A waterfall of stars

The galaxy UGCA 193, seen here by the NASA/ESA Hubble Space Telescope, is a galaxy in the constellation of Sextans (The Sextant). Looking rather like a waterfall, UGCA 193 appears to host many young stars, especially in its lower portion, creating a striking blue haze and the sense that the stars are falling from “above”.

The blue colour of UGCA 193 indicates the stars that we see are hot —  some with temperatures exceeding 6 times that of our Sun. We know that cooler stars appear to our eyes more red, and hotter stars appear more blue. As the mass and surface temperature of a star, and therefore its colour, are linked, heavier stars are able to “burn” at higher temperatures resulting in a blue glow from their surface.