Transcript Comets

Comet
cartoon
from 1857:
Will a
comet
impact
destroy
Earth?
The 684 A.D.
apparition of Halley’s
comet, published in the
1497 Nuremberg
Chronicles
Woodcut showing P. Apian’s observation of Halley’s comet in August, 1531 A.D.
Aristotle’s teachings dominated the ancient world and
“science” and religion in medieval Europe. Aristotelian
doctrine taught that comets were phenomena of
Earth’s atmosphere.
Tycho Brahe showed that widely spaced observers see
a given comet in the same place in the sky. “Parallax”
indicates that near objects in the sky appear to move to
different parts of the sky when viewed from different
parts of the world, distant once do not. Hence, comets
come from far away space!
In 1705 Edmund Halley
found that the bright comets
of 1531, 1607, and
1682 had almost the same
orbits and returned every 76
years. He concluded that
they were, in fact, one and
the same comet. He then
predicted the return of this
comet in 1758, which indeed
took place.
Thus, Halley showed that
comets orbit the Sun in
elliptical orbits with variable
periods.
1656-1742
I visited Halley’s house and observatory
at Oxford University, England, in the
summer of 1987
32 perihelia passages of
Halley’s comet, all but the
last two have been
observed and recorded
1910 apparition
Telescopic view of Comet Halley
The orbits of a number
of short-period comets,
including Halley
First “recovery” of comet Halley on October 16, 1982, as it
was making its way into the inner Solar System, to an
apparition in 1986
Comet Halley on
January 20, 1986,
near apparition.
The lower image
illustrates the
brightness of the
comet
Comet Halley on
March 21, 1986, after
having rounded the
Sun, and on its way out
of the inner Solar
System
Comet Halley on March 21, 1986, loses its tail due to instabilities
of the magnetic field of the Sun
Characteristic features of comets
3.
2.
1.
4.
Source of comets:
a. The Kuiper Belt 40 – 100 AU
b. The Oort Cloud 30,000 – 100,000 A.U
During the 1986 apparition, the European spacecraft
Giotto flew by comet Halley, imaged it, and analyzed the
dust and gases escaping from it
Artist’s conception of the surface of a comet: Jets carry dust
and gas into space, and leave dark surface crust
On September 22, 2001, the spacecraft Deep Space 1 flew
by comet Borrelly and imaged the ~ 8 x 4 km object
The spacecraft Deep Impact was designed to collide with comet Temple 2 on
July 3, 2005. The violent impact ejected material into space that was analyzed
with the Infrared Spitzer Space Telescope
Collision of the Deep Impact spacecraft on July 4, 2005, with comet
Temple 2, as imaged by telescopes and spacecraft
Telescope views
Spacecraft views
The Deep Impact spacecraft finds very diverse topography on the surface
of comet Temple 2
The detection of water ice, carbon dioxide, complex carbon molecules, and
much more in the ejecta from the collision of the Deep Impact spacecraft
with comet Temple 2
In January, 2004, the Stardust spacecraft flew by comet
Wild 2 and collected and returned to Earth cometary dust
Results from the Stardust mission to comet Wild 2:
Multiple jets of gas from the comet nucleus
January 15th, 2006 – Stardust returns to Earth!
Aerogel is used to collect the comet dust grains which travel at very high
speeds
Read more about it at:http://stardustathome.ssl.berkeley.edu/prereg.html
Cometary dust collected by the Stardust Mission contains the high-temperature phase
olivine, an Fe-Mg-silicate
Comets produce meteor showers on Earth
View of night sky during meteor
shower
Interplanetary dust particles (IDPs) and grains from meteor
showers (cometary dust) can be collected with high-flying aircraft
such as U-2s and studied in terrestrial laboratories with
sophisticated analytical techniques
16
18
O
O
200 nm
Example: TEM image of complex IDP consisting of numerous submicron-sized grains
(left), containing presolar grains: Oxygen isotope false color images are scaled so that
areas with similar color in both images have 18O/16O similar to those on Earth.
Strong16O but weak 18O signals characterize presolar grains, typically formed in lowmass AGB stars
Comet Shoemaker-Levy 9 in 1993 had been gravitationally
broken into many pieces due to close approach to the
planet Jupiter
On July 18, 1994, the fragments of comet Shoemaker-Levy impacted
Jupiter, causing the greatest explosions ever witnessed by mankind!
Hubble Space Telescope
image of the impacts of a
number of the fragments of
comet Shoemaker-Levy
with the planet Jupiter,
causing the greatest
explosions ever witnessed by
mankind!
Comet summary