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

• Published in: Nature (London) Vol. 491; no. 7425; pp. 566 - 569
• Main 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., Thirouin, A., Gutiérrez, P. J., Lecacheux, J., Gillon, M., Maury, A., Colas, F., Licandro, J., Mueller, T., Jacques, C., Weaver, D., Milone, A., Salvo, R., Bruzzone, S., Organero, F., Behrend, R., Roland, S., Vieira-Martins, R., Widemann, T., Roques, F., Santos-Sanz, P., Hestroffer, D., Dhillon, V. S., Marsh, T. R., Harlingten, C., Bagatin, A. Campo, Alonso, M. L., Ortiz, M., Colazo, C., Lima, H. J. F., Oliveira, A. S., Kerber, L. O., Smiljanic, R., Pimentel, E., Giacchini, B., Cacella, P., Emilio, M.
• Format: Journal Article Web Resource
• Language: English
• Published: London Nature Publishing Group UK 22-11-2012; Nature Publishing Group
• Subjects: 639/33/445; Albedo; Asteroids (minor planets); Astronomy; Astrophysics; Atmosphere; Atmospheres; Aérospatiale, astronomie & astrophysique; Barometric pressure; Density; Dwarf planets; Earth, ocean, space; Exact sciences and technology; Humanities and Social Sciences; letter; Light; Minor planets; multidisciplinary; Physical, chemical, mathematical & earth Sciences; Physics; Physique, chimie, mathématiques & sciences de la terre; Planets; Planets, their satellites and rings. Asteroids; Pluto; Science; Solar system; Space science, astronomy & astrophysics; Stellar occultation; Studies; Sun; Telescopes; Brazil; Planetary atmospheres; Occultations; Upper bound; Albedo; Dwarf planet; Pluto planet
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/nature11597

The icy dwarf planet Makemake has projected axes of 1,430 ± 9 and 1,502 ± 45 km and a V-band geometric albedo larger than Pluto’s but smaller than Eris’s, with no global Pluto-like atmosphere.
Makemake shapes up against Pluto and Eris
Makemake is thought to be the third-largest dwarf planet in our Solar System, a little smaller than Pluto and Eris, but until now knowledge of its size and albedo were only approximate. This paper reports the results of observations of the occultation of a faint star known as NOMAD 1181-0235723 by Makemake on 23 April 2011. The data confirm that Makemake is smaller than Pluto and Eris, with axes of 1,430±9 km and 1,502±45 km. Makemake's mean geometric albedo — the ratio of light reflected to light received — is intermediate between that of Pluto and that of Eris. All three are icy, making them among the most reflective objects in the Solar System. And the occultation light curves rule out the presence of a global Pluto-like atmosphere on Makemake, although the presence of dark terrain might imply the presence of a localized atmosphere.
Pluto and Eris are icy dwarf planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies
1
,
2
. Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos
3
. Makemake is another icy dwarf planet with a spectrum similar to Eris and Pluto
4
, 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
5
,
6
, there has been no constraint on its density and there were expectations that it could have a Pluto-like atmosphere
4
,
7
,
8
. 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
σ
) and 1,502 ± 45 km, implying a V-band geometric albedo
p
V
= 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
σ
) 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.