Neptune long-lived atmospheric features in 2013–2015 from small (28-cm) to large (10-m) telescopes

Journal Article · Wed Jun 14 00:00:00 EDT 2017 · Icarus

DOI:https://doi.org/10.1016/j.icarus.2017.06.009· OSTI ID:1836918

Hueso, R. ^[1]; de Pater, I. ^[2]; Simon, A. ^[3]; Sánchez-Lavega, A. ^[1]; Delcroix, M. ^[4]; Wong, M. H. ^[5]; Tollefson, J. W. ^[5]; Baranec, C. ^[6]; de Kleer, K. ^[7]; Luszcz-Cook, S. H. ^[8]; Orton, G. S. ^[9]; Hammel, H. B. ^[10]; Gómez-Forrellad, J. M. ^[11]; Ordonez-Etxeberria, I. ^[1]; Sromovsky, L. ^[12]; Fry, P. ^[12]; Colas, F. ^[13]; Rojas, J. F. ^[1]; Pérez-Hoyos, S. ^[1]; Gorczynski, P. ^[14] ; Guarro, J. ^[14]; Kivits, W. ^[14]; Miles, P. ^[14]; Millika, D. ^[14]; Nicholas, P. ^[14]; Sussenbach, J. ^[14]; Wesley, A. ^[14]; Sayanagi, K. ^[15]; Ammons, S. M. ^[16]; Gates, E. L. ^[17]; Gavel, D. ^[17]; Victor Garcia, E. ^[16]; Law, N. M. ^[18]; Mendikoa, I. ^[1]; Riddle, R. ^[19]

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1. Universidad del País Vasco, Bilbao (Spain)
2. Univ. of California, Berkeley, CA (United States); Delft Univ. of Technology (Netherlands)
3. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
4. Sociéte Astronomique de France, Paris (France)
5. Univ. of California, Berkeley, CA (United States)
6. Univ. of Hawaii at Manoa, Honolulu, HI (United States)
7. Netherlands Institute for Space Research, Utrecht (The Netherlands)
8. American Museum of Natural History (AMNH), New York, NY (United States); Columbia Univ., New York, NY (United States)
9. California Institute of Technology (CalTech), Pasadena, CA (United States). Jet Propulsion Lab. (JPL)
10. Association of Universities for Research in Astronomy, Washington DC (United States)
11. Fundació Observatori Esteve Duran, Seva (Spain)
12. Univ. of Wisconsin, Madison, WI (United States)
13. Observatoire de Paris, Paris (France)
14. Planetary Virtual Observatory Laboratory, Bilbao (Spain). International Outer Planet Watch
15. Hampton Univ., Hampton, VA (United States)
16. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
17. Lick Observatory, Mount Hamilton, CA (United States)
18. Univ. of North Carolina, Chapel Hill, NC (United States)
19. California Institute of Technology (CalTech), Pasadena, CA (United States)

Since 2013, observations of Neptune with small telescopes (28–50 cm) have resulted in several detections of long-lived bright atmospheric features that have also been observed by large telescopes such as Keck II or Hubble. The combination of both types of images allows the study of the long-term evolution of major cloud systems in the planet. In 2013 and 2014 two bright features were present on the planet at southern mid-latitudes. These may have merged in late 2014, possibly leading to the formation of a single bright feature observed during 2015 at the same latitude. This cloud system was first observed in January 2015 and nearly continuously from July to December 2015 in observations with telescopes in the 2-10-m class and in images from amateur astronomers. These images show the bright spot as a compact feature at -40.1 ± 1.6° planetographic latitude well resolved from a nearby bright zonal band that extended from -42° to -20°. The size of this system depends on wavelength and varies from a longitudinal extension of 8000 ± 900 km and latitudinal extension of 6500 ± 900 km in Keck II images in H and Ks bands to 5100 ± 1400 km in longitude and 4500 ± 1400 km in latitude in HST images in 657 nm. Over July to September 2015 the structure drifted westward in longitude at a rate of 24.48 ± 0.03°/day or -94 ± 3 m/s. This is about 30 m/s slower than the zonal winds measured at the time of the Voyager 2 flyby. Tracking its motion from July to November 2015 suggests a longitudinal oscillation of 16° in amplitude with a 90-day period, typical of dark spots on Neptune and similar to the Great Red Spot oscillation in Jupiter. The limited time covered by high-resolution observations only covers one full oscillation and other interpretations of the changing motions could be possible. HST images in September 2015 show the presence of a dark spot at short wavelengths located in the southern flank (planetographic latitude -47.0°) of the bright compact cloud observed throughout 2015. The drift rate of the bright cloud and dark spot translates to a zonal speed of -87.0 ± 2.0 m/s, which matches the Voyager 2 zonal speeds at the latitude of the dark spot. Identification of a few other features in 2015 enabled the extraction of some limited wind information over this period. This work demonstrates the need of frequently monitoring Neptune to understand its atmospheric dynamics and shows excellent opportunities for professional and amateur collaborations.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1836918
• Report Number(s): LLNL-JRNL-829489; 1045531; TRN: US2300388
• Journal Information: Icarus, Vol. 295, Issue N/A; ISSN 0019-1035
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
Neptune
Neptune - atmosphere
Atmospheres - dynamics