In a large saute pan, with deep sides, bring the nectarines, orange juice, sugar and tarragon to a boil. Reduce the heat to medium and simmer until the nectarines are very tender, 8 to 10 minutes.

Transfer the fruit mixture to a bowl and alow it to cool to room temperature. Stir in the yogurt.

Working in batches, puree the soup using a blender, food processor, or hand blender until smooth. Chill for at least 2 to 3 hours and serve cold.