We're DOOMED!!

[The Mad Monk]

Originally posted by shawnmmcc
Creating many smaller fragments, one of which is much more likely to create a substantial ocean strike. I loathe most modern Science Fantasy movies.

As recent events have proven, Deep Impact was pretty on-target about the consequences of an ocean strike.

[Dauphin]

Originally posted by DanS
I have heard that the chances of a cataclysmic asteroid strike in the next century are 1 in 140 or something.

Some have used these chances to make the case for having human settlements on celestial bodies other than Earth -- i.e., making human beings a multi-body species. I am having trouble finding a rebuttal to this case.

140 to 1? That means that we average a cataclysm event every 14,000? Guess it depends on your definition of cataclysm.

If you mean a good shot at total annihilation of mankind, then I would say based on empirical evidence its closer to 500,000 to 1 per century.

[The Mad Monk]

Originally posted by chegitz guevara

HOLLYWOOD predictions of a rogue asteroid colliding with Earth and threatening life as we know it has become a real possibility, according to a new warning from NASA.

On Christmas Eve, NASA issued its highest-ever threat warning when it gave asteroid 2004 MN4 a rating of four on the 10-point Torino Scale used to rate intergalactic threats. The highest previous rating was one.

The rating for 2004 MN4 means there is a 1.6 per cent chance it and Earth will collide when they crosses paths on April 13, 2029.

Astronomy educator Paul Floyd said 2004 MN4 was first discovered in March 2004, but contact was lost until it was rediscovered on December 19.

He said it is about 440m in diameter and is larger than many of the asteroids to collide with the Earth in its recent history.

He said if it was a stony type like most asteroids, much of it could vapourise in the atmosphere.

He said if it was an iron type that remained intact as it passed through the atmosphere, 2004 MN4's size meant it could have an impact equivalent to between 100 to 150 hydrogen bombs.

Astronomers need a long time to work out asteroids' risk rating as Earth is a small target.

"Intergalactic" threats? Are we worried about something from M31 coming our way?

Intergalactic is stretching it a bit, but interstellar wouldn't be:

Cosmic Cannon: How an Exploding Star Could Fry Earth
By Robert Roy Britt
Senior Science Writer
posted: 07:00 am ET
19 June 2001



Shooting out jets of energy or blobs of stuff the size of Earth at nearly light-speed, exploding stars called supernovae may hold more potential peril than anyone had ever imagined, according to a growing suspicion among some researchers.

While scientists have long tried to link supernovae to mass extinctions on Earth, there is no solid evidence. But recent observations of high-energy emissions in space have some scientists suggesting that our planet may in fact get fried every now and then.

[inset]

For three decades, scientists have been puzzling over brief but intense flashes of energy known as gamma ray bursts. These GRBs, as they are called, pack more punch than any other cosmic event. Their source has been a mystery, but so far they have been observed only coming from the far corners of the cosmos.


This massive supernovae, Eta Carinae, is less than 8,000 light years away. It doubled in brightness in less than 18 months recently. Yikes.

But for the past three years, increasing evidence has linked GRBs to supernovae, a far more common event. The latest thinking, though controversial, goes like this:

A giant aged star casts off its outer shell in a last gasp that sends a bubble of matter and energy racing outward. The rest of the star's matter implodes.

Jets of material, or perhaps individual blobs of matter, are later hurled in two opposite directions, at nearly the speed of light, along the axis of the rotating stellar corpse. These expulsions pierce the supernova's original expanding bubble, generating a flash of high-energy radiation known as gamma rays.

If the jets or blobs happen to be pointed our way, we see the event. And if one were to be generated nearby in our galaxy and were directed at Earth, some scientists say the planet could be toast.

Fry a planet

How bad could it be? While no one can say for sure, one gamma ray expert has generated a frightening scenario.

Stanford E. Woosley, an astrophysicist at the University of California, Santa Cruz, said that even from the far side of our galaxy, a GRB would be as bright as the Sun -- not in visible light, but in gamma rays. Luckily, most gamma rays -- all but the highest energy versions -- do not penetrate Earth's atmosphere. But the visible light does.

"Something this intense would create an optical flash by scattering electrons in the upper atmosphere and creating something like a super-aurora," Woosley said. It's an idea he's working on but has not yet published.

"The flash of heat and light might flash-burn anything not in the shade," he said. "Heating the atmosphere would cause big winds. The air would be much hotter for weeks, as hot as an oven depending on the distance. This would affect the other side of the Earth eventually."

