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Fraser
2008-Jun-03, 08:10 PM
If you were stuck inside your house, you'd never know what it looks like from the outside. That's the situation with the Milky Way. We're inside it, so we don't really know what its structure looks like. There are other examples of grand spirals that we can see, but this is like seeing other houses [...]

More... (http://www.universetoday.com/2008/06/03/the-milky-way-has-only-two-spiral-arms/)

BigDon
2008-Jun-03, 09:07 PM
I thought the news that the Milky Way was a barred spiral was at least four or five years old?

And the names of the other three arms I understand, but who is Norma?

01101001
2008-Jun-03, 09:24 PM
I thought the news that the Milky Way was a barred spiral was at least four or five years old?

And the names of the other three arms I understand, but who is Norma?


This news is that there are two major arms instead of the 4 that were thought.

See the comparison of images between 2005 and 2008 in Two of the Milky Way's Spiral Arms Go Missing (http://www.bautforum.com/astronomy/74979-two-milky-ways-spiral-arms-go-missing.html#post1254402).

Astronomy Answers (http://www.astro.uu.nl/~strous/cgi-bin/glossary.cgi?l=en&o=Norma)

Norma (Level) is a southern constellation, close to the ecliptic, close to the Milky Way.

BigDon
2008-Jun-03, 09:28 PM
Thanks 011,

I thought it be something like that, but with humans in the loop you can never tell.

bautforum
2008-Jun-04, 12:48 AM
So who's living in the other Spiral Arm I wonder?

We are still living in the Sagittarius arm, right?

01101001
2008-Jun-04, 01:33 AM
So who's living in the other Spiral Arm I wonder?

Do you think some member knows who, if anyone, lives in the other spiral arm?


We are still living in the Sagittarius arm, right?

From the article (http://www.universetoday.com/2008/06/03/the-milky-way-has-only-two-spiral-arms/) above:


As expected, astronomers found an increase in density in stars towards the Scutum-Centaurus Arm, but no increase towards the Sagittarius and Norma arms. The Perseus arm wraps around the outer portion of our galaxy and can't be seen in the Spitzer images.

I.e. Sagittarius and Norma didn't have the right stuff to be major arms. And:


We live in minor arm called the Orion Arm, or the Orion Spur, located between the Sagittarius and Perseus Arms.

Check out the annotated image (http://www.spitzer.caltech.edu/Media/releases/ssc2008-10/ssc2008-10b.shtml) that came from the Spitzer site. It locates the Sun, the Orion Spur and the Sagittarius now-minor Arm for you.