Has it already happened?
There’s not really one instant where a new star goes from not shining to shining where a human looking up at night would see a star “turn on.” The process of turning on takes between 10,000 - 1,000,000 years, depending on the size of the star and how many stages you include in the process.
It doesn’t really matter how long it takes. There will be a day in that period when it becomes visible.
Well, not exactly…
Sure, hair grows long over time - but there isn’t really a day where you’d look at someone and suddenly see the “Long hair” … It happens gradually…
Hair grows over time and yesterday it was under 3 inches today it’s over 3 inches. A tiny change over a threshold.
There’s a threshold of visibility for stars. Yesterday it wasn’t visible to the eye. Today it’s barely visible.
Yes, and as per the comment you originally replied to - there isn’t a moment there where the star appears to “turn on”. To put it more simply, a star sort of “fades in”. You wouldn’t really percieve the fade beginning, in the same way you don’t perceive hair growing… Probably not the greatest analogy but I thought it’d help make sense of it…
I think “barely visible” isn’t going to be a lightbulb turning on moment.
Even for high-mass stars, the time it takes for a star to form from a molecular cloud is on the order of a million years (see Figs 5 and 6 of this paper). A human lifetime is essentially just a snapshot of this process; you’re not really going to see a new star form over such timescales (unless you count supernovae as “new stars”).
Also, all of the stars visible to the unaided eye are relatively close: only a few thousand light years away at most. All of the other stars in the milky way are too far away to see as anything more than a collective haze.
It has certainly happened. We know of stars that are younger than humans.
But has someone directly observed this happening? Well, it depends. As already noted, star formation takes a long time. It’s not like dark, cold dust suddenly collapses and ignites into a star. During the formation process, the dust is compressed, and as you might recall, as volume decreases on a mass, pressure and temperature increase. As it heats up, it starts emitting radiation. So it’s possible to observe this even before becoming a true main sequence star. And we have definitely observed a lot of those, and if you go outside and point your sufficiently powerful telescope in the right direction, you too can see one with your own eyes!
Yes. New stars are still being born. We can also see stars going supernova that we couldn’t see with our bare eyes before.
Yes, it has already happened. When you look.up the sky, you are pretty much looking at ghosts. Due to the speed of light being finite.
Naw, most of the stars you can see in the sky are close enough that’s probably not true.
Using a telescope, that’s a different story.
Well yeah, but I mean has there been or could there be a time where someone actively looking at the sky sees a new star appear before their eyes and it wasn’t a super nova of a star dying or a newly formed star relatively nearby? IE the star has been there longer than Earth existed, but it is so far away it took until today to finally arrive where we could see it.
I know it has limited speed, but does it have a limited range before it would just always be invisible beyond a certain range based on size and luminosity, like a flashlight? I am ptetty sure atmosphere has something to do with that, but not 100% certain if light could travel in a vaccum forever.
Disclaimer: This is not my field of expertise
Okay I will try going through this piece by piece:
- has there been or could there be a time where someone actively looking at the sky sees a new star appear before their eyes - The probability to experience a new star with naked eyes or even a regular telescope is very low. You will have to know the exact location where you would like to look into the sky and perhaps the timing too. - As @Bjorn says we have observatories working 24/7 around the globe and new stars are always popping up.
- does it have a limited range before it would just always be invisible beyond a certain range based on size and luminosity, like a flashlight?
- Photons can travel the vacuum forever. Flashlight has limited range only due to photons getting diffused or barricaded by some other molecules present in their path.
- However, we know space is not exactly pure vacuum and that means signals we receive from the stars are still going to be inaccurate.
Since our discussion was mostly on eyes, I found this article for you, hopefully this satisfies your curiosity. :) https://www.johncbarentine.com/astronomical-visibility.html
We know of old supernovae because ancient astronomers catalogued them as new stars (nova means new). Maybe they also managed to find new stars.
The new Vera C. Rubin Observatory should help us with finding new stars and other objects. It will scan the whole southern night sky in three days, marking all changes when it gets to the same patch of sky again.
If sharks have a culture they might have recorded the appearance of Polaris, the north star. Sharks have been longer on earth than Polaris has existed.
deleted by creator
