies resolved in both latitude and longitude using the upgraded VLA. Simultaneously-obtained images in the visible (HST) and NIR (adaptive optics on Keck) will characterize clouds and storms. ALMA data at continuum wavelengths and in the spectral windows of several disequilibrium species (e.g., CO, HCN, PH3) will be obtained. Students and the amateur astronomy community will contribute to this research. The investigators also regularly give talks to the public about their research, and will present the story of Neptune and how it relates to planet formation in general.