[xp38]

The discovery of Sedna – 10 billion kilometres from Earth – is a testament to the new generation of high-powered telescopes.

10 billion kilometers is approximately 6 billion miles. Is that a typo in the article?

[SunkenCiv]

The distance from Earth to any other body in orbit around the Sun (or in orbit around such an object) varies depending on where the Sun is in relation to both. Sometimes Jupiter is about 600 million miles away, sometimes about 400 million.

This new object is on a tremendously eccentric orbit, so it's quite far away right now.

Similarly, Pluto is an average distance from the Sun (radius) of 5,913,520,000 km, making the diameter, hmm, something like 11 billion km (because at some point it's closer to the Sun than Neptune and more eccentric).

Hope that helps.