接近太阳表面中心之处,一个黑子群清晰可见。
Close to the centre of the sun, a group of sunspots is visible.
如果传播路径上有一个黑子区,(声波的)传播时间将会短一些。
If there is a sunspot region along one of these paths, the travel time will be a little bit shorter.
第一位皇家天文学家,约翰·弗拉姆斯蒂德,则在1684年,间隔十年后,观测到了一个黑子。
John Flamsteed, the first Astronomer Royal, observed one in 1684, after a gap of ten years.
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