On July 3 at 10:52 p.m. Pacific time, the NASA Deep Impact probe slammed
into comet P/9 Tempel 1 at 23,000 miles per hour. The collision not only blew
a crater into the comet but also ejected many tons of material off
the comet's surface. This material reflected the sunlight, making
the comet more than double in brightness.
SSU NASA E/PO team members
Dr. Phil Plait, Dr. Kevin McLin, Tim Graves, and Logan Hill spent their
July 3rd evening taking images of the celestial collision.
Below are the images from the event.
This animation is made of 53 separate images
taken over the course of 42 minutes, from 18 minutes before the impact to
24 minutes after. Each image is a 30-second exposure (except for
two 60-second exposures shortly before impact).
As the comet orbits the Sun, it appears to move
against the background stars from the lower right to upper left.
The comet appears to jump in the middle of the sequence because of a
time gap between images-- the telescope was being prepared to
take the impact images, which took a minute or two. So the jump is not real!
Note how the comet appears to brighten about halfway through the sequence
when the 800 pound impactor slammed into the comet.
Note: other bright points of light appear to move in the sequence,
as well as a faint fuzzy blob above the comet.
These are not real; they are artifacts of the digital detector used to make
This image is a composite of the same 53 images as in the animation,
but this time they were aligned to keep the comet in the same spot,
making the stars appear as streaks. Note the fuzz around the
comet; that is the gas being expelled by the comet as it is heated
by the Sun, as well as the ejecta thrown out by the collision
of the Deep Impact probe. The gap in the star streaks is caused by
a gap in the sequence of images.
This image is once again the same 53 individual images, but
aligned so that the stars do not move. As the comet moved
between images, it appears to leave a streak (the gap is due
to the imaging technique mentioned above). In this image,
the brightening of the comet is very obvious. According to
our measurements, it got brighter by about 2.5 times. Interestingly,
it got brighter by a few percent before the impact. Comets
sometimes emit jets of material which reflect sunlight, making
them brighter. Tempel 1 has undergone several such outbursts, and one
may have been happening right before the impact.