2018/03/09 by Anthony Mallama, Liming Li, Mallama, Anthony +1
Engineering · Physics and Astronomy · #Astro and Planetary Science #Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Planetary Science and Exploration #Space Exploration and Technology #astro-ph.EP
paper · pdf · doi:10.48550/arxiv.1803.03568
arxiv created 2018/03/09 · openalex publication_date 2018/03/09 · arxiv updated 2018/03/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Mid-IR albedo values of Neptune are derived from Spitzer Space Telescope measurements reported by Stauffer et al. (2016). The method of this derivation is described and the results indicate that the geometric albedo was about 1% or less at the time of the observations in 2016. Short-term mid-IR variability of Neptune, evidenced by the Spitzer observations themselves, indicates an albedo at 3.6 microns ranging from 0.2% to 0.6% with a mean of 0.4%. The corresponding albedos at 4.5 microns are 0.7%, 1.3% and 0.9%. Furthermore, the 60-year history of visible-light brightness variations, which show that Neptune was significantly fainter a few decades ago, suggests that the mid-IR albedo during that earlier period of time may have been much less than 1%. The albedo values reported here can have implications for models of Neptune's atmosphere. However, the mid-IR brightness of Neptune cannot contribute very strongly to its total albedo because the Sun emits only about 2% of its flux long-ward of 3 micron. By contrast, the Sun emits 42% of its flux at visible and near-UV wavelengths where the planet's albedo is in the tens of percents.