Comets


Meteor

There is danger in the sky: Sodom and Gomorrah 'destroyed by a comet', say astronomers

Geoffrey Lean
The Independent
Sun, 30 Mar 1997 12:25 UTC
Image
© Unknown
Sodom and Gomorrah may have been destroyed by debris from a comet, startling new archaeological and astronomical research suggests. Another bombardment from space may have brought on the Dark Ages.

The research, to be presented to a conference at Cambridge University this summer, provides dramatic evidence for an extraterrestrial cause for the wholesale collapse of several civilisations around 2200BC.

The conference, on natural catastrophes during Bronze Age civilisations, will bring together astronomers, archaeologists, geologists and other scientists to try to find an explanation for the near-simultaneous fall of the Old Kingdom of ancient Egypt, the Sumerian civilisation in Mesopotamia and the Harrapin Civilisation of the Indus Valley. In all, some 40 cities are thought to have disappeared, in a series of catastrophes.

Astronomers calculate that the Earth is bombarded by a particular dense storm of meteorites over a couple of centuries every 2,500 years - the last two blitzes would have occurred around 2200-2000BC and 400-600AD.
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Meteor

Best of the Web: 25 Sun-Diving Comets in 10 days?

Dr. Tony Phillips
Science@NASA
Fri, 14 Jan 2011 08:42 UTC
The sun has just experienced a storm - not of explosive flares and hot plasma, but of icy comets.

"The storm began on Dec 13th and ended on the 22nd," says Karl Battams of the Naval Research Lab in Washington, DC. "During that time, the Solar and Heliospheric Observatory (SOHO) detected 25 comets diving into the sun. It was crazy!"

Sundiving comets - a.k.a. "sungrazers" - are nothing new. SOHO typically sees one every few days, plunging inward and disintegrating as solar heat sublimes its volatile ices. "But 25 comets in just ten days, that's unprecedented," says Battams.


"The comets were 10-meter class objects, about the size of a room or a house," notes Matthew Knight of the Lowell Observatory in Flagstaff, Arizona. "As comets go, these are considered small."

SOHO excels at this kind of work. The spacecraft's coronagraph uses an opaque disk to block the glare of the sun like an artificial eclipse, revealing faint objects that no Earth-bound telescope could possibly see. Every day, amateur astronomers from around the world scrutinize the images in search of new comets. Since SOHO was launched in 1996, more than 2000 comets have been found in this way, an all-time record for any astronomer or space mission.

Battams and Knight think the comet-storm of Dec. 2010 might herald a much bigger sungrazer to come, something people could see with the naked eye, perhaps even during the day.

"It's just a matter of time," says Battams. "We know there are some big ones out there."
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Meteor

Some Comets Like it Hot - Comet Ikeya-Seki October 29, 1965

Dr. Tony Phillips
Science@NASA
Fri, 07 Jul 2000 08:51 UTC
Image
© Roger LyndsThis 4-minute exposure of comet Ikeya-Seki was captured by Roger Lynds at Kitt Peak, Arizona, on the morning of 1965 October 29.
July 7, 2000 -- In October 1965 comet Ikeya-Seki swooped past the Sun barely 450 thousand kilometers above our star's bubbling, fiery surface. Gas and dust exploded away from the comet's core as fierce solar radiation vaporized the icy nucleus. Most comets wouldn't survive passing as close to the Sun as the Moon is to the Earth, but Ikeya-Seki literally came through with flying colors. When the comet emerged from perihelion (closest approach to the Sun) it was so bright that observers on the street with very clear skies could see it during broad daylight if the Sun was hidden behind a house or even an outstretched hand.

"In Japan (where observers spied the comet 1/2 degree from the Sun) it was described as 10 times brighter than the Full Moon," recounted Brian Marsden of the Harvard Center for Astrophysics in the December 1965 issue of Sky & Telescope. "At Kitt Peak National Observatory in Arizona, Stephen Maran observed the comet with binoculars from within the shadow of a black disk erected to hide the Sun. '[It was] the most splendid thing I have ever seen,' he noted."

Ikeya-Seki, a.k.a. "The Great Comet of 1965", is a member of the family of comets called Kreutz sungrazers (after the nineteenth-century German astronomer who studied them in some detail). These ill-fated visitors to the inner solar system have been seen to pass less than 50,000 km above the Sun's photosphere. Most never make it past perihelion -- they are completely obliterated. But the few that do, like Ikeya-Seki, can be very bright.
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Meteor

Abnormal Sunbound comets may mean larger one to come


TheWeatherSpace.com
Thu, 13 Jan 2011 20:30 UTC
sun
© thewetherspace.com

In the last 10 days astronomers have counted at least 25 comets on the NASA SOHO Spacecraft, plunging into the Sun. It could mean a larger one ahead.

