Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation.

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Title:	Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation.
Authors:	Ortiz, J. L., Sicardy, B., Braga-Ribas, F., Alvarez-Candal, A., Lellouch, E., Duffard, R., Pinilla-Alonso, N., Ivanov, V. D., Littlefair, S. P., Camargo, J. I. B., Assafin, M., Unda-Sanzana, E., Jehin, E., Morales, N., Tancredi, G., Gil-Hutton, R., de la Cueva, I., Colque, J. P., Da Silva Neto, D. N., Manfroid, J.
Source:	Nature. 11/22/2012, Vol. 491 Issue 7425, p566-569. 4p. 2 Diagrams, 1 Chart, 1 Graph.
Subjects:	Pluto (Dwarf planet), Eris (Dwarf planet), Makemake (Dwarf planet), Occultations (Astronomy), Albedo, Spectrum analysis
Abstract:	Pluto and Eris are icy dwarf planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies. Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos. Makemake is another icy dwarf planet with a spectrum similar to Eris and Pluto, and is currently at a distance to the Sun intermediate between the two. Although Makemake's size (1,420?±?60?km) and albedo are roughly known, there has been no constraint on its density and there were expectations that it could have a Pluto-like atmosphere. Here we report the results from a stellar occultation by Makemake on 2011 April 23. Our preferred solution that fits the occultation chords corresponds to a body with projected axes of 1,430?±?9?km (1?) and 1,502?±?45?km, implying a V-band geometric albedo pV = 0.77?±?0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4-12?nanobar (1?) for the surface pressure, although a localized atmosphere is possible. A density of 1.7?±?0.3?g?cm?3 is inferred from the data. [ABSTRACT FROM AUTHOR]
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Database:	Psychology and Behavioral Sciences Collection

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Abstract:	Pluto and Eris are icy dwarf planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies. Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos. Makemake is another icy dwarf planet with a spectrum similar to Eris and Pluto, and is currently at a distance to the Sun intermediate between the two. Although Makemake's size (1,420?±?60?km) and albedo are roughly known, there has been no constraint on its density and there were expectations that it could have a Pluto-like atmosphere. Here we report the results from a stellar occultation by Makemake on 2011 April 23. Our preferred solution that fits the occultation chords corresponds to a body with projected axes of 1,430?±?9?km (1?) and 1,502?±?45?km, implying a V-band geometric albedo pV = 0.77?±?0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4-12?nanobar (1?) for the surface pressure, although a localized atmosphere is possible. A density of 1.7?±?0.3?g?cm?3 is inferred from the data. [ABSTRACT FROM AUTHOR]
ISSN:	00280836
DOI:	10.1038/nature11597