The extreme stargazer's guide to the cosmos

AS A teenager, Bryan Gaensler gazed at the heavens from the backyard of his Sydney home, fascinated by a light that had suddenly appeared in the night sky.

It was February 1987, and a distant star in the constellation of Dorado had ended its life suddenly in a massive explosion, so bright that it was visible to the human eye.

Gaensler had been a fan of astronomy since he was a child, and seeing this supernova strengthened his resolve to pursue a career studying the universe, he says.

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''I was able to spot it [the supernova] every night until it gradually faded away over the next few weeks. It was a huge thrill to know that the light that was entering my eyes had begun its journey in an unimaginably violent detonation 170,000 years earlier,'' Gaensler recalls.

Gaensler, an Australian Laureate Fellow at the University of Sydney and director of the Centre of Excellence for All-sky Astrophysics, recounts this teenage experience in his new book, Extreme Cosmos, which takes the reader on a tour of the most extraordinary features of our universe.

Among his insights into the brightest, heaviest, fastest and hottest celestial bodies are descriptions of a neutron star so magnetic it would wipe data from a credit card 100,000 kilometres away, a star that is 1500 times the size of our sun and another star moving at about 2.5 million kilometres an hour.

When he was very young, Gaensler imagined his main preoccupation as an astronomer would be to discover new stars. And his first stellar find - in 1994 - was a big thrill, he writes.

''I sat quietly for a few minutes, alone with my discovery, cherishing the fact that there was something out there that only I knew about.'' But he later realised the main aim of those who study the universe is to try to understand how it works.

We live in a rather insalubrious spot in the cosmos to do this, on a small planet orbiting an ordinary star in a quiet suburb of the Milky Way, he says. And, clever though humans are, our brains evolved to help us survive as hunter-gatherers rather than comprehend the unimaginably large numbers that are needed to describe the complexity of the cosmos.

This makes it all the more remarkable that, in a little more than 100 years, people have learnt so much about the 13.7 billion-year history of the universe since the Big Bang.

The largest structure found so far is the Sloan Great Wall a ''colossal filament of thousands of galaxies'' that stretches for 1.4 billion light years.

And the fastest object measured - the Oh My God particle - was detected in the United States 20 years ago. It is thought to have been a proton, travelling at almost the speed of light, which is just over a billion kilometres an hour.

Supernovae, such as the one Gaensler saw as a teenager, are bright. But gamma ray bursts are 100 to 1000 times more luminous, and the record setter occurred in 2008. It was easily visible to the eye for about 30 seconds, even though it came from 7.5 billion light years away - meaning it occurred even before our sun and earth were born.

Even though much has been learnt, each new find raises more questions, says Gaensler, a former Young Australian of the Year. ''There is an endless road of discovery and delight ahead. The golden age of astronomy is only now just beginning.''

  

Source : http://www.smh.com.au/

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Skeletons may hold the key to male infertility

FOR years, scientists thought they understood the skeleton. It serves as structural support for the body. It stores calcium and phosphate. It contributes to blood-cell development. And it serves, indispensably, as the creepy mascot of horror movies.

But as it turns out, there might be still more to bone.

A few years ago, researchers at Columbia University Medical Centre discovered, to everyone's surprise, that the skeleton seems to help regulate blood sugar. Now the team, led by a geneticist and endocrinologist at the university, Dr Gerard Karsenty, has found that bone might also play an unexpected role in reproduction. If the work pans out, it might help to explain some cases of low fertility in men.

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''It's definitely an attention-grabber,'' says Dr William Crowley, of Harvard Medical School, who was not part of the research.

It is well known that the hormones oestrogen and testosterone, produced in the ovaries and testes, help to regulate bone growth. When women reach menopause, oestrogen levels decrease along with bone mass, putting them at increased risk of osteoporosis. As men age, their testosterone and oestrogen levels also decline. Men lose bone but much more slowly than women do. ''We thought that if the sex organs talk to the skeleton, then the skeleton should talk back to the sex organs,'' Karsenty says.

And, apparently, it does.

Early this year, Karsenty's team published a study demonstrating that in mice a protein called osteocalcin, which is produced by bone-forming cells called osteoblasts, binds to a specific receptor on cells of the testes. Male mice that were unable to make osteocalcin (due to genetic manipulation) produced less testosterone and were less fertile. When they mated, they had fewer and smaller offspring.