Ocean life would be spared in Woosley's scenario.

But there is no consensus on whether gamma ray bursts are actually linked to supernovae, and there's even less agreement over how dangerous they might be.

Still, NASA scientists acknowledge the threat, describing it this way on a GRB informational Web page:

"A gamma ray burst originating in our neck of the Milky Way, within a thousand light-years or so, could lead to mass extinction on Earth. Gamma rays interacting in the Earth's atmosphere would burn away the ozone layer, allowing deadly ultraviolet radiation to penetrate through the atmosphere. The influx of radiation would lead to widespread cancer and other diseases."

Cold War error

Nobody was looking for gamma ray bursts when they were discovered in 1967 after U.S. satellites were deployed to monitor possible violations of the Nuclear Test Ban Treaty. At first, researchers thought they were seeing something generated in our galaxy. But later evidence showed the sources to be scattered throughout the universe, all well beyond our galaxy.

Until recent years, researchers suspected that GRBs were the result of two massive objects, such as incredibly dense aged stars called neutron stars, falling together.

But more and more, supernovae are also suspects. The first link came on April 25, 1998 when GRB 980425 was spotted coming from the direction of a known supernova, SN 1998bw.

Talk about a powerful combination.

"These dying stars (supernovae) emit about as much energy in their seconds-long final fling as in their whole history. The GRBs are apparently a thousand times or so brighter than that," said John G. Learned, a particle astrophysicist at the University of Hawaii.

"We are starting to think that GRBs could be just another view -- one you do not want to witness in our galaxy -- of supernovae," Learned said. "Perhaps these GRBs are just jets coming from supernovae, and we call them GRBs when the jet is pointed right at us.

Learned said these jets, or cannonballs as one idea suggests, traveling at a terrific speed about 99.99999 percent of the speed of light, "may even [have] been the source of the great extinctions of life on Earth every few hundred million years." (Other scientists suspect asteroid impacts or climate change as primary causes.)

Cosmic cannon

While most researchers imagine a supernova's expulsion as a jet of high-speed energy, a more fantastical idea conjures an image of a giant cosmic cannon lobbing Earth-sized globs of matter into space.

The idea was developed by Arnon Dar of the Israel Institute of Technology and Alvaro De Rujula of CERN -- the European Organization for Nuclear Research. The genesis of their idea was published in Physical Review Letters in 1998 and was modified and updated last year.

It starts with the same supernova scenario -- the death of giant stars, which were plentiful in the early universe. (In fact, when scientists see a gamma ray burst, they are typically witnessing something that occurred billions of years ago, and the light is just now arriving.)

A day or two after a supernova has sent its initial bubble racing into space, Dar explains that some of the ejected material can fall back. Ultimately, this generates a hyperdense neutron star or, in some cases, a black hole. A swirling disk of material, called an accretion disk, develops around this object.

In Dar's cannonball model, large amounts of matter sometimes slap against the central object. The globs of matter are hurled outward at near light-speed, racing in opposite directions along the object's axis of rotation (just like the jets in the more common explanation).

These globs generate a GRB when they overtake the escaping supernova material.

Dar said there is "a growing body of direct and indirect evidence" for the scenario. He added that such an event would occur in our galaxy and be pointed our way once every 100 million years. Dar noted that the five greatest known mass extinctions on Earth are also separated by 100 million years, on average.

And, Dar said, it could happen again.

The real threat from such events, Dar said, is not even the "normal" gamma rays that researchers are only beginning to understand. Instead, higher energy gamma rays and cosmic rays, thought to be created by the same events but not currently measurable, are the true death rays of the cosmos.

When these bursts of energy interact with our atmosphere, Dar said they would produce a lethal dose of byproducts -- particles called muons.

"Most of the species on Earth -- on the ground, underground and in the oceans, seas and lakes down to tens of yards (meters) -- will be extinct directly by these penetrating muons," Dar said.

Next Page: "It would be very bad for us."

Cosmic Cannon: How an Exploding Star Could Fry Earth (cont.)




Hypernova

Jerry Fishman, chief scientist for gamma ray astronomy at NASA's Marshall Space Flight Center, said most supernovae do not generate these high-speed emissions, jets or blobs and thus have no potential to generate a GRB.

Only a few, which he and other researchers have come to call hypernovae, are capable. Their origins involve stars 50 to 100 times as massive as our Sun.

"These are very rare objects, but they were perhaps more numerous in star-forming regions of the early (distant) universe," Fishman said. But, he added, "there are likely to be several of the massive pre-hypernovae stars in our galaxy. If any go off within several hundred parsecs (a parsec equals about 3.26 light-years) and are beamed toward Earth, it would be very bad for us."

