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

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

Source of comets: b. The Oort Cloud 30,000 – 100,000 A.U a. The Kuiper Belt 40 – 100 AU

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, 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 15 th, 2006 – Stardust returns to Earth!

Read more about it at: Aerogel is used to collect the comet dust grains which travel at very high speeds

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 O 18 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 18 O/ 16 O similar to those on Earth. Strong 16 O but weak 18 O signals characterize presolar grains, typically formed in low- mass 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