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Post Info TOPIC: Pluto Occultation
Blobrana


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RE: Pluto Occultation
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Title: Pluto's atmosphere from stellar occultations in 2012 and 2013
Author: A. Dias-Oliveira, B. Sicardy, E. Lellouch, R. Vieira-Martins, M. Assafin, J. I. B. Camargo, F. Braga-Ribas, A. R. Gomes-Júnior, G. Benedetti-Rossi, F. Colas, A. De****, A. Doressoundiram, C. Dumas, M. Emilio, J. Fabrega Polleri, R. Gil-Hutton, M. Gillon, J. Girard, G. Hau, V. D. Ivanov, E. Jehin, J. Lecacheux, R. Leiva, C. Lopez-Sisterna, L. Mancini, A. Maury, E. Meza, N. Morales, L. Nagy, C. Opitom, J. L. Ortiz, J. Pollock, F. Roques, C. Snodgrass, J. F. Soulier, A. Thirouin, L. Vanzi, T. Widemann, D. E. Reichart, A. P. LaCluyze, J. B. Haislip, K. M. Ivarsen, M. Dominik, U. Jřrgensen, J. Skottfelt

We analyse two multi-chord stellar occultations by Pluto observed on July 18th, 2012 and May 4th, 2013, and monitored respectively from five and six sites. They provide a total of fifteen light-curves, twelve of them being used for a simultaneous fit that uses a unique temperature profile, assuming a clear (no-haze) and pure N_2 atmosphere, but allowing for a possible pressure variation between the two dates. We find a solution that fits satisfactorily (i.e. within the noise level) all the twelve light-curves, providing atmospheric constraints between ~1,190 km (pressure ~ 11 \mubar) and ~ 1,450 km (pressure ~0.1 \mubar) from Pluto's center. Our main results are: (1) the best-fitting temperature profile shows a stratosphere with strong positive gradient between 1,190 km (at 36 K, 11 \mubar) and r = 1,215 km (6.0 \mubar), where a temperature maximum of 110 K is reached; above it is a mesosphere with negative thermal gradient of -0.2 K/km up to ~ 1,390 km (0.25 \mubar), where, the mesosphere connects itself to a more isothermal upper branch around 81 K; (2) the pressure shows a small (6 %) but significant increase (6-\sigma level) between the two dates; (3) without troposphere, Pluto's radius is found to be R_P = 1,190 ± 5km. Allowing for a troposphere, R_P is constrained to lie between 1,168 and 1,195 km; (4) the currently measured CO abundance is too small to explain the mesospheric negative thermal gradient. Cooling by HCN is possible, but only if this species is largely saturated; Alternative explanations like zonal winds or vertical compositional variations of the atmosphere are unable to explain the observed mesospheric trend.

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Blobrana


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Posts: 131433
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RE: Pluto Occultation 04.06.12
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Pluto's Atmosphere Probed from Carter Observatory

Carter Observatory has helped in an international collaboration to probe the depths of Pluto's atmosphere.
On the evening of June 4 Pluto passed in front of a faint star in the constellation Sagittarius, so that from certain parts of New Zealand and southeast Australia Pluto's atmosphere was expected to partially obscure the star's light. By monitoring any change in brightness as Pluto moved past the star, astronomers hoped to determine whether Pluto's atmosphere has changed in size in the last few years. This information is of critical importance in planning the flyby of NASA's New Horizons spacecraft in July 2015 after its ten year flight from Earth.
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Blobrana


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RE: Pluto Occultation 14.06.12
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Possible Pluto occultation Wednesday night (2012/06/14 03:28 UT) from US East coast.

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Blobrana


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RE: Pluto Occultation
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On June 22nd, 19:11 UT, 2008, Pluto and Charon occulted the magnitude 12 star UCAC 25370733

Position(2000): RA 17 58 33.0142, Dec 17 02 38.351

The 77.5 second event could be seen from  Antarctica

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Blobrana


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Tasmania's amateur astronomers are being encouraged to participate in a rare star-gazing event this evening.
Astronomers are gathering in Hobart, Launceston, New Zealand and country New South Wales for an opportunity to see Pluto's atmosphere as it passes by other stars in the galaxy.
The best viewing conditions are from 11:30 tonight.
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Blobrana


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Swarms of astronomers are expected to pack major observatories in Arizona this weekend hoping to see a rare "occultation" as Pluto crosses in front of a star and blots out its light.
Sunday morning's event is exciting for scientists because it will give them a better idea of the size and makeup of Pluto's atmosphere.

Source

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Blobrana


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Arizona Telescopes Focus On Pluto Early March 18
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Telescopes from Wyoming to Mexico City and from California to central Texas will point at Pluto as the dwarf planet occults a star in the Sagittarius constellation next Sunday.
University of Arizona astronomers will host colleagues from Paris Observatory, the Massachusetts Institute of Technology and Lowell Observatory at UA telescopes for the not-to-be-missed event.

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Blobrana


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RE: Pluto Occultation
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 The Pluto occultation of 18 March 2007
(visible from S.W. USA, Northern Mexico)
On 18 March 2007 a little bit before 11:00 UT, Pluto and its atmosphere will occult a V~15 star for up to 6 mn for central events.
Because the star UCAC2 25823784 is very red, observations in R, I, or J, H, K, are most suggested.
Even though larger telescopes will yield higher SNR, smaller amateur instruments (25-50 cm) can yield extremely valuable contribution for pinning down the astrometry of the event (combining various occultation chords), by helping to detect a possible central flash, and by giving firmer confirmation on possible changes occurring right now in Pluto's tenuous atmosphere.

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Blobrana


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June 12 Occultation
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The data retrieved by Dr. French and others in Australia and New Zealand on June 12 show that Pluto's atmosphere today is a lot like it was at the time of two occultation events in 2002, but fairly different than in 1980s occultation events. Most specifically, Pluto's lower atmosphere seems to have undergone some kind of change in its haze content or thermal properties since the 1980s, when it passed perihelion (closest approach to the Sun).

We'll have to wait a few months for data analysis to yield quantitative results, but I can say without reservation that Pluto's atmosphere "hasn't collapsed yet" (though there can be no guarantees about what will happen before we arrive in 2015). Meanwhile, New Horizons races towards Pluto, to assay its atmosphere in exquisite detail.

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Blobrana


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RE: Pluto Occultation
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Astronomers say they have gained valuable data about the atmosphere of Pluto from observations in Tasmania last week.
International astronomers met to record what is known as an occultation, a rare event in which Pluto passed in front of a star.
The group took measurements of shadows cast by Pluto during the eclipse and it is hoped these will show whether it is surrounded by rings.
Tasmanian astronomer John Greenhill says data from French and American astronomers will provide a better understanding of Pluto's atmospheric layers.

"Both of those just got images, so they got video recordings of images taken every second or every half second and they had to take those back to home and analyse them, so at this stage no light curve has been generated to my knowledge, but I expect we will have it within a week or so" - John Greenhill .

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