If going in this direction, I’d want justification for position and age still being separate elements. Elements are clearly suitable or necessary when you want multiple values, order-sensitivity, or to contain something other than a single text value. But that’s not the case here, and I find “hierarchical structure” or “property grouping” to be weak justification.

So then:

  <star
    bayerName="Beta Pictoris"
    spectralType="A6V"
    mass="1.75"
    luminosity="8.7"
    rightAscension="05h 47m 17.1s"
    declination="−51°03′59″"
    distance="63.4ly"
    minAge="20My"
    maxAge="24My"/>

We are, of course, playing into the article’s second footnote here.

(Also: I’m curious why you turned the original document’s ″ (U+2033 DOUBLE PRIME) into " (", U+0022 QUOTATION MARK).)