"We are trying to get a better estimate of how dangerous a particular event will be," says Brian Thomas of Washburn University in Topeka, Kansas.

Thomas and his colleagues will be studying the wide-range of astrophysical phenomena that could fling high energy radiation across interstellar space to Earth's doorstep [as occured in a colossal blast detected in 2004]. The team also will radiate different types of phytoplankton to understand how life would be affected by a stellar blast, since life around the globe is highly dependent on these microscopic plants.

The danger from stellar explosions has been considered before, but this will be the first comprehensive study. "We are building on previous work by broadening it to a wide range of astrophysical events and by making the biological modeling more precise," Thomas says. The project is part of NASA's Exobiology and Evolutionary Biology Program. 

A recent U.S. military policy decision now explicitly states that observations by hush-hush government spacecraft of incoming bolides and fireballs are classified secret and are not to be released, SPACE.com has learned.

The satellites' main objectives include detecting nuclear bomb tests, and their characterizations of asteroids and lesser meteoroids as they crash through the atmosphere has been a byproduct data bonanza for scientists.

In the journal Nature today, two French scientists, using arcane mathematical models, predict that in the distant future, the Earth and planet after planet will collide with each other as an inevitable part of the solar system's long-term evolution.

For many millennia, the scientists say, the orbits of the solar system's eight planets will remain stable, just as they are today, but eventually small eccentricities in their flight paths around the sun could cause Mercury, Mars, Venus and Earth to smash into each other, either one at a time or all at once - the ultimate chaotic disaster.

Today astronomers said that a certain type of gamma-ray burst, the most energetic explosions in the universe, can light up areas of galaxies, but only in these more energetic wavelengths of the electromagnetic spectrum, revealing intense star formation and death.

A survey of so-called "dark" gamma-ray bursts, which shine brightly in the gamma and X-ray parts of the spectrum but show barely a spark of visible light, found that these beacons can shed light on the dusty corners of galaxies where stars are born.

Asteroids, comets and other impactors from space have been suggested as the causes behind some of the world's great mass extinctions , including the disappearance of the dinosaurs.

Impact evidence from lunar samples, meteorites and the pockmarked surfaces of the inner planets paints a picture of a violent environment in the solar system during the Hadean Eon 4.5 to 3.8 billion years ago, particularly through a cataclysmic event known as the Late Heavy Bombardment about 3.9 million years ago.

The black holes are crash victims, ejected from their original host galaxies when worlds collided, a process that Ryan O'Leary and Abraham Loeb, with the Harvard-Smithsonian Center for Astrophysics, suspect was instrumental in building our own galaxy and probably many others.

"Our work was theoretical, but we have an idea of what these clusters would look like, Loeb told Discovery News. 

Like hurricanes, a weak cycle refers to the number of storms, but it only takes one powerful storm to create chaos, said scientist Doug Biesecker of the National Oceanic and Atmospheric Administration's space weather prediction center.

A report by the National Academy of Sciences found that if a storm as severe as one in 1859 occurred today, it could cause $1 trillion to $2 trillion in damage the first year and take four to 10 years to recover.

The 1859 storm shorted out telegraph wires, causing fires in North America and Europe, sent readings of Earth's magnetic field soaring, and produced northern lights so bright that people read newspapers by their light. Today there's a lot more than telegraph lines at stake. Vulnerable electrical grids circle the globe, satellites now vital for all forms of communications can be severely disrupted along with the global positioning system. Indeed, the panel warned that a strong blast of solar wind can threaten national security, transportation, financial services and other essential functions.

The crater, discovered in 1978 in northern Yucutan and measuring about 180 kilometers (112 miles) in diameter, records a massive extra-terrestrial impact.

When spherules from the impact were found just below the Cretaceous-Tertiary (K-T) boundary, it was quickly identified as the "smoking gun" responsible for the mass extinction event that took place 65 million years ago.

It was this event which saw the demise of dinosaurs, along with countless other plant and animal species. However, a number of scientists have since disagreed with this interpretation.

The disappearance of sunspots happens every few years, but this time it’s gone on far longer than anyone expected – and there is no sign of the Sun waking up. “This is the lowest we’ve ever seen. We thought we’d be out of it by now, but we’re not,” says Marc Hairston of the University of Texas. And it’s not just the sunspots that are causing concern. There is also the so-called solar wind – streams of particles the Sun pours out – that is at its weakest since records began. In addition, the Sun’s magnetic axis is tilted to an unusual degree. “This is the quietest Sun we’ve seen in almost a century,” says NASA solar scientist David Hathaway. But this is not just a scientific curiosity. It could affect everyone on Earth and force what for many is the unthinkable: a reappraisal of the science behind recent global warming.

