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Sararin samaniyaMasana sun tantanceNazarin bayanaiKaratun minti 4

TAURARI KORE KAƊAI DA AKA SANI FARAREN DODANNI NE

Duba sararin samaniya da dare, launukan taurari ba su da ƙarfi amma na gaske ne: Betelgeuse da Antares suna kama da ja-ja, Sirius da Rigel kuma ɗan shuɗi-shuɗi. Ga taurari na yau da kullum, launi ma’aunin zafi ne. Hasken su yana bin na wani jiki mai zafi na misali, baƙin jiki (blackbody), wanda yake tafiya daga lemu zuwa fari zuwa shuɗi yayin da yake ƙara zafi.

Amma yawancin taurari sun yi nisa da yawa ba za a iya ganin su da ido kawai ba, kuma ko ta na’urar hangen nesa, ido ba ya iya tantance launi sosai cikin duhu. Hotuna masu launuka na ilimin taurari galibi launin ƙarya ne: Sloan Digital Sky Survey, misali, yana sanya ratsinsa i, r da g a kan ja, kore da shuɗi, ko da yake idon ɗan adam yana rufe ratsin g da r ne kawai. Yana da amfani ga kimiyya, amma yana ɓatarwa game da ainihin yadda taurarin suke.

Sararin iska mai cunkoso kamar ruwa

Fararen dodanni su ne ragowar da yawancin taurari suke bari bayan sun mutu, masu matuƙar cunkoso. Sararin iskokinsu na iya matsuwa ƙwarai — har zuwa kusan gram 1 a kowane santimita mai kubi ga mafi sanyi, wato cunkoson ruwa. A irin wannan yanayi, ƙwayoyin zarra na carbon, calcium ko sodium suna shanye haske a cikin ratsi masu matuƙar faɗi, faɗin ɗaruruwa zuwa dubban ångström. Hasken da ya tsere na iya yin nisa sosai da na baƙin jiki.

Mark Hollands, Boris Gänsicke da Pier-Emmanuel Tremblay na Jami’ar Warwick, tare da Detlev Koester na Jami’ar Kiel, sun yi wata tambaya mai sauƙi da babu wanda ya amsa ga waɗannan taurari: wane launi za su nuna ga ɗan adam da yake kusa har yana iya ganin fayafayansu?

Daga bakan haske zuwa allo

Amsar ta fito ne daga kimiyyar launi, fannin da ke daidaita allon kwamfuta da hasken wuta. Ƙungiyar ta haɗa (integrated) kowane bakan haske (spectrum) a kan lanƙwasan misali da ke bayyana yadda idon ɗan adam yake jin haske (ayyukan daidaita launi na CIE 1931, CIE 1931 colour-matching functions), sannan ta mayar da sakamakon zuwa sararin launi na misali na allon kwamfuta, sRGB. Don tabbatarwa, samfurin Rana yana fitowa a matsayin fari mai ɗan ɗumi kaɗan, lambar hex #FFF1EC; farin dodo na hydrogen mai digiri 10,000 kuma, shuɗi mai kodadde.

Sun yi amfani da wannan a kan samfuran sararin iska, a kan bakan haske da dama da aka lura da su waɗanda aka zaɓa saboda baƙuntarsu, da kuma a kan cikakkiyar ƙidaya ta fararen dodanni 152 da ke tsakanin parsec 20 daga Rana.

Tarin launukan matattun taurari

Fararen dodanni masu sararin iska na hydrogen ko helium zalla suna aiki kusan kamar baƙin jiki. Sauran ba haka ba ne.

  • Ruwan hoda da shunayya. Fararen dodanni masu yawan carbon, waɗanda ƙwayoyin C₂ ɗinsu suke shanye ratsi masu faɗi a tsakiyar hasken da ake gani, suna faɗuwa ƙasa da launukan baƙin jiki. Ɗaya daga cikinsu, WD J1011+2845, mai nisan parsec 14.7, yana fitar da yawancin hasken da ake gani fiye da nanomita 600. Launinsa ruwan hoda ne mai zurfi irin na salmon — a cewar marubutan, mai yiwuwa shi ne tauraro mafi ja da aka sani ta fuskar launin da ake gani.
  • Shuɗi-kore (cyan). Wasu fararen dodanni masu sanyi da ke da gaurayen hydrogen da helium, hasken su ja da na infrared ana shanye shi ta ƙwayoyin da ke karo da juna. Mafiya tsanani daga cikinsu suna zama cyan.
  • Rawaya. A WD J0744+4649, calcium yana haɗiye yawancin hasken da ke ƙasa da nanomita 460: tauraron ba lemu ba ne, amma rawaya.
  • Kore. WD J1330+6435, a digiri 4,240, hasken sa na lemu sodium ne ke shanye shi, na shunayya kuma calcium. Abin da ya rage yana kai kololuwa a kusan nanomita 500: kore mai haske (chartreuse). Marubutan ba su san wani tauraro na kowane iri da aka ce kore ne ba, wanda ke sa fararen dodanni su zama, har yanzu, hanya ɗaya tilo da aka sani ta samar da tauraro kore. Bakan haskensa yana da ɗan hayaniya, sun lura, amma wani tsohon samfuri yana ba da launi mai kama da haka.
  • Shuɗi a digiri 4,000. WD J2356−2054 yana da kusan digiri 4,000 kawai, amma sodium yana share tsakiyar hasken sa da ake gani sosai har yake kama da shuɗi mai haske — ya fi kowane baƙin jiki shuɗi, don haka ba za a ma iya ba shi zafin launi (colour temperature) ba.

Farare ne bayan komai

Ƙidayar maƙwabtan parsec 20 tana ba da labari mafi natsuwa. Kusan 3.4% ne kawai na waɗannan fararen dodanni ke kauce wa launukan baƙin jiki a fili: rawaya biyu da ruwan hoda uku. Ga sauran 147, zafin launinsu yana tsakanin digiri 3,000 zuwa 25,000, kuma tsakiyarsu (median), kelvin 6,768, tana ba da lambar hex #F9F5FF — mai matuƙar kusanci da farin misali na allon kwamfuta. Marubutan sun yarda cewa hakan ya ɗan ba su dariya: hoton da aka saba da shi na fararen dodanni masu shuɗi-shuɗi ba wakili ba ne na gaskiya, son kai ne na binciken sararin samaniya da ke fifita taurari masu haske da zafi. A matsakaici, fararen dodanni da gaske farare ne.

Zana fayafayan

Ƙungiyar ta kuma samar da hotunan fayafayan kansu, tana la’akari da yadda tauraro yake ƙara duhu zuwa gefensa. Ga fararen dodanni na hydrogen, fayafayan suna kama da kusan shimfiɗaɗɗu. Ga masu yawan carbon da ƙarafa, gefen yana ƙara duhu sosai har ma yana sauya launi: kore WD J1330+6435 yana zama lemu a cikin pixels na ƙarshe na gefen fayafansa. Fuskokin waɗannan taurari har yanzu sun fi kowane allo haske nesa ba kusa ba, amma marubutan suna sa ran waɗannan hotuna za su yi amfani wajen yaɗa ilimi ga jama’a. Suna kuma sa ran ƙarin abubuwan mamaki: tsakanin tauraro kore da shuɗin, wasu fararen dodanni kore, cyan da shuɗi masu haske mai yiwuwa suna jira a binciken sararin samaniya na gaba.