New Planet - Where is Xena?
Where is "Xena"?
It's believed that the "10th planet" originated in the Kuiper Belt, a region beyond the orbit of Neptune and extending out perhaps 30 times the distance from Earth to the Sun.
The belt is believed to contain space rocks and other debris - including many comets - left over from formation of the Solar System. But comets aren't all the Kuiper Belt contains. In just the last two years, in fact, astronomers have found several objects ranging in size from about half that of Pluto up to the current 1.5-times-Pluto-size of planet "Xena".
It's believed that gravitational tugs from the outer planets alter the orbits of some Kuiper Belt objects, causing them to journey sunward and form medium-period comets like the famous Halley's Comet, as well as short-period comets that orbit the Sun in 20 years or less. It's also believed that gravitational tugs send objects outwards to orbit the Sun at great distances, and this appears to be the case "Xena", Sedna and other Kuiper Belt Objects.
As the accompanying diagram shows, "Xena" is in a highly elongated orbit that takes it out well beyond the realm of Pluto and then back in again. At its closest point, "Xena" comes within 38 AU (one AU equals the distance from the Earth to the Sun, or about 93 million miles) of the center of the Solar System. Then, 274 years later, it's out 97 AU, or some 9 billion miles from the Sun.
Currently, the planet is about as far away as it can get. Owners of big telescopes - those 14 inches and larger - can see the new planet in the constellation Cetus in the hours before dawn during the first half of August.