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AaronStrat
2008-Dec-09, 02:03 AM
Hi there.
1st time poster.
I read today that all of the stars that we can see with the naked eye are in the Milky Way. Is this true?

I guess this kind of surprised me. The more I think about it, the easier it is to believe and understand it, but the book was also written in 1991.

Please enlighten me if you would.

Aaron

Jens
2008-Dec-09, 02:34 AM
Yes, that's true, and fairly easy to explain. We are inside our galaxy, which is really huge, so any star that is close enough to be able to be seen will always be on of those stars. Other galaxies are so far away that you can't make out the individual stars with the naked eye.

It's kind of like saying that all the leaves you can see individually are within your own garden. If you look at a faraway mountain, you can't see the individual leaves.

Veeger
2008-Dec-09, 02:41 AM
Good explanation Jens.

aurora
2008-Dec-09, 03:32 AM
If you know exactly where to look, and you have reasonably dark skies, you can see a tiny smudge which is the Andromeda galaxy. That is the most distant object most of us can see with unaided vision.

If you live in the southern hemisphere, you can see the large and small Magellanic clouds quite easily. They are dwarf galaxies, and outside the Milky Way.

Swift
2008-Dec-09, 04:01 AM
I hadn't thought about this, but are any of the objects we as see naked eye point objects in the night sky galaxies (other than the Andromeda galaxy and the Magellanic clouds aurora mentioned)?

Veeger
2008-Dec-09, 04:13 AM
One may be able to make out the Magellanic clouds or the Andromeda galaxy with the naked eye as fuzzy patches but there is no way to pick out individual stars that far away. (Unless one should go super nova. )

Gigabyte
2008-Dec-09, 04:18 AM
A super nova in another galaxy, visible on earth, makes the statement that the stars you see will always be in our galaxy, well, it means that isn't true.

Doesn't it?

Gigabyte
2008-Dec-09, 04:19 AM
That question was needlessly convoluted, but I couldn't quite figure out how to arrange it.

Veeger
2008-Dec-09, 04:28 AM
A super nova in another galaxy, visible on earth, makes the statement that the stars you see will always be in our galaxy, well, it means that isn't true.

Doesn't it?

True, but I've been star gazing for 40+ years and never seen one. I guess the odds are pretty slim, and even worse if you live where I live.

Jeff Root
2008-Dec-09, 04:29 AM
Swift,

No, Andromeda, the two Magellanic Clouds, and for people with really
good eyesight, the Triangulum galaxy (M33), and possibly one other,
which I forget but suspect is probably Andromeda's companion M110,
are the only visible objects outside the Milky Way. The Triangulum
galaxy appears twice the size of the full moon, but is very faint, so
few people ever see it. Those who do are generally under age 20,
because they have larger pupils.

-- Jeff, in Minneapolis

01101001
2008-Dec-09, 04:30 AM
A super nova in another galaxy, visible on earth, makes the statement that the stars you see will always be in our galaxy, well, it means that isn't true.

Doesn't it?


That question was needlessly convoluted, but I couldn't quite figure out how to arrange it.

Alphabetically!


A Doesn't always another be earth, galaxy, galaxy, in in isn't it it? makes means nova on our see stars statement super that that the the true. visible well, will you

Swift
2008-Dec-09, 04:33 AM
Thanks Jeff. A cool fact to share on my next night hike.

Of course, in Ohio, most objects seen in the night sky are not outside the Earth's lower atmosphere, and consist of water droplets. ;)

sohh_fly
2008-Dec-09, 04:37 AM
how about stars, that have been flung out of their parent galaxy , maybe heading toward the MW, would their motion be detectable?
Speaking of stars, is their a census of if and how many stars are around the MW with no galaxy to call home ?

Jeff Root
2008-Dec-09, 04:49 AM
The brightest supernova since the invention of the telescope was
Supernova 1987A, in the the Large Magellanic Cloud. It had a visual
apparent magnitude at its brightest of +4, which made it dimmer than
any star in a list of the 314 stars brighter than apparent magnitude
3.55, but definitely visible to the unaided eye under good conditions.

-- Jeff, in Minneapolis

Gigabyte
2008-Dec-09, 04:53 AM
Did you mean: Large Magellanic Cloud?

Gigabyte
2008-Dec-09, 04:58 AM
Does this mean a super nova in a distant galaxy may not be visible?

Jeff Root
2008-Dec-09, 05:43 AM
Some say Magellan, some say Magellen... Let's call the whole thing off.

-- Jeff, in Millinipelus

Jens
2008-Dec-09, 07:10 AM
Alphabetically!

A Doesn't always another be earth, galaxy, galaxy, in in isn't it it? makes means nova on our see stars statement super that that the the true. visible well, will you


Why does "doesn't" come before "always"? :confused: Just a glitch?

