Best way to implement a constant that will be used in more than one class

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C#

Java

So this question doesn't have to do with a specific application, it's just something that i've been wondering overall. Let's say you're creating a class called Star.Inside the class in several places and elsewhere in the application, the value of the speed of light, which is a constant (186000 miles/second), is needed. What would be the best way to implement this? Preferably I need it implemented in the Star class itself.

What I have tried:

lot's of different options in the past, just trying to find out what the best way. to do it is.