Distance from Sun to outside galaxy?

[Holocene]

Distance from Sun to "outside" galaxy?

Does anyone have a general figure regarding the distance from the Sun to the nearest place officially "outside" the Milky Way galaxy?

Thnaks.

 

[mgb_phys]

Depends what you mean by awayfrom the milky way, but at the sun's distance from the centre the galaxy is about 3000 years thick - so you could say 1500 lyr

 

[tony873004]

By "place" do you simply mean an area of space? In that case, just Google for "size of Milky Way" and "Sun's position in the Milky Way" and subtract the 2 answers to get the distance from the Sun to the edge of the Galaxy. I would guess around 100,000 light years.

Or do you want to know the closest non-Milky Way object to the Sun? The Large and Small Magellanic Clouds are satellite galaxies of the Milky Way. They are roughly 200,000 light years away.

 

[DaveC426913]

tony, moving along the galactic plane is not the fastest way to exit the galaxy.


As mgb_phys explains, the fastest way is to travel straight "up" or straight "down" relative to the galactic plane.

According to him, that's a mere 1500ly in wither direction. I would have thought it was more than that, but I'll defer to him.

 

[mgb_phys]

I quote the noted cosmologist E. Idle

Our galaxy itself contains a hundred billion stars.
It's a hundred thousand light years side to side.
It bulges in the middle, sixteen thousand light years thick,
But out by us, it's just three thousand light years wide.
We're thirty thousand light years from galactic central point.
We go 'round every two hundred million years,
And our galaxy is only one of millions of billions
In this amazing and expanding universe.

The song is pretty accurate and is a good way of memorising a lot of astronomical distances - most astronomers can sing all of it ( generally rather badly )

 

[tony873004]

tony, moving along the galactic plane is not the fastest way to