... DI at ESO Campaign - Update July 4, 2005

Eagerly awaiting the images of the impact of Deep Impact with Comet 9P/Tempel 1, astronomers at the ESO La Silla Paranal Observatory spent their second night of observations of Comet Tempel. The weather was excellent in Paranal, with a very good image quality, but clouds started to appear at sunset over La Silla, making it difficult for the mid-sized telescopes located there to observe efficiently. A first set of TIMMI2 images was obtained.


ESO PR Photo 02a/05

FORS2 Image of Comet Tempel 1

Caption: Image taken with FORS2 on Antu on the night of July 3 to 4, 2005.

At Paranal, however, a wealth of data could be collected that will prove most useful for comparing with post-impact observations. FORS2 made broadband images and performed visible spectroscopy of the comet. No significant changes compared to the previous night were seen. UVES on Kueyen continued its high-dispersion spectroscopic monitoring of the coma, while VISIR on Melipal made a series of of mid-IR filter imaging before switching to spectroscopy in N band taking over the task originally foreseen for TIMMI2 at the 3.6m telescope in La Silla after this site got clouded out.


ESO DI FORS2

Thermal infrared image of Comet Tempel 1

Caption: PAH2 filter image of the comet, taken with VISIR at the UT3 telescope of the ESO VLT observatory on 4 July 2005, a few hours before impact. The VISIR spectrum shows the energy distribution of the thermal light emission from the dust in the inner coma. It allows to characterize the temperature of the grains due to the heating by the Sun and some other physical properties of the dust (like for instance grain sizes). The emission features around 9.5 micron and beyond 13 micron are of terrestrial origin and unrelated with the comet dust. The spectrum was taken with 4 different instrument settings in order to cover the complete N band wavelength region of the atmospheric window.

Generally, the comet appears unchanged compared to yesterday's observations. Things may change for next night, following the impact of the 360 kg impactor on Comet Tempel 1.

After the observations, the astronomers all watched live the impact as shown by the spacecraft. They were delighted to see the impactor hitting the comet at the right time and position. "I am deeply impressed" said team leader Olivier Hainaut at Paranal. "This was very convincing", added Hermann Boehnhardt. "We look very much forward to be able to observe the comet again tonight", he added. "Given what we have seen until now, we have great expectations".


More Information

The purpose of these pre-impact observations is to acquire an unprecedented and complete set of data with in total eleven instruments. The observations cover the wavelength domain between 350 nm (ultraviolet side of the visible light) and 20 micrometer (thermal infrared). These observations will be used to obtain a detailed understanding of the effects of the impact, as they will serve as reference for post-impact observations. The final aim of the campaign is the characterization of the cometary gas and dust that was embedded into the cometary nucleus during its formation some 4.6 billion years ago, i.e. before the planets including our own one were born, thus giving us an insight in the formation conditions of the solar system.


Note

[1]: Leading scientists of the ESO DI campaign: H. Boehnhardt (MPI, Lindau, Germany), O. Hainaut (ESO), H.U. Kaufl (ESO), H. Rauer (DLR, Germany).

Members of the ESO DI observing team on site: N. Ageorges (ESO, Chile), S. Bagnulo (ESO, Chile), L. Barrera (UMCE, Chile), H. Boehnhardt (MPS, Germany), T. Bonev (Astr. Inst. Sofia, Bulgaria), O. Hainaut (ESO, Chile), E. Jehin (ESO, Chile), H.U. Kaufl (ESO, Germany), F. Kerber (ESO, Germany), J. Manfroid (U.Liège, Belgium), O. Marco (ESO, Chile), E. Pantin (CEA, France), E. Pompei (ESO, Chile), C. Sterken (Vrije Universiteit Brussel, Belgium), G.P. Tozzi (Obs. Arcetri, Italy), M. Weiler (DLR, Germany)

Members of the ESO DI observing team not on site: C. Arpigny (U.Liège, Belgium), A. Cochran (McDonald, USA), C. Delahodde (Univ. Florida, USA), Y. Fernandez (Univ. Hawaii, USA), D. Hutsemekers (U.Liège, Belgium), H. Kawakita (Gunma, Japan), J. Knollenberg (DLR, Germany), L. Kolokolova (Univ. Maryland, USA), M. Kretlow (MPS, Germany), M. Kueppers (MPS, Germany), E. Kuehrt (DLR, Germany), L. Lara (IAA, Spain), J. Licandro (IAC, Spain), C. Lisse (Univ. Maryland, USA), K. Meech (U.Hawaii, USA), R. Schulz (ESTEC, The Netherlands), G. Schwehm (ESTEC, The Netherlands), M. Sterzik (ESO, Chile), J.A. Stüwe (Leiden, The Netherlands), I. Surdej (Univ. Liège, Belgium and ESO, Garching), D. Wooden (Ames, USA), J.-M. Zucconi (Besancon, France)