Observation of 26 cm radio signals, formed due to hyperfine transition of cosmic hydrogen offer an alternative tool to the study of early visata. As for neutral epoch of the infant visata when no light was emitted, 26 cm lines are perhaps only window. However, these redshifted radio signals emitted by cosmic hydrogen in the early visata are extremely feeble and have been elusive so far. In 2018, EDGE experiment reported detection of 26 cm signals but the findings could not be independently confirmed. The main issue was instrument systematic and contamination with the other signals from the sky. The REACH Experiment is to employ unique methodology to overcome the bottleneck. It is hoped that this research group will reliably be able to detect these elusive signals in near future. If successful, REACH Experiment may bring ‘26 cm radio astronomy’ to the forefront in the study of early visata and help us much in unravelling the mysteries of early visata.
When it comes to the study of ankstyvoji visata, name of recently launched Jameso Webbo kosminis teleskopas (JWST) pops up in our mind. JWST, a successor of hugely successful Hablo telescope, is a space-based, infrared observatory equipped to capture optical/infrared signals from the early stars and galaxies formed in the Visata soon after the Big Bang1. Tačiau, JWST has some limitation so far as picking up signals from the neutral epoch of ankstyvoji visata yra susirūpinęs.
Table: Epochs in the history of visata since the Big Bang
(Šaltinis: Kosmologijos filosofija – 21 cm fonas. Prieiga prie http://philosophy-of-cosmology.ox.ac.uk/images/21-cm-background.jpg)
Up to 380 k years after the big bang, the visata was filled with ionised gas and was fully opaque. Between 380k – 400 million years, the visata had become neutral and transparent. The epoch of reionisation started after this phase starting 400 million after the big bang.
During the neutral epoch of early visata, kai visata was filled with neutral gases and was transparent, no optical signal was emitted (hence called dark age). Unionized material does not emit light. This poses a challenge in study of early Visata of neutral epoch. However, microwave radiation of 21 cm wavelength (corresponding to 1420 MHz) emitted by the cold, neutral cosmic hydrogen during this epoch as a result of hyperfine transition (from parallel spin to more stable anti-parallel spin) offers opportunities to researchers. This 21 cm microwave radiation would be redshifted upon reaching Earth and will be observed at 200MHz to 10 MHz frequencies as radio waves2,3.
21 cm radijo astronomija: Observation of 21-centimeter cosmic hydrogen signals offers an alternative approach to the study of early visata especially of neutral epoch phase that was devoid of any light emission. This can also inform us about new physics such as distribution of matter over time, dark energy, dark matter, neutrino masses, and inflation2.
However, the 21-cm signals emitted by the cosmic hydrogen during early visata phase is elusive. It is expected to be extremely weak (about one hundred thousand times weaker than other radio signals also emanating from the sky). As a result, this approach is still in infancy.
2018 m. mokslininkai pranešė aptikę tokį radijo signalą 78 MHz dažniu, kurio profilis iš esmės atitiko lūkesčius dėl pirminio kosminio vandenilio skleidžiamo 21 centimetro signalo.4. Tačiau šis pirminio 21 cm radijo signalo aptikimas negalėjo būti nepriklausomai patvirtintas, todėl iki šiol nepavyko nustatyti eksperimento patikimumo. Atrodo, kad pagrindinė problema yra užteršimas pirmame plane esančiais radijo signalais.
Paskutinis etapas – 21 m. liepos 2022 d. Radijo eksperimento kosminio vandenilio analizei (REACH) ataskaita. REACH taikys naują eksperimentinį metodą šiems silpniems nepagaunamiems kosminiams radijo signalams aptikti, taigi suteiks naują viltį patvirtinti 21 centimetro kosminius signalus.
Kosminio vandenilio analizės radijo eksperimentas (REACH) yra dangaus vidurkis 21 cm eksperimentas. Taip siekiama pagerinti stebėjimus, sprendžiant problemas, su kuriomis susiduria instrumentai, susiję su likutiniais sistemingais duomenų signalais. Jame pagrindinis dėmesys skiriamas sistematikos aptikimui ir bendrai paaiškinimui kartu su priekiniais planais ir kosmologiniu signalu, naudojant Bajeso statistiką. Eksperimentas apima tuo pačiu metu atliekamus stebėjimus naudojant dvi skirtingas antenas, itin plačiajuostę sistemą (raudonojo poslinkio diapazonas nuo 7.5 iki 28) ir imtuvo kalibratorių, pagrįstą lauko matavimais.
This development is significant given its potential to be one of the best tools (and cost effective too vis-a-vis space-based observatories like Jamesas Webbas) for study of early visata as well as possibility of ushering in of new fundamental physics.
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Nuorodos:
- Prasad U., 2021. James Webb kosminis teleskopas (JWST): pirmoji kosmoso observatorija, skirta ankstyvosios visatos studijoms. Mokslinis Europos. Paskelbta 6 m. lapkričio 2021 d http://scientificeuropean.co.uk/sciences/space/james-webb-space-telescope-jwst-the-first-space-observatory-dedicated-to-the-study-of-early-universe/
- Pritchard JA ir Loeb A., 2012. 21 cm kosmologija XXI amžiuje. Ataskaitos apie fizikos pažangą 21 75. Prieiga https://iopscience.iop.org/article/10.1088/0034-4885/75/8/086901. Išankstinis spausdinimas „arXiv“ pasiekiamas adresu https://arxiv.org/abs/1109.6012 pdf versija https://arxiv.org/pdf/1109.6012.pdf
- Oksfordo universitetas. Kosmologijos filosofija – 21 cm fonas. Galimas adresu http://philosophy-of-cosmology.ox.ac.uk/21cm-background.html
- Bowman, J., Rogers, A., Monsalve, R. ir kt. Sugerties profilis, kurio centras yra 78 megahercų vidutiniame dangaus spektre. Gamta 555, 67–70 (2018). https://doi.org/10.1038/nature25792
- de Lera Acedo, E., de Villiers, DIL, Razavi-Ghods, N. ir kt. REACH radiometras, skirtas aptikti 21 cm vandenilio signalą nuo raudonojo poslinkio z ≈ 7.5–28. Nat Astron (2022). https://doi.org/10.1038/s41550-022-01709-9
- Eloy de Lera Acedo 2022. Kūdikių Visatos paslapčių atskleidimas naudojant REACH radiometrą. Galima internetu adresu https://astronomycommunity.nature.com/posts/u
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