CaltechAUTHORS
Published November 1, 2023 | Published
Journal Article Metadata-only

Evolution of Neptune at near-infrared wavelengths from 1994 through 2022

Chavez, Erandi1 ORCID icon
de Pater, Imke1 ORCID icon
Redwing, Erin1 ORCID icon
Molter, Edward M.1 ORCID icon
Roman, Michael T.2 ORCID icon
Zorzi, Andrea3
Alvarez, Carlos4 ORCID icon
Campbell, Randy4 ORCID icon
de Kleer, Katherine R.5 ORCID icon
Hueso, Ricardo6 ORCID icon
Wong, Michael H.1 ORCID icon
Gates, Elinor7 ORCID icon
Lynam, Paul David7
Davies, Ashley G.8 ORCID icon
Aycock, Joel4
Mcilroy, Jason9
Pelletier, John4
Ridenour, Anthony4
Stickel, Terry4
  • 1. ROR icon University of California, Berkeley
  • 2. ROR icon University of Leicester
  • 3. ROR icon Stanford University
  • 4. ROR icon W.M. Keck Observatory
  • 5. ROR icon California Institute of Technology
  • 6. ROR icon University of the Basque Country
  • 7. Lick Observatory
  • 8. ROR icon Jet Propulsion Lab
  • 9. NASA Armstrong Flight Research Center
An error occurred while generating the citation.

Abstract

Using archival near-infrared observations from the Keck and Lick Observatories and the Hubble Space Telescope, we document the evolution of Neptune’s cloud activity from 1994 to 2022. We calculate the fraction of Neptune’s disk that contained clouds, as well as the average brightness of both cloud features and cloud-free background over the planet’s disk. We observe cloud activity and brightness maxima during 2002 and 2015, and minima during 2007 and 2020, the latter of which is particularly deep. Neptune’s lack of cloud activity in 2020 is characterized by a near-total loss of clouds at mid-latitudes and continued activity at the South Pole. We find that the periodic variations in Neptune’s disk-averaged brightness in the near-infrared H (1.6μm), K (2.1μm), FWCH4P15 (893 nm), F953N (955 nm), FWCH4P15 (965 nm), and F845M (845 nm) bands are dominated by discrete cloud activity, rather than changes in the background haze. The clear positive correlation we find between cloud activity and Solar Lyman-Alpha (121.56 nm) irradiance lends support to the theory that the periodicity in Neptune’s cloud activity results from photochemical cloud/haze production triggered by Solar ultraviolet emissions.

Copyright and License

© 2023 Elsevier Inc.

Acknowledgement

We would like to thank the two anonymous referees whose comments greatly improved this manuscript. This work has been supported by the National Science Foundation, United States, NSF Grant AST-1615004 to UC Berkeley. M. Roman was supported by a European Research Council Consolidator Grant (under the European Union’s Horizon 2020 research and innovation programme, grant agreement No 723890) at the University of Leicester.
Many of the images were obtained with the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation, United States . The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
We further made use of data obtained with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute.
This work used data acquired from the NASA/ESA HST Space Telescope, associated with OPAL program (PI: Simon, GO13937), and archived by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. All maps are available at http://dx.doi.org/10.17909/T9G593.
STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5–26555
Research at Lick Observatory is partially supported by a generous gift from Google.

Software References

astropy, matplotlib, nirc2_reduce, numpy, pandas, scipy

Data Availability

All data are publically available and are also available upon request.

Additional details

Related works Funding Dates Caltech Custom Metadata
Created:
April 3, 2025
Modified:
April 3, 2025