These comets could be part of a larger comet, according to astronomers. The comet may come without notice, much like the cosmic visitor named Comet Ikeya-Seki in 1965, which was seen in broad daylight and came without warning.

One candidate would be the newly discovered Comet 2010 X1 Elenin, which comes very close to our planet in the Fall of 2011. The comet will be so bright you can see it with the unaided eye even in a small city.
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Sun

Sundiving Comet Storm

Dr.Tony Phillips
NASA Science
Wed, 12 Jan 2011 20:28 UTC
The sun has just experienced a storm - not of explosive flares and hot plasma, but of icy comets.

"The storm began on Dec 13th and ended on the 22nd," says Karl Battams of the Naval Research Lab in Washington, DC. "During that time, the Solar and Heliospheric Observatory (SOHO) detected 25 comets diving into the sun. It was crazy!"

Sundiving comets - a.k.a. "sungrazers" - are nothing new. SOHO typically sees one every few days, plunging inward and disintegrating as solar heat sublimes its volatile ices. "But 25 comets in just ten days, that's unprecedented," says Battams.

"The comets were 10-meter class objects, about the size of a room or a house," notes Matthew Knight of the Lowell Observatory in Flagstaff, Arizona. "As comets go, these are considered small."

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Meteor

Apocalypse then: How a comet ended the Roman Empire

Steve Connor
The Independent
Sat, 09 Sep 2000 13:51 UTC
Image
© Unknown
A close shave with a comet nearly 1,500 years ago caused a catastrophic change in the global climate, leading to famine, plague, the end of the Roman Empire, the birth of the Dark Ages and even the legend of King Arthur, a leading British scientist said at the British Association meeting in London yesterday.

Debris from the near miss bombarded the Earth with meteors, which threw enough dust and water vapour into the atmosphere to cut out sunlight and cool the planet to cause crop failure across the northern hemisphere. The cataclysmic famines weakened people's resistance to disease and led to the great plague of the emperor Justinian. It could also be responsible for the Arthurian stories about gods appearing in the sky followed by a fertile kingdom becoming a wasteland.

Mike Baillie, professor of palaeoecology at Queen's University in Belfast, said the central piece of evidence for a sudden global climate change about AD540 comes from the study of tree rings, which highlight the years when plant growth was poor or non-existent. "Oaks live for a long period and in order for a lot of them to show narrow rings at the same time it must have been a profoundly unpleasant event as far as the tree is concerned," Professor Baillie said.

"The event of AD540 is in or at the start of the Dark Ages and in my view probably caused the Dark Ages. It was a catastrophic environmental downturn which shows up in trees from Siberia, Scandinavia, northern Europe, north America and South America," he said. "The idea is that the Earth was hit by a 'cosmic swarm', a whole stack of cometary debris in a short period of time and that loaded the atmosphere with dust and debris and caused some sort of environmental downturn," Professor Baillie explained.

Tree rings round the world clearly indicate a major climate change unprecedented in the past two millenniums. This could have cooled the Earth by a few degrees, enough to cause crops to fail for several years in succession.

"It only requires a few degrees cooler conditions across the year for a few years, wiping out several consecutive harvests, and you've got a serious problem for any agricultural society," Professor Baillie said.
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Magnify

Comet or Asteroid? Big Space Rock Has Identity Crisis


Yahoo News / Space.com
Sat, 08 Jan 2011 01:51 UTC
596 Scheila
© Kevin HeiderA picture showing the faint tail of the celestial body 596 Scheila, which was once thought to be an asteroid. Researchers now think it may be a dormant comet coming back to life

A huge asteroid discovered more than 100 years ago may not be an asteroid at all, but a dormant comet that is just now coming back to life, according to new observations.

The object, known as 596 Scheila, is about 70 miles (113 kilometers) wide and has a faint, wispy tail that suggests it may actually be a comet, researchers said. If that's the case, then 596 Scheila would be only the sixth known comet to reside in the main asteroid belt, a vast region of space rocks that lies between the orbits of Mars and Jupiter.

