Pluto’s atmosphere – 29 June 2015 ground-based stellar occultation at time of New Horizons flyby
B. Sicardy, J. Talbot, E. Meza, J. I. B. Camargo, J. Desmars, D. Gault, D. Herald, S. Kerr, H. Pavlov, F. Braga-Ribas, M. Assafin, G. Benedetti-Rossi, A. Dias-Oliveira, A. Ramos-Gomes-Jr., R. Vieira-Martins, D. Berard, P. Kervella, J. Lecacheux, E. Lellouch, W. Beisker, D. Dunham, M. Jelinek, R. Duffard, J. L. Ortiz, A. J. Castro-Tirado, R. Cunniffe, R. Querel, P. A. Yock, A. A. Cole, A. B. Giles, K. M. Hill, J. P. Beaulieu, M. Harnisch, R. Jansen, A. Pennell, S. Todd, W. H. Allen, P. B. Graham, B. Loader, G. McKay, J. Milner, S. Parker, M. A. Barry, J. Bradshaw, J. Broughton, L. Davis, H. Devillepoix, J. Drummond, L. Field, M. Forbes, D. Giles, R. Glassey, R. Groom, D. Hooper, R. Horvat, G. Hudson, R. Idaczyk, D. Jenke, B. Lade, J. Newman, P. Nosworthy, P. Purcell, P. F. Skilton, M. Streamer, et al. (4 additional authors not shown)
(Submitted on 21 Jan 2016)
We present results from a multi-chord Pluto stellar occultation observed on 29 June 2015 from New Zealand and Australia. This occurred only two weeks before the NASA New Horizons flyby of the Pluto system and serves as a useful comparison between ground-based and space results. We find that Pluto’s atmosphere is still expanding, with a significant pressure increase of 5 +/- 2% since 2013 and a factor of almost three since 1988. This trend rules out, as of today, an atmospheric collapse associated with Pluto’s recession from the Sun. A central flash, a rare occurrence, was observed from several sites in New Zealand. The flash shape and amplitude are compatible with a spherical and transparent atmospheric layer of roughly 3 km in thickness whose base lies at about 4 km above Pluto’s surface, and where an average thermal gradient of about 5 K/km prevails. We discuss the possibility that small departures between the observed and modeled flash are caused by local topographic features (mountains) along Pluto’s limb that block the stellar light. Finally, using two possible temperature profiles, and extrapolating our pressure profile from our deepest accessible level down to the surface, we estimate a range of 12.4-13.2 microbar for the surface pressure.
Comments: 11 pages, 2 tables, 3 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1601.05672 [astro-ph.EP] (or arXiv:1601.05672v1 [astro-ph.EP] for this version)
Submission history
From: Bruno Sicardy Prof.
[v1] Thu, 21 Jan 2016 15:13:23 GMT (349kb,D)
http://arxiv.org/abs/1601.05672
