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Puny Dwarf Planet, Named 'Goblin,' Found Far Beyond Pluto
A scrawny dwarf planet nicknamed "the Goblin" has been discovered well beyond Pluto.
A round frozen world just 186 miles (300 kilometers) across, the Goblin was spotted by astronomers in 2015 around Halloween, thus its spooky name. But it wasn't publicly unveiled until Tuesday following further observations with ground telescopes.
小妖精（Goblin）是一个直径仅186英里（300公里）的圆形冰冻星球，它在2015年万圣节前后被天文学家发现，因而得名。但直到星期二地面望远镜的进一步观测之后，它才被公之于众。
Scott Sheppard of the Carnegie Institution for Science, one of the astronomers who made the discovery, said the Goblin is on the small end for a dwarf planet. It is officially known as 2015 TG387 by the International Astronomical Union's Minor Planet Center.
This is the third dwarf planet recently found to be orbiting on the frigid fringes of our solar system.
Goblin's orbit is extremely elongated — so stretched out, in fact, that it takes 40,000 years for it to circle the sun.
At its most distant, the Goblin is 2,300 times farther from the sun than Earth. That's 2,300 astronomical units, or AU. One AU is the distance from Earth to the sun, or roughly 93 million miles (150 million kilometers).
At its closest, the Goblin is 65 times farther from the sun than Earth, or 65 AU. Pluto, by comparison, is approximately 30 to 50 AU.
Sheppard, along with Northern Arizona University's Chad Trujillo and the University of Hawaii's David Tholen, spotted the Goblin in October 2015 when it was relatively nearby — around 80 AU.
The two other dwarf planets are Sedna, discovered in 2003, which is about 620 miles (1,000 kilometers) across, and 2012 VP113, about 310 miles (500 kilometers). They were found by some of the same astronomers.
Thousands — even a million — more such objects could be way out there orbiting in the so-called Inner Oort Cloud, according to the researchers. They're in hot pursuit of them, as well as a potentially bigger-than-Earth planet known as Planet 9, or Planet X, believed by some scientists to be orbiting at a distance of hundreds of AU.
"These objects are on elongated orbits, and we can only detect them when they are closest to the Sun. For some 99 percent of their orbits, they are too distant and thus too faint for us to observe them. We are only seeing the tip of the iceberg,'' Sheppard said in an email.
Sheppard said the faraway objects are "like bread crumbs leading us to Planet X.''
"The more of them we can find, the better we can understand the outer solar system and the possible planet that we think is shaping their orbits — a discovery that would redefine our knowledge of the solar system's evolution,'' he said in a statement.

巴特西

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