ngc 4921

 ngc 4921 komaa samooh mein ack varjit sarpil akashganga haye, joe komaa berenis nakshatr mein sthit haye. yeh prithvi seey lagbhag 320 million prakaash varsh door haye. akashganga mein ack baar sanrachana key saath ack kendrak haye joe dhool key ack alag valay seey ghiraa huaa haye jisamen haal hii mein baney germ neele sitaare hain. baahari bhaag mein asamanya roop seey chikani, kharaab roop seey vishisht sarpil bhujaaen hoti hain.
1976 mein, kanadai khagolshastri sidney vaine daine burg ney iss akashganga koo "anaemic" key roop mein vargeekrit kiya kyonki cumm darr parr taare bunn rahey hain. unhone kahaa kii isaki satah kii chamak asamanya roop seey cumm haye aur yeh ullekhaniya roop seey faile hue sarpil bhujaaon koo pradarshit kartaa haye. phir bhee, yeh komaa samooh mein sabse chamkili sarpil akashganga haye. 
yeh akashganga samooh key kendra key paas sthit haye aur iska ausat samooh wegg kii tulanaa mein uchch saapeksh wegg (7,560 kimmy/aiss) haye. 21 semi tarang dairdhya hydrogen rekha parr jaanch karane parr, ngc 4921 mein aich. aaee. kii bhaari kamee paaee gaee, joe darshaata haye kii isamen hydrogen cumm haye. hydrogen kaa vitaran bhee see sarpil bhuja kii or gaharaai seey vichalit huaa haye aur akashganga kii optical disk kii tulanaa mein cumm vistaarit haye. yeh antargangiya madhyam key saath baatchit key kaaran hoe sakata haye, joe raam dabaav key madhyam seey gais koo hataa rhaa haye. gais key kuchh tantu joe chheen liye gaye hain, akashganga mein vaapas gir rahey hain, jisase ngc 4921 sambhavatah iss girawat kaa pahala avalokan sakshya haye.
4 maee, 1959 koo iss akashganga mein ack supernova visfot dekhaa gayaa thaa. ell. palomar vedhshala mein schmitt doorbeen kaa upayog karate hue humason. yeh akashganga key kendra seey kaafee door dikhaai diyaa, aur ise aiss. aine. 1959bee key roop mein naamit kiya gayaa thaa. yeh 18.5 key anumaanit shikhar parimaan taka pahunch gayaa. prakaash vakr badey magellanic baadal mein supernova aiss. aine. 1987aeye key samaan saabit huaa, aur yeh "asamanya photometric vyavhaar" pradarshit kartaa haye.

