We post here an update about the unusual activity of 217P/LINEAR (see our previous post http://bit.ly/32cXXc ). We did not use invasive image processing routines (as the Larson-Sekanina filtering) in order to minimize the risk of introducing any artefact in the images. In the panels you will find only ordinary grayscale palette images, azimuthal median subtractions and 1/r theoretical coma subtractions, in order to enhance inner coma details:
2009 Aug. 15, David Cardenosa:
2009 Aug. 20, Michael Jaeger:
2009 Aug. 21, David Cardenosa:
2009 Aug. 22, David Cardenosa:
2009 Aug 22, Guido-Sostero:
2009, Sept.3, Paul Camilleri:
Central condensation evolution during the rise of the phenomena:
From what is possible to see from the above images, we might bracket the rise of the event between Aug. 20 and Aug. 21. It had a rather quick evolution (matter of hours) and then it settled down in some days.
We would exclude a foreshortening effect. In our opinion we have witnessed a transient phenomena that has interested the nucleus of the comets and/or its surroundings for a relatively short time. Currently (i.e. after a couple of weeks from the event) the comet seems to have recevered to its pre-something occurence.
We are grateful with the authors of the images.
by Giovanni Sostero & Ernesto Guido