et ▁ ▁X - ray ▁observations ▁offer ▁the ▁possibility ▁to ▁detect ▁( X - ray ▁dark ) ▁plan ets ▁as ▁they ▁eclipse ▁part ▁of ▁the ▁cor ona ▁of ▁their ▁parent ▁star ▁while ▁in ▁trans it . ▁" S uch ▁methods ▁are ▁particularly ▁prom ising ▁for ▁low - mass ▁stars ▁as ▁a ▁Jup iter - like ▁planet ▁could ▁eclipse ▁a ▁rather ▁significant ▁cor onal ▁area ." ▁ ▁As ▁X - ray ▁detect ors ▁have ▁become ▁more ▁sensitive , ▁they ▁have ▁observed ▁that ▁some ▁plan ets ▁and ▁other ▁normally ▁X - ray ▁non - l um ines cent ▁cel est ial ▁objects ▁under ▁certain ▁conditions ▁emit , ▁flu ores ce , ▁or ▁reflect ▁X - ray s . ▁ ▁Com et ▁L ul in ▁ ▁NASA ' s ▁Swift ▁G amma - R ay ▁Bur st ▁Mission ▁satellite ▁was ▁monitoring ▁Com et ▁L ul in ▁as ▁it ▁closed ▁to ▁ 6 3 ▁G m ▁of ▁Earth . ▁For ▁the ▁first ▁time , ▁astronom ers ▁can ▁see ▁simultane ous ▁U V ▁and ▁X - ray ▁images ▁of ▁a ▁com et . ▁" The ▁solar ▁wind — a ▁fast - mov ing ▁stream ▁of ▁particles ▁from ▁the ▁sun — inter act s ▁with ▁the ▁com et ' s ▁bro ader ▁cloud ▁of ▁atoms . ▁This ▁causes ▁the ▁solar ▁wind ▁to ▁light ▁up ▁with ▁X - ray s , ▁and ▁that ' s ▁what ▁Swift ' s ▁X RT ▁sees ", ▁said ▁Stefan ▁Im ml er , ▁of ▁the ▁God d ard ▁Space ▁Fl ight ▁Center . ▁This