The asteroid-turned-comet discovery was somewhat serendipitous. On the night of Dec. 11, astronomer Steve Larson, a scientist with the Catalina Sky Survey in Tucson, Ariz., was searching for potentially hazardous asteroids when he came across an object with a bright core and a faint tail.
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Meteor

2000th Comet Spotted By SOHO

Karen C. Fox
RedOrbit
Tue, 28 Dec 2010 14:25 UTC
200th Comet
© SOHO/Karl BattamsSOHO's 2000th comet, spotted by a Polish amateur astronomer on December 26, 2010.
As people on Earth celebrate the holidays and prepare to ring in the New Year, an ESA/NASA spacecraft has quietly reached its own milestone: on December 26, the Solar and Heliospheric Observatory (SOHO) discovered its 2000th comet.

Drawing on help from citizen scientists around the world, SOHO has become the single greatest comet finder of all time. This is all the more impressive since SOHO was not specifically designed to find comets, but to monitor the sun.

"Since it launched on December 2, 1995 to observe the sun, SOHO has more than doubled the number of comets for which orbits have been determined over the last three hundred years," says Joe Gurman, the U.S. project scientist for SOHO at NASA's Goddard Space Flight Center in Greenbelt, Md.

Of course, it is not SOHO itself that discovers the comets -- that is the province of the dozens of amateur astronomer volunteers who daily pore over the fuzzy lights dancing across the pictures produced by SOHO's LASCO (or Large Angle and Spectrometric Coronagraph) cameras. Over 70 people representing 18 different countries have helped spot comets over the last 15 years by searching through the publicly available SOHO images online.

The 1999th and 2000th comet were both discovered on December 26 by Michal Kusiak, an astronomy student at Jagiellonian University in Krakow, Poland. Kusiak found his first SOHO comet in November 2007 and has since found more than 100.
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Meteor

Bright Prospects for Comet Elenin?

Kelly Beatty
Sky & Telescope
Fri, 24 Dec 2010 14:26 UTC
It doesn't look like much now - just a 19th-magnitude smudge tucked away in southwestern Virgo - but a newly discovered comet could become something special 10 months from now.

Comet Elenin
© Leonid Elenin / ISON-NMComet Elenin (C/2010 X1) appears as a tiny, faint smudge in this stack of four 240-second exposures taken on the morning of December 10, 2010, with a remote-controlled telescope in New Mexico. (The quadrupled stars are due to the comet's motion between exposures.)
Comet Elenin (C/2010 X1) made its debut on December 10th when Leonid Elenin, an observer in Lyubertsy, Russia, remotely acquired four 4-minute-long images using an 18-inch (45-cm) telescope at the ISON-NM observatory near Mayhill, New Mexico. Follow-up images by Aleksei Sergeyev and Artem Novichenko at Maidanak Observatory in Uzbekistan revealed more about the new find: a teardrop-shaped, very diffuse coma just 6 arcseconds across and a tiny tail.

What's gotten hearts beating a little faster since the discovery is that Comet Elenin is still more than 4 astronomical units (375 million miles) from the Sun and headed inbound. It's still early, and the orbit is certain to change in the weeks ahead, but right now it appears the comet's perihelion will occur well inside Earth's orbit, about 0.45 a.u. (42 million miles) from the Sun, on September 5th.

Right now, odds are that Comet Elenin will become an easy target for binoculars around mid-August and reach naked-eye visibility for a couple of weeks around perihelion. The comet's elongation from the Sun shrinks to just 1° following perihelion, but soon thereafter the comet gets enough separate to position itself nicely for viewing in the predawn sky.
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Meteor

Smash Earth on your computer! Website lets you calculate damage from comet or asteroid


MSNBC / SPACE.com
Thu, 16 Dec 2010 11:19 UTC
Image
© Information Technology at Purdue/Michele Rund
A new website lets astronomers - and anyone who likes to watch stuff blow up - calculate the damage a comet or asteroid would cause if it hit Earth.

The interactive website, called Impact: Earth!, is scientifically accurate enough to be used by the Department of Homeland Security and NASA, but user-friendly enough for elementary school students, according to the researchers who developed it.

The site could help scientists and the public alike better understand the destructive potential of comets and asteroids, which have caused massive extinction events in our planet's past, researchers said.

"There have been big impacts in the past, and we expect big impacts in the future," said Jay Melosh of Purdue University, who led the creation of Impact: Earth!. "This site gives the lowdown on what happens when such an impact occurs."
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