Comets


Meteor

Zadunaisky's Math Determined Halley's Comet Orbit

Buenos Aires, Argentina - Pedro Elias Zadunaisky, an Argentine astronomer and mathematician whose calculations helped determine the orbit of Saturn's outermost moon, Phoebe, as well as Halley's Comet, died Wednesday. He was 91.

Zadunaisky was a pioneer in celestial mechanics, applying mathematical models to determine how gravity and other forces alter the orbits of other objects in the solar system.

Zadunaisky also was a Senior Astronomer at the Smithsonian Astrophysical Observatory and in the 1960s researched the orbits of celestial bodies at NASA's Goddard Space Flight Center, calculating the orbits of the first U.S. Earth satellite, Explorer I, as well as other satellites during the U.S. space race against Russia.

Born in the Argentine city of Rosario on Dec. 10, 1917, Zadunaisky earned a civil engineering degree at the National University of Rosario, then pursued applied mathematics and specialized in celestial mechanics. He earned three Guggenheim fellowships for research at Columbia University in 1957, Princeton University in 1958 and at the University of Texas at Austin in 1977.

Telescope

Astronomical Birth Event Results in a Multitude of 'Baby' Comets

Image
© NASAThis 2007 image taken from the Hubble Space Telescope shows a jellyfish-shaped Comet Holmes
Astronomers who were dazzled by the 2007 explosion of a comet into the largest object in the solar system have discovered it gave birth to a bunch of baby comets.

Reporting the "largest comet birth ever seen" were David Jewitt, Rachel Stevenson and Jan Kleyna, who observed the event through a Mauna Kea telescope.

Jewitt, a professor, and Stevenson, his graduate student, left the University of Hawaii Institute for Astronomy this summer to join the University of California, Los Angeles. Kleyna is an astrobiology postdoctoral researcher at the institute.

Telescope

Mini-Comets Within a Comet Lit Up 17P/Holmes During Megaoutburst

Image
© Jewitt/Stevenson/KleynaReveals the expansion of the coma of comet Holmes over 9 nights in 2007 November.
Astronomers from the University of California, Los Angeles and the University of Hawaii have discovered multiple fragments ejected during the largest cometary outburst ever witnessed. Images and animations showing fragments rapidly flying away from the nucleus of comet 17P/Holmes will be presented by Rachel Stevenson at the European Planetary Science Congress in Potsdam, Germany, on Wednesday 16 September.

Stevenson, together with colleagues Jan Kleyna and David Jewitt, began observing comet Holmes in October 2007 soon after it was reported that the small (3.6 km wide) body had brightened by a million times in less than a day. They continued observing for several weeks after the outburst using the Canada- France- Hawaii Telescope in Hawaii and watched as the dust cloud ejected by the comet grew to be larger than the Sun.

The astronomers examined a sequence of images taken over nine nights in November 2007 using a digital filter that enhances sharp discontinuities within images. The filter, called a Laplacian filter, is particularly good at picking out faint small-scale features that would otherwise remain undetected against the bright background of the expanding comet. They found numerous small objects that moved radially away from the nucleus at speeds up to 125 metres per second (280 mph). These objects were too bright to simply be bare rocks, but instead were more like mini-comets creating their own dust clouds as the ice sublimated from their surfaces.

Meteor

Jupiter Captured Comet as Temporary Moon

Image
© NASA
Jupiter's gravity well has been known to capture objects - evidenced by the recent impact on the gas giant discovered by amateur astronomer Anthony Wesley. But one object captured by Jupiter in the mid 1900's was later able to escape from the planet's clutches.

Researchers have found comet 147P/Kushida-Muramatsu was captured as a temporary moon of Jupiter, and remained trapped in an irregular orbit for about twelve years. "Our results demonstrate some of the routes taken by cometary bodies through interplanetary space that can allow them either to enter or to escape situations where they are in orbit around the planet Jupiter," said team member Dr. David Archer.

With this discovery, five such objects have now been discovered where the phenomenon of temporary satellite capture (TSC) has occurred, but this new research suggests it might happen more frequently than was expected. Kushida-Muramatsu orbited Jupiter between 1949 and 1961, the third longest capture period of the five objects.

Meteor

Found: first amino acid on a comet

Image
© NASA/Jet Propulsion LaboratoryAn amino acid called glycine has been found in dust collected by the Stardust spacecraft, which flew by Comet Wild 2 in 2004
An amino acid has been found on a comet for the first time, a new analysis of samples from NASA's Stardust mission reveals. The discovery confirms that some of the building blocks of life were delivered to the early Earth from space.

Amino acids are crucial to life because they form the basis of proteins, the molecules that run cells. The acids form when organic, carbon-containing compounds and water are zapped with a source of energy, such as photons - a process that can take place on Earth or in space.

Meteor

NASA Researchers Make First Discovery of Life's Building Block in Comet

Image
© NASA/JPL This is an artist's concept of the Stardust spacecraft beginning its flight through gas and dust around comet Wild 2. The white area represents the comet. The collection grid is the tennis-racket-shaped object extending out from the back of the spacecraft.
NASA scientists have discovered glycine, a fundamental building block of life, in samples of comet Wild 2 returned by NASA's Stardust spacecraft.

"Glycine is an amino acid used by living organisms to make proteins, and this is the first time an amino acid has been found in a comet," said Dr. Jamie Elsila of NASA's Goddard Space Flight Center in Greenbelt, Md. "Our discovery supports the theory that some of life's ingredients formed in space and were delivered to Earth long ago by meteorite and comet impacts."

Meteor

Comet Swarm Delivered Earth's Oceans?

Comet
© Nicolle Rager-Fuller, NSFA comet slams into what is now Chesapeake Bay in an artist's conception.
A barrage of comets may have delivered Earth's oceans around 3.85 billion years ago, a new study suggests.

