What is the correct size and shape of the Milky Way?

[willpittenger]

I was taught as a kid (nearly 40 years ago) that the Milky Way is a spiral galaxy. Now The History Channel's <i>The Universe</i> show has it as a barred spiral. They also seemed confused about the size of the Milky Way. One moment they are saying that Andromeda is the same size. Next thing I knew, they claimed it was twice our size.<br /><br />What is correct? <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[bdewoody]

They said that the central core was approximately twice the size of the Milky Way core. But they also said it is difficult to get an exact picture of our galaxy since we are in it. It's kinda like trying to describe what your car looks like having only seen it from the inside. You may know what it's mass is and how fast it's moving but thats about it. <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>

 

[dragon04]

If you google up a few sources, most are in agreement of a diameter of 100,000LY for the MW.<br /><br />M31 on the other hand has been updated to have a diameter of about 220,000LY<br /><br />I found this interesting...<br /><br /><font color="yellow">On January 7, 2007, a team of astronomers announced the discovery of low-metallicity, red giant stars up to some 500,000 light-years from Andromeda's core which suggests that the galaxy is much larger than originally thought, so that Andromeda's luminous halo may actually overlap with that of the Milky Way </font><br /><br />Link <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[weeman]

Ah, very interesting! Thanks for expanding my brain a little more Dragon <img src="/images/icons/smile.gif" /> It expands every time I log on to this board.<br /><br />The more recent estimates of stars also suggest that Andromeda is much larger than the Milky Way. Using NASA's Spitzer Telescope, many scientists have now calculated an estimate that boosts Andromeda's star count to one trillion! Any idea how much one trillion really is?<br /><br />A trillion seconds is 31,688 years. <br /><br />If you had one trillion pennies, you could stack them into a giant cube measuring 273 ft high, 273 ft wide, and 273 ft thick. It would way a hefty 3.1 million tons, and if you made one single stack of the pennies, they would make nearly two roundtrips to the Moon. <br /><br />I'm bored, if ya can't tell <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

[spacecrusader]

well isn't the milky way in like some sort of space cloud? Or am i just thinking of something completely random.

 

[CalliArcale]

The Milky Way belongs to a galactic cluster called the Local Group. Andromeda also belongs to this group. That's probably what you're thinking of. The Local Group itself is part of the Virgo Supercluster. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[nyrath]

<blockquote><font class="small">In reply to:</font><hr /><p>I was taught as a kid (nearly 40 years ago) that the Milky Way is a spiral galaxy. Now The History Channel's The Universe show has it as a barred spiral.<p><hr /></p></p></blockquote><br /><br />This is because 40 years ago astronomers figured that the Milky Way was an ordinary spiral. It wasn't until about 15 years ago that evidence started accumulating that it was a barred spiral.<br /><br />http://apod.nasa.gov/apod/ap050825.html

 

[dragon04]

I suspect that as the resolution of instruments increases, sizes will be redefined again and again.<br /><br /> <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>