ates ▁into ▁a ▁dens er ▁region ▁that ▁is ▁he ated ▁and ▁forms ▁the ▁visible ▁inf ra red ▁shape . ▁ ▁The ▁term ▁" d ust ▁wave " ▁is ▁applied ▁when ▁the ▁dust ▁p iles ▁up ▁but ▁the ▁gas ▁is ▁largely ▁una ffect ed , ▁as ▁opposed ▁to ▁a ▁" bow ▁wave " ▁where ▁both ▁dust ▁and ▁gas ▁are ▁stopped . ▁ ▁D ust ▁waves ▁occur ▁when ▁the ▁inter stell ar ▁medium ▁is ▁sufficiently ▁dense ▁and ▁the ▁stell ar ▁wind ▁sufficiently ▁weak ▁that ▁the ▁dust ▁stand - off ▁distance ▁is ▁larger ▁than ▁the ▁stand - off ▁distance ▁of ▁a ▁bow ▁shock . ▁ ▁This ▁would ▁clearly ▁be ▁more ▁likely ▁for ▁slow - mov ing ▁stars , ▁but ▁slow - mov ing ▁l umin ous ▁stars ▁may ▁not ▁have ▁lif et imes ▁long ▁enough ▁to ▁produce ▁a ▁bow ▁wave . ▁ ▁Low ▁lum inos ity ▁late ▁class ▁O ▁stars ▁should ▁commonly ▁produce ▁bow ▁waves ▁if ▁this ▁model ▁is ▁correct . ▁ ▁References ▁ ▁External ▁links ▁Turn ▁Left ▁at ▁Or ion ▁N aked ▁eye ▁and ▁teles cop ic ▁views ▁ σ ▁Or ion is ▁Research ers ▁page ▁at ▁Instituto ▁de ▁Ast ro f ís ica ▁de ▁And al uc ía ▁January ▁double ▁star ▁Ob ser ving ▁guide ▁from ▁Astronom ical ▁Society ▁of ▁Southern ▁Africa ▁Bright ▁and ▁Multiple ▁Stars ▁Gallery ▁taken ▁at ▁F res no ▁State ' s ▁Camp us ▁Observ atory , ▁largely ▁by ▁students ▁ ▁Category : Or ion ▁( const ell ation ) ▁Category : Or ion ▁M ole cular ▁Cloud ▁Complex ▁ 5