Has any other star come close to our So­lar Sys­tem?

Focus-Science and Technology - - Q & A - DAVE WHITE, RM

Un­like plan­ets, stars seem fixed in the night sky. Yet in re­al­ity, they too are mov­ing through space: their vast dis­tance means it just takes a long time for their move­ment to be­come ob­vi­ous.

Over the long his­tory of the So­lar Sys­tem, count­less stars have ap­proached our plan­e­tary neigh­bour­hood. While there’s no ev­i­dence of a di­rect col­li­sion, the or­bits of the outer plan­ets are thought to have changed dra­mat­i­cally dur­ing the early his­tory of the So­lar Sys­tem. It’s pos­si­ble that this was due to grav­i­ta­tional jostling among the plan­ets them­selves, but a stel­lar in­truder can’t be ruled out.

Even a ‘near miss’ could have dev­as­tat­ing con­se­quences. Far be­yond the known plan­ets lies a vast col­lec­tion of icy de­bris and comets sur­round­ing the Sun known as the Oort Cloud. A star pass­ing even a light-year or so away from us could stir these up, hurl­ing cos­mic mis­siles at the plan­ets.

To as­sess the risk, as­tronomers at the Max Planck In­sti­tute for Astronomy, Ger­many, re­cently pub­lished an anal­y­sis of the move­ment of over seven mil­lion stars. For­tu­nately, they found just one – co­de­named Gliese 710 – likely to dis­turb the Oort Cloud over the next mil­lion years or so.

Bee or­chids, found across Europe, the Mid­dle East and North Africa, tempt male bees to visit them by re­sem­bling a fe­male bee. Can you see the sim­i­lar­ity?

The Oort Cloud is thought to sur­round our So­lar Sys­tem in a halo-like fash­ion

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