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“If Planet Nine is real, it would be on such an odd orbit and so far out in the outer Solar System, that it would really challenge our ideas of planet formation and dynamics,” Ann-Marie Madigan, assistant professor of astrophysics... Madigan isn’t searching for just one planet — she’s looking for an entire belt of celestial objects. Like Planet Nine, this proposed Zderic-Madigan, or ZM, belt would be really out there, far beyond the Kuiper belt, with some of its closest bodies being more than twice as far from the Sun as Pluto at perihelion. Unlike the Kuiper belt, this...

From the start, Sedna was an odd-ball. Its 11,400 year orbit takes it from a perihelion of 76 astronomical units (for context, Neptune is an average of 30 AUs from the Sun) to an amazing 936 AUs from the Sun. (A thousand AUs is 1.6% of a light year, and 0.4% of the way to Proxima Centauri, the closest star to our solar system). Currently at a distance of 86 AU and headed towards perihelion in 2076, we’re lucky we caught Sedna as it ‘neared’ (we use the term ‘near’ loosely in this case!) the Sun. But this strange path...

Small objects could be rounded worlds, based on likely sizes, experts say. Three relatively bright space rocks recently found in Pluto's neighborhood may be new members of the dwarf planet family, astronomers say. The objects were discovered in a little studied section of the Kuiper belt, a region of the solar system that starts beyond the orbit of Neptune and extends 5.1 billion miles (8.2 billion kilometers) from the sun. Astronomer Scott Sheppard, of the Carnegie Institute of Washington, and colleagues found the bodies using the 1.3-meter Warsaw University Telescope at Las Campanas in Chile. The region of the Kuiper...

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....

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...

If you can make sense of it, here's the article: Stellar encounters as the origin of distant Solar System objects in highly eccentric orbits SCOTT J. KENYON AND BENJAMIN C. BROMLEY The Kuiper belt extends from the orbit of Neptune at 30 AU to an abrupt outer edge about 50 AU from the Sun. Beyond the edge is a sparse population of objects with large orbital eccentricities. Neptune shapes the dynamics of most Kuiper belt objects, but the recently discovered planet 2003 VB12 (Sedna) has an eccentric orbit with a perihelion distance of 70 AU, far beyond Neptune's gravitational influence....

Orbit of solar system object SQ372 (blue) compared with the orbits of Neptune Pluto and Sedna (white, green, red). Credit: N. Kaib. Astronomers announced today that a new "minor planet" with an unusual orbit has been found just two billion miles from Earth, closer than Neptune. Using the Sloan Digital Sky Survey, astronomers detected a small, comet-like object called 2006 SQ372, which is likely made of rock and ice. However, its orbit never brings it close enough to the sun for it to develop a tail. Its unusual orbit is an ellipse that is four times longer than it...

Odd orbits of remote objects hint at unseen world, new calculations suggest. An as yet undiscovered planet might be orbiting at the dark fringes of the solar system, according to new research.Too far out to be easily spotted by telescopes, the potential unseen planet appears to be making its presence felt by disturbing the orbits of so-called Kuiper belt objects, said Rodney Gomes, an astronomer at the National Observatory of Brazil in Rio de Janeiro. Kuiper belt objects are small icy bodies—including some dwarf planets—that lie beyond the orbit of Neptune. Once considered the ninth planet in our system, the...

LOS ANGELES - The astronomers who claim to have discovered the 10th planet in the solar system have made another intriguing announcement: it has a moon. While observing the new, so-called planet from Hawaii last month, a team of astronomers led by Michael Brown of the California Institute of Technology spotted a faint object trailing next to it. Because it was moving, astronomers ruled it was a moon and not a background star, which is stationary. The moon discovery is important because it can help scientists determine the new planet's mass. In July, Brown announced the discovery of an icy,...

The European Space Agency is considering a unique experiment that could explain strange gravitational phenomena in the outer solar system. Since 1998 astronomers have known that the space probes Pioneer 10 and Pioneer 11 are following trajectories that cannot be explained by conventional physics. Launched in 1972 and 1973, respectively, to explore the outer planets, the Pioneer craft are now at the edge of the solar system, with Pioneer 10 being some 86 astronomical units (about 13 billion kilometres) from the Sun. But they are not quite where they should be, based on the gravitational pull of the known bodies...

