To see such a planet, which is less than a billionth as bright as its host star, astronomers have to block out the star using a small opaque disk known as a coronagraph.

• 为了观察这类行星，由于其亮度不到主星的10亿分之一，天文学家必须利用日冕仪（不透明的小圆盘）来挡住恒星。