'Walnut' asteroid will fly "comparatively close" to Earth: astronomer An American astronomer describes what will happen when an asteroid nicknamed 'Walnut' will fly by Earth just 4.8 million kilometers away: "it doesn’t threaten us, but on solar system scales, it is kind of nearby." This rare event is " a chance to make another measurements, see how its orbit is changing, and see if downstream it poses a threat" explains the curator of the famous Griffith Observatory in Los Angeles. IMAGES AND SOUNDBITES