Dark Matter May Have Powered Universe's First Stars

Dark matter may have fueled the formation of the universe's first stars—vast, invisible giants totally unlike the blazing suns of today—scientists say.

According to a new theory, disintegrating fragments of the mysterious substance could have created "dark stars" hundreds of thousands of times wider than the sun around 13 billion years ago, just after the big bang.

Because these stars weren't fueled by fusing hydrogen and helium like known present-day stars, they would have been completely invisible—but scorching hot.

The findings "drastically alter the current theoretical framework for the formation of the first stars," said study co-author Paolo Gondolo, an astrophysicist at the University of Utah.

Scientists still don't know what dark matter is exactly, so the research could shed light on it and other astronomical mysteries, he added.

"We are always searching for ways to determine the nature of dark matter," Gondolo said.

The paper will appear in next month's issue of the journal Physical Review Letters.

Annihilation Engine

According to some theories of the universe, dark matter likely consists of hypothetical particles called neutralinos.

The new paper suggests that neutralinos annihilated each other in the early universe, producing subatomic particles called quarks and their antimatter counterparts, antiquarks.

The heat from this process was enough to prevent embryonic hydrogen and helium from cooling and shrinking. Such contraction ignites the self-sustaining fusion process that powers conventional stars.

"The heating can counteract the cooling, and so the star stops contracting for a while, forming a dark star" some 80 million to 100 million years after the big bang, Gondolo said.

Dark stars, made up mostly hydrogen and helium, would be vastly larger than the sun and other stars—up to 15,000 times the size of our solar system. And instead of shining, they would glow in the infrared.

"With your bare eyes, you can't see a dark star," Gondolo said. "But the radiation would fry you."

Wide-Ranging Implications

The theory may have wide-ranging implications about the importance of dark matter in the earliest stages of the universe.

For example, dark matter is widely believed to have helped with early galaxy formation, said Rennan Barkana, an astrophysicist at Tel Aviv University in Israel who was not involved with the new paper.

But until now it was thought that "the dark matter does not play any significant role in the formation of the star itself," he said.

That's important, because the substance is believed to make up most of the universe's matter, partly because galaxies rotate faster than can be explained by the visible matter within them.

In total, about 23 percent of the universe is thought to be dark matter, as opposed to 4 percent for the ordinary matter that makes up stars, planets, and moons.

The remaining 73 percent is thought to be dark energy, an even more mysterious force helping the universe to expand at increasing rates.

Search Is On

Emanuele Ripamonti, an astronomer at Universita' dell'Insubria in Como, Italy, said that in order for the new research to be plausible, the formation of stars from dark matter must rely on a cascade of events that are not yet well studied.

"Every time they make a choice, the authors pick the 'most likely' option, but in some cases there is no real consensus" about what would happen, he said.

Barkana called the theory intriguing and novel but agreed that more research is necessary.

"It is unclear whether in the end an observational prediction will come out that will allow the dark star possibility to be clearly distinguished from other scenarios," he said.

If dark stars exist, however, they would likely give themselves away by spewing gamma rays, neutrinos, and antimatter, study author Gondolo said. The stars would also be associated with clouds of cold, molecular hydrogen gas that wouldn't normally harbor such energetic particles.

If found, dark stars wouldn't only provide insights into dark matter, he added. They could also help unravel phenomena like the formation of heavy elements—thought to come from exploding conventional stars—and the rapid formation of black holes, which defies theoretical predictions.

"Without detailed simulations, we cannot pinpoint the further evolution of dark stars," he said. "We have to search for them."

"Zombie" Roaches Lose Free Will Due to Wasp Venom

The parasitic jewel wasp uses a venom injected directly into a cockroach's brain to inhibit its victim's free will, scientists have discovered.

The venom blocks a chemical substance called octopamine in the cockroach's brain that controls its motivation to walk, the study found.

Unable to fight back, the "zombie" cockroach can be pulled into the wasp's underground lair, where an egg is laid in its abdomen. The larva later hatches and eats the still living but incapacitated cockroach from the inside out.

"The whole thing takes about seven to eight days, during which the meat has to be fresh," said study co-author and neurobiologist Frederic Libersat of Ben-Gurion University of the Negev in Be'ér Sheva, Israel.

"If you kill a cockroach, it rots within a day."

The mature wasp emerges from the bug victim's body after about a month.

The study recently appeared in the Journal of Experimental Biology.

