Cosmos - - Cosmos Science Club -

An alien space­craft could eas­ily visit our So­lar Sys­tem with­out us ever notic­ing. As­tronomers es­ti­mate at least one in­ter­stel­lar as­ter­oid sim­i­lar to `Ou­mua­mua passes through our So­lar Sys­tem ev­ery year, but it is hard to recog­nise a faint, fast pin­prick of light in the vast­ness of space. In­deed, `Ou­mua­mua was al­ready on its way out of the sys­tem by the time it was spot­ted.

The only rea­son we now have any chance of spot­ting in­ter­stel­lar ob­jects is thanks to new au­to­mated sur­veys like PAN-STARRS, the Catalina sky sur­vey and the ATLAS sur­vey, which scour the sky for mov­ing ob­jects.

Horner says: “We’re only just reach­ing the tech­no­log­i­cal level to have a good chance of catch­ing these things.” If `Ou­mua­mua had come along just a fort­night ear­lier or later, he be­lieves PAN-STARRS prob­a­bly would have missed it, due to it be­ing too far from Earth or too close to the Sun to see.

Fu­ture tech­nol­ogy will ex­pand our abil­i­ties to spot and study these far-flung vis­i­tors. The much more pow­er­ful Large Synop­tic Sur­vey Tele­scope (LSST) be­ing built in Chile, UCLA’S Je­witt says, should de­tect in­ter­stel­lar ob­jects “by the bucket-load”.

Iden­ti­fy­ing and care­fully study­ing these ob­jects will al­low us to build up a data­base of their prop­er­ties. If an alien-built in­ter­stel­lar vis­i­tor does ar­rive, we’ll have a bet­ter chance of recog­nis­ing its true na­ture.

Then the real fun will be­gin. LAU­REN FUGE is a free­lance science writer based in Ade­laide, Aus­tralia.

IM­AGES 01 Brian Do­miniecki / Getty Im­ages 02 ESO/M. Korn­messer

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