Friday, May 16, 2008

Strong evidence for albedo changes on the surface of Pluto - by reconstructing 1930s photometry

Yet another unusual paper by Louisiana State Univ. astronomer Brad Schaefer et al.: "We are reporting on a new accurate photographic light curve of Pluto for 1933-1934 when the heliocentric distance was 40 AU. [...] We find that the average B-band mean opposition magnitude of Pluto in 1933-1934 was 15.73±0.01, and we see a roughly sinusoidal modulation on the rotational period (6.38 days) with a peak-to-peak amplitude of 0.11±0.03 mag. With this, we show that Pluto darkened by 5% from 1933-1934 to 1953-1955." In contrast to a known darkening from 1954 onwards this effect cannot be due to our changing viewing geometry: "Thus, we now have strong evidence for albedo changes on the surface of Pluto, and these are most easily explained by the systematic sublimation of frosts from the sunward pole that led to a drop in the mean surface albedo."

In other news current images still show the storm on Saturn of which also a more recent Cassini image (from April 23) has been published. • Comet C/2005 L3 (McNaught) is a bit brighter than expected. • Even from a perfect spot there weren't too many Eta Aquarids visible. • Mira's strange tail is also emmitting in neutral hydrogen. • A more and more complete picture of the famous March 19 GRB is forming.

• First there was a cryptic NASA announcement about "the discovery of an object in our Galaxy astronomers have been hunting for more than 50 years", followed by rampant speculation everywhere - now we know what it was, namely the youngest known galactic SNR. And more than a few are angry about the hype fueled by NASA. Especially since the paper was out since March 10th ...

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