Astronomers are always observing stars or galaxies that are faint, i.e., not very bright. This is usually because by pushing the limit we learn more about the Universe. A team of astronomers led by Harvey Richer from UBC have used the Hubble Space Telescope to observe the faintest stars ever observed, in the globular cluster NGC 6397.
Their research revealed the lowest mass stars on the main sequences in this cluster. These are the smallest stars that will burn hydrogen through fusion and live many billions of years rather than simply fading away after 1 billion years or so.
Richer and colleagues also detected a characteristic change in the color of white dwarfs in the cluster that is related to the onset of molecular hydrogen being formed in the cooling atmospheres as the white dwarfs die. With this information in hand, astronomers can learn more about the physics of low mass stars and white dwarfs and perhaps improve the estimate of the ages of these stars and the universe.