Thursday, May 29, 2008

Rare stellar occultation by Neptune's Triton observed!

These events happen only once a decade or so and are of high scientific value for understanding the atmosphere of Triton, Neptune's largest satellite - and now word has come out that another such observing campaign has been quite successful! (Please pardon the mix of French, English and German - and you may have to save the image to disk and open it with a PDF viewer.) On May 21 a 13 mag. star was occulted (alt. diagram, and now Bruno Sicardy reports: "For the first time in the last 11 years, Triton's atmosphere has been successfuly detected from two stations in Namibia (Hakos and Tivoli, summing five telescopes), and from two mobile stations set up at La Reunion Island (Maido and La Fournaise, summing four telescopes). [...]

One of the main scientific issues is now to see whether Triton's atmosphere have suffered drastic changes since 1997, knowing that the satellite reached an 'extreme' southern summer solstice in 2000. Then, the sub-solar latitude reached ~50°S. This happens every 600 years or so, and may have significantly heated up the nitrogen ice cap, triggered an enhanced geyser activity in the south polar regions of Triton, and induced a related pressure increase of the nitrogen atmosphere. [...] Two other stations in Namibia (Windhoek and Grunau) were clouded out. All the stations set up in South Africa (SAAO, Cape Town, Springbok) were clouded out. A third station in La Reunion (Les Makes) was also clouded out." There is also an update on the mutual occultations of the satellites of 2003 EL61.

In other news there is now a press release on the fastest-rotating asteroid reported here a week ago, stressing that this was an amateur discovery using the Faulkes telescopes. • Comet Boattini looks strange, at least with heavy image processing. • The lightcurve of comet Pons-Winnecke is going down again; here are pictures of May 23 and other dates. • A nice sungrazing comet was detected on May 23. • There's a Nova Oph 2008, but only at 10th mag: map, alert, observation, picture. • And finally some recent hi-res ISS pics: On May 31 shuttle Discovery should join the view.

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