Zombie Science

The team of researchers at Ben-Gurion University believe that the octopamine discovery is an important piece of the puzzle of how the tropical wasp's venom turns its victims into the living dead.

Octopamine is a brain substance that places insects in an alert state, inspires them to move, and allows them to perform demanding physical tasks.

"It serves the same functions as noradrenaline, which is involved in the fight-or-flight reaction ... in the vertebrate brain," Libersat said.

The team determined that the wasp injects its venom into a specific area of the cockroach's brain, the protocerebrum.

This region, which contains octopamine-secreting nerve cells, controls the ability to start walking. The venom interferes with the release of octopamine, they found.

The researchers then reversed the process: they injected an octopamine-like substance directly into the protocerebrum of cockroaches that had already been turned into zombies by wasp stings.

The result was significant recovery and restoration of the cockroach's free will.

"This helps us understand how movement is initiated in animals," Libersat said. "We know how movement itself is generated, but to understand what makes an animal decide to move or not to move is a different issue."

Parasite Strategies

The jewel wasp is the only parasite known to inject its venom directly into its host's brain.

But other parasites also control the behavior of their hosts, said David Richman, curator of the Arthropod Museum at New Mexico State University in Las Cruces, who was not involved in the new study.

"This is not uncommon. There are a tremendous number of parasites, and they all have different strategies for survival and for propagation of their species," Richman said.

The behaviors of land snails, grasshoppers, and types of ants, for example, can all be affected by parasites.

"Not only that," Richman added, "[some parasites] can take over certain aspects of the host's biology, particularly as you get into microorganisms."

Shuttle Atlantis Launch Delayed

NASA called off Thursday's launch of space shuttle Atlantis after detecting problems with a pair of fuel gauges in the shuttle's external tank.

Shuttle managers said they would try again Friday—if the problem can be solved before then.

Engineers were testing the four engine-cutoff sensors in Atlantis's liquid hydrogen tank, and two of them failed.

Even though they were commanded to indicate the tank was empty, the two kept showing the tank was full, said NASA spokesman Paul Foerman.

At least three of the sensors must work properly to proceed with a launch.

Officials said the problem might be related to wiring and connectors, rather than the sensors themselves. It was not immediately clear how any repairs might be made.

The sensors are critical to ensure that the shuttle's three main engines don't shut down too soon or too late during liftoff. Problems with the sensors have delayed shuttle launches before, most recently in September 2006. The trouble began cropping up following the 2003 Columbia disaster.

NASA had been hoping for an on-time takeoff. Each of the year's three previous shuttle countdowns had ended with an on-the-dot departure.

Atlantis is loaded with Europe's long-awaited space station lab, named Columbus.

The seven astronauts had yet to board their spaceship when the delay was announced.

About 750 Europeans connected to the scientific laboratory—a 2 billion U.S. dollar project begun nearly a quarter-century ago—were in town for the launch and had begun gathering at the space center.

It was yet another disappointing flight delay for the European Space Agency, which has been working on Columbus for more than 22 years.

Columbus is "our cornerstone, our baby, our module, our laboratory," Alan Thirkettle, the European Space Agency's station program manager, said Wednesday.

Columbus will be the second laboratory added to the international space station. NASA's Destiny lab made its debut in 2001, and Japan's huge lab Kibo—which means "hope"—will go up in three sections beginning on the next shuttle mission in February.

Once Columbus arrives at the space station, scientific work can start almost immediately inside the lab, which is essentially packaged and ready to go.

Aside from the interruption caused by the 2003 Columbia tragedy, the actual building of the space station in orbit has gone well, NASA Administrator Michael Griffin said.

That's in stark contrast to the space station's planning and development, which dragged on for years and contributed to Columbus' prolonged grounding.

"We the United States, as the senior partner in the space station coalition, did not plan it well," NASA Administrator Michael Griffin said Thursday, on the eve of Columbus' originally scheduled launch. "It has taken far too long, and I'll just leave it at that."

Copyright 2007 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

Shark Ate Amphibian Ate Fish: First "Food-Chain Fossil"

About 290 million years ago, Earth's lakes were a shark-eat-amphibian-eat-fish world, new fossil evidence reveals.

A new fossil discovery looks like a set of Russian dolls: It's the preserved remains of a fish, which was eaten by an amphibian, which was then eaten by a shark.

The fossil provides the first ever snapshot of an ancient, three-level, vertebrate food chain.

