The question might seems like taken inspiration from motion picture Sixth sense with little digression from ghost to star but the fact remains the same that the question is intriguing and deserves an explanation.However, the credibilty of this notion needs to be verified pragmatically. So, why should we wait now, let's find out.....

Light travels at about 300,000 km/s. It is the fastest thing in the Universe. But it is not infinitely fast. So it also takes some noticeable time if the distance is too large, like light years, which is equal to 9.4605284 x 1012 kilometers and astronomical unit to measure the distance (of stars etc.). For an instance, it takes light more than eight minutes to reach Earth from Sun. It is also a well known fact that we see objects when light travels from object to our eyes (Read : How do we see colors). If we will combine two of the previous facts we will come to know that what we see as sun's current image is actually not the current but Sun's image as it was eight minutes ago.

Sun is only few light years far from earth. However, the most nearest star to the earth is Alpha Centauri and light takes more than four years to get from there to here.One of the most distant naked eye stars is Deneb in the constellation Cygnus, which is almost 3,000 light years away. The light we're seeing from Deneb started its journey towards us when ancient Rome was just a few hamlets and not even on the map for real estate speculators.

Stars are much like us as they also go through the same life cycle as we do.They are born, they live for an amount of time, and they die. Some fade away, some explode, but in the end, like us, they are also mortal.There are a few stars that could possibly explode in the near future, such as the red giant star Betelgeuse in the constellation of Orion. It's about 650 light years away, if it had exploded a couple centuries ago, we still wouldn't know.

So that might be a possibility that the star you love to gaze every night may not be existing anymore and might have exploded long before you came on this earth.

However, number of such kind of stars are fewer for naked eye viewer as there are around 6000 stars only that can be seen by naked eyes.Rest of the stars are too distant to be seen with naked eyes.Furthermore, the Milky Way is 100,000 light-years across, and only a few stars in it have a shorter lifespan than that. On average, very roughly, only two or three stars are expected to go supernova in the galaxy per century, so the light from a few thousand of such explosions is already on its way here. That may sound like a lot, but the Milky Way has something like 200 billion stars in it. So really, the number already dead but still shining in our sky is very small.