What Is This?S

This thing looks like a potato or a chunk of root ginger—but it's not. In fact, it's something far larger, and more exciting, but can you guess what it is?

The image was taken just last week by a team of Chinese scientists. The black background and shadow on the object's surface might give you a little clue as to what it is—but we're not giving away the answer just yet.

Instead, we'll post the solution here in an hour or so. Until then, try and work out exactly what it is amongst yourselves in the comments—without cheating and resorting to Google Images.

Update: Here's the answer