Scientists focus on specific characteristics of stars such as their mass and composition.
Although there are many facts about stars known to scientists, calculating their age is not a simple matter.
First, to calculate their mass, their orbital velocity is taken into account. And to determine their material, scientists observe the spectrum of colors emitted by the star.
The only star whose age is known almost exactly is the sun. For the other stars the calculations hide surprises even if they are very well thought out.
The three main methods are,
• Hertzsprung-Russell diagrams: It considers that the largest stars reach the end of their existence earlier than the smallest ones and that they ‘burn’ with their own hydrogen. It is not an exact method but it is the best available.
• Rotation rate: Stars in younger clusters tend to rotate faster. But some stars do not ‘lose’ speed as the years pass. This method is best for stars that are younger than the sun.
• Stellar seismology: Stars are observed with telescopes for a very long time to obtain a lot of data that might help calculate their age. Kepler telescopes are best suited for this purpose.
[Source: http://www.sciencenews.org]
