nasa solar system
how in the world NASA calculates the age of a solar system or planet?
They use the spectral analysis to determine what the start is using as fuel. For example, our star burns by converting hydrogen to helium (that more complex than that, but I'm making it simpler.) Based on the ratio of helium to hydrogen as an astronomer, found (based on analysis spectral), you can tell how long something has burnt. For example, our star, if there were more hydrogen than helium, you can calculate that the star had lived most of his life already. Since we know that the rate of a star to merge the two elements, it gives us a time scale. Similar calculations can be made by the stars below, adding, of course, how close we are. One star In particular, Beltegeuse in the Orion Nebula, is due to go nova any day now, because he used most of its fuel.
NASA I – A Stroll Through the Solar System