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A duo of planetary astronomers has grabbed media attention by claiming a planet four times the size of Jupiter may be lurking in the outer solar system. They call the planet Tyche. Many astronomers, however, say it probably isn't there. The claim by John Matese and Daniel Whitmire of the University of Lousiana-Lafayette is not new: They have been making a case for Tyche since 1999, suggesting that the giant planet's presence in a far-flung region of solar system called the Oort cloud would explain the unusual orbital paths of some comets that originate there.

The last extinction event, 11 million years ago, saw 10 per cent of the Earth’s inhabitants wiped out. This means there is around 16million years until the next event takes place, although the graph shows that it occasionally the event takes place up to 10 million years early. Asteroids crashing into the Earth are commonly believed to be one of the main reasons behind mass extinctions like that suffered by the dinosaurs - the Cretaceous-Tertiary (KT) extinction. The extinction wiped out more than half of all species on the planet clearing the way for mammals to become the dominant species...

IN THE dark reaches of the solar system lurk swarms of hidden worlds. Too small and too distant to reflect sunlight, they have remained under the cover of darkness for billions of years. But now the outer solar system is giving up its secrets. And with them comes an astonishing claim: "It's quite possible that there is a halo of planets surrounding our solar system, just waiting to be found," says Eugene Chiang, an astronomer at the University of California, Berkeley. What makes Chiang's claim so surprising is the sheer number and size of these planets. Weighing more than...

Our sun may have a companion that disturbs comets from the edge of the solar system — a giant planet with up to four times the mass of Jupiter, researchers suggest. A NASA space telescope launched last year may soon detect such a stealth companion to our sun, if it actually exists, in the distant icy realm of the comet-birthing Oort cloud, which surrounds our solar system with billions of icy objects. The potential jumbo Jupiter would likely be a world so frigid it is difficult to spot, researchers said. It could be found up to 30,000 astronomical units from...

"What we're really saying," he explains, "is that there's suggestive evidence there might be something out there." And if a new planet exists — something Matese is emphatically not claiming at this point — then the Wide-field Infrared Survey Explorer (WISE) satellite should already have an image of it stored somewhere in its enormous database. How suggestive the evidence actually is, though, depends on whom you ask. If you ask Ned Wright, a UCLA astrophysicist and WISE principal investigator, he'll tell you, "It's really kind of flimsy. It's there, but they don't have super data." So while the latest version...

The 4.6-billion-year history of our solar system is nowhere crystal clear, astronomers admit. Instead, it's filled with questions as to the origin of some of its most remarkable feats. Here is a top 6 of these mysteries, as compiled by New Scientist... Another thing that concerns astronomers is the existence of Planet X, a hypothetical celestial body that supposedly circles our Sun on an orbit somewhere behind Pluto. Experts say that the distance it revolves around the Sun can only imply that the planet is frozen, but say that it could be as big as Mars, or even Earth. However,...

A theory is hereby proposed that an unknown mega-massive planet has, for billions of years, been orbiting at 77.2 AU from the sun -- within a 44 AU-wide, virtually empty Great Void that surrounds the Kuiper Belt (One AU = 93 million miles, the mean Earth-Sun distance). The Void is postulated to have been formed by strong gravitational attraction of the unknown planet having removed all CKBOs (Classical Kuiper Belt Objects) that had existed previously in the vicinity of the massive planet's huge orbit... The 77.2 AU distance from the sun of the proposed unknown planet is derived from a...

In 1846, researchers noticed that Uranus was wobbling in a way that confounded Newton's Law of Motion. This meant they had two options: rewrite the most time-honoured of the laws of physics, or "invent" a new planet to account for the extra gravitational pull. Compared to Newton's reputation, an eighth planet seemed much less massive and Neptune was discovered. Today scientists working in the University of Louisiana have discovered a statistical anomaly of similar proportions. Professors John Matese, Patrick Whitman and Daniel Whitmire have studied the orbits of comets for 20 years, and their recent findings have led to startling...

We assume that if the sun has a companion, it has a period of 27 Myr corresponding to the periodicity seen in cometary impacts on earth. Based on this assumption, it is seen that the inner Lagrangian point of the interaction between the Sun and its companion is in the Oort cloud. From this we calculate the mass – distance relation for the companion. We then compute the expected apparent magnitude (visible and J band) for the companion using the models of Burrows... We then compare this with the catalogue completeness of optical and infrared catalogues to show that the...

Japanese scientists believe another planet, up to two-thirds the size of Earth, is orbiting in the far reaches of the Solar System... "Because of the very cold temperature, its surface would be covered with ice, icy ammonia and methane," said lead researcher Tadashi Mukai. The study by Mukai and co-worker Patryk Lykawka will be published in the April issue of the Astronomical Journal. "The possibility is high that a yet unknown, planet-class celestial body, measuring 30 per cent to 70 per cent of the Earth's mass, exists in the outer edges of the Solar System," says a statement released by...

Nasa scientists are searching for an invisible 'Death Star' that circles the Sun, which catapults potentially catastrophic comets at the Earth. The star, also known as Nemesis, is five times the size of Jupiter and could be to blame for the impact that wiped out the dinosaurs 65 million years ago. The bombardment of icy missiles is being blamed by some scientists for mass extinctions of life that they say happen every 26 million years Nemesis is predicted to lie at a distance equal to 25,000 times that of the Earth from the Sun, or a third of a light-year....

Scientists believe they may have found a new planet in the far reaches of the solar system, up to four times the mass of Jupiter. Its orbit would be thousands of times further from the Sun than the Earth's - which could explain why it has so far remained undiscovered. Data which could prove the existence of Tyche, a gas giant in the outer Oort Cloud, is set to be released later this year - although some believe proof has already been garnered by Nasa with its pace telescope, Wise, and is waiting to be pored over. A new world?...