Glossary term: 近地天體
Description: 除了太陽和行星，太陽系還包含許多較小的天體，特別是小行星和彗星。小行星或彗星與地球相撞會帶來災難性的後果。到目前為止，我們所知道的天體中還沒有一個會與地球相撞，但還是有一些天體值得我們關注。任何小行星或彗星在其軌道上接近太陽的距離超過地球-太陽距離的 1.3 倍（天文學術語：1.3 天文單位），都被稱為近地天體（NEO）。大多數近地天體都是近地小行星（NEA）。
如果近地天體具有以下特性，則被稱為潛在危險天體（PHO）：首先，它需要比地球-太陽距離的 5%（比 0.05 個天文單位）更接近地球軌道。此外，這種天體還需要有一定的大小--否則就不會對地球構成威脅。太陽系中較小天體的大小很難測量，因此天文學家採用了絕對亮度的最小值來代表--畢竟，天體越大，亮度就可能越高。要成為 PHO，天體的絕對亮度必須達到或超過 22.0 等（天文學測量亮度的標準方法是等級制）。大多數 PHO 都是潛在危險小行星（PHA）。
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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher The translation of this term and its definition is still awaiting approval
This is an automated transliteration of the simplified Chinese translation of this term
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