IRTF Image of Comet Hale-Bopp
Observers: Alan Tokunaga, Roland Meier
Location: Infrared Telescope Facility, Mauna Kea Observatory, Hawaii
Date: March 8, 1997
Comet Hale-Bopp observed during
from Mauna Kea
That does not mean that we cannot do anything: while direct imaging at
visible wavelengths is difficult, there are many other techniques that allow
us to obtain some very interesting information on the comet. This infrared
image of Hale-Bopp (obtained at a wavelength of 3.672 micron) was recorded
with the NASA Infrared Telescope Facility (IRTF) at Mauna Kea Observatory,
on March 8, 1997. The observations were done during DAYTIME when the comet
was invisible to the human eye, but still could not hide from special IR
detectors! During the day, the sunlight heats the ground and the air around
the telescope, creating a lot of turbulence that tends to blur the
observations, which is why this image appears less sharp than the ones
obtained during the night - for example the one we obtained on February 17.
However, the advantage is that the comet can be observed for a long time,
high in the sky, while at night it is very low on the horizon and raises
only shortly before sunrise.
This false color image depicts the heat emitted by the dust: the brighter
the color the more dust is present. The field of view is extremely small.
Each pixel of this image corresponds to roughly 45 miles at the distance of
the comet's nucleus, which is a "dirty snow ball" approximately 25 miles in
diameter. Because of the Sun's irradiation, the uppermost layers of the
nucleus are sublimating (i.e., the ice is evaporating directly from solid to
gas), dragging along large amounts of dust (tons per second) that hide the
nucleus from our direct view. Ultimately, this dust spreads out and forms
the visible (dust) tail of the comet. This image was used to center an
infrared spectrograph on the comet.
(Observers: Alan Tokunaga and Roland Meier, IfA, UH)
Roland Meier & Olivier Hainaut
Comet Hale-Bopp Home Page