Large changes in Pluto's atmosphere as revealed by recent stellar occultations

Sicardy, B.; Widemann, Thomas; Lellouch, E.; Veillet, Christian; Cuillandre, Jean-Charles; Colas, François; Roques, F.; Beisker, W.; Kretlow, M.; Lagrange, A.-M.; Gendron, É.; Lacombe, F.; Lecacheux, J.; Birnbaum, C.; Fienga, A.; Leyrat, C.; Maury, A.; Raynaud, E.; Renner, S.; Schultheis, M.; Brooks, Kate; Delsanti, A.; Hainaut, O.; Gilmozzi, R.; Lidman, C.; Spyromilio, J.; Rapaport, M.; Rosenzweig, P.; Naranjo, O.; Porras, L. Omar; Díaz, Franklin Chang; Calderón, Homero; Carrillo, S.; Carvajal, Ana María; Recalde, E.; Cavero, L. Gaviria; Montalvo, Carlos; Barría, Daniela; Campos, Rodrigo Prates; Duffárd, R.; Levato, H.

doi:10.1038/nature01766

Cited by 120 publications

(94 citation statements)

References 16 publications

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“…To quantify this statement, we combined our spectroscopic data with a new assessment of stellar occultation lightcurves. Besides the isothermal part and the "kink" feature mentioned previously, recent high-quality, occultation curves (Sicardy et al 2003;Elliot et al 2003Elliot et al , 2007E. Young et al 2008;) exhibit several remarkable characteristics: (i) a low residual flux during occultation, typically less than 3% of the unattenuated stellar flux; (ii) the conspicuous absence of caustic spikes in the bottom part of the lightcurves; (iii) the existence of a central flash caused by Pluto's limb curvature, in occultations in which the Earth passed near the geometric center of the shadow.…”

Section: Combination With Inferences From Stellar Occultationsmentioning

confidence: 99%

“…Pluto's upper atmosphere is isothermal (T ∼ 100 K at altitudes above 1215 km from Pluto's center) and has undergone a pressure expansion by a factor of 2 from 1988 to 2002, probably related to seasonal cycles, followed by a stabilization over 2002(Sicardy et al 2003Elliot et al 2003Elliot et al , 2007; E. ). Below the 1215 km level, occultation lightcurves are characterized by a sharp drop ("kink") in flux, interpreted as due to either a ∼10 km-thick thermally inverted layer (stratosphere) or absorption by a low-altitude haze with significant opacity (>0.15 in vertical viewing).…”

Section: Introductionmentioning

confidence: 99%

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Pluto's lower atmosphere structure and methane abundance from high-resolution spectroscopy and stellar occultations

Lellouch¹,

Sicardy

Bérgh³

et al. 2009

A&A

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119

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Context. Pluto possesses a thin atmosphere, primarily composed of nitrogen, in which the detection of methane has been reported. Aims. The goal is to constrain essential but so far unknown parameters of Pluto's atmosphere, such as the surface pressure, lower atmosphere thermal stucture, and methane mixing ratio. Methods. We use high-resolution spectroscopic observations of gaseous methane and a novel analysis of occultation lightcurves. Results. We show that (i) Pluto's surface pressure is currently in the 6.5-24 μbar range, (ii) the methane mixing ratio is 0.5 ± 0.1%, adequate to explain Pluto's inverted thermal structure and ∼100 K upper atmosphere temperature, and (iii) a troposphere is not required by our data, but if present, it has a depth of at most 17 km, i.e. less than one pressure scale height; in this case methane is supersaturated in most of it. The atmospheric and bulk surface abundances of methane are strikingly similar, a possible consequence of a CH 4 -rich top surface layer.

