![]() ![]() The most massive O-type stars shine with a power of a million times more than the power of our Sun - a fuel consumption rate that's ridiculously high. On the other hand, a star with just 0.2 solar masses will live for 560 billion years and a star with just 0.1 solar masses may live for 10 trillion years, much longer than "just" the 10 billion years of life expectancy of our Sun. Considering that this star has only twice as much fuel to burn at 11 times the released energy you can expect the lifetime of the Sun to be more than 5 times longer. A star twice as massive as the Sun has a luminosity of more than 11 times that of the Sun. This is because the luminosity of a star - and with it the released energy or power - approximately increases with the 3.5th power of the star's mass. You might expect that more massive stars live longer since they have more fuel (hydrogen) to burn, but the opposite is true. The lifetime of a star strongly depends on its mass. Stars do not live forever they can only shine for a certain amount of time. The image below gives you an overview of the different types of stars as well as their size and the colour with which they shine.Ĭlassification of stars, Source: Wikimedia Commons user Kieff Our Sun, for example, is a G-type star, somewhere in the middle. Stars come in various sizes, from the smallest and coolest, so called M-type stars, to the heaviest and hottest O-type stars. In order to maintain nuclear fusion in their cores, stars have core temperatures ranging from 4 million to 40 million degrees Kelvin. ![]() During most of their lifespan stars generate radiant energy by fusing hydrogen into helium, a process that converts mass into energy and releases energy in the form of radiation of various wavelengths. The Sun, for example, is composed of 74.9% hydrogen and 23.8% helium, leaving less than 2% for all other elements heavier than helium. ![]() The composition can vary significantly, mainly depending on the age of the star and whether it was born in the early times of our universe or more recently. Stars typically consist of 70-75% hydrogen, about 25% helium and some heavier trace elements. A plasma is a gas that's so hot that the nuclei and the electrons of the atoms have separated, so it's essentially a hot "soup" that contains positive ions (atom nuclei) and electrons. Stars are massive and luminous spheres of hot plasma. the astonishing answer can be found in the last paragraph of this article.Ĭontents Introduction Classification of stars The formation of stars Structure of stars Hydrostatic equilibrium Nuclear fusion The death of a star How many stars are in the universe? Introduction The question is: for how long do these 80 million people need to continue counting until they have counted all the known stars in the universe? Try to guess. ![]() In the time you have read the text up to here (15 seconds) they have already counted a total of 1.2 billion different stars - or more than all the stars in the Small Magellanic Cloud, one of the closest galaxies to the Milky Way. They simultaneously start counting with every single person counting one star every second, so together they can manage to count 80 million stars each second. Here is a nice analogy: let's say 80 million people come together to jointly count all the stars that exist in our known universe. First of all, let's try to get an understanding of how many stars there are in the universe. ![]()
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