Fertility in female mice, on the other hand, was not affected by osteocalcin. Cells in their ovaries lacked the receptors to which the bone hormone binds. ''We were surprised by that,'' Karsenty says. ''We thought we'd find a hormone that regulated fertility in both sexes.'' Another compound, as yet unknown, might play the analogous role in females. Human testicular cells also have receptors for the hormone osteocalcin, Karsenty has found.

''I don't know of any hormone that functions in mice but not to some extent in humans,'' says a researcher at Maryland's Johns Hopkins University, Thomas Clemens. Still, the magnitude of the effect might not be the same as in mice.

The main hormone that stimulates testosterone production, in mice and men, is luteinizing, a protein made in the brain. Luteinizing hormone is ''the on-off switch'' for testosterone, Crowley says. Osteocalcin, on the other hand, looks more like a ''dimmer switch'' that modulates the process.

The question is, is it a critical mechanism or a back-up system? Does osteocalcin play a large role in problems such as low sperm count and low testosterone, or is it more peripheral?

Scientists now plan to study men with these problems and to measure their osteocalcin levels, Crowley says. Some of them might have a defect in osteocalcin that underlies their condition.

But, he says: ''I suspect this will turn out to be one chapter in an interesting and more complicated mystery.''

Karsenty has long argued that bone plays a central role in regulating body physiology. ''The body is not an assembly of silos that don't speak to each other but is full of surprising examples of crosstalk,'' he says.

In 2007, he showed that bone helps to regulate blood sugar, a result that startled hormone specialists. Working with mice, he reported that osteocalcin boosts insulin production in the pancreas and increases insulin sensitivity. Insulin, in turn, acts to lower blood sugar.

That work could prove relevant to diabetes, in which the body either does not produce enough insulin or stops heeding it.

Now, Karsenty hopes to unravel the complicated links binding the skeleton, sugar and gender. Bone mass tends to decline with age, he notes, as do blood-sugar control and fertility.

''One idea is that bone might not just be a victim of ageing. It might also be a contributor.''

Source : http://www.smh.com.au/

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Stars fade as universe starts to run out of gas

GALAXIES are running out of gas - a discovery that explains why fewer stars are being born now than in the past. The culprit for this dimming of the lights appears to be the mysterious dark energy that pervades the cosmos and is pushing it ever faster apart.

A CSIRO astronomer, Robert Braun, said that star formation peaked early in the universe's history, about 8 to 10 billion years ago, then began to decline.

At first the drop-off in star birth was slow. ''Now it's really plummeting,'' Dr Braun said.

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To find out why, he and his colleagues looked back in time with the Mopra radio telescope near Coonabarabran. They compared galaxies that existed between 3 and 5 billion years ago with those today, and found the older ones had much more hydrogen gas in them - the stuff from which stars are born.

Dr Braun said galaxies needed to be constantly replenished with hydrogen gas that was pulled in by gravity, but the amount of intergalactic gas being captured had been reduced. ''Today, it's become more and more difficult for the gas to fall in,'' he said. ''Our results help us understand why the lights are going out.''

The decline in star formation, and influx of gas, appears to have coincided with the time when the repulsive force of dark energy began to dominate the attractive force of gravity, causing galaxies to fly apart at an increasing rate.

''This accelerating expansion could have made it increasingly difficult for galaxies to capture the additional gas they need to fuel future generations of star formation,'' Dr Braun said.

Source : http://www.smh.com.au/

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A star is torn - and it doesn't happen all that often

WHEN a star is torn apart it's a rare event, happening only once every 10,000 years per galaxy. The odds of the light show also being captured by telescope or analysed by astronomers are slim.

So there was some excitement when an international group of astronomers reviewing observations taken in 2006 realised just what they were looking at.

The team, including Sydney University astrophysicist Sean Farrell, spent three years reviewing archival footage taken by the European Space Agency's X-ray telescope in the hope of spotting a rare event or object.

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They found it in the form of a bright flare - a sign of a star being ripped apart by a supermassive black hole - in a galaxy some 500 million light years away.

The stray star was observed again in 2007 at increased brightness, according to the study's leader, Dacheng Lin.

