Si­lence, please!

Our wide, open and very ra­dio-quiet out­back is ra­dioas­tron­omy heaven.

Australian Geographic - - Geo Buzz -

TO­DAY’S AS­TRONOMERS make use of ev­ery mes­sen­ger va­ri­ety bring­ing in­for­ma­tion from dis­tant ce­les­tial ob­jects. Su­batomic par­ti­cles and grav­i­ta­tional rip­ples in space-time are re­cent ad­di­tions to the list of emis­saries. But most of what we know of the Uni­verse ar­rives via elec­tro­mag­netic waves – from gamma rays to ra­dio. A wide range of nat­u­ral pro­cesses pro­duces these sig­nals, al­low­ing us to build a truly mul­ti­fac­eted pic­ture of the cos­mos.

I’ve spent most of my ca­reer in op­ti­cal as­tron­omy us­ing ob­ser­va­tions made with vis­i­ble light. But Aus­tralia has a long tra­di­tion of ex­cel­lence in ra­dioas­tron­omy. Our ra­dioas­tronomers are world lead­ers in the in­stru­men­ta­tion and tech­niques ex­plor­ing the Uni­verse at these wave­lengths.

They also have some­thing else. Just as op­ti­cal as­tronomers need free­dom from ar­ti­fi­cial light to ob­serve faint stars and gal­ax­ies, ra­dioas­tronomers need its equiv­a­lent – ra­dio-quiet­ness. If you have a te­le­scope ca­pa­ble of pick­ing up a mo­bile phone sig­nal at the dis­tance of Pluto, it’s use­less putting it near an ur­ban cen­tre where you’re in a ca­coph­ony of hu­man-made ra­dio sig­nals.

One of Earth’s most ra­dio-quiet lo­ca­tions is in Western Aus­tralia’s in­te­rior, some 300km north-east of Ger­ald­ton, on Wa­jarri Ya­matji land. This is home to the Murchi­son Ra­dio-As­tron­omy Ob­ser­va­tory, a vast scrub­land host­ing sev­eral state-of-theart te­le­scope ar­rays.They in­clude Aus­tralia’s pre­cur­sors to the Square Kilo­me­tre Ar­ray – the next ma­jor in­ter­na­tional ra­dioas­tron­omy project, which will be­come the world’s big­gest te­le­scope in the 2020s.

Although quite new, the Murchi­son ob­ser­va­tory has al­ready net­ted amaz­ing dis­cov­er­ies. One has fea­tured here – the ra­dio sig­na­ture of the Uni­verse’s first stars, born 180 mil­lion years af­ter the Big Bang (AG 144).When you re­alise this in­cred­i­bly weak sig­nal was found in the mid­dle of the FM ra­dio wave­band, you be­gin to ap­pre­ci­ate the true sig­nif­i­cance of WA’s most un­sung nat­u­ral as­set – ra­dio si­lence.

These dish an­ten­nas of Aus­tralia’s Square Kilo­me­tre Ar­ray Pathfinder will func­tion as part of the world’s big­gest te­le­scope next decade.

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