A Companion Star To Our Sun?

"Heavy snows are driven and fall from the world's four corners; the murder frost prevails. The Sun is darkened at noon; it sheds no gladness; devouring tempests bellow and never end. In vain do men await the coming of summer. Thrice winter follows winter over a world which is snow-smitten, frost-fettered, and chained in ice." 

"Fimbul Winter" from Norse saga, Twilight of the Gods

Our species, Homo sapiens, arose approximately 250,000 years ago. In the beginning, we used tools of stone and sought shelter in caves. Today, our shelters scrape clouds and our tools allow us to see galaxies far beyond our own, or peer deep into the heart of matter itself. So much progress in such a short time, for in geological terms, the reign of our species has been but the proverbial blink of an eye. Imagine, however, what our record of achievement would be had our history been disrupted no less than five times by titanic nuclear wars, each delivering a destructive blast 10,000 times more powerful than the combined yield of all existing nuclear weapons in our world today.

Such upheaval is what many other species, including the dinosaurs, may have faced during the history of our planet, according to a theory set forth by a Lawrence Berkeley Laboratory (LBL) scientist and his colleagues. The theory postulates that every 26 to 30 million years, life on Earth is severely jeopardized by the arrival of a small companion star to the sun. Dubbed "Nemesis" (after the Greek goddess of retribution), the companion star through its gravitational pull unleashes a furious storm of comets into the inner solar system that lasts anywhere from 100,000 years to two million years. Of the billions of comets sent swarming toward the sun, several strike the Earth, triggering a nightmarish sequence of ecological catastrophes.

"We expect that in a typical comet storm, there would be perhaps 10 impacts spread out over two million years, with intervals averaging 50,000 years between impacts," says LBL astrophysicist Richard Muller. In 1984, Muller, along with UC Berkeley astronomer Marc Davis and Piet Hut, an astronomer with the Institute for Advanced Study at Princeton University, announced the Nemesis theory in Nature magazine. As could be expected, it was and remains controversial. However, although the evidence for the existence of Nemesis is still circumstantial, this evidence continues to mount, and the theory has so far withstood all challenges.

Nemesis was the culmination of a chain of events that began in 1977, in Gubbio, Italy, a tiny village halfway between Rome and Florence. Walter Alvarez, a UC Berkeley geologist, was collecting samples of the limestone rock there for a study on paleomagnetism. The limestone rock outside of Gubbio is a big attraction for geologists and paleontologists because it provides a complete geological record of the end of the Cretaceous period and the beginning of the Tertiary period. This transition took place 65 million years ago, and is of special significance to our species, for it marked the close of the "Age of Reptiles," when dinosaurs ruled the Earth. Sometimes referred to as "the Great Dying," the massive extinction that engulfed the dinosaurs claimed nearly 75 percent of all the species of life on our planet, including most types of plants and many types of microscopic organisms. As much as 95 percent of all living creatures might have perished at the peak of destruction.

Sandwiched between the limestone of the two periods, forming a clear line of demarcation, is a thin maybe one-half-inch thick layer of red clay. Immediately below this clay layer, the Cretaceous limestone is heavily populated with a wide mix of the tiny fossils of marine creatures called forams. Above the clay layer, in the Tertiary limestone, however, the fossils of but a single species of foram can be seen. The clay layer itself contains no foram fossils at all.

When Walter Alvarez brought his samples back to Berkeley, his father, LBL Nobel laureate physicist Luis Alvarez, suggested that subjecting them to neutron activation analysis could help determine how long it took for the clay layer to form. The analysis, performed by LBL nuclear chemists Frank Asaro and Helen Michel, revealed to the surprise of everyone involved that the clay was about 600 times richer in iridium than the surrounding limestone. A silvery-white metal, related to platinum, iridium is quite scarce in the Earth's crust, found usually in concentrations of only 20 parts per trillion. When the Earth was formed, most of the iridium sank into the planet's core, 3,000 miles below the surface, where the concentration of the metal is 10,000 times that in the crust. Other sources of high iridium concentrations are extraterrestrial objects, such as meteorites or comets.

Subsequent samples collected from clay layers found at locations in Denmark and New Zealand, where the geological record of the Cretaceous-Tertiary boundaries are also complete, revealed the same iridium anomaly, plus an abundance of soot. This iridium anomaly has now been identified at more than 75 sites worldwide, by scientists from 11 different laboratories. Iridium is generally found in combination with platinum, gold, and several other elements. Measuring the concentrations of these elements and comparing their ratio to iridium indicated that the widely scattered iridium all came from the same source.

Putting all of the data together, Luis Alvarez concluded that the iridium anomaly was the result of a collision between the Earth and an extraterrestrial object approximately six miles in diameter. He speculated further that it was this collision that led to the death of the dinosaurs and all of the other species that perished during the Great Dying.

When a rock the size of San Francisco, traveling at approximately 45,000 miles per hour, hits the Earth, there is an instantaneous release of approximately 100 million megatons of kinetic energy six billion times the force of the Hiroshima bomb. Luis and Walter Alvarez predicted the effects of such an explosion, based on the aftermath of the volcanic eruption of Krakatoa in 1883, the biggest eruption ever recorded.

If the impact takes place on land, a heavy shroud of fine dust particles from the shattered planetary crust and the pulverized meteorite or comet would be swept high into the stratosphere by the mushrooming fireball, where it would slowly spread, wrapping the entire globe in a dense cocoon. The fireball's blazing heat would ignite enormous wildfires, the soot and debris from which would rise up and add to the sky-blackening dust, creating an extended period of endless night.

Said Walter Alvarez in a report for the American Geophysical Union, "For a few months, it would be so dark you literally could not see your hand in front of your face."

The darkness would shut down the photosynthetic process, killing all but the hardiest of plant species and driving the food chain into a state of collapse. Worldwide starvation would ensue as animals that feed on the plants die and the predators in turn follow. Extremely cold temperatures brought on by the darkness might usher in an ice age. Even if the impact takes place in the ocean, dust (from the crushed ocean floor) would still be shot above the atmosphere, only accompanying the dust would be tremendous volumes of vaporized water. After the dust finally settled, the water vapor would still remain. Solar heat reflected off the Earth's surface would be prevented from escaping into outer space by this thick moisture, and the consequence would be an oppressive greenhouse effect.

"The bitter cold would be followed by a sweltering heat," said Walter Alvarez in his AGU report.

To make matters worse, the energy released by the impact could serve as a catalyst to combine atmospheric nitrogen and oxygen into nitric acid that would fall back on the surface as corrosive precipitation.

Read the rest of this fascinating article HERE.

An update on the NEMESIS search.

"We may not have an answer to the Nemesis question until mid-2013. WISE needs to scan the sky twice in order to generate the time-lapsed images astronomers use to detect objects in the outer solar system. The change in location of an object between the time of the first scan and the second tells astronomers about the object’s location and orbit.  Then comes the long task of analyzing the data.

“I don't suspect we'll have completed the search for candidate objects until mid-2012, and then we may need up to a year of time to complete telescopic follow-up of those objects,” said (Davy) Kirkpatrick (of NASA’s Infrared Processing and Analysis Center at Caltech).