Free_Astronomy_-_SeptemberOctober_2019

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SPACE CHRONICLES

by IAC

The early days of

the Milky Way

revealed by Gaia

E

arly days of the Milky Way,

artist impression. [Gabriel

Pérez Díaz, SMM (IAC)]

T

he universe 13 billion years ago

was very different from the

universe we know today. It is

understood that stars were forming

at a very rapid rate, forming the first

dwarf galaxies, whose mergers gave

rise to the more massive present-day

galaxies, including our own.

However, the exact chain of the

events which produced the Milky

Way was not known until now.

Exact measurements of position,

brightness and distance for around

a million stars of our galaxy within

6 , 500 light-years of the Sun, ob-

tained with the Gaia space tele-

scope, have allowed a team from the

IAC to reveal some of its early stages.

“We have analyzed, and compared

with theoretical models, the distri-

bution of colours and magnitudes

(brightnesses) of the stars in the

Milky Way, splitting them into sev-

eral components, the so-called stel-

lar halo (a spherical structure which

surrounds spiral galaxies) and the

thick disc (stars forming the disc of

our Galaxy, but occupying a certain

height range)”, explains Carme Gal-

lart, a researcher at the IAC and the

chronicles EN_l'Astrofilo 29/08/2019 15:56 Page 20