Sunspots are the most visible sign of an active sun - islands of magnetism on the sun's surface where convection is inhibited, making the gas cooler and darker when seen from Earth - and the fact that they're vanishing means we're heading into a period of solar lethargy.

Where will it all end? Solar activity varies over an 11-year cycle, but it experiences longer-term variations, highs and lows that can last around a century.

French, a doctoral candidate in aerospace engineering at North Carolina State University, has determined a way to effectively divert asteroids and other threatening objects from impacting Earth by attaching a long tether and ballast to the incoming object. By attaching the ballast, French explains, "you change the object's center of mass, effectively changing the object's orbit and allowing it to pass by the Earth, rather than impacting it."

Sound far-fetched? NASA's Near Earth Object Program has identified more than 1,000 "potentially hazardous asteroids" and they are finding more all the time. "While none of these objects is currently projected to hit Earth in the near future, slight changes in the orbits of these bodies, which could be caused by the gravitational pull of other objects, push from the solar wind, or some other effect could cause an intersection," French explains.

There are no sunspots, very few solar flares - and our nearest star is the quietest it has been for a very long time.

The observations are baffling astronomers, who are due to study new pictures of the Sun, taken from space, at the UK National Astronomy Meeting.

The Sun normally undergoes an 11-year cycle of activity. At its peak, it has a tumultuous boiling atmosphere that spits out flares and planet-sized chunks of super-hot gas. This is followed by a calmer period.

Last year, it was expected that it would have been hotting up after a quiet spell. But instead it hit a 50-year year low in solar wind pressure, a 55-year low in radio emissions, and a 100-year low in sunspot activity.

According to Prof Louise Hara of University College London, it is unclear why this is happening or when the Sun is likely to become more active again.

"There's no sign of us coming out of it yet," she told BBC News.

The chance of an impact are extremely remote — only about 1 in 45,000 — but the asteroid, named Apophis , will be back. Analysis of the asteroid's orbit show it will return to Earth seven years later.

Astronomers don't yet know if Apophis' second visit will be a rendezvous or a collision , as its orbit will be bent by Earth's gravity during the 2029 flyby.

"It can't even be said for certain what side of the sun (the asteroid) will be on in," said Jon Giorgini, a senior analyst with the Solar System Dynamics group at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

It was one of the most important changes to have happened to the Earth's atmosphere and it was the reason why today we can breathe life-giving oxygen. And yet the Great Oxidation Event has remained a mystery – until now.

Without oxygen, life on Earth would not exist as we know it. It has provided the supercharged air that has fuelled an explosion in the diversity and size of all living organisms, from the smallest shrimp to the biggest dinosaur. About 21 per cent of air is oxygen, a vital ingredient for living organisms to carry out the most efficient method of converting food into energy using aerobic respiration. Yet an oxygen-rich atmosphere did not always exist, and the explanation for how it came about has eluded generations of scientists.

Now a team of researchers led by Kurt Konhauser of the University of Alberta in Edmonton, Canada, has come up with a convincing explanation for why oxygen suddenly began to accumulate in the early atmosphere of the Earth about 2.7 billion years ago, when life consisted of nothing more complex than single-cell microbes. The Great Oxidation Event happened, they believe, when one group of oxygen-destroying microbes began to die off, leaving another group of oxygen-producing microbes to gain the ascendancy. The trigger for this event was a fall in a trace metal called nickel, which led to the inexorable rise of oxygen – and life – on Earth.

At least that is what an international team of scientists has reported in the most recent edition of the Proceedings of the Russian Academy of Sciences (Dokladi Earth Sciences). At the Permian/Triassic boundary, 250 million years ago, about 90 percent of the animal and plant species ashore became extinct. Previously it was thought that volcanic eruptions , the impacts of asteroids , or methane hydrate were instigating causes.

The mysterious boom and flash of light seen over parts of Virginia Sunday night was not a meteor, but actually exploding space junk from the second stage of a Russian Soyuz rocket falling back to Earth, according to an official with the U.S. Naval Observatory.

