When we look at the stars with just our eyes...

No telescope ...

When we look at the stars , are all the stars we see from the Milky
Way Galaxy ?
Or do we see stars from other galaxy's ?

"PTP" == Phineas T Puddleduck writes:

PTP In article , SAT
PTP W-7 wrote:

No telescope ...

When we look at the stars , are all the stars we see from the Milky
Way Galaxy ? Or do we see stars from other galaxy's ?

PTP The stars we see with our naked eye are from our galaxy.

With a few exceptions. If one is in a dark location in the northern
hemisphere, one can see the Andromeda Galaxy. From the southern
hemisphere, one can see the Large and Small Magellanic Clouds, both
satellite galaxies to our own. Of course, one can not distinguish one
star from another in these galaxies with the naked eye, but one can
see the combined light from many stars in another galaxy with the
naked eye.


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"SAT W-7" wrote in message
...
No telescope ...

When we look at the stars , are all the stars we see from the Milky
Way Galaxy ? Or do we see stars from other galaxy's ?

With naked eye, not only are the stars you see in the night sky all
in our own galaxy, but all are in our immediate galactic neighborhood,
which is pretty sparsely populated. Some bright, massive stars can
be resolved in the outer spiral arms of the Andromeda
(nearby--galactically speaking--large galaxy) galaxy, with large earthbound
telescopes and photographic exposures.

But no star other than the Sun is any more than a point, even in the largest
telescopes....they're just too distant for more.

-----
Jay McKenzie
http://home.bellsouth.net/p/pwp-wstviews

"s" == smallg writes:

s "SAT W-7" wrote in message
s ...
No telescope ...

When we look at the stars , are all the stars we see from the Milky
Way Galaxy ? Or do we see stars from other galaxy's ?

s With naked eye, not only are the stars you see in the night sky all
s in our own galaxy, but all are in our immediate galactic
s neighborhood, which is pretty sparsely populated.

Not entirely. There are a number of stars that one can see that are
more than 1000 light years away, for instance, Deneb, Alnilan, and
Wezen are among the 50 brightest stars in the sky.

s Some bright, massive stars can be resolved in the outer spiral arms
s of the Andromeda (...) galaxy, with large earthbound telescopes
s and photographic exposures.

s But no star other than the Sun is any more than a point, even in
s the largest telescopes....they're just too distant for more.

No, the stellar disk of a number of stars have been resolved. The
most notable is Betelgeuse, as it was first resolved by Michelson in
1920.

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"Joseph Lazio" wrote in message
...

Not entirely. There are a number of stars that one can see that are
more than 1000 light years away, for instance, Deneb, Alnilan, and
Wezen are among the 50 brightest stars in the sky.

Yeah, but still in our galactic neighborhood, as the galaxy itself is
probably
100K lt-yrs across, although those mentioned would be a few blocks
over so to speak.... most of the other 6,000 or so visible to a person with
good vision on a dark night on Earth are well closer.

s Some bright, massive stars can be resolved in the outer spiral arms
s of the Andromeda (...) galaxy, with large earthbound telescopes
s and photographic exposures.

s But no star other than the Sun is any more than a point, even in
s the largest telescopes....they're just too distant for more.

No, the stellar disk of a number of stars have been resolved. The
most notable is Betelgeuse, as it was first resolved by Michelson in
1920.

Well, not resolved in the traditional optical sense. The stars are too far
away for that.
Belelgeuse is a red giant
and relatively nearby. Measuring angular diameter with interferometry
(as he did) is not really "resolving." I just did a quick search for ya.
The first paragraph pretty much echoes what I wrote, and it's
a good article you might want to read. The team was able
to utilize microlensing to obtain resolved *spectra* "across the
full face of a normal star other than the sun." Here's a snip (notice
their quotation marks around 'resolve.'):

--begin excerpts--
Like our Sun, stars are large gaseous spheres. However, while we are able to
perceive the Sun's disk, all other stars are so far away that they normally
appear as points of light. Only specialized observing techniques, like
interferometry, are able to "resolve" the images of nearby stars and to show
them as extended balls of fire.

But opportunities may sometimes arise that allow amazing observational feats
in this field. Indeed, an international team of astronomers has just
"resolved" a single, normal star some 25,000 light years away, or about 1.6
billion times more distant than the Sun, by taking advantage of a multiple
microlensing event.

During such a rare event, the light from the remote star is amplified by the
gravity of a faint object that passes in front of it, as seen from the
Earth. In fact, this gravitational lens acts as a magnifying glass that
focusses different parts of the star's image at different times.

