ESA mission confirms exactly when the Sun will die
Our Sun is condemned. In billions of years, the Sun will exhaust its hydrogen and become a red giant before becoming a white dwarf. It’s a well-known story, and an astronomer has understood it for decades. Now, thanks to the latest data from Gaia, we know the future of the Sun in much greater detail.
The chronology of human civilization is only a jolt in the life of a star. We haven’t been around long enough to witness the birth, life and death of a star. But we can understand stellar evolution by observing other stars that may be older or younger than the Sun. It’s similar to how you might understand how humans live and die by looking at a collection of photographs all taken at once in a single day.
One of the earliest snapshots of stellar evolution was taken in the early 1900s. First as a data table by Ejnar Hertzsprung in 1905, but more famously as a diagram by Henry Norris Russell in 1914. Now known as Hertzsprung-Russell diagrams, or HR diagrams, they plot the color or spectral class of a star against its absolute. magnitude. Color is a measure of a star’s temperature, and absolute magnitude is a gauge of its size.
Early HR diagrams only contained data for about 300 stars, but even then it was clear that most stars lay along a linear path known as the main sequence. Since most stars are in the main sequence, it stands to reason that stars spend most of their lives as main sequence stars. Small stars shine at cool temperatures, while larger, more massive stars burn hotter.
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 these are exceptions. As astronomers gathered more data, they could see how the largest main-sequence stars entered a giant stage before becoming white dwarfs or neutron stars. Overall, a star’s mass determines its lifespan and fate.
We now know that while a star’s mass is an important aspect of stellar evolution, its chemical composition also plays an important role. Two stars of similar mass but different composition can have very different lifetimes. This is where the Gaia survey comes in.
While the first stellar surveys counted hundreds or thousands of stars, Gaia has more than a billion. In the latest data release, the Gaia team created an HR diagram of over 4 million stars within 5,000 light-years of Earth. For these stars, we know not only their size and their spectral temperature but also their chemical composition.
This means that the Gaia team could create an HR diagram of stars with mass and composition similar to that of the Sun. The result traces the evolutionary path of Sun-like stars from main sequence to red giants. According to the data, the Sun will reach its maximum temperature at the age of 8 billion years, then go into the red giant phase before finally dying around 11 billion years.
The Gaia team also found nearly 6,000 stars close to the Sun’s twins, with similar mass, temperature, composition and age. By observing these stars, astronomers will better understand if our Sun is typical. For example, do these other stars have solar cycles similar to the Sun? Do some have periods of intense solar flares or are they quite stable like the Sun?
With so much data gathered, Gaia is revealing new details about our own star, how it might behave in the near future, and how it will die in the distant future. We have known for a long time that the end is near for the Sun, but we are beginning to learn how and when the end will come.
This article was originally published on Universe today by Brian Koberlein. Read the original article here.