One leading proposal would define a planet as any object whose diameter exceeds 2,000 kilometers and that is round as a result of gravity, criteria that would encompass anything Pluto-size or larger, including Xena. But that doesn't sit well with some astronomers, who are irked that the scrawny iceball with the cockeyed orbit earned membership into the club in the first place. "Pluto is an impostor," says Harvard astronomer Brian Marsden, a member of the IAU committee. "The simplest thing is to get rid of it and say we've got eight."

Scientists are over the moon at the W.M. Keck Observatory and the California Institute of Technology over a new discovery of a satellite orbiting the Solar System's 10th planet (2003 UB313). The newly discovered moon orbits the farthest object ever seen in the Solar System. The existence of the moon will help astronomers resolve the question of whether 2003 UB313, temporarily nicknamed "Xena," is more massive than Pluto and hence the 10th planet. A paper describing the discovery was submitted to the Astrophysical Journal Letters on October 3, 2005. "We were surprised because this is a completely different type of...

In a report published in the January 2005 issue of The Astronomical Journal, planetary scientist Dr. Alan Stern of the Space Science and Engineering Division at Southwest Research Institute (SwRI) shows Sedna could have formed far beyond the distance of Pluto... Stern's Sedna formation simulations assumed that Sedna's original orbit, while distant from the Sun, was circular. Astronomers agree that Sedna could not have formed in its present, eccentric orbit because such an orbit allows only violent collisions that prevent the growth of small bodies. Stern's simulations further assumed that the solar nebula -- the disk of material out of...

SCIENTISTS have found a new world orbiting the solar system – more than 3 billion kilometres further away from the Sun than Pluto and 40 years away from Earth in a space shuttle. NASA is expected to announce today the discovery of the space object, which some experts believe could be a new planet. It is provisionally known as Sedna, after the Inuit goddess of the sea. The discovery of Sedna – 10 billion kilometres from Earth – is a testament to the new generation of high-powered telescopes. Measurements suggest Sedna's diameter is almost 2000km – the biggest find...

A US astronomer has said he had discovered a 10th planet in the outer reaches of the solar system that could force a redrawing the astronomical map. If confirmed, the discovery yesterday by Mike Brown of the respected California Institute of Technology would be the first of a planet since Pluto was identified in 1930 and shatter the notion that nine planets circle the sun. "Get out your pens. Start re-writing textbooks today," said Brown, a professor of planetary astronomy, announcing what he called "the 10th planet of the solar system," one that is larger than Pluto. "It's the farthest...

Astronomers have found a large object in the Solar System's outer reaches. It is being hailed as "a great discovery". Details of the object are still sketchy. It never comes closer to the Sun than Neptune and spends most of its time much further out than Pluto. It is one of the largest objects ever found in the outer Solar System and is almost certainly made of ice and rock. It is at least 1,500km (930 miles) across and may be larger than Pluto, which is 2,274km (1,400 miles) across. The uncertainty in estimates of its size is due to...

The distant planetoid Sedna appears to be covered in a tar-like sludge that gives it a distinctly red hue, a new study reveals. The findings suggests the dark crust was baked-on by the Sun and has been untouched by other objects for millions of years. Sedna appears to be nearly the size of Pluto and was discovered in November 2003. It is the most distant object ever seen within the solar system and travels on an elongated path that stretches from 74 to 900 times the distance between the Sun and the Earth. Astronomers have struggled to explain such an...

Astronomy Picture of the Day Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2004 June 4 Sedna at Noon Illustration Credit: Adolf Schaller, ESA, NASA Explanation: Standing on Sedna - the solar system's most distant known planetoid - your view of the Sun at high noon might look something like this. An artist's dramatic vision, the picture shows the Sun suspended above the nearby horizon as a bright star immersed in the dusty ecliptic plane. Within the dust-scattered sunlight are more...

Our corner of the galaxy got a little stranger this week with the discovery of Sedna, the most distant object ever spotted in the solar system. Now astronomers are puzzling over how it got there. The most intriguing idea is that there might be another world as big as Earth, a gravitational bully lurking in some unexplored corner of the solar system. Here's the problem: Scientists can't figure out how Sedna, which is about three-fourths as big as Pluto, came to have such a strange orbit around the Sun. Sedna's path is highly elliptic. It ranges from 76 astronomical units...

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...