For astronomical calculations, days are specified as the number of days from a reference point — you don't need to identify years, months, or weeks.
对于天文的计算，天被指定为从一个参照点开始的天的数量——不必识别年、月或者星期。
2
Three studies, presented at a meeting of the American Astronomical Society's solar physics division, all point towards declining sunspot activity into the next decade.
3项发表在美国天文学会的太阳物理学分部会议上的研究都表明，下一个十年中太阳黑子活动将有所衰弱。
3
The mirror of an astronomical telescope forms at its focal point an image of a star on the axis of the mirror.