The result traces the evolutionary path of Sun-like stars from the main sequence to the red giants. This means the Gaia team could create an HR diagram of stars with a similar mass and composition to the Sun. For these stars, we know not only their size and spectral temperature but also know their chemical composition.
In the latest data release, the Gaia team created an HR diagram of more than 4 million stars within 5,000 light-years of Earth. Whereas early stellar surveys had hundreds or thousands of stars, Gaia has more than a billion. Two stars similar in mass but different in composition can have very different lifetimes. We now know that while the mass of a star is an important aspect of stellar evolution, its chemical composition also plays an important role. By and large, the mass of a star determines its lifetime and fate. As astronomers gathered more data, they could see how larger main sequence stars entered a giant stage before becoming white dwarfs or neutron stars. The HR diagrams showed that some stars such as red giants were large but cool, and others known as white dwarfs were small and hot, but those were the exceptions. Small stars shine at cool temperatures, while larger more massive stars burn hotter. Since most stars are within the main sequence, it stands to reason that stars spend most of their lives as main sequence stars. The early HR diagrams only had data for about 300 stars, but even then it was clear most stars lay along a linear path known as the main sequence. The first HR diagram vs Gaia’s modern diagram. Color is a measure of a star’s temperature, and absolute magnitude is a gauge of its size. Now known as Hertzsprung-Russell diagrams, or HR diagrams, they plot the color or spectral class of a star versus its absolute magnitude. First as a data table by Ejnar Hertzsprung in 1905, but more famously done as a diagram by Henry Norris Russell in 1914. One of the first snapshots of stellar evolution was done in the early 1900s. It’s similar to the way you might understand how humans live and die by looking at a collection of photographs all taken at the same time on a single day. But we can understand stellar evolution by observing other stars that may be older or younger than the Sun. We haven’t been around long enough to watch a star’s birth, life, and death. The timeline of human civilization is a mere blip in the lifetime of a star. Now, thanks to the latest data from Gaia, we know the Sun’s future in much greater detail. It’s a well-known story, and one astronomer has understood it for decades. This lifespan began roughly 4.6 billion years ago, and will continue for about another 4.5 5.5 billion years, when it will deplete its supply of hydrogen, helium, and collapse into a white dwarf. Billions of years from now, the Sun will deplete its hydrogen fuel and swell to a red giant before becoming a white dwarf.