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There’s something odd floating around in the outer solar system. Actually, there’s lots of odd things floating around in the outer solar system, but 2002 UX25 is one of the most baffling. The mid-sized Kuiper belt object (KBO) measures 650 kilometers (400 miles) across, and yet it has a density less than water (less than 1 gram per cubic centimeter). Yes, if you put it in a huge bathtub, 2002 UX25 would float. ...planetary scientist Mike Brown, of the California Institute of Technology (Caltech) in Pasadena, has taken a measure of 2002 UX25′s density and discovered that it is “the...

Many galaxies appear to have stronger gravity - and thus more mass - than can be explained by their visible matter alone. Overly massive galaxies are most often attributed to dark matter, an invisible substance that interacts with matter through gravity. To date, though, no one has directly detected dark matter particles. But a well-established notion in physics could hold another explanation for their size. This says that empty space is really a frothy, turbulent sea full of virtual particles - matter and antimatter that spring in and out of existence so fast that we can't see them. Though they...

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....

A distant, icy rock whose discovery shook up the solar system and led to Pluto's planetary demise has been given a name: Eris. The christening of Eris, named after the Greek goddess of chaos and strife, was announced by the International Astronomical Union on Wednesday. Weeks earlier, the professional astronomers' group stripped Pluto of its planethood under new controversial guidelines. Since its discovery last year, Eris, which had been known as 2003 UB313, ignited a debate about what constitutes a planet. Astronomers were split over how to classify the object because there was no universal definition. Some argued it should...

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....

When is a planet not a planet? That is what astronomers will be asking themselves after yesterday's announcement of the biggest planetary body discovered in the solar system in more than 70 years. The new body, called Quaoar (pronounced Kwah-o-ar), is a round world that orbits the sun every 288 years, at a distance greater than that of any of the nine planets. At 1250 kilometres wide, it is bigger than any of the asteroids. In fact, it is bigger than all the asteroids put together. But it is also just over half the size of the smallest planet in...

2015 TG387, a newfound object in the far outer solar system, way beyond Pluto. The orbit of 2015 TG387 shares peculiarities with those of other extremely far-flung bodies, which appear to have been shaped by the gravity of a very large object in that distant, frigid realm — the hypothesized Planet Nine, also known as Planet X. "These distant objects are like breadcrumbs leading us to Planet X," And 2015 TG387 is special among these bread crumbs, because it was found during a relatively uniform survey of the northern and southern skies rather than a targeted hunt for clustered objects...

Don't sleep on NASA's New Horizons spacecraft. The history-making probe, which famously zoomed past Pluto in July 2015, is closing in on its next flyby target, a frigid chunk of ice and rock about 4 billion miles (6.4 billion kilometers) from Earth dubbed Ultima Thule.  New Horizons is now just 80 million miles (130 million km) from Ultima Thule, mission members said Wednesday (Sept. 19). That's less than the distance from Earth to the sun (about 93 million miles). [Destination Pluto: NASA's New Horizons Mission in Pictures]  The spacecraft has already begun photographing Ultima Thule for navigation purposes and remains...

MU69 is a relatively small Kuiper Belt object. It is estimated to have a diameter of 30 miles (48 km) — that’s more than 10 times larger and 1,000 times more massive than typical comets, but only about 0.5 to 1% of the size of the dwarf planet Pluto. This object was discovered in June 2014 by astronomers using the NASA/ESA Hubble Space Telescope.Also known as PT1 and 1110113Y, and nicknamed Ultima Thule, MU69 orbits the Sun once every 293 years at a distance of more than 4 billion miles (6.5 billion km) from Earth.The MU69 flyby will be the...

More clues about where to search for a possible ninth planet lurking in the fringes of our solar system are emerging from the Kuiper belt, the icy debris field beyond Neptune. And new calculations suggest that the putative planet might be brighter — and a bit easier to find — than once thought. Evidence for the existence of Planet Nine is scant, based on apparent alignments among the orbits of the six most distant denizens of the Kuiper belt (SN: 2/20/16, p. 6). Their oval orbits all point in roughly the same direction and lie in about the same plane,...

Explanation: The night side of Pluto spans this shadowy scene. The spacebased view with the Sun behind the distant world was captured by New Horizons last July. The spacecraft was at a range of over 21,000 kilometers, about 19 minutes after its closest approach. A denizen of the Kuiper Belt in dramatic silhouette, the image also reveals Pluto's tenuous, surprisingly complex layers of hazy atmosphere. The crescent twilight landscape near the top of the frame includes southern areas of nitrogen ice plains informally known as Sputnik Planum and rugged mountains of water-ice in the Norgay Montes.

There may be an alien planet lurking within Earth's own solar system. If the hypothetical Planet Nine does indeed exist, the sun probably ripped the world away from another star long ago, a new study suggests. "It is almost ironic that while astronomers often find exoplanets hundreds of light-years away in other solar systems, there's probably one hiding in our own backyard," study lead author Alexander Mustill, an astronomer at Lund University in Sweden, said in a statement. [The Evidence for Planet Nine in Pictures]. Earlier this year, astronomers Konstantin Batygin and Mike Brown, both of the California Institute of...

Known as 2014 MU69, the object is thought to be unchanged since the birth of the solar system 4.6 billion years ago.... ... Johns Hopkins Applied Physics Laboratory in Laurel submitted plans last month to NASA to fly past the relatively tiny chunk of icy matter on New Year's Day 2019. If NASA approves it, the extended New Horizon mission could give a close-up view of what has so far only appeared to scientists as a faint dot of light. ... The object is in a 300-year orbit around the sun in the Kuiper Belt, a region of space beyond...

And this new planet could be huge. Back in January, the astronomer who led the charge to have Pluto demoted to dwarf planet status announced that he’d just found evidence that a huge, icy planet could be lurking on the edge of the Solar System, just past Neptune. Mike Brown, a planetary astronomer at Caltech University, estimated that the hypothetical 'Planet Nine' appears to be circling the Sun on a super-elongated orbit that takes an incredible 10,000 to 20,000 years to complete. And now, thanks to a newly detected Kuiper Belt Object (KBO) that’s acting really strange, Brown says the...

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...

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...

In July, New Horizons crosses the next great frontier in our solar system. Mankind is about to visit one of the strangest places in our solar system. Out beyond Neptune, the Kuiper belt is home to hordes of cold, lumpy worlds -- some of which are large enough to have their own moons, but none of which we've seen up-close before. That's going to change this summer, when NASA's New Horizons spacecraft flies by "the king of the Kuiper belt": Pluto. It's no longer considered a planet, but Pluto is still an important member of our solar system, and one...

Beyond Neptune lies a reservoir of... icy debris left to roam the solar system's dim outer limits having never coalesced into planets... Named for astronomer Gerard Kuiper, who in 1951 predicted the existence of this 3-billion-kilometer-wide swath of icy chunks, the Kuiper belt didn't begin to reveal itself to observers until 1992. Since then, researchers have found more than a thousand bodies filling a doughnut-shaped belt, which extends 30 to about 50 astronomical units from the sun. One astronomical unit is the average distance between the Earth and sun... The puffed-up, elongated orbits and present-day sparseness of the belt all...

The question about the origin of oceans on Earth is one of the most important questions with respect to the formation of our planet and the origin of life. The most popular theory is that water was brought by impacts of comets and asteroids. Data from the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument aboard the European Space Agency’s Rosetta spacecraft indicate that terrestrial water did not come from comets like 67P/Churyumov-Gerasimenko. The findings were published today in the journal Science. Researchers agree that water must have been delivered to Earth by small bodies at a later...

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...