Jens
2008-Dec-09, 07:12 AM
A super nova in another galaxy, visible on earth, makes the statement that the stars you see will always be in our galaxy, well, it means that isn't true.

Doesn't it?

Yes, I suppose that under exceptional circumstances, you could see individual stars outside of our galaxy. But it would be quite rare.

slang
2008-Dec-09, 07:46 AM
Why does "doesn't" come before "always"? :confused: Just a glitch?

ASCII (http://en.wikipedia.org/wiki/ASCII) has the upper case letters before the lowercase.


A super nova in another galaxy, visible on earth, makes the statement that the stars you see will always be in our galaxy, well, it means that isn't true.

I suppose technically you might argue that a blown up star isn't a star anymore. ;)

01101001
2008-Dec-09, 08:15 AM
ASCII (http://en.wikipedia.org/wiki/ASCII) has the upper case letters before the lowercase.

Aye. Or should I say "i" (AKA 01101001).

It was a case-sensitive sort done by a cold, calculating machine.

i ! ! i ! i i ! ! i i ! i ! ! i ! i i ! i ! ! i i ! ! i ! i i !

Peter B
2008-Dec-09, 10:56 AM
How big an object in the sky is the Andromeda Galaxy? And whereabouts in the sky are it and Triangulum? Are either visible in southern skies?

joema
2008-Dec-09, 01:16 PM
...I read today that all of the stars that we can see with the naked eye are in the Milky Way. Is this true?...

Not only with your naked eye, but also with an amateur telescope. Even professional telescopes couldn't clearly resolve stars outside our galaxy until the early 20th century.

Up until the early 1920s, most scientists thought our galaxy was all there was. Any nebula were all within our own galaxy. By this common viewpoint, there were no other galaxies.

Edwin Hubble used the the-new 100-inch Mt. Wilson telescope to resolve stars outside our galaxy for the first time, and published the results in the mid-1920s. This was the first clear proof that other galaxies than our own existed, and changed the prevailing view.

However if you define globular clusters as outside our galaxy -- technically they are outside, although close by -- these were first resolved into discrete stars by William Herschel using his 48 inch telescope in the 1780s. Several globular clusters can be seen with the naked eye under good conditions, although not resolved into discrete stars.

You can see M31 (Andromeda) and M33 under good conditions without a telescope, but they are just faint smudges of light, not individual stars.

Observers in the southern hemisphere can see the Magellanic clouds unassisted, but can't resolve individual stars. These were once thought to be satellite galaxies of the Milky Way, but recent research indicates they're just passing by: http://news.bbc.co.uk/1/hi/sci/tech/6249421.stm

In 1994 it was determined the closest galaxy to ours is the Sagittarius Dwarf Elliptical Galaxy, distance about 70,000 light years from earth (1/3 the distance of the Magellanic Clouds). However it can't be seen with the naked eye nor an amateur telescope:
http://en.wikipedia.org/wiki/Sagittarius_Dwarf_Elliptical_Galaxy

Buttercup
2008-Dec-09, 01:29 PM
Keep in mind the magnitude limit for the average human eye is 6 or 6.5. Many of our galaxy's stars are beyond that reach even...(the Milky Way is the galactic core; highly concentrated).

ngc3314
2008-Dec-09, 02:14 PM
The brightest supernova since the invention of the telescope was
Supernova 1987A, in the the Large Magellanic Cloud. It had a visual
apparent magnitude at its brightest of +4, which made it dimmer than
any star in a list of the 314 stars brighter than apparent magnitude
3.55, but definitely visible to the unaided eye under good conditions.

-- Jeff, in Minneapolis

Nit: peak was near V magnitude 2.8 (see graph here (http://www.eso.org/gallery/v/ESOPIA/illustrations/phot-08c-07.tif.html)). The more luminous SN1885 in Andromeda in principle just reached naked-eye visibility (V=5.8 or something estimated), but realistically it would have blended with the diffuse light of the galaxy core and I have trouble picturing it being seen as a distinct object.

aurora
2008-Dec-09, 03:13 PM
How big an object in the sky is the Andromeda Galaxy? And whereabouts in the sky are it and Triangulum? Are either visible in southern skies?

Is the constellation Andromeda ever above the horizon for you?

Check a star chart or planetarium software, online or in a magazine.

Gigabyte
2008-Dec-09, 03:41 PM
How big an object in the sky is the Andromeda Galaxy? And whereabouts in the sky are it and Triangulum? Are either visible in southern skies?

I actually know the answer to part of that! It is in the constellation Andromeda! (That is how it got it's name)

For other stuff, I use Wikipedia (http://en.wikipedia.org/wiki/Andromeda_Galaxy). Except for how big is it, then I like this picture

http://apod.nasa.gov/apod/ap061228.html

which makes you realize how friggin big it is.

