DUNIYOYI UKU DA YA KAMATA A CE AN HAƊIYE SU

A ƙarshen rayuwarsa, tauraro kamar Rana yana hawa abin da masana falaki ke kira reshen ƙattan taurari ja (red-giant branch): layukansa na waje suna kumbura da darajoji da dama na girma (orders of magnitude). Jan igiyar ruwa (tides) da asarar nauyin tauraron ya kamata su jawo ciki kuma su haɗiye duk wata duniya da ke kewaya shi a kusa sosai — cikin kusan astronomical unit ɗaya (tazarar Duniya da Rana) ga taurari irin Rana. Binciken taurari da suka tsufa yana samun ƙattan duniyoyi kaɗan ƙwarai a kan gajerun kewayoyi.

A ƙolin wannan reshe, helium yana kama wuta a cibiyar tauraron, kuma tauraron yana sake raguwa. Yana zama a wani mataki ƙarami da ake kira red clump (tarin ja), yana ƙona helium a cibiyarsa. Don haka duk wata duniya da aka gani kusa da tauraron red clump dole ne ta tsallake lokacin da tauraronta yake a mafi girmansa. Har zuwa yanzu, duniya ɗaya kawai irin wannan “haramtacciya” aka ba da rahotonta.

Sauraron taurari

Wahalar ita ce bambance matakan biyu. Ƙaton tauraro da ke kan hanyarsa ta hawa da ƙaton tauraro a kan red clump suna kama da juna a haskensu. Amma ba sa girgiza iri ɗaya. Taurari suna kai-da-komo (oscillate), kuma girgizarsu tana bincika yawan (density) cibiyarsu: wannan shi ne asteroseismology (nazarin girgizar taurari).

Wen-Xu Lin, Sheng-Bang Qian da abokan aiki a Yunnan University da Chinese Academy of Sciences sun tantance kowane sanannen tauraro mai duniya ta wannan hanya, ta amfani da lanƙwasar haske (light curves) da aikin TESS ya naɗa. Taurari uku sun fito a matsayin tabbas a kan red clump: 24 Boo, HD 12648 da TYC 4282-605-1. Ƙungiyar sai ta sake nazarin ma’aunan shekaru da dama na girgizar (wobble) kowane tauraro, wadda jan duniyarsa ke haddasawa, daga cibiyoyin lura (observatories) uku.

Kewayoyi a cikin tsohon tauraron

Duniyoyin uku:

• 24 Boo b tana zagaye tauraronta cikin kwana 30.3, a nisan astronomical unit 0.183 — duniya mafi kusa da aka sani a kewayen ƙaton tauraro na red clump. Mafi ƙarancin nauyinta kusan kashi uku cikin huɗu na na Jupiter ne.
• TYC 4282-605-1 b: kwana 101.6, au 0.489, aƙalla sau 14 na nauyin Jupiter.
• HD 12648 b: kwana 132.9, au 0.516, aƙalla sau 2.5 na nauyin Jupiter.

Taurarin kansu yanzu sun fi Rana faɗi kusan sau 10 zuwa 12. Tambayar ita ce faɗinsu a ƙolin reshen ƙattan taurari ja. Ƙungiyar ta lissafa wannan mafi girman radius da samfuran juyin halittar taurari (stellar-evolution models), tana sauya bayanai marasa tabbas na convection (gaurayawar zafi) da abin da taurarin suka ƙunsa (composition). Kewayar 24 Boo b tana ƙasa da kowane lanƙwasa da aka gwada, haka ma ta TYC 4282-605-1 b. HD 12648 b tana kusa da iyakar: damar cewa an haɗiye ta tana sauka daga kusan tabbas zuwa 43% ga saitin convection mafi dacewa.

Samfurin kewayar kanta — asarar nauyi, ja daga iskar tauraro (stellar wind), tides — yana ba da ƙa’ida mai sauƙi: a ƙarƙashin juyin halitta na yau da kullum na tauraro guda ɗaya, duniyar da aka gani a kewayen tauraron red clump bai kamata ta taɓa kewayawa kusa fiye da mafi girman radius da tauraron ya taɓa kaiwa ba. 24 Boo b da TYC 4282-605-1 b suna yi a ƙarƙashin kowane samfurin da aka gwada; ga HD 12648 b, ya dogara da saitin convection.

Nisan kewaya idan aka kwatanta da radius ɗin tauraron da duniyar ke kewaya (host star) ga duniyoyin da aka tabbatar: duniyoyin uku na wannan bincike (lu’u-lu’u ja) suna tsakanin taurari masu girman red clump, a kusa fiye da yadda aka saba. — Hoto na 2d, Lin da abokan aiki (2026), arXiv:2611.04544.

Ta yaya za su tsira?

Marubutan sun lissafa yiwuwa, a fili a matsayin ra’ayoyi ba hanyoyin da suka tabbatar ba:

1. Tarihin taurari biyu (binary). Idan tauraron da duniya ke kewaya ya taɓa musayar nauyi da abokin tafiyarsa, ko ya haɗe da shi, ƙila lulluɓinsa (envelope) bai taɓa kumbura sosai haka ba. Girgizar 24 Boo tana nuna haɗi (coupling) mai rauni fiye da yadda aka saba ga tauraron da ke da ƙarancin abubuwa masu nauyi (heavy elements) haka, alamar cewa ƙila tarihinsa ba na tauraro guda ɗaya ba ne. Abin da haɗewa ta samar zai iya kuma riƙe ko sake gina faifai (disk) inda duniyoyi na “ƙarni na biyu” za su iya samuwa.
2. Faifai daga duniyar da aka haɗiye. Idan an haɗiye wata duniya ta ciki, makamashin (energy) da ta zuba a cikin tauraron zai iya fitar da iskar gas zuwa wani faifai na wucin gadi, wanda zai iya jawo wata duniya ta waje da ta tsira zuwa ciki bayan tauraron ya ragu.
3. Tsira da ƙyar. Wata duniya ƙila ta nutse cikin lulluɓin da ya kumbura kusa da ƙolin reshen, sannan ta sake samun kanta a waje saboda lulluɓin ya ja baya da sauri fiye da yadda kewayarta ta ragu.

Kama wata duniya mai yawo ita kaɗai (free-floating planet) ko sake tsara duniyoyi a cikin tsarin mai duniyoyi da yawa ana ganin ba su da yiwuwa sosai.

Duniya haramtacciya ɗaya abin mamaki ne kawai (anomaly). Da uku, marubutan suna magana game da sabon rukuni na tsarin duniyoyi da suka tsufa — da kuma kimiyyar lissafi (physics) a kewayen taurari masu tsufa wadda samfuran yanzu ba su ƙunsa ba tukuna.