MATATTUN TAURARI BIYU A KAN HANYAR KEWAYAWA MAFI MIƘEWA DA AKA TAƁA GANI

Ma’auratan taurarin neutron — rugujewar tsakiyar da manyan taurari ke barin baya — suna kewaye juna kuma a hankali suna rasa kuzari a matsayin raƙuman nauyi (gravitational waves). An gano na farko a 1974 (PSR B1913+16), kuma a yau an san sama da 30. Wasu daga ƙarshe suna haɗewa, suna haifar da al’amura kamar GW170817 da GW190425 da LIGO ta gano. Nawa irin waɗannan ma’aurata ke tsira a Milky Way, kuma a kan wace hanyar kewayawa, tambayoyi ne na tushe ga ilimin falaki na raƙuman nauyi da kuma labarin yadda taurari biyu ke canzawa.

Hanyar kewayawa ta tarihi

PSR J0653+0443 pulsar ne — tauraron neutron wanda hasken rediyonsa ke share Duniya kamar fitilar gaɓar teku — yana juyawa sau ɗaya kowace millisecond 47.5. Na’urar hangen nesa ta rediyo ta China mai faɗin mita ɗari biyar, Five-hundred-meter Aperture Spherical radio Telescope (FAST), ce ta fara gano shi a ranar 20 ga Nuwamba 2022, kuma yana da nisan kusan kiloparsec 1 (kusan shekarun haske 3,000), a cikin hannun Perseus na galaxy ɗinmu.

Ta hanyar auna lokacin bugunsa na sama da shekaru biyu, Z. L. Yang, J. L. Han da abokan aikinsu a National Astronomical Observatories of China da jami’o’in abokan hulɗa sun gano cewa yana kewaye wani tauraron neutron. Nauyin: nauyin Rana 1.38 ga pulsar, 1.44 ga abokinsa.

Hanyar kewayawar ta ban mamaki ce:

• tsawon zagaye na kwanaki 79.084, mafi tsawo a cikin dukkan taurarin neutron biyu-biyu da aka sani;
• eccentricity — 0 ga da’ira, kusa da 1 ga hanyar kewayawa da aka miƙe har ta kusa zama lanƙwasa a buɗe — na 0.99238692 — mafi girma da aka taɓa auna wa kowane taurari biyu; tarihin baya, na taurari biyu na yau da kullum, shi ne 0.985;
• mintuna 46 kawai don tafiya daga wannan gefen abokin zuwa wancan, yayin da galibin kwanaki 79 ɗin ake shafe su nesa;
• a mafi kusancin wuri, tazara ta radius na Rana 0.83, kusan km 580,000 — ƙasa da radius na Rana kanta — da gudun dangi na kilomita 1,140 a daƙiƙa, mafi girma a kowane taurarin neutron biyu da aka sani.

FAST tasa ce da ba ta motsi: tana ganin wani ratsi na sama kawai da ke bisanta, kuma mafi kusancin wuri ba koyaushe yake faɗawa cikin wannan ratsin ba. Tsakanin 2025 da 2028, wucewa biyu ne kawai ke faɗawa cikin ganinta: 19 ga Fabrairu 2025 da 21 ga Afrilu 2027. Ƙungiyar ta bi ta farkon na awa biyu, ma’auni ɗaya a kowane minti.

Kusufi da siffar ƙwai mai girgiza

A lokacin wannan wucewar, siginar rediyon pulsar ta ɓace na daƙiƙa 85 yayin da ya wuce bayan muhallin maganadisu na abokinsa. Wannan yana nufin muna ganin hanyar kewayawar kusan daga gefe. Kusufi na biyu ne kawai da aka taɓa gani a cikin taurarin neutron biyu, bayan shahararren pulsar biyu PSR J0737−3039A.

General relativity tana sa siffar ƙwan ta juya a hankali — ci gaban mafi kusancin wuri (advance of periastron) — wurin mafi kusanci na hanyar kewayawar yana zagayawa a hankali —, wanda aka auna a nan a digiri 0.017791 a shekara, kamar yadda aka yi hasashe. Amma wannan ci gaba ba ɗaya yake ba: yana sauri kusa da mafi kusancin wuri. A kan wannan hanyar kewayawa da ta kusa zama parabola, alƙiblar kewayawar tana sauyawa a cikin wucewar kanta, tana matsar da pulsar ɗin zuwa gare mu sannan nesa da mu, tana gaggauta sannan tana jinkirta bugunsa tsakanin −2.91 da +2.49 millisecond, fiye da ninki goma na kowane irin tsarin.

An haife shi daga shuri mai ƙarfi

Ana tunanin irin waɗannan ma’aurata suna fitowa ne daga manyan taurari biyu da ke fashewa ɗaya bayan ɗaya. A cewar marubutan, matsanancin eccentricity zai iya fitowa ne kawai daga babban “shuri” (kick) da aka ba tauraron neutron na biyu yayin da tsakiyar ƙarfen tauraron da ya haife shi ke rushewa. Kwaikwayonsu suna nuna shuri fiye da kusan kilomita 400 a daƙiƙa.

Sun kuma kwaikwayi kusan manyan taurari biyu-biyu biliyan ɗaya. A cikin taurarin neutron biyu-biyu da suka tsira, waɗanda ke da eccentricity sama da 0.95 da tsawon zagaye na kwanaki 50 zuwa 110 suna ƙasa da kashi 0.5%. Duk da haka wannan ya bayyana a cikin 28 kawai da aka sani a wajen gungun taurari masu siffar ƙwallo (globular clusters), a cikin faifan galaxy. A kalaman marubutan, “ko dai muna da sa’a sosai ko kuma ka’idar canjin taurari biyu ta yanzu da fahimtar yanzu ta supernova na rushewar tsakiya suna buƙatar gyara”.

Fashe-fashen raƙuman nauyi

Saboda taurari biyun suna kusantar juna sau ɗaya kawai a kowane kwanaki 79, suna fitar da raƙuman nauyi a cikin fashe-fashe na lokaci-lokaci. Fitarwar tana kaiwa ƙololuwa kusa da millihertz 0.357, zagaye ɗaya kowane mintuna 47 — tsawon wucewa mafi kusanci. Wannan ya yi rauni sosai ga cibiyoyin lura na sararin samaniya na raƙuman nauyi da aka tsara, LISA, Taiji da TianQin, amma ra’ayoyin nan gaba da aka gabatar kamar LISAmax za su iya gano shi cikin shekaru goma. Ma’auratan za su haɗe cikin kusan shekaru biliyan 2.5, su ƙare da wani al’amari kamar GW170817.