One known supernova, suspected by some of being a hypernova, sits right in our cosmic backyard. Eta Carinae is the most luminous object in our galaxy and less than 8,000 light-years away. The exploding star is thought to be 100 times more massive than our Sun and it radiates about 5 million times more power.


As seen from Earth, Eta Carinae brightened dramatically about 150 years ago, then faded to become a dim star. But it has brightened again since about 1940 and it doubled in brightness between 1998 and 1999.

Dar said Eta Carinae does not seem to point in our direction.

An uncertain premise

Abraham Loeb, a professor of astronomy at Harvard University, is not convinced there is any connection between GRBs and supernovae. He said there is an important theoretical roadblock that researchers must still knock down: "Instabilities on the surface of such a jet will tend to mix it with the dense medium that it traverses and the feasibility of penetrating a full envelope of a massive star was not demonstrated yet."

And while Loeb does not rule out the possibility that GRBs could harm life on Earth, he noted that the danger is not likely an imminent one.

"I do not think GRBs pose a danger to life on Earth more substantial than other astrophysical catastrophes such as normal supernovae, which are much more frequent," he said.

Many theories have been put forth suggesting supernovae alone might be dangerous, and experts say it might be true for those within about 30 light-years. Possible effects are similar to those outlined for GRBs -- brief doses of high-level radiation -- but are not widely agreed upon.

Eli Waxman, of the Weizmann Institute of Science in Israel, is even less worried.

"Gamma rays would be absorbed high in the atmosphere, affecting the ozone layer and producing some strange isotopes, but I think the energy is not sufficient to cause extinction," Waxman said.

Answers hidden in even stranger concepts

Regardless of their dangers, GRBs and their enigmatic sources create a captivating puzzle that researchers around the world would like to solve.

One way astronomers are gaining new insight into GRBs is by using the orbiting Chandra X-ray Telescope to study an afterglow of the events that generate GRBs. The Hubble Space Telescope can also observe an optical afterglow.

But to really get under the hood of a GRB, some researchers are hoping to observe and study some related particle ejections that exist so far only in theory.

Learned, the University of Hawaii researcher, said that when the expanding bubble of a supernova is pierced, the interaction ought to also generate "a terrific hail" of super-high-energy neutrinos. These invisible particles are thought to zoom through space at nearly the speed of light. While not confirmed to exist yet, less energetic versions have been observed.

Several efforts to detect neutrinos are underway. One is a distribution of sensors buried in Antarctic ice. Another employs the Moon as a detection device.

Arnon Dar, co-creator of the cannonball model, won't be surprised if these and other efforts eventually uncover an extreme cosmic irony.

"The solar system and the elements we and our planet Earth are made of were created by a local supernova some 5 billion years ago," Dar said. "Ironically, GRBs from other galactic supernovae may also be a main cause of the major mass extinctions on our planet."

Click here for more news and information about GRBs, supernovae and other deep-space objects. See also "Asteroids" for more about mass extinctions.

http://www.space.com/scienceastronomy/astronomy/gammaray_bursts_010522-1.html

Some nice pics there.

[The Mad Monk]

One error in there: eta carinae is not a supernova. Sure, it burped up a dozen solar masses 150 years ago, but that isn't a supernova, that's a bit of indigestion.

When it does finally go -- and it will -- everybody will know.

[Dauphin]

Eta Carinae is cool.

Had a poster/photograph of it on my wall at university.

[Dauphin]

I still have some prints of other astronomical phenomenon lying around somewhere....

[Dis]

friday the 13th (concidence?- I think not ), this thing will come closer to the Earth than the moon, or some telecommunication satellites.

http://news.independent.co.uk/world/science_technology/story.jsp?story=611219

[Dis]

Originally posted by Last Conformist
Not much beyond some fireworks in the sky. Well, debris could head our way, which might be unpleasant if they're big enough, but on the whole it shouldn't be much to worry about.

The formation of a fairly large (20km) lunar crater was observed in 1178.

that would be sooo cool. I'd love to have a party outside, get drunk and watch the moon get ****ed up.

[Ogie Oglethorpe]

Originally posted by Kuciwalker
Blunt cucumbers break on impact.

Leaving nasty sharp edges like a beer bottle in a bar fight.

[Provost Harrison]

Originally posted by Starchild
Or Hull. Might improve the place.

Or Norwich, heaven forbid