So say a star is 200 light years away, after the light has reached us, why do we stop seeing that star?

Question

Thanks guys, so basically we keep seeing that star once the light has reached us. I know it's a bit of a stupid question but I needed to get a few basics cleared up.

Answer 1

think of light as a string....

The speed of light travels to earth from a distant star, but there is a delay between when a proton of light leaves the star and when it arrives on earth.

The distance of a star will determine the time it takes for a proton to travel to earth and be "seen".

For instance, the sun roughly 8 days away at the speed of light. This means that it would take the "light" 8 days to get here. The sunshine you are seeing was actually created 8 days ago by a reaction on the sun.

Similarly, the light from a star (basically just a sun from another solarsystem) was emitted X days/months/years ago.

When the protons finally find their way to earth you start "seeing" the star... When you stop "seeing" the star that means that the star went out (imploded, exploded, burnt out, whatever) however many years (same as distance in light years) prior to you seeing that proton.


So, in your basic question. If a star is 200 light years away, this means that the light being seen was created 200 years earlier and it's taken 200 years to get to earth. This also means that when you stop seeing that specific star, you can safely assume that the star was extinguished 200 years from the last glimmer of light.

Answer 2

We.....don't. Whatever gave you the idea that the stars vanish as we look at them? If a star is say, 938 light years away, the light you see as you look at it is 938 years out from the star that produced it. The star of course produces a steady stream of light, but as the photons hit your eyes, they are 938 years old. A moment later, you see the light that the star emitted a moment after the previous, and so on, in a continuous stream. I don't know if I'm expressing this clearly, time intervals at interstellar distances can be confusing to discuss.


Addendum: basicfib got it {mostly} right. He said protons but meant photons, and the Sun is a mere 8 light minutes away, not days. Also, the reaction which produces photons takes place not 'on' it, but deep within the Sun's core, which is so dense that it takes an average photon roughly one million years to reach the surface and be emitted

Answer 3

If the star exploded 200 light years ago, we would still see the light. The star would not be there though.

Answer 4

Not sure what you mean by "why do we stop seeing that star".

We don't "stop seeing that star".
The only way we would "stop seeing that star" would be if it stopped shining. We see the stars shining steadily in the sky night after night, year after year, century after century.
The light leaving the star isn't just a short burst like a flashbulb going off. The star continues to shine 24/7, just like our own sun does.

Answer 5

we don't

The only way we would stop seeing the star is if it reached the end of it's life cycle which is a very rare event to witness.

Another way would be if suddenly there was a cloud of dust that moved between the star and our Earth to block out the light from our sight.

The light would also be stopped with clouds in our atmosphere or when the Sun was in the sky preventing us from seeing any stars during the daytime.

Answer 6

If the light source (star) is 200 light years away, and we suddenly stop seeing that particular star's light, then, something happened to that star.
If it went nova or supernova, we would still see the light from the resulting explosion...
If it went suddenly, mysteriously dark, then I think you may have stumbled across an event no one else has witnessed in recorded history...
A 'vanishing star'.
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Answer 7

it took the light 200 years to reach us, so possibilities are that the star has burnt out or imploded by the time the light reaches earth

Answer 8

They light takes ~200 years to reach us.
The star is constantly putting out light.
The light you see is always ~200 years old.
It's like water from a hose.
As long as it keeps coming, you keep getting wet.

Answer 9

say the star is born 200 light years away.it would take 200 years to see the star,becuz the light takes 200 years to get to our eyes.then the star gets destroyed,so after 200 years the the star will be gone to our eyes.

Answer 10

Uh... as long as the star keeps shining, we keep seeing it's light. If it were to blow up RIGHT NOW, we wouldn't know about it for 200 years.