CHIME, A DX OF 1.5 BILLION OF LIGHT YEARS

E' di poche ore fa la notizia che il radiotelescopio canadese conosciuto con l'acronimo CHIME (Canadian Hydrogen Intensity Mapping Experiment) ha rilevato sei impulsi della durata di pochi millesimi di secondo  definiti "anomali"provenienti da una galassia distante un miliardo e mezzo di anni luce dalla terra.  Si tratta dei misteriosi fast radio burst il cui studio è uno degli scopi del radiotelescopio canadese costato 16 milioni di dollari e che è entrato in servizio nella seconda parte del 2018. Ubicato un un remoto sito del nord ovest canadese, all'interno della  della British Columbia, questo radiotelescopio non ricalca la concezione classica delle grandi parabole orientabili che ben conosciamo e gli elementi dell'antenna, distributi su una superficie equivalente a quella di un campo di calcio sono costituiti da 4 cilindri con orientamento nord-sud. Il sistema è in grado di operare anche su frequenze "basse" intorno ai 400 MHz. Il radiotelescopio effettua un monitoraggio h24 dell'emisfero settentrionale e il team di scienziati che vi lavora si aspetta la scoperta di altri segnali "ripetuti" sulla vasta gamma di frequenze monitorate. Alla realizzazione del progetto CHIME hanno collaborato L'Università della British Columbia, la MCGill University, l'Università di Toronto, il Dominion Radio Astrophisical Obsevatory e altre istituzioni pubbliche e private del Nord America. L'area dove sorge il radiotelescopio è protetta da una legislazione che vieta l'emissione di onde elettromagnetiche di provenienza umana, ovvero niente telefonini, radio e altri strumenti che utilizzano le onde radio per molti chilometri intorno al sito. Queste le caratteristiche del radiotelescopio così come riportate dal sito ufficiale del CHIME:

 https://chime-experiment.ca/location

CHIME consists of four adjacent 20m x 100m cylindrical reflectors oriented north-south. The focal axis of each cylinder is lined with 256 dual-polarization antennas, each of which receives radiation from a large swath of sky that nearly stretches from the northern horizon to the southern horizon. This gives CHIME its enormous field of view. The CHIME antennas are custom-designed to have good sensitivity from 400 to 800 MHz, in both linear polarizations. This gives CHIME its large frequency coverage. Signals from the antennas are amplified in two stages, using low-noise amplifiers developed by the cell-phone industry. This novel application of consumer technology makes CHIME affordable. The 2048 signals from these inputs (256 antennas x 2 polarizations x 4 cylinders) are fed to the F-Engine for the initial stage of digital processing.

FAST RADIO BURST DETECTOR

To search for FRBs, CHIME will continuously scan 1024 separate points or “beams” on the sky 24/7. Each beam is sampled at 16,000 different frequencies and at a rate of 1000 times per second, corresponding to 130 billion bits of data per second to be sifted through in real time. The data are packaged in the X-engine and shipped via a high-speed network to the FRB backend search engine, which is housed in its own 40-foot shipping container under the CHIME telescope. The FRB search backend will consist of 128 compute nodes with over 2500 CPU cores and 32,000 GB of RAM. Each compute node will search eight individual beams for FRBs. Candidate FRBs are then passed to a second stage of processing which combines information from all 1024 beams to determine the location, distance and characteristics of the burst. Once an FRB event has been detected, an automatic alert will be sent, within seconds of the arrival of the burst, to the CHIME team and to the wider astrophysical community allowing for rapid follow up of the burst. 

It is a few hours ago the news that the Canadian radio telescope known by the acronym CHIME (Canadian Hydrogen Intensity Mapping Experiment) has detected six impulses lasting a few thousandths of a second defined as "anomalous" coming from a galaxy distant one and a half billion light years from the earth. These are the mysterious fast radio bursts whose study is one of the purposes of the Canadian radio telescope costing 16 million dollars and which entered service in the second part of 2018. Located at a remote site of the Canadian Northwest, within the British Columbia, this radio telescope does not follow the classic conception of the large orientable parabola that we know well and the elements of the antenna, distributed on a surface equivalent to that of a football field, consist of 4 cylinders with north-south orientation. The system is able to operate even on "low" frequencies around 400 MHz. The radio telescope performs a 24-hour monitoring of the northern hemisphere and the team of scientists working there expects the discovery of other "repeated" signals on the wide range of monitored frequencies. The University of British Columbia, MCGill University, the University of Toronto, the Dominion Radio Astrophisical Obsevatory and other public and private institutions in North America collaborated on the realization of the CHIME project. The area where the radio telescope is located is protected by legislation that prohibits the emission of electromagnetic waves of human origin, ie no mobile phones, radios and other instruments that use radio waves for many kilometers around the site. These are the characteristics of the radio telescope as reported by the official website of CHIME:

 https://chime-experiment.ca/location

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