Stars??

I was outside looking up at the night sky and I was wondering how many stars
there were that I was looking at that weren't actually there. Does anyone
know? Since it takes millions of years for their light to reach us, is it
possible that we're looking at stars that aren't even there? If anyone
could post a reply to this with something other than spam or cult
proselytizing that'd be great. Thank you all for your time.

wrote in message
m...
I was outside looking up at the night sky and I was wondering how many
stars there were that I was looking at that weren't actually there. Does
anyone know? Since it takes millions of years for their light to reach us,
is it possible that we're looking at stars that aren't even there? If
anyone could post a reply to this with something other than spam or cult
proselytizing that'd be great. Thank you all for your time.

Hi Jerry - unfortunately the question sounds like you're trolling - even for
a person who hasn't posted to this newsgroup. In my completely uninformed
state, I would venture a guess is that there is likely an infinite number of
stars we can't see, some of whose light hasn't reached us yet, or some that
are just so faint the light is imperceptible with current telescopes of
other equipment. Maybe what you're asking is, if a new star ignited today, a
million light years from here, then yes, we wouldn't be able to see it in
the night sky for a million years. Conversely, if an existing star the same
distance blew out, we could see it for a million years before it goes out.
What always gets me is, they're all up they're moving so really, all the
star are actually in different positions than we see in the sky, some more
drastic than others depending on the distance.

I hope that answers your question and I hope some posters with a lot more
technical knowledge can respond.

I'm hoping, since I'm about to ask a question, someone will be as kind.

Peace,
Steve

"Steve Latham" wrote in message
news:4ohId.13481$Os6.687@trnddc08...
wrote in message
m...
I was outside looking up at the night sky and I was wondering how many
stars there were that I was looking at that weren't actually there. Does
anyone know? Since it takes millions of years for their light to reach
us,
is it possible that we're looking at stars that aren't even there? If
anyone could post a reply to this with something other than spam or cult
proselytizing that'd be great. Thank you all for your time.

Hi Jerry - unfortunately the question sounds like you're trolling - even
for
a person who hasn't posted to this newsgroup. In my completely uninformed
state, I would venture a guess is that there is likely an infinite number
of
stars we can't see, some of whose light hasn't reached us yet, or some
that
are just so faint the light is imperceptible with current telescopes of
other equipment. Maybe what you're asking is, if a new star ignited today,
a
million light years from here, then yes, we wouldn't be able to see it in
the night sky for a million years. Conversely, if an existing star the
same
distance blew out, we could see it for a million years before it goes out.
What always gets me is, they're all up they're moving so really, all the
star are actually in different positions than we see in the sky, some more
drastic than others depending on the distance.

I hope that answers your question and I hope some posters with a lot more
technical knowledge can respond.

I'm hoping, since I'm about to ask a question, someone will be as kind.

Peace,
Steve

I don't think he was trolling at all, but only asking what you speculated in
your "Conversely" statement, except on an "as of now" basis. That is, of
all the stars that appear "up there", how many (say via an approximate
percentage) are now extinguished. Unfortunately, I can't answer it either,
but would guess it's quite low, like 1 - 3%(?). This guess (SWAG?) is just
based on the life span of stars. Regards, Brett.

wrote:

I was outside looking up at the night sky and I was wondering how many stars
there were that I was looking at that weren't actually there. Does anyone
know? Since it takes millions of years for their light to reach us, is it
possible that we're looking at stars that aren't even there? If anyone
could post a reply to this with something other than spam or cult
proselytizing that'd be great. Thank you all for your time.

Of the thousands of stars you can see individually with the naked
eye, most are 'only' from tens to hundreds of light-years away. Stars
whose light takes millions of years to reach us are in other galaxies
and therefore too faint to see, even the brightest ones, without very
powerful telescopes. (But given dark skies you can certainly see a
few of the nearest large galaxies unaided: their billions of stars
all together produce enough light to appear as faintly glowing shapes.)

Considering as well that the lifetimes of most stars are in the
billions of years (see the current thread titled "Star sizes and
longevity", in which Bob Weber posted some examples according to
size), if you were able to instantly teleport to any star you can
spot, odds are you'd find it still there. However, there are a few
star-forming regions near enough to the solar system that their
short-lived supergiants are visible, yet far enough away that there's
a reasonable chance they'd have enough time to do something dramatic
while their light is still in transit. We might suppose the
probability that a star with a life-expectancy of 'only' a million
years, a thousand light-years away, has become a supernova and died
since the light we see departed, to be on the order of one in a thousand.

Many supernovae are observed every year in other galaxies, and
occasionally these briefly reach naked-eye visibility despite their
distance; of course these stars no longer exist as such.

Something else to consider: your question assumes that the concept of
simultaneity can apply over interstellar distances, while relativity
theory makes this idea pretty much meaningless, or at least of zero
practical value. Since the photons that arrive here have come as soon
as anything possibly could, we might as well call their departure
time 'now'.

--
Odysseus