The First Stars Could Have Survived to This Day express
The first stars ignited from clouds that contained nothing but hydrogen and helium. Heavy elements (carbon, oxygen, iron) came later, forged inside stars. But among those pioneers, there could have been lightweight stars, with masses just below that of the Sun. Such stars live for a very long time, billions of years, and could have survived to this day.
Astrophysicists built computer models of how such stars change with age. They varied how much mass a star loses and how its layers mix. It turned out that at the end of its life, a star can shed its outer envelope and leave behind a white dwarf the size of Earth but with half the Sun's mass.
Such white dwarfs could be searched for in the outskirts of the Milky Way. Finding even one would be direct proof that not all first stars were giants. It would be like finding a house in a modern city built from stones that are billions of years old.
The models also showed that during flares, the star emits neutrinos — elusive particles that barely interact with matter. Future detectors could catch such a signal. Then we would learn about the birth of the first stars not from light, but from these 'ghosts.'
A white dwarf is a star compressed to the size of Earth: a teaspoon of its material would weigh as much as a truck.