But as NPR's Joe Palca reports close is a relative term when it comes to astronomical distance.

但是据npr新闻的乔·帕尔卡报道，谈及天文距离时，“接近”是一个相对的说法。

youdao

This distance is known as the 'astronomical unit' or AU.

这个距离被称为“天文单位”或 AU。

youdao

An astronomical unit is the distance between Earth and our sun.

一个天文单位是地球与太阳之间的距离。

youdao

In 1989, Pluto was as close to the Sun as it gets during its long year - less than 30 astronomical units (AU), or 30 times the distance between Earth and the Sun.

BBC: Scientists plan Pluto flyby

BJ8 sailed past the Earth at a distance of 5m kilometres (3m miles) a pretty close shave by astronomical standards.

ECONOMIST: Celestial mechanics: A rock in a hard place | The