HASKEN GAMMA NA MILKY WAY: ALAMA CE, KO LOKACI MARAS KYAU?

Fermi Large Area Telescope tana ganin ƙarin hasken gamma na kusan gigaelectronvolt ɗaya (GeV, ma’aunin ƙarfi na ƙananan ƙwayoyi) da ke fitowa daga kusan digiri 10 na tsakiyar Milky Way fiye da yadda sanannun maɓuɓɓuga da samfuran hasken da ke yaɗuwa na damin taurarin za su iya bayyanawa. Isabel Sands, ta Kavli Institute for Astrophysics and Space Research a MIT, da Philip Hopkins, na TAPIR a Caltech, sun ce asalinsa tambaya ce da ba a amsa ba tsawon kusan shekaru ashirin. Wasu bincike suna ganin wannan “ƙarin tsakiyar damin taurari” (galactic centre excess) a matsayin ƙwaƙƙwarar shaidar ƙwayoyin ɓoyayyen abu da ke halaka juna suna komawa hasken gamma. Wasu kuma suna danganta shi da maɓuɓɓuga masu kama da ɗigo da ba a rarrabe su ba (unresolved point sources) — wani taro da ya yi rauni har ba za a iya ganinsu ɗaya bayan ɗaya ba — kamar wani sabon rukuni na pulsars na millisecond, matattun taurari da ke juyawa da sauri ƙwarai.

Ɓangarorin biyu duka sun gamu da matsala. Wasu bincike sun gano cewa ƙarin yana bin dunƙulen taurari na tsakiyar damin taurarin (bulge), abin da ke nuni ga asali na falaki (astrophysical). Kuma da alama tsakiyar ba ta da isassun tsarin taurarin da za su haifi pulsars ɗin da ake buƙata.

Damin taurari da aka daskarar a lokaci

Marubutan sun nuna wani rauni da kusan dukan binciken baya suka raba. Don hasashen hasken gamma na “yau da kullum”, suna dogara ga manhajoji da ke ɗaukar hasken sararin samaniya — ƙwayoyi masu caji masu sauri kamar protons, electrons da tsakiyoyin zarra masu nauyi — kamar suna cikin yanayin tsayayye (steady state), an baza su daidai a kewayen gatarin damin taurarin. Irin waɗannan manhajoji ba za su iya bin wani abu da ke canjawa da lokaci ba: iskokin damin taurari, iskar gas da ke ɗaure da filayen maganaɗisu, hargitsi (turbulence).

A cikin kwaikwayon da aka yi amfani da su a nan, supernovae ne ke harba hasken sararin samaniya. Yayin da suke tafiya, suna samar da hasken gamma ta hanyoyi uku, biyu daga cikinsu sun dogara da yawan iskar gas da suka ci karo da ita. Idan aka tsara su a matsayin hazo mai natsuwa da aka ɗauki matsakaicinsa, duk wani rashin daidaito na gaske yana saura a matsayin ragowar da ba a bayyana ba.

Milky Way biyu na kama-da-wane

Sands da Hopkins sun ɗauki damin taurari uku da aka kwaikwaya masu kama da Milky Way daga aikin FIRE-2, waɗanda aka girmar tun farkon sararin halitta tare da filayen maganaɗisu, iskar gas da nau’o’in ƙwayoyin hasken sararin samaniya da dama. An cire ɗaya, m12i, saboda faifansa ya lanƙwasa sosai, ba kamar namu ba. Sai ya rage m12f, mai faifai mafi shimfiɗa, da m12m, mai dunƙule mafi bayyana. Babu ɗayansu da ya haɗa da hasken ɓoyayyen abu ko pulsars: hasken gamma kaɗai yana fitowa ne daga hasken sararin samaniya da supernovae suka harba.

Ga kowane damin taurari, ƙungiyar ta gina wani mizani na “natsuwa”: matsakaicin dukan hotunan lokaci (snapshots) — damin taurarin da aka kwaikwaya da aka ajiye a lokuta masu bi da juna — waɗanda jimillar hasken gamma ɗinsu ke ƙasa da tsaka-tsaki (median). Sun cire shi daga kowane hoton lokaci tsakanin shekaru miliyan 460 da miliyan 20 da suka wuce, kuma suka yi nazarin abin da ya rage — ragowar (residuals) — a cikin digiri 10 da 20 na tsakiya.

Yadda kowace tsakiyar damin taurari da aka kwaikwaya ke kaucewa daga matsakaicin natsuwarta, bisa ƙarfi: zirare masu launi sun mamaye rabin tsakiya na dukan hotunan lokaci (siga uku, waɗanda ke ƙirga hasken daga zurfi daban-daban a kan layin ganinmu), kuma baƙaƙen ɗigo suna nuna ƙarin da Fermi ta auna, can cikinsu. — Hoto na 3, Sands & Hopkins (2026), arXiv:2610.32845.

