A dataset provided by the European Space Agency

Name GT1_mkidger_2
Title A last chance to measure the size of the nucleus of Comet Hale-Bopp directly in the IR


DOI https://doi.org/10.5270/esa-edwrwmd
Author kidger, m.
Description Comet C/1995 O1 (Hale-Bopp) was one of the three intrinsically brightest comets of the
last 600 years. It is generally agreed to be a giant object with a nucleus of diameter in the
range 40-80km compared to the 15x8km of 1P/Halley. It is also one of the most
intensively studied objects in history and the only giant comet ever to be studied
intensively with modern detectors. The large flux, long lead time to perihelion and
exceptional period of visibility (19 months with the naked eye and, so far, at least 17
years telescopically) have contributed to an unprecedented degree of knowledge and
understanding of this comet. The fact that the comet was known to be active at 13AU
pre-perihelion (and possibly even at 17AU) and that it has been active a well past 20AU
post-perihelion has demonstrated its extraordinary duration of activity.

In June 2010 Hale-Bopp will pass the orbit of Neptune and now finally appears to be
inactive. This will allow us to attack the problem of the one great unknown about the
comet: the size of the nucleus. Dozens of size estimates have been published, ranging
from under 15km to 250km, but it is generally acknowledged that radio techniques have
underestimated the size, whereas infrared techniques and PSF fitting have tended to
overestimate it. Given that the rotation period, rotation mode and pole orientation are
well-determined, an accurate value for the diameter of the nucleus will allow dynamical
information on the mass and even the internal structure of the nucleus to be determined.

We propose to observe Hale-Bopp in PACS blue+red using the technique of background
subtraction to obtain 4-sigma at 1mJy, equivalent to detecting a nucleus of diameter
around 40km. We request that these observations be scheduled in the optimum window in
June 2010 to subtract out the confusion noise. Combining PACS with visibl...e data, we
will obtain, at worst, a strong model-constraining upper limit to the nucleus diameter and
albedo that should stand for 2500 years.
Publication Evidence for Fresh Frost Layer on the Bare Nucleus of Comet Hale-Bopp at 32 AU Distance . Szabó Gyula M. et al. . The Astrophysical Journal, Volume 761, Issue 1, article id. 8, 7 pp. (2012). . 761 . 10.1088\/0004-637X\/761\/1\/8 . 2012ApJ...761....8S ,
Instrument PACS_PacsPhoto_largeScan
Temporal Coverage 2010-06-10T00:35:11Z/2010-06-10T11:07:56Z
Version SPG v14.2.0
Mission Description Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.
Creator Contact https://support.cosmos.esa.int/h®erschel/
Date Published 2011-06-10T10:16:10Z
Publisher And Registrant European Space Agency
Credit Guidelines European Space Agency, kidger, m., 2011, GT1_mkidger_2, SPG v14.2.0, European Space Agency, https://doi.org/10.5270/esa-edwrwmd