How do you find the age of stars?

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When we look in the dark sky on a clear night, it is easy to get overwhelmed by the beauty of the stars above. We connect dots, find patterns, and even choose our favorite clusters. As amateur star-gazers, one thing we can't do is determine the age of those stars. Are they a billion years old? 10 billion?

Luckily, scientists have developed many ways to achieve the age of a star, giving us a clearer picture of the history of the universe, and even helping us discover intelligent life in the universe!

Secrets of Star Clusters:

There are somewhat different constraints in estimating the age of a star, but when a cluster contains a star the general approximation is much easier. These star clusters are usually formed at the same time, but not necessarily all have the same properties. Therefore, if you can determine the size and brightness of a series of wires in a cluster, it can be easy to determine their overall lifespan by knowing that they were all formed at about the same time.

Most stars spend about 90% of their lives in the "main sequence" phase, where they are continuously ejecting energy and radiation due to the nuclear furnace inside them. The largest stars are "blue-hot" and extremely bright, while the lowest massive stars are "red-hot" and quite faint. Once a star is formed, the properties of the star (brightness and temperature) do not change very much during the main sequence phase.

This relationship between mass, brightness, and age means that star clusters can tell many stories. For example, you can see the hottest, bluest and most massive star in a star cluster that does not have a "main sequence", and calculate how hot and bright it is. The mass of the star tells us how much fuel was in it, while the brightness tells us how fast it is burning that fuel. Therefore, it is possible to calculate the age of the star, and later, the age of the other stars in the cluster. Today, researchers believe they have a 10–20% margin of error for star age estimation.

But what about the stars alone?

While star clusters are easily and somewhat "easy" to age, things are a bit more difficult for stars alone, as there is no reference to how long they shine. His "spin", however, can prove to be very useful in this context, especially since the Kepler Space Telescope has begun to dive deep into the horrors of space to find answers. Prior to Kepler, Earth-based telescopes could not look directly at the stars, which were half or more old due to the interference of the Earth's atmosphere. The incredibly powerful lenses of the Kepler spacecraft are capable of directly observing distant stars, where they can detect "starspots", which are deep patches on the surface

There is a direct relationship between mass, spin rate, and the age of a star, so if you know the mass and spin rate, it is possible to determine the age. The speed with which these starspots reappear on the star's surface, noted by the Kepler telescope, can tell how fast the star is rotating. The dips in brightness that make up these starspots are very difficult to spot, as they only account for about 1-2% reduction in total light output from the star, but Kepler can handle the task.

Stars get smaller as they age, but researchers are still not sure how much. In fact, the solitary star is similar to the stars in the situational challenge clusters of age measurements. Without a set reference - a "spin clock", so to speak - it can be difficult, but measuring the spin rates of stars with a known age (using the techniques in the previous section) helps establish a baseline Can. First, a researcher can measure the spin of a star in a star cluster, and then compare that measurement to the spin rate of a similarly sized single star. Voila - We can make a stellar birthday cake with the right number of candles.