But by February this year, when the team searched for it using a NASA X-ray telescope, they could find no trace of the star, which had been obliterated by a supermassive black hole.

''We've been pretty lucky,'' Dr Farrell said. ''We had indeed stumbled on to a very rare extreme event … we were very lucky that the telescope happened to have this event in its field of view.''

Dr Farrell said the star had strayed too close to the black hole's narrow boundary, and astronomers were able to establish its destruction because of the swirling debris which emitted X-rays picked up by the telescopes. Because X-rays do not penetrate Earth's atmosphere, the telescopes are located in space.

From the X-rays astronomers can also effectively take the temperature of the black hole, which reveals its mass.

The find, reported in the upcoming edition of Astrophysics Journal, is notable for the rarity of the event and for the information that scientists hope to glean from it.

Supermassive black holes exist in the middle of galaxies and have three traits - mass, spin and charge. Learning more about their characteristics could also test and refine Albert Einstein's theories. Relatively little is known about supermassive black holes, although they have the potential to reveal a great deal about the formation of galaxies.

''This is very important as their influence on galaxies has an enormous effect on gas, stars, planets and, of course, life itself," Dr Farrell said.

"By studying the boundaries of black holes we can gain crucial knowledge about these extreme objects and their impact in the universe."

Source : http://www.smh.com.au/

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Rare fossil of sea reptile found on Alaska beach

ANCHORAGE, Alaska- Alaska scientists have discovered the fossil of a rare, prehistoric marine reptile that is likely the most complete remnant of the creature ever found in North America.

The nearly complete fossilized skeleton is of a thalattosaur, a long-tailed sea creature that plied warm, shallow waters in the early days of dinosaurs and became extinct at the end of the Triassic period some 200 million years ago.

The discovery of the fossil, found during an extreme low tide along the shore of the Tongass National Forest, was announced this week by the Museum of the North at the University of Alaska, Fairbanks.

"We were just having our morning coffee out on the outcropping when somebody said, 'What's that?'" Jim Baichtal, the U.S. Forest Service's Tongass geologist and part of the discovery team, said on Thursday.

Geologists had been conducting field surveys at the site when the fossil was spotted.

Unlike most thalattosaur discoveries, which are fossilized remnants of individual bones and bone fragments, this specimen appeared to be a nearly full skeleton.

"In North America, this may be the most articulated specimen that we have right now," Baichtal said.

Scientists excavated the fossil in June and have been studying it to determine whether it represents a previously unknown species.

There are only about a dozen full thalattosaur specimens in the world, Baichtal said. "So the probability of this being something that wasn't seen before is probably pretty high," he said.

The find is likely the most northern discovery as well, Baichtal said. The fossil was found near the Tlingit Indian village of Kake in southeast Alaska.

Other thalattosaur discoveries have been made in British Columbia, Canada, as well as in Nevada and the Alps, though the best finds have been made in China, he said.

SITE WAS TROPICAL

At the time this particular animal was trapped in sediment, about 200 million to 220 million years ago, the site was close to the equator and tropical, Baichtal said.

"This was a warm, volcanic island with reefs surrounding it," similar to Hawaii, he said. Plate tectonics eventually sent the site drifting north to its present location in Alaska, he said.

The fossil from the Tongass beach is now at the Museum of the North, where scientists will do further work to separate the rock from the bone.

Thalattosaurs inhabited the seas for about 30 million years, a relatively brief time geologically, said Pat Druckenmiller, earth sciences curator for the Museum of the North. They measured about three to 10 feet long, with half to a third of that taken up by the tail, he said.

"The rest of its body would be kind of reminiscent of a big lizard," he said, with legs modified to work as paddles.

Some had no teeth, some had pointy teeth that might have been useful for spearing fish, and some had flat teeth that might have been used to crush shells, Druckenmiller said.

The Alaska fossil appears to include the outline of soft-body tissue that surrounded the bone.

"That's really rare," Druckenmiller said. "That might give us some idea of what the actual body shape was."

Scientists will return to the site later to try to excavate the rest of the fossil, still embedded in beach rock, Druckenmiller said.

"We don't know if the skull will be there or not, but I have high hopes that it will be there," he said.