An animal's last meal is very rarely preserved, because corrosive acids quickly erupt from the decaying stomach, dissolving any food remnants before fossilization can take place.

But in this case, "the shark didn't just die and sink down and decompose," said Jürgen Kriwet, a paleontologist from Berlin's Museum of Natural History and co-author of a new study on the find.

"It was probably still alive when it got trapped under a rapid influx of sediment from surrounding hills," he said.

A Single Food Chain

The fossilized trio lived 290 million years ago in the shallow coastal waters of a freshwater lake in the Saar-Nahe Basin of southwestern Germany. The lake had previously been linked to the sea but was landlocked for millions of years before the three animals lived and died.

Several pieces of evidence suggest the animals must have formed part of a single food chain.

For one thing, "the orientation of the fossils fits perfectly," Kriwet said.

Permian-period sharks—like the one in the fossil—were only 19 inches (50 centimeters) long and ambushed their prey, swimming up from behind and swallowing it whole.

The fossilized amphibian is also in exactly the right position to suggest it had been eaten—it was lying tail-first along the shark's digestive tract, according to Kriwet.

"Also, the fish remains are fully enclosed within the amphibian's outer covering of scales," he added. That confirms that it was indeed eaten by the amphibian and not the shark.

Before the shark ate it, the amphibian had caught a young fish known as an acanthodian, which was covered in bony spines.

"The fish was swallowed side on, otherwise the spines could have got stuck in the amphibian's mouth or throat," Kriwet said.

"The fish is situated in quite the correct area of digestive tract of the amphibian," said said study co-author Ulriche Heidtke, a paleontologist from the National History Museum of the Palatinate in Bad Dürkheim, Germany.

"It clearly shows the hallmarks of digestion, [such as] disintegration," he added.

If the shark had eaten the fish first and then the amphibian, they would be placed one after the other in the shark's stomach, he explained.

John Maisey, a curator of paleontology at the American Museum of Natural History in New York, was not involved in this study.

"Well-documented examples of predator-prey relationships such as this are very rare," he said.

Such fossils allow scientists to reconstruct parts of extinct food chains, Maisey added.

"Three tiers are exceptional—if [only] we could find a four-tier example."

Unusual Sharks

Unlike their ancient ancestors, no modern-day sharks are fully adapted to living in fresh water.

"Today we find some rays and skates—close relatives of sharks—living in fresh water, but sharks invade lakes and rivers only for a short time," said study co-author Kriwet.

"We don't understand why this is," he said.

Another odd difference is that none of the sharks that swim through the oceans today are known to eat amphibians.

"There are no reports of sharks eating amphibians, even in the tropics, where there are large amphibians living close to the lakes and rivers that sharks temporarily enter," Kriwet said.

These ancient amphibians—known as temnospondyls—were reminiscent of modern-day crocodiles but lived in a world that was still crocodile free. (Related news: "Ancient Amphibians Bit Instead of Sucking, Skull Study Says" [April 16, 2007].)

"The amphibians had a short legs, long snouts, big teeth, and a long tail that they used as a rudder, much like crocodiles today," Kriwet said.

"Before the Permian extinction event, amphibians and sharks were the main top predators," he said.

The Permian extinction, Earth's most extreme die-off, occurred 251 million years ago.

"But by the end of the Triassic [199.6 million years ago]," Kriwet said, "there was a shift to crocodiles and bony fish being the top predators."

Cuban Bananas "Storm" Dutch Beach

On the Dutch island of Terschelling, beaches are often awash in treasures—like the bunches of Cuban bananas that floated ashore this week (top photo).

It was sneakers (bottom photo) and aluminum briefcases in February 2006. The shore was covered with sweaters before that.

The island was molded into its current shape by a violent storm in 1296, according to its official web site. Things have been washing ashore ever since.

This week's boon comes from six banana crates—originally from Cuba—that fell off a cargo ship during a recent storm.

Local beachcombers came early Wednesday for a look, said Gossen Buren, a shipping official at the local lighthouse, according to the Associated Press.

"But not as many as when we had the sneakers," he said.

One of the West Frisian Islands, Terschelling lies about 70 miles (110 kilometers) north of Amsterdam.

It is surrounded by pockets of polder—land previously under water—:and a deceptive sea that has been stealing cargo for centuries, sometimes capsizing ships

For the moment the island has more bananas than it can use.

"I think everybody on the island has a bunch now," Buren said.

