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O.R. Hainaut, C.E. Delahodde, H. Boehnhardt (ESO/Chile), E. Dotto, M.A. Barucci (Paris/Meudon), K.J. Meech, J. Bauer (IfA/Hawaii), R.M West (ESO/Garcching), A. Doressoundiram (CalTech), G.P. Tozzi (Arcetri/Italy)
The Kuiper Belt being the source of Short Period Comets, it is expected that the nature of TNOs be the same as that of pristine SP comets. The suspected conditions prevailing at the time and place of their formation support the idea that the water ice trapped large quantities of very volatile material while condensing. These hypotheses, together with recent observations of activity in very distant comets (at r > 23AU) and with the behaviour of Pluto's atmosphere, indicate that cometary activity in TNOs should indeed be possible, even in the 30--45AU heliocentric distance range.
We will present various observations, by this group and others, that are interpreted as direct evidences of TNO cometary activity. Most notably, Fletcher et al. [1] announced the detection of a coma around 1994 TB, using HST. We have obtained a detailed portrait of 1996 TO66 [2,3]: a dramatic change of that object's rotational lightcurve between 1997 and 1998 is interpreted as the signature of a cometary outburst. Finally, Brown et al. [4] just published Keck NIR spectra of 1996 TO66 obtained almost simultaneously with our 1998 data, showing the presence of water ice on that object, further reinforcing the conviction of its cometary nature. We also plan to present VLT data of TO66, in the hope that they will cast additional light on the nature and state of that object.
Finally, we will open the discussion on the the possible consequences of cometary activity in TNOs, for instance on the problem of their color diversity.
[1] Fletcher, E., A. Fitzsimmons, I. P. Williams, N. Thomas and W.-H. Ip (1999): "HST observations of the Kuiper Belt", in Minor Bodies in the Outer Solar System, Proceesings of the MBOSS-1998 meeting held at ESO, Nov.1998, Fitzsimmons (Ed), in press [2] O.R. Hainaut, C.E. Delahodde, H.Boehnhardt, E. Dotto, M.A. Barucci, K.J. Meech, J.M. Bauer and A. Doressoundiram (1999): "Physical properties of TNO 1996 TO66", submitted to A&A.
[3] Delahodde C.E., O.R. Hainaut, H.Boehnhardt and R.M.West (1999): "Physical observations of 1996 TO66", in Minor Bodies in the Outer Solar System, Proceesings of the MBOSS-1998 meeting held at ESO, Nov.1998, Fitzsimmons (Ed), in press
[4] Brown, R.H., D.P. Cruikshank and Y. Pendleton (1999): "Water Ice on KBO 1996 TO66", ApJ 519, L101
The author(s) of this abstract have provided an email address for comments about the abstract: ohainaut@eso.org