Astronomers find edge of Milky Way

Stars discovered at the edge of our galaxy are over one million light years away, almost halfway to the neighbouring Andromeda galaxy
 

Next Generation Virgo Cluster Survey detects 208 distant variable stars called RR Lyrae – old stars that brighten and dim at regular intervals
           
1 Rapid expansion

2 Slow contraction
 
5-24 hours
                    

Pulsation allows scientists to calculate distance by star’s average brightness
Furthest is 1.04 million light years from galactic centre 

Spiral arms

Galactic centre “bulge”
                                                                                                                               Earth 25,800 light years from centre
                                                                                                                                                                                THIN DISK
100,000 light years diameter
                         
INNER HALO
                        
OUTER HALO
    
Oldest stars in galaxy, rotating in opposite direction to inner halo. 
Mostly dark matter, contains majority of galactic mass – around 1.5 trillion times that of our sun


Halo not to scale
    

Sources: AAAS, NASA 
Picture: NASA/JPL-Caltech 
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