Gigabyte
2008-Dec-09, 03:41 PM
It's huge!

antoniseb
2008-Dec-09, 05:03 PM
Individual stars that we can see unaided are all in the Milky Way. There was an incident recently in which a GRB had a visible component that could have been seen unaided, even though it was billions of lightyears away, but I don't think this mean that the statement the OP was asking about was wrong.

Veeger
2008-Dec-09, 09:34 PM
How big an object in the sky is the Andromeda Galaxy? And whereabouts in the sky are it and Triangulum? Are either visible in southern skies?

I'm surprised no one answered this for you. Andromeda is about 3 degrees along the major axis as astronomer's measure size but the part that is bright enough to actually see with the naked eye is more like about 1 degree which is about twice the apparent diameter of the sun. It is located at 41 degrees north. M33, the Triangulum galaxy is smaller and much dimmer than M31 (Andromeda galaxy). I have never seen it with the naked eye. It is located about 30.5 degrees north so both should be visible from all points in Australia.

Jeff Root
2008-Dec-09, 09:53 PM
I probably misinterpreted my source on the magnitude of Supernova 1987A.
Most likely, it meant that the supernova was magnitude 4 at the time it was
discovered. It continued to brighten for some days after that.

-- Jeff, in Minneapolis

joema
2008-Dec-09, 10:14 PM
How big an object in the sky is the Andromeda Galaxy? And whereabouts in the sky are it and Triangulum? Are either visible in southern skies?

If you install either Google Earth or Microsoft Worldwide Telescope, they'll let you pan & zoom around the night sky and see where it is. Both are free downloads.

Google Earth (select view/sky option when running it): http://earth.google.com/
Worldwide Telescope: http://www.worldwidetelescope.org/Home.aspx

AGN Fuel
2008-Dec-10, 02:39 AM
Hi Peter,

You may have trouble seeing it from Canberra due to the light pollution - it's dim and from our latitudes it doesn't get too far above the northern horizon at max altitude (so you have atmospheric issues as well).

I can see it at the right time of year if I'm up on my roof on the Central Coast, but interestingly I could never make it out from the dark sky site at Koolang because of trees to the north!

Veeger
2008-Dec-10, 04:12 AM
Skies where I live are quite polluted as well. Limiting at about mag 4.0-4.5 under good conditions, say 4:00AM when the air is cool and dry. I've been under dark skies in upstate New York and parts of Canada, mag 6.0 at least, and probably mag. 5.5 an hour outside of Omaha in the open country. I've also been under some really dark skies in Austria and northeast Italy in the foothills of the Alps. Of course traveling, I don't have a telescope so I soak in what I can by eyeball.

I have long had a dream to look at the Magellanic Clouds, and some of the other southern sky sights before my eyes get weak.

WayneFrancis
2008-Dec-10, 04:21 AM
A super nova in another galaxy, visible on earth, makes the statement that the stars you see will always be in our galaxy, well, it means that isn't true.

Doesn't it?

Technically the statement is still turn. A supernova does not fit the definition of a star

star : a celestial body of hot gases that radiates energy derived from thermonuclear reactions in the interior
saying a supernova is a star is a bit like saying a corpse is a living person :P

How is that for A.R.

Veeger
2008-Dec-10, 04:30 AM
Technically the statement is still turn. A supernova does not fit the definition of a star

saying a supernova is a star is a bit like saying a corpse is a living person :P

How is that for A.R.

By my definition, a supernova is a one of the stages in the life-time of a high mass star. According to models and observations, the star doesn't obliterate itself. It usually collapses into a white dwarf or BH, and these are types of stars.

WayneFrancis
2008-Dec-10, 05:06 AM
By my definition, a supernova is a one of the stages in the life-time of a high mass star. According to models and observations, the star doesn't obliterate itself. It usually collapses into a white dwarf or BH, and these are types of stars.

I know...Its kind of like saying Pluto isn't a planet.

in the future when our sun is just a hunk of cold carbon would you still call it a star? At what point does the "star" cease being a star?

astromark
2008-Dec-10, 07:54 AM
For goodness sake, stop being so trivial, pedantic. Pathetic... oops maybe not that one..:)
Yes every so often... ( hardly ever ) A star in a distant Galaxy blows off large amounts of stellar stuff. We call it a NOVA. Step up the scale a little, when it is a more massive star we call it a Super nova.. For a comparatively brief period of time it becomes very bright. They have been seen from Earth. The fact remains that we do not see stars of other galaxies. To say we do is stretching the truth.
Yes they are stars if the mass of it lifts it above the brown dwarf class. Even after they have blown off there atmosphere and colapsed... and then the star is a black hole. It stops being a star when it fails to produce energy.
Pluto is still a planet... just a dwarf one.