Kumburin da ke zuwa suna tafiya

Ragowar ba sa taɓa zama cak. Ƙari masu faɗin digiri 1 zuwa sama da digiri 10 suna bayyana duk inda wani supernova ko tarin su ya fashe kwanan nan, galibi sun fi wanda Fermi ke aunawa girma sosai. A kowane tsari da aka gwada, ainihin ƙarin yana faɗawa cikin sauƙi a cikin rabin tsakiya na ragowar da aka kwaikwaya (tsakanin kaso na 25 da na 75, wato percentiles). Kusa da kowane wuri mai haske yawanci akwai wanda ya dusashe: fashe-fashen suna tura iskar gas da ke kewaye nesa.

Sannan sai lamarin da ya ba takardar ma’anarta. A cikin hoton lokaci ɗaya na m12f, ragowar tana kama da ƙarin Fermi a girma da siffa duka, kuma kusan zagaye ce a cikin digiri 10 na tsakiya. Tana fitowa ne daga aƙalla tarin supernovae daban-daban guda uku.

Hotunan lokaci goma na damin taurari m12f a cikin shekaru miliyan 100, an yi musu launi bisa tsawon lokacin da ya wuce tun faruwarsu: lanƙwasa mai kauri tana bin ƙarin da Fermi ta auna (baƙaƙen ɗigo) sosai; sauran suna hawa da sauka a kowane ƙarfi. — Hoto na 5, Sands & Hopkins (2026), arXiv:2610.32845.

Dalilin shi ne lokaci. A cikin kiloparsec na tsakiya (kusan shekarun haske 3,260), hasken sararin samaniya yana ɗaukar kusan shekaru miliyan ɗaya kafin ya bazu — kusan daidai da lokacin da iskar gas da ke kewaye, da bakan hasken gamma, ke ɗauka kafin su canza. Yawanci ba sa samun lokacin bazuwa daidai kafin hargitsi na gaba.

An kama shi a lokacin rashin sa’a?

Tsakiyar Milky Way ita ce kaɗai tsakiyar damin taurari da Fermi za ta iya lura da ita dalla-dalla. Zai iya zama dacewa ce kawai, a cewar marubutan, cewa bakanta yana nuna ƙari na 1–10 GeV a yanzu. Suna kiran wannan tasirin duba-wani-wuri (look-elsewhere effect): watakila mun kama damin taurarinmu a lokacin da bai dace ba.

Suna ba da fassara biyu. Ta taka-tsantsan: ta hanyar ɗaukar yanayin tsayayye, binciken baya sun raina rashin tabbas da ke fitowa daga maɓuɓɓuga na yau da kullum gaba ɗaya. Ta tsattsauran ra’ayi: hauhawar wucin gadi a hasken da ke yaɗuwa zai iya bayyana ƙarin ba tare da ɓoyayyen abu ko sababbin pulsars ba. Ko ta yaya, suna jayayya cewa dole ne a sake duba samfuran da ake amfani da su wajen nazarin bayanan Fermi.

Abin da damin taurari biyu ba za su iya faɗi ba

Takardar ba ta ba da wata yiwuwa (probability) ba. Da damin taurari biyu kawai da aka kwaikwaya, marubutan ba za su iya auna yadda ilimin physics na hasken sararin samaniya na yau da kullum ke samar da mai kama da shi akai-akai ba — abin da wani ƙwaƙƙwaran iƙirarin ƙididdiga zai buƙata. Damin taurarinsu suna samar da taurari sau 10 zuwa 100 da sauri a kiloparsec na tsakiya fiye da yankin tsakiyar Milky Way, don haka mai yiwuwa sun fi hargitsi. Ba su haɗa da baƙin rami (black hole) na tsakiya ba kuma suna amfani da samfuri ɗaya na yaɗuwar hasken sararin samaniya daga cikin da yawa; wasu samfuran mai yiwuwa za su ƙara ƙarin sauye-sauye a ƙananan ma’auni.

Suna kiran aikin hujjar ra’ayi (proof of concept), kuma suna ba da shawarar wani gwaji. Idan sauran tsakiyoyin damin taurari suna da ƙari a wasu matakan ƙarfi daban, hakan zai fifita wani maɓuɓɓugin falaki mai canjawa sosai. Idan dukansu suna nuna kumburin 1–10 GeV iri ɗaya, hakan zai zama hujja mai gamsarwa ga ɓoyayyen abu.