"I'm pretty convinced that what these folks saw was the second stage of the Soyuz rocket that launched the crew up to the space station," said Jeff Chester of the Naval Observatory in Washington, D.C.

Residents of the areas around Norfolk and Virginia Beach, Va., began calling 911 last night with reports of hearing a loud boom and seeing a streak of light that lit up the sky, according to news reports.

Were the events connected? Scientists cannot say for sure, but it's quite likely. Slowdowns in solar activity -- evidenced by reductions in sunspot numbers -- are known to coincide with decreases in the amount of energy discharged by the sun. During the Little Ice Age, though, few would have thought to track total solar irradiance (TSI), the amount of solar energy striking Earth's upper atmosphere. In fact, the scientific instrument needed to make such measurements -- a spaceborne radiometer -- was still three centuries into the future.

A year later and millions of Americans are dead and the nation's infrastructure lies in tatters. The World Bank declares America a developing nation. Europe, Scandinavia, China and Japan are also struggling to recover from the same fateful event - a violent storm, 150 million kilometres away on the surface of the sun.

It sounds ridiculous. Surely the sun couldn't create so profound a disaster on Earth. Yet an extraordinary report funded by NASA and issued by the US National Academy of Sciences (NAS) in January this year claims it could do just that.

Over the last few decades, western civilisations have busily sown the seeds of their own destruction. Our modern way of life, with its reliance on technology, has unwittingly exposed us to an extraordinary danger: plasma balls spewed from the surface of the sun could wipe out our power grids, with catastrophic consequences.

The map is based on data collected by NASA's Fermi Gamma-ray Space Telescope, which has scopes and cameras that peer out into the universe — from within our solar system to galaxies billions of light-years away — in search of the sources of the highest energy radiation, called gamma rays.

Gamma rays sit on the far left of the electromagnetic, or light, spectrum, with shorter wavelengths and higher energy than ultraviolet light and even X-rays.

Many of our own solar system's comets are found in the Kuiper Belt, a debris-filled disk that extends from Neptune's orbit (30 AU) out to almost twice that distance. Other stars have been shown to have similar debris disks.

"The debris is dust and larger fragments produced by the break-up of comets or asteroids as they collide amongst themselves," says Jane Greaves of the University of St. Andrews in Scotland. 

Roughly 20 percent of nearby sun-like stars have debris disks that are more substantial than our Kuiper Belt, according to data from the Spitzer space telescope. More debris means more comets, but does this also mean more killer impacts for any Earth-like planets that might be orbiting these stars?

The object, known as 2009 DD45, thought to be 21-47m (68-152ft) across, raced by our planet at 1344 GMT on Monday.

The gap was just 72,000 km (44,750 miles); a fifth of the distance between our planet and the Moon.

These rare events aren't typically wayward missiles, or satellite debris (as was thought when one such streak recently lit up the skies over Texas), or alien invasions. But they do come from outer space.

Scientists aptly call the objects fireballs because they are the brightest meteors, or "shooting stars," that fall to Earth.

A fireball as bright as the full moon raced across the Spanish skies on July 11, 2008, and was tracked by the Spanish Fireball Network. Researchers used the tracking data to trace the path of the comet backwards through the sky and space; they think the boulder may be a chunk of a comet that broke up nearly 90 years ago. Their conclusions are detailed in the Feb. 11 online issue of the journal Monthly Notices of the Royal Astronomical Society.

It'll still be 61 million kilometres away -- about 160 times the distance between the Earth and the moon. But for most locations in the Northern Hemisphere, it should be visible to the naked eye in dark locations over the next few days, according to NASA.

The comet is expected to appear about a third of the way up the southern sky, a few degrees from Saturn in the constellation Leo. 

"Burst emissions at these energies are still poorly understood, and Fermi is giving us the tools to figure them out," says Large Area Telescope Principal Investigator Peter Michelson, a Stanford University physics professor affiliated with the Department of Energy's SLAC National Accelerator Laboratory.

The explosion, designated GRB 080916C, occurred at 7:13 p.m. EDT Sept. 15 (after midnight GMT, Sept. 16) in the constellation Carina. Fermi's other instrument, the Gamma-ray Burst Monitor (GBM), simultaneously recorded the event. Together, the two instruments provide a view of the blast's gamma-ray emission from energies ranging from 3,000 to more than 5 billion times that of visible light.