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...for astronomer Scott Sheppard of the Carnegie Institution for Science in Washington DC, it was a much quieter affair. "It wasn't like there was a eureka moment," he says. "The evidence just built up slowly." He's a master of understatement. Ever since he and his collaborator Chad Trujillo of Northern Arizona University, first published their suspicions about the unseen planet in 2014, the evidence has only continued to grow. Yet when asked how convinced he is that the new world, which he calls Planet X (though many other astronomers call it Planet 9), is really out there, Sheppard will only...

( Video at Link) A newly discovered object is the most-distant body ever observed in the solar system — and the first object ever found orbiting at more than 100 times the distance from Earth to the sun. The discovery team nicknamed the object "Farout," and its provisional designation from the International Astronomical Union is 2018 VG18. Preliminary research suggests it's a round, pinkish dwarf planet. The same team spotted a faraway dwarf planet nicknamed "The Goblin" in October. A newly discovered object is the most-distant body ever observed in the solar system — and the first object ever found...

The discovery team nicknamed the object "Farout," and its provisional designation from the International Astronomical Union is 2018 VG18. Preliminary research suggests it's a round, pinkish dwarf planet. The same team spotted a faraway dwarf planet nicknamed "The Goblin" in October. The object is more than 3.5 times the current distance between Pluto and the sun (34 AU), and it outpaces the previous farthest-known solar system object, the dwarf planet Eris, which is currently about 96 AU from the sun. NASA's Voyager 2 spacecraft recently entered interstellar space at about 120 AU, leaving the sun's "sphere of influence" called the...

A team of astronomers has discovered the most-distant body ever observed in our Solar System. It is the first known Solar System object that has been detected at a distance that is more than 100 times farther than Earth is from the Sun. ..." The Magellan observations confirmed that 2018 VG18 is around 120 AU, making it the first Solar System object observed beyond 100 AU. Its brightness suggests that it is about 500 km in diameter, likely making it spherical in shape and a dwarf planet."

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...

The paper ... noted that a number of large, very remote objects share a similar orbital angle. That's suspicious if you're an astronomer expecting to see a random distribution of objects. The key orbital feature is known, rather obtusely, as the “argument of perihelion.” We're not shy of complicated orbital concepts (we try to toss around the phrase "obliquity of the ecliptic" whenever possible), but this one is not very easy to explain. "The argument of perihelion is the angle at which an object comes to perihelion with respect to the ecliptic plane," Sheppard said in an e-mail. Mike Brown,...

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...