Ask all about space

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All About Space - - Contents -

ex­o­plan­ets have al­ready been di­rectly im­aged or­bit­ing the stars Fo­ma­l­haut and Beta pic­toris, as well as three ex­o­plan­ets or­bit­ing hr 8799. these plan­ets are large Jupiter-sized bod­ies or­bit­ing far from their host star and are ob­served with spe­cial in­stru­ments called coro­n­a­graphs that are used to block the starlight while leav­ing the plan­ets vis­i­ble.

in order to get a clear im­age of a pos­si­ble hab­it­able ex­o­planet, such as an earth-ana­logue, the ob­ser­va­tion would need to be able to re­solve the star from the planet and deal with the very large con­trast in light be­tween the two. to get a feel for these two dif­fi­cult tasks, get a bright torch (flash­light) and a small mar­ble. have a friend stand across a room from you, hold the mar­ble against the torch and shine the light di­rectly into your eyes. can you see the mar­ble? Small, close-in ex­o­plan­ets or­bit very near in an­gle to their stars and shine very dimly by re­flected light. Just build­ing a big tele­scope alone will not al­low the ob­ser­va­tion. astronomers are work­ing to make spe­cial tele­scopes such as the James Webb Space tele­scope (JWSt) and spe­cial in­stru­ments (star shades and vor­tex coro­n­a­graphs) that can be placed in space, above the dis­rupt­ing ef­fects of our at­mos­phere, in hopes of ob­tain­ing a di­rect im­age and mea­sure­ment of an earth-like

planet, per­haps re­veal­ing sig­na­tures of life. Dr Steve How­ell is a se­nior re­search sci­en­tist at NASA’s Ames Re­search Cen­ter

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