Scientists have long suspected that Earth and its near neighbors were walloped by tens of thousands of impactors during an ancient event known as the Late Heavy Bombardment.

This pummeling disfigured the moon, leaving behind massive craters that are still visible, preserved for millennia in the moon's airless environment. But it's been unclear whether the impactors were icy comets or rocky asteroids.

Now, based on levels of a certain metal in ancient Earth rocks, a team led by Uffe Jorgensen of the Niels Bohr Institute in Denmark says comets were the culprits.

Whether Earth had oceans before any comets arrived has been intensely debated, Jorgensen noted.

Meteor

Shuttle Plumes Hint at Comet Crash in Siberia

Image
© NASANight-Shining Clouds
Tracking plumes from space shuttle launches provided researchers with one of the strongest pieces of evidence that a comet crash was responsible for flattening a Siberian forest in 1908.

The crash, which leveled trees for hundreds of miles in Siberia, was followed by the appearance of extremely bright clouds, visible by night.

Similar clouds triggered by the flights of space shuttles through atmosphere were found over the planet's poles two days after a launch from Florida, research published in last week's Geophysical Research Letters shows.

Comment: For more in-depth reading on Tunguska read: Tunguska, Psychopathy and the Sixth Extinction


Meteor

England: Whitchurch, Shropshire - 2 Large 'fireballs' seen, one resembling a comet without a tail

Posted: July 30, 2009

Location of Sighting: Blackpark Road, Whitchurch, Shropshire
Date of Sighting: Saturday 4th July 2009
Time: 11.20-11.30

Witness Statement: Whilst sitting in the hot tub, looking up at the stars, we both noticed a bright light, which looked similar to a large Chinese lantern, it sort of drifted across the sky in a northerly direction, it suddenly changed direction and headed south east and upwards quite quickly, the light appeared to be a ball of fire, and we watched it for about 4-5 minutes.

Blackbox

Go Back To Sleep - Comet Collisions Won't Spark The End Of The World

Hale Bopp
© UnknownComet Hale-Bopp.
Evidence indicates that it is highly unlikely that a comet crash would result in Earth's demise, researchers at the University of Washington said on Thursday.

Writing in Science Express, the online edition of the journal Science, researchers acknowledged that while most scientists agree that an asteroid collision 65 million years ago caused the mass extinction of the dinosaurs, they tend to differ in opinion on how many other mass extinctions have resulted from similar events.

Researchers used computer models to simulate the formation of comet clouds in the solar system for 1.2 billion years. They pinpointed a body called the Oort Cloud as the source for many long-period comets that find their way into Earth's path.

Formed 4.5 billion years ago from the nebula that formed our solar system, the Oort Cloud spans from about 93 billion miles from the sun to about three light years away. Scientist said the Oort Cloud could contain literally billions of comets, many of which are so small and distant to be seen.

Comment: Regarding the claim that "the gravitational pulls of Jupiter and Saturn act as comet deflectors", let's see what Clube and Napier, British astronomers and writers of The Cosmic Serpent, have to say:
The giant comets normally reside far beyond the planets, in a spherical cloud surrounding the Sun, called the Oort cloud. There is also evidence for a flattened disk of comets closer to the inner solar system, called the Edgeworth/Kuiper belt. What prompts members of either of these comet repositories to enter the realm of the planets? Clube and Napier suggest a galactic influence. The solar system periodically passes through the plane of the galaxy as the Sun (and the solar system with it) orbits the galactic center. Each passage may dislodge giant comets and divert them closer to the Sun. The outer planets, particularly Jupiter, may then perturb some of these giant comets into orbits which enter the inner solar system. These comets, stressed both by gravity and by heat from the sun, may fragment into a cloud of smaller objects with dynamically similar orbits.

Chiron offers a good example of a giant comet as called for by Clube and Napier's giant comet hypothesis. Chiron is somewhere between 148 and 208 kilometers in diameter. Currently Chiron's unstable "parking orbit" lies mostly between Saturn and Uranus. Chiron may end up injected into the inner solar system within a hundred thousand years, or ejected from the solar system on a similar time scale. It is also possible that Chiron has already visited the inner solar system.

The Taurid complex and the Kreutz sungrazer group are two families of objects which most likely represent the fragmented remains of two giant comets in the current era. SOHO has recently discovered many new members of the Kreutz group which were previously unknown.

The Kreutz progenitor was injected into a retrograde orbit and attained the sungrazing state at a high inclination to the ecliptic. Hence the debris of its "children" does not pose a threat to the Earth. The Taurid progenitor on the other hand ended up in a short-period low-inclination prograde orbit. This is why the Earth can encounter its debris with potentially calamitous results.

What would happen should the Earth pass through the orbit of a disintegrating giant comet just before or after the comet passes that same point? Since larger fragments tend to cluster close to the nucleus of the comet, chances would increase that the Earth would be bombarded by these larger fragments. The severity of this comet fragment shower would far exceed any ordinary meteor shower. Not only would "shooting stars" and bright fireballs caused by small debris appear, but so too would large airbursts and possibly ground impacts. These would result in significant destruction should they occur over an inhabited area. If a large enough fragment struck in the ocean -- say, 200 meters or so in diameter -- it would raise tsunamis even at a great distance that would sweep away coastal habitations.

Duncan Steel, a colleague of Clube and Napier, refers to this process as coherent catastrophism. Widespread destruction derives from the coherent arrival of many impactors within a few days, as opposed to the sporadic arrival of objects spread randomly in space. The shower repeats for a period of years until the cometary orbit precesses so that the Earth no longer encounters the dense part of the debris field. (Of course, sporadic debris unrelated to the disintegrating comet may impact at any time as well.)