Using the FORS1 multi-mode instrument at the 8.2-m VLT ANTU telescope on
Paranal during a microlensing event, the team was able to obtain detailed
spectra of the different parts of the remote star. In doing so, they managed
to probe its gaseous atmosphere at different depths.

This is the first time that it has been possible to obtain detailed,
spatially resolved spectra across the full face of a normal star other than
the Sun.

snip

The face of a star
Distant stars appear as small points of light, even to the largest
telescopes on Earth. They are simply too far away to be "resolved" by normal
telescopes, and no information can therefore be obtained about what the
stellar surfaces look like. This is a fundamental obstacle to the detailed
study of stars other than the Sun.

We know, however, that the disk of a star does not present itself as a
uniform surface. As is the case of the Sun that exhibits variable structures
like sunspots (in particular at the time of the present solar maximum),
other stars may also have "star-spots".

Another general feature of solar and stellar disks is that they appear
fainter towards the periphery. This phenomenon is known as "limb darkening"
and is actually a matter of the viewing angle. When we look towards the
middle of the solar disk, we see into rather deep and hot layers of its
atmosphere. Contrarily, when we view the very edge of the solar disk, we
only see the upper, cooler and dimmer parts.

Thus, by looking at different areas of its disk, we are able to probe
different depths of the solar atmosphere. This in turn permits to determine
the structure (temperature, pressure, chemical composition, etc.) of the
upper layers of the Sun.

For more distant stars, however, their disks appear much too small for this
kind of detailed observation. Despite much instrumental progress, therefore,
fundamental observational information about stars is still lacking,
especially for stars different from the Sun.

This is one of the main reasons why the astronomers are thrilled by a new
series of spectra from the FORS1 multi-mode instrument at the 8.2-m VLT ANTU
telescope at Paranal. They "resolve" for the first time the surface of a
normal star some 25,000 light-years away.

This amazing observational feat has been possible with some help from a
natural "magnifying glass". The road leading to this remarkable result is an
instructive and interesting one.

--end excerpts--

Here's the link: http://spaceflightnow.com/news/n0105/06esostellar/

-----
Jay McKenzie
http://home.bellsouth.net/p/pwp-wstviews

"smallg" wrote in
:


"Joseph Lazio" wrote in message
...

Not entirely. There are a number of stars that one can see that are
more than 1000 light years away, for instance, Deneb, Alnilan, and
Wezen are among the 50 brightest stars in the sky.

Yeah, but still in our galactic neighborhood, as the galaxy itself is
probably
100K lt-yrs across, although those mentioned would be a few blocks
over so to speak.... most of the other 6,000 or so visible to a person
with good vision on a dark night on Earth are well closer.

s Some bright, massive stars can be resolved in the outer spiral arms
s of the Andromeda (...) galaxy, with large earthbound telescopes
s and photographic exposures.

s But no star other than the Sun is any more than a point, even in
s the largest telescopes....they're just too distant for more.

No, the stellar disk of a number of stars have been resolved. The
most notable is Betelgeuse, as it was first resolved by Michelson in
1920.

Well, not resolved in the traditional optical sense. The stars are too
far away for that.
Belelgeuse is a red giant
and relatively nearby. Measuring angular diameter with interferometry
(as he did) is not really "resolving." I just did a quick search for
ya. The first paragraph pretty much echoes what I wrote, and it's
a good article you might want to read. The team was able
to utilize microlensing to obtain resolved *spectra* "across the
full face of a normal star other than the sun." Here's a snip (notice
their quotation marks around 'resolve.'):

It actually is resolved. The speckle interferometry is just a way of
removing atmospheric turbulence. The HST which doesn't have a particularly
large mirror can easily resolve Betelguese as a disk.

http://hubblesite.org/newscenter/new...eases/1996/04/

Klazmon.

In article ,
"smallg" writes:
Belelgeuse is a red giant and relatively nearby.

Betelgeuse is a supergiant, actually, but indeed nearby.

Measuring angular diameter with interferometry
is not really "resolving."

Astronomers use "resolve" to mean any method that detects finite
angular size. Two-element interferometry (as pioneered by Michelson)
"resolves" stellar disks but doesn't "image" them. "Speckle
interferometry" detects surface features, though one can quibble
whether it's really imaging. Lunar occultations also detect surface
features. Modern multi-element interferometers do even better. And
as someone mentioned, the disk of Betelgeuse has been imaged with
HST; no quibbling possible about that. These studies give quite a
bit of information on limb darkening and starspots.

The general point is correct, though: study of stars other than the
Sun is much hindered by lack of angular resolution, and the VLT
micro-lensing study is very much to be commended.

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