protoplanetary nebula
...that a protoplanetary nebula is a short-lived phase of stellar evolution?
...that a <b id="mwCWQ"><a href="./Protoplanetary_nebula" id="mwCWU" rel="mw:WikiLink" title="Protoplanetary nebula">protoplanetary nebula</a></b> is a short-lived phase of <a href="./Stellar_evolution" id="mwCWY" rel="mw:WikiLink" title="Stellar evolution">stellar evolution</a>?