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Fwd: VLT First Images of Comet Tempel 1 After Impact

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  • Frits Westra
    ... From: esonews@eso.org Subject: VLT First Images of Comet Tempel 1 After Impact Date: Tue, 05 Jul 2005 14:25:17 +0200 Dear subscribers, On the night of July
    Message 1 of 1 , Jul 5, 2005
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      ------- Forwarded message -------
      From: esonews@...
      Subject: VLT First Images of Comet Tempel 1 After Impact
      Date: Tue, 05 Jul 2005 14:25:17 +0200

      Dear subscribers,

      On the night of July 4, 2005, all ESO telescopes continued their extensive
      observing campaign of Comet Tempel 1. But this time, they were able to see
      the effect of the impact on the comet. The astronomers were clearly not

      The impact occurred at 07:52 CEST but because the comet has already set in
      Chile at that time, observers at the La Silla Paranal Observatory could
      only start observing several hours later. The first observations were done
      in the infrared by TMMI2 at the 3.6m telescope at La Silla, at 21:20 CEST
      (still daylight in Chile).

      These first observations showed the comet to be 2 to 3 times brighter in
      the infrared than the day before the impact. The coma is also much more
      extended than it was until before the impact.

      At sunset in Chile, all 7 telescopes of the La Silla Paranal Observatory
      went into operations. The FORS2 multi-mode instrument on Antu, one of the
      8.2m Unit Telescope of the VLT array, took stunning images, showing that
      the morphology of the comet had dramatically changed: a new bright
      fan-like structure was now visible.

      The fan lies in the southern part of the image and is rather bright and
      well defined. This feature is an addition to those that were already
      visible during the previous days, that seems to still be underlying the
      new one. Behind this fan, the old coma from yesterday is still present.
      The new structure is about 15,000 km large, indicating that the matter has
      been ejected with a speed of about 700 to 1,000 km/h.

      Further observations during the week will study the evolution of this fan,
      revealing if the probe has activated a new region of the surface and how
      long that region remains active.

      The fan is visible through the reflection of sunlight on dust grains. The
      fact that the big plume is not uniform in colour probably indicates that
      different dust size are traveling at different speeds.

      Other telescopes have provided observations of the comet as well. NACO
      took some images of the central part of the coma, while UVES performed
      high-dispersion spectroscopy of the comet, in order to compare with the
      previous nights. First estimates indicate the emission lines to be more
      pronounced by 10 to 20 %.

      At La Silla, the SOFI instrument at the NTT telescope, imaged the comet in
      the near-infared. An image in the J-band also shows the dust shell from
      the impact in the south-western quadrant of the coma. The very inner coma
      (indicated by the white box) shows on-going enhanced activity compared to
      the pre-impact level.

      The astronomers at the La Silla Paranal Observatory will continue to
      observe Comet Tempel 1 for another four days in order to monitor precisely
      its long-term behaviour.

      All the images and links are available at

      With kind regards,

      The ESO Public Affairs Dept.

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