Some locals had suggested sending the extra bananas to nearby zoos, he added.

Leaves' Fall Colors Have "Dirty" Secret, Study Finds

New Englanders are blaming this year's lackluster fall-color season on drought, but if you don't like the colors in your own backyard, you might blame the dirt, a new study says.

In an undergraduate research project, Emily Habinck, who has since graduated from the University of North Carolina at Charlotte, found that autumn leaf color is related to the richness of the soil.

She determined that on a North Carolina floodplain that was rich in nitrate—a nitrogen-containing nutrient—yellow-leafed trees dominated. But in the poorer soils of the hillside behind it, there were more reds.

Even among the trees that typically bear red leaves no matter the conditions, poorer soils made for redder hues.

Habinck based her study on her faculty advisor's observation that floodplain trees tended to be yellow and that soil nutrients might have something to do with it.

While Habinck was at work on the project, William Hoch, a plant physiologist at Montana State University, wrote a paper suggesting an additional link between the red-leaf pigment anthocyanin and autumn sunlight.

"It wasn't until I read his paper that it became a full story," Habinck said.

Leaf Protection

Leaves turn color in the fall as trees start shutting down their energy production and withdrawing nutrients into their roots.

"[The tree] pulls as many of these in as it can, then tries to drop just a skeleton of a leaf when it's done," Hoch said in a telephone interview.

But nutrient withdrawal takes time, and the process leaves the leaves vulnerable to damage from sunlight.

Anthocyanins protect leaves by "shading" them from excessive sunlight during the plant's relatively vulnerable autumn season, Hoch explained.

In a study of plants that had been genetically modified not to be produce anthocyanins, Hoch found that the modified plants were unable to send as many nutrients to their roots for winter storage.

"So the bottom line is that the plants that were able to produce red pigments were able to squeeze more of the nutrients out of their leaves than the ones that couldn't," he said.

Thus, Hoch says, plants living in nutrient-poor soils benefit more from anthocyanin than those living on better soils.

Scientists only recently made these connections, Habnick said, because when most other leaf-peepers are taking their fall-color tours, biologists are busy with academics.

"Most people's field season is in the summer," she said.

"Brainbows" Illuminate the Mind's Wiring

Genetically engineered mice furnished with fluorescent proteins are providing the most detailed pictures yet of the brain's intricate circuitry.
The innovation offers an intimate peek into the development and inner workings of the nervous system at the level of individual neurons, researchers say.

"Imagine the brain as a radio for which we never had a good wiring diagram," said Jeff Lichtman, a neurobiologist at Harvard University and a co-author of the study.

"The aim of this work is to tag the individual wires with their own color" to get a better idea of their connections, he added.

If every cell in the brain were imaged using a single color, Lichtman explained, numerous wires bunched together would be indistinguishable.

But the various fluorescent proteins used in the new research make the multitudes of strands that comprise the complex tissue of the nervous system stand out from each other.

In their effort to tease out the details of connections in the nervous system, Lichtman and his colleagues developed about 30 lines of mice.

The team incorporated a chain of three different fluorescent protein genes—which they call a brainbow—into these mice.

The researchers then crossed the genetically engineered mice with mice that expressed an Cre, an enzyme in their brains.

In the offspring of this cross, Cre randomly snipped off or rearranged the brainbow sequence. This process caused just one of the brainbow colors to turn on at any given point.

Since each cell contains multiple copies of the brainbow, the end result is a unique mixture of red, green, and blue colors in each cell—and a random riot of color in the brain overall.

"It is like a television monitor where three basic colors—red, blue, and green—mix together and form various other colors," said Lichtman, whose findings will appear tomorrow in the journal Nature.

Shape Matters

Ed Lein is director of neuroscience at the Allen Institute for Brain Science in Seattle, Washington.

The Harvard researchers, he said, have essentially developed a novel technique that allows one to look at the shape of many different neurons simultaneously.

"The shape of the neuron is a pretty powerful piece of information. It allows you to infer, and in some cases demonstrate, who that cell is connected to," Lein said. " It lets you look at detailed microcircuitry in the brain."

The technique, he explained, will help researchers look at the shape of cells during embryo development and postnatal development in real time—and perhaps understand the progression of disease.

"It is too difficult to trace the 'wires' of the brain, because they are so thin and it is easy to make mistakes," said Sebastian Seung, a computational neuroscientist at MIT.

"The brainbow technique makes it easier to trace them."