Focus-Science and Technology - - DISCOVERIES -

It’s time to remap the cos­mos. ESA’s Gaia mis­sion has pro­duced the most de­tailed pic­ture yet of the night sky, pin­point­ing the po­si­tions of nearly two bil­lion stars.

Launched in De­cem­ber 2013, the Gaia space ob­ser­va­tory is cre­at­ing a three-di­men­sional map of the Milky Way. Af­ter an initial data re­lease in 2016, this sec­ond phase cov­ers the pe­riod from 25 July 2014 to 23 May 2016, and in­creases the num­ber of sur­veyed stars from two mil­lion to al­most 1.7 bil­lion. It also ramps up the ac­cu­racy, with a max­i­mum pre­ci­sion equiv­a­lent to some­one on the Earth be­ing able to spot a coin on the sur­face of the Moon.

As well as their po­si­tions, Gaia also mea­sured the bright­ness and colour of most of the stars, the ve­loc­ity across the sky of more than 1.3 bil­lion of them, the sur­face tem­per­a­tures of about 100 mil­lion and the ef­fect of in­ter­stel­lar dust on 87 mil­lion. It also mea­sured the po­si­tions of more than 14,000 as­ter­oids in our So­lar Sys­tem and, much fur­ther afield, of half a mil­lion quasars – lu­mi­nous ga­lac­tic nu­clei pow­ered by su­per­mas­sive black holes.

As­tronomers are now ea­gerly sift­ing through all this new data. “The new Gaia data are so pow­er­ful that ex­cit­ing re­sults are just jump­ing at us,” said An­tonella Val­lenari, one of the lead sci­en­tists in­volved in the project. “It feels like we are in­au­gu­rat­ing a new era of ga­lac­tic archaeology.”

Of par­tic­u­lar in­ter­est so far are mea­sure­ments sug­gest­ing that fast-mov­ing stars in the Milky Way’s outer ‘halo’ re­gion con­sist of two sep­a­rate stel­lar pop­u­la­tions that were cre­ated through two dif­fer­ent pro­cesses.

Fur­ther ob­ser­va­tions should shed more light on these stars, and help us piece to­gether how our home gal­axy came into be­ing.

NASA’s Gaia space mis­sion is giv­ing us a much clearer pic­ture of the Milky Way

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