Sentence:  Brown clicked on a button to have the computer calculate just how far away the object was, and came up with a distance farther than Pluto, even farther than <WSD>Sedna</WSD>: about 97 AU. Then he ran some quick calculations to estimate how big the object was, assuming that it was as reflective as <WSD>Sedna</WSD>. 
Meaning of the word marked with <WSD> tags:  (Q15610) (90377 Sedna), a trans-Neptunian object, possibly a dwarf planet, whose eccentric detached orbit is wholly beyond the Kuiper belt.