A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Astronomy and Astrophysics » Research
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

A retrograde Milky Way?



 
 
Thread Tools Display Modes
  #1  
Old March 30th 15, 09:29 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
external usenet poster
 
Posts: 273
Default A retrograde Milky Way?

Looking down on the Milky Way from the north galactic pole, our galaxy
rotates clockwise. For a planet in the solar system, the corresponding
rotation would be deemed retrograde. Why was the north galactic pole
defined in this way? Because it is in the northern hemisphere (i.e. has
positive declination)? Were it roughly near the Earth's northern axis,
or the northern axis of the solar system, then this would make sense,
but since it has a declination of less than 30 degrees, I think it would
be more intuitive to define it so that the rotation is prograde.
  #2  
Old March 30th 15, 07:32 PM posted to sci.astro.research
Jos Bergervoet
external usenet poster
 
Posts: 126
Default A retrograde Milky Way?

On 3/30/2015 10:29 AM, Phillip Helbig (undress to reply) wrote:
Looking down on the Milky Way from the north galactic pole, our galaxy
rotates clockwise. For a planet in the solar system, the corresponding
rotation would be deemed retrograde. Why was the north galactic pole
defined in this way? Because it is in the northern hemisphere (i.e. has
positive declination)? Were it roughly near the Earth's northern axis,
or the northern axis of the solar system, then this would make sense,
but since it has a declination of less than 30 degrees, I think it would
be more intuitive to define it so that the rotation is prograde.


How about the magnetism? The earth's north-pole is actually
the magnetic south-pole, so perhaps it was to avoid creating
this inconsistency again? :-)

--
Jos
  #3  
Old April 1st 15, 05:45 PM posted to sci.astro.research
Steve Willner
external usenet poster
 
Posts: 1,172
Default A retrograde Milky Way?

In article ,
"Phillip Helbig (undress to reply)" writes:
Why was the north galactic pole defined in this way? Because it
is in the northern hemisphere


While I can't cite definitive evidence, I'm sure that was the reason.

There is a specific IAU resolution defining the north pole of any
solar system body as the pole pointing north of the invariable plane
of the solar system. That's a poor definition in my opinion, but it
got a majority vote.

... so that the rotation is prograde.


The traditional astronomical word is "direct." "Prograde" is a
neologism that no true astronomer would use.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Retrograde Satellites HVAC Misc 1 August 23rd 09 04:49 PM
retrograde motion? [email protected] Astronomy Misc 2 January 29th 09 12:05 PM
Mercury in retrograde Tom Hise Amateur Astronomy 44 October 22nd 08 08:52 AM
Retrograde Sun of NASA oriel36[_2_] Amateur Astronomy 0 September 2nd 08 03:02 PM
retrograde MAT[_4_] Amateur Astronomy 1 April 27th 08 12:26 PM


All times are GMT +1. The time now is 09:28 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.