Population 1 stars are typically younger, larger, and more metal-rich than Population 2 stars. They are found in the disk of the galaxy and have a higher concentration of heavy elements, such as carbon, nitrogen, and oxygen. Population 2 stars, on the other hand, are older, smaller, and more metal-poor. They are found in the halo and bulge of the galaxy and have a lower concentration of heavy elements.
Metallicity refers to the abundance of elements heavier than hydrogen and helium in a star. It is an important factor in determining a star's characteristics, such as its color, temperature, and lifespan. Generally, stars with higher metallicity have a longer lifespan and are more likely to have planets orbiting them.
Metal-rich stars are typically formed from the remnants of previous generations of stars, as heavier elements are created during the fusion process. On the other hand, metal-poor stars are formed from the primordial gas and dust that existed shortly after the Big Bang. They have not undergone as many generations of star formation and therefore have a lower metallicity.
The metallicity of a star can affect the formation and composition of its planetary system. Higher metallicity stars are more likely to have rocky, Earth-like planets, as the heavier elements are necessary for the formation of solid planets. On the other hand, lower metallicity stars may have gas giants, but are less likely to have smaller, rocky planets.
Astronomers can determine the metallicity of stars by analyzing their spectra, which is a measurement of the different wavelengths of light emitted by the star. The presence and strength of certain absorption lines indicate the abundance of specific elements, allowing astronomers to calculate the overall metallicity of the star. This method is known as spectroscopy.