▁it ▁will ▁have ▁to ▁again ▁resort ▁to ▁the ▁res erves ▁of ▁hydro gen ▁and ▁hel ium ▁in ▁its ▁outer ▁layers ▁and ▁will ▁expand ▁a ▁second ▁time , ▁turning ▁into ▁what ▁is ▁known ▁as ▁an ▁asympt otic ▁giant . ▁Here ▁the ▁lum inos ity ▁of ▁the ▁Sun ▁will ▁increase ▁again , ▁reaching ▁about ▁ 2 , 0 9 0 ▁present ▁lum inos ities , ▁and ▁it ▁will ▁cool ▁to ▁about ▁ 3 5 0 0   K . ▁This ▁phase ▁last s ▁about ▁ 3 0   mill ion ▁years , ▁after ▁which , ▁over ▁the ▁course ▁of ▁a ▁further ▁ 1 0 0 , 0 0 0   year s , ▁the ▁Sun ' s ▁remaining ▁outer ▁layers ▁will ▁fall ▁away , ▁e ject ing ▁a ▁vast ▁stream ▁of ▁matter ▁into ▁space ▁and ▁forming ▁a ▁h alo ▁known ▁( mis leading ly ) ▁as ▁a ▁planet ary ▁ne b ula . ▁The ▁e ject ed ▁material ▁will ▁contain ▁the ▁hel ium ▁and ▁carbon ▁produced ▁by ▁the ▁Sun ' s ▁nuclear ▁re actions , ▁continu ing ▁the ▁en rich ment ▁of ▁the ▁inter stell ar ▁medium ▁with ▁heavy ▁elements ▁for ▁future ▁gener ations ▁of ▁stars . ▁ ▁This ▁is ▁a ▁relatively ▁peace ful ▁event , ▁nothing ▁a kin ▁to ▁a ▁super n ova , ▁which ▁the ▁Sun ▁is ▁too ▁small ▁to ▁under go ▁as ▁part ▁of ▁its ▁evolution . ▁Any ▁observer ▁present ▁to ▁witness ▁this ▁occurrence ▁would ▁see ▁a ▁massive ▁increase ▁in ▁the ▁speed ▁of ▁the ▁solar ▁wind , ▁but ▁not ▁enough ▁to ▁destroy