Issue |
A&A
Volume 387, Number 3, June I 2002
|
|
---|---|---|
Page(s) | 1107 - 1113 | |
Section | Celestial mechanics and astrometry | |
DOI | https://doi.org/10.1051/0004-6361:20020494 | |
Published online | 17 May 2002 |
VLT observations of comet 46P/Wirtanen*
1
European Southern Observatory ESO, Alonso de Cordova 3107, PO Box 19001, Santiago 19, Chile e-mail: hboehnha@eso.org;cdelahod@eso.org;tsekiguc@eso.org;ohainaut@eso.org;ramestic@eso.org
2
Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 50125 Firenze, Italy e-mail: tozzi@arcetri.astro.it
3
European Southern Observatory ESO, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany e-mail: jspyromi@eso.org;mtarengh@eso.org;rwest@eso.org
4
European Space Agency ESA, ESTEC, Keplerlaan, 2200 AG Noordwijk, The Netherlands e-mail: rschulz@estec.esa.nl;gschwehm@estec.esa.nl
Corresponding author: H. Boehnhardt, hboehnha@eso.org
Received:
4
December
2001
Accepted:
28
March
2002
Comet 46P/Wirtanen, prime target of ESA's
ROSETTA mission, was successfully observed at the Very Large Telescope
Observatory in Chile: on 17 May 1999 with the Test Camera
at the Cassegrain focus of the 8.2-m VLT Kueyen telescope
and on 8 December 2001 with FORS1 at Unit Telescope 4 Yepun.
May 1999: no coma was detected at heliocentric distance AU.
From the measured
brightness in the Bessell R-filter, a mean nucleus radius of
m is
derived (for a geometric albedo of 0.04 and a phase darkening of 0.04 mag/deg).
The nucleus signal varies during the 2.7 h observing interval and a peak-to-peak
amplitude of ~0.38 mag is determined. The measured lightcurve is in
agreement with a rotation period of 6–7.5 hours and a ratio of
the main nucleus axes of at least 1.4. The non-detection of a coma allows one
to put an approximate upper limit for Afρ of <0.45 cm (suggesting
a dust production rate of 0.05 kg/s).
December 2001: a weak and condensed coma seems to be present in the
seeing disk of the comet at 2.9 AU inbound, causing a higher brightness
than expected from
the previous size estimates of the nucleus. The colour of the comet
appears very red (
spectral gradient ~47%/100 nm). The Afρ
value of the comet was
cm (equivalent to a dust production
rate of about 1 kg/s).
Key words: comets: individual: 46P/Wirtanen / comets: general
© ESO, 2002
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