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Section: Combination With Inferences From Stellar Occultationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Pluto's lower atmosphere structure and methane abundance from high-resolution spectroscopy and stellar occultations

Lellouch¹,

Sicardy

Bérgh³

et al. 2009

A&A

Self Cite

119

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“…Another factor was the entering of Pluto in front of the projected Galactic plane, increasing the frequency of possible events. Successful examples of these new prediction methods are the stellar occultation campaigns of 2002 for Pluto (Sicardy et al 2003) and of 2005 for Charon (Sicardy et al 2006). Since 2004, our group has been engaged on a systematic effort to derive astrometric predictions for stellar occultations by Pluto and its satellites.…”

Section: Stellar Occultation Predictions: Astrometric Rationalementioning

confidence: 99%

“…Its upper atmosphere is isothermal with T ≈ 100 K above about 1215 km from the center. Pressure roughly doubled between 1988-2002 after Pluto s 1989 perihelion passage and then stabilized over 2002−2007(Sicardy et al 2003Elliot et al 2003Elliot et al , 2007Young et al 2008). Pluto s atmosphere is thought to be mainly N 2 , with a measured CH 4 abundance of 0.5% ± 0.1% and some undetermined amount of CO (Lellouch et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Precise predictions of stellar occultations by Pluto, Charon, Nix, and Hydra for 2008–2015

Assafin¹,

Camargo

Martins

et al. 2010

A&A

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Context. We investigate transneptunian objects, including Pluto and its satellites, by stellar occultations. Aims. Our aim is to derive precise, astrometric predictions for stellar occultations by Pluto and its satellites Charon, Hydra and Nix for 2008−2015. We construct an astrometric star catalog in the UCAC2 system covering Pluto s sky path. Conclusions. Recurrent issues in stellar occultation predictions were addressed and properly overcome: body ephemeris offsets, catalog zero-point position errors and field-of-view size, long-term predictions and stellar proper motions, faint-visual versus brightinfrared stars and star/body astrometric follow-up. In particular, we highlight the usefulness of the obtained astrometric catalog as a reference frame for star/body astrometric follow-up before and after future events involving the Pluto system. Besides, it also furnishes useful photometric information for field stars in the flux calibration of observed light curves. Updates on the ephemeris offsets and candidate star positions (geometric conditions of predictions and finding charts) are made available by the group at www.lesia. obspm.fr/perso/bruno-sicardy/. Also based on observations made at

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“…The size of Eris was recently constrained by an occultation, and in turn, its density and albedo (Sicardy et al 2011). And occultations have let us discover and monitor the rapid changes to Pluto's and Triton's atmospheres Sicardy et al 2003;Olkin et al 1997).…”

Section: Introductionmentioning

confidence: 99%

A Fourier Optics Method for Calculating Stellar Occultation Light Curves by Objects With Thin Atmospheres

Young

2012

The Astronomical Journal

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A stellar occultation occurs when a solar system object passes in front of a distant star. The light curves resulting from stellar occultations can reveal many aspects of the obscuring object. For airless bodies, the diffraction light curve specifies the object's size, distance and, if several chords are observed, shape. Occultation light curves are especially sensitive to the presence of atmospheres; the refraction light curve is a function of the atmosphere's density, pressure, and temperature profiles. The goal of this paper is to develop a practical algorithm to model the simultaneous effects of diffraction and refraction for objects in which both phenomena are observable. The algorithm we present is flexible: it can be used to calculate light curves by objects with arbitrary shapes and arbitrary atmospheres (including the presence of opacity sources such as hazes), provided that the atmosphere can be represented by a thin screen with a phase delay and an opacity defined at each location in the screen. Because the algorithm is limited at present to thin atmospheres (in which rays from a star are bent but undergo virtually no translation as they pass through an atmosphere), the gas giants, Earth, Mars, and Venus are not treated. Examples of stellar occultations are presented for round or irregularly shaped objects having thin atmospheres of various column densities.

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Large changes in Pluto's atmosphere as revealed by recent stellar occultations

Cited by 120 publications

References 16 publications

Pluto's lower atmosphere structure and methane abundance from high-resolution spectroscopy and stellar occultations

Pluto's lower atmosphere structure and methane abundance from high-resolution spectroscopy and stellar occultations

Precise predictions of stellar occultations by Pluto, Charon, Nix, and Hydra for 2008–2015

A Fourier Optics Method for Calculating Stellar Occultation Light Curves by Objects With Thin Atmospheres

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