THE BIG SKY

Canal Boat - - Boater’s Break - WITH SEB JAY

SEVEN BRIGHT STARS in the shape of a long-han­dled saucepan sit over the north­ern hori­zon mid-evening this Oc­to­ber. It’s a con­stel­la­tion you might al­ready know by one of many names. The Plough, the Big Dip­per, the Great Bear – dif­fer­ent tags for the same fa­mil­iar group­ing of dis­tant suns, which be­tween them hold a se­cret.

Train your eyes on the mid­dle star in that line of three form­ing the pan’s han­dle. How many points of light do you see there? One or two? The ea­gle-eyed among you might see a fainter star nes­tled above the brighter one. Binoc­u­lars re­veal the pair­ing nicely, but get a small tele­scope on them and you’ll find that the brighter one it­self splits out into two white stars to make a vis­ual triple star sys­tem known as Al­cor and Mizar.

But that’s not the real se­cret. Hid­den in the glare of each star is a smaller com­pan­ion star. Each com­pan­ion or­bits so close to the par­ent star as to ren­der them in­vis­i­ble to the eye in all but the largest of pro­fes­sional tele­scopes. It makes Al­cor and Mizar a sex­tu­plet star sys­tem – and one that soon could be an­nounced as harbouring its own plan­ets!

Look north from your boat on a clear evening and you’ll find the Plough. Im­age by Jeff Horne.

canalboat.co.uk

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