Astronomers Spot the Debris From Planets That Formed 10 Billion Years ago - by BrianKoberlein
The fate of the Sun is sealed. It was sealed by gravity in the earliest days of its formation. In several billion years the Sun will swell to a red giant, cast off much of its thin outer layers, then collapse to become a white dwarf. The white dwarfs we see in the nearby galaxy tell us of our Sun’s future. Its core will collapse to about the size of Earth, and then it will gradually cool as it fades into the dark.
. They don’t experience any nuclear fusion or gravitational heating, so once formed they just gradually cool down. Generally, the cooler a white dwarf is, the older it is. The hottest white dwarfs can have temperatures of nearly 150,000 K, and the coolest ones about 4,000 K. So when a team of astronomers found a couple of white dwarfs with temperatures just above 3,000 K, they knew they had found very ancient white dwarfs.
A white dwarf has an inert core of carbon and oxygen, and outer layers of hydrogen and helium. Image Credit: NRIAG. Given the estimated rate of cooling, these two white dwarfs are around 10 billion years old. They were likely among the first stars in the Milky Way and died 5 billion years before our solar system formed. From Gaia observations, their orbital motion within the galaxy puts them within the galactic plane, so they could help astronomers better understand the age and history of our galaxy. But both of them also have unusual spectra, showing evidence of heavier elements.
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