(Editing by Steve Gorman and Cynthia Johnston)

Source :  http://www.reuters.com

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With space shuttle era over, U.S. robot set for Mars

CAPE CANAVERAL, Florida - NASA moved on to a new chapter in space exploration on Friday, a day after the end of its shuttle program, by announcing details of plans to determine if Mars has or ever had the ingredients for life.

Managers at the U.S. space agency said a robotic science laboratory, being prepared for a November 25 launch, will land in August 2012 near a mountain in a crater on the planet most like Earth in the solar system.

The announcement came after the final curtain fell on NASA's 30-year-old space shuttle program with Thursday's landing of shuttle Atlantis at the Kennedy Space Center.

A detailed blueprint of NASA's follow-on space exploration strategy is still pending and many Americans fear the demise of the shuttle program means the United States is relinquishing its leadership in space.

But U.S. President Barack Obama has said the objective is to build new spaceships that can travel beyond the shuttle's near-Earth orbit and eventually send astronauts to asteroids, Mars and other destinations in deep space.

At a Cape Canaveral briefing next Wednesday, NASA officials will discuss preparations for the agency's upcoming Juno mission to Jupiter. The unmanned spacecraft, set for launch in August, is expected to reach Jupiter's orbit in July 2016 and should further understanding of the solar system's beginnings by revealing the origin and evolution of its largest planet.

"A lot of attention has been given to the event that concluded yesterday with the landing of the space shuttle, marking really the turning of the page to a new chapter in human exploration of space," said NASA chief scientist Waleed Abdalati.

"Things change, things evolve, but what remains constant is the urge to explore, to reach out beyond where we are and understand our surroundings and our place in it," Abdalati said at the National Air and Space Museum in Washington, D.C., where the landing site for the Mars Science Laboratory was announced.

NASA plans to turn over its three space shuttles to museums and regroup for development of the new manned exploration program. This will be aimed at the inner solar system, which so far has only been explored by robots, albeit increasingly more capable ones.

Among the most sophisticated probes in the offing is the plutonium-powered roving Mars Science Lab, nicknamed Curiosity, which is being prepared for launch in November.

Twice as long and five times heavier than previous Mars rovers, Curiosity packs 10 science instruments, including two for on-site chemical analysis of pulverized rock. With it, scientists hope to learn if Mars has or ever had the organics necessary for life -- at least life as it appears on Earth.

"STUNNING" ROCK MOUNTAIN

Scientists spent five years mulling 60 possible landing sites before narrowing the list to four: Eberwalde Crater, Mawrth Vallis, Holden Crater and -- the winner -- Gale Crater, which sports a stunning three-mile-(5 km-)high mountain of rocks rising from the crater floor. That's about twice the height of the stack of rocks exposed in the Grand Canyon.

Analysis from Mars-orbiting spacecraft shows the base of Gale Crater's mountain includes both clays and sulfate salts, the only site among the four finalists with both types of materials available.

"Those are key classes of minerals that tell us about the environment on Mars and the interaction with water. Water is critical to habitability," said geologist Dawn Sumner, with the University of California at Davis.

Scientists do not know how the mountain formed, but it may be the eroded remnant of sediment that once completely filled the crater.

"If you start at the bottom and you go to the top, it's like reading a novel and we think that Gale Crater is going to be a great novel," said lead mission scientist John Grotzinger, with the California Institute of Technology in Pasadena.

Though Curiosity's mission is scheduled to last two years, scientists hope the rover will live past its warranty.

One of a pair of Mars rovers that arrived for concurrent three-month surveys in January 2004 is still working. Its twin succumbed to the harsh Martian environment only last year. They returned evidence that Mars was once far wetter and warmer than the dry, cold desert that exists today.

"Gale Crater is interesting to explore because it crosses what we think is a major time boundary on Mars recorded in its mineral history," said Brown University geologist Jack Mustard.

"That boundary marks a change from an early wet, hospitable environment that would have been suitable for life to a middle period where conditions may have become more hostile. We believe that at Gale Crater, we have located that boundary where life may have sprung up and where it may have been extinguished. That's why we're going there," he added.

Kennedy Space Center is overseeing preparations for Curiosity's launch from Cape Canaveral Air Force Station, which is adjacent to the space shuttle's now-dormant launch pads.

(Editing by Tom Brown and Todd Eastham)

Source : http://www.reuters.com

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