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The Oort Cloud is a theoretical spherical cloud of predominantly icy planetesimals that is believed to surround the Sun at a distance of up to around 100,000 AU (2 ly). This places it in interstellar space, beyond the Sun’s Heliosphere where it defines the cosmological boundary between the Solar System and the region of the Sun’s gravitational dominance. Like the Kuiper Belt and the Scattered Disc, the Oort Cloud is a reservoirs of trans-Neptunian objects, though it is over a thousands times more distant from our Sun as these other two. The idea of a cloud of icy infinitesimals was...

Stars Passing Close to the Sunby Paul Gilster on January 2, 2015 Every time I mention stellar distances I’m forced to remind myself that the cosmos is anything but static. Barnard’s Star, for instance, is roughly six light years away, a red dwarf that was the target of the original Daedalus starship designers back in the 1970s. But that distance is changing. If we were a species with a longer lifetime, we could wait about eight thousand years, at which time Barnard’s Star would close to less than four light years. No star shows a larger proper motion relative to...

A stream of dusty fragments from a comet born in the outermost reaches of the solar system has hit the Earth on a path that leads astronomers to conclude the comet itself could be "potentially hazardous" if it crashes into the planet. The comet's location is unknown, making it difficult to say when it will approach Earth, but "the orbits of the dust trail tells us that the comet is on a path that could eventually hit us," said Peter Jenniskens, an astronomer at the SETI Institute and the NASA Ames Research Center in Mountain View. "It's very unlikely," he...

Probe to 'look inside' asteroids By Paul Rincon BBC News Online science staff in Paris, France Studies of asteroids would aid Earth-protection strategies A new space mission concept unveiled at a Paris conference aims to look inside asteroids to reveal how they are made. Deep Interior would use radar to probe the origin and evolution of two near-Earth objects less than 1km across. The mission, which could launch some time later this decade, would also give clues to how the planets evolved. The perceived threat of asteroids colliding with our planet has renewed interest in space missions to understand these...

Scientists Find Another Huge Mini-World in Outer Solar System The most distant object ever seen orbiting the Sun is nearly as large as Pluto, expanding astronomers notions of how the solar system formed and what resides in its outskirts. The round world is currently three times farther away than Pluto from the Sun, a distance that expands even further on its 10,000-year orbit. It sits in a part of the solar system that some astronomers had thought empty. It is redder and brighter than anything astronomers have seen in the outer solar system, and scientists don't know why. The object...