Scientists have made new discoveries that challenge some old theories about white dwarfs. Scientists have used new data collected using the Hubble Space Telescope to understand that white dwarfs may continue to burn hydrogen during the final stages of their lives. By burning hydrogen in the final stages, white dwarfs may appear to be younger than they actually are.
Scientists believe this revelation could have consequences for how the ages of star clusters are measured. The team says white dwarfs can slow down their aging rate by burning hydrogen present on their surface. The evidence also points out that white dwarfs can still undergo stable thermonuclear activity, which contradicts previously held beliefs.
Two globular clusters were compared
White dwarfs are stars that slowly cool down and have thrown their outer layers into space during the final stages of its life. Around 98% of all stars in the universe will eventually end their lives as white dwarfs, making them the most common object in the universe. Scientists suggest that by studying more about white dwarfs, they can determine more about the earlier stages of a star’s life.
To investigate white dwarfs, the team compared the objects residing inside two globular clusters called M3 and M13. Both star clusters are very similar in terms of age and metallicity. However, the number of stars, which eventually leads to white dwarfs, is considerably different. The color of the stars within the clusters at an evolutionary stage known as the Horizontal Branch are bluer within cluster M13, which signifies hotter stars.
New way to measure age of stars?
Since the globular clusters are so similar but their stars have different temperatures, they are best for observing how different populations of white dwarfs cool. Hubble Space Telescope observed both white dwarfs between the two clusters. M3 contained standard white dwarfs that are cooling stellar cores.
M13, on the other hand, packs two populations of white dwarfs that include standard and another type that still packs a layer of hydrogen, allowing it to burn and cool at a slower pace. Around 70% of white dwarfs burn hydrogen present on their surface. The discovery could be very useful for astronomers and change the way how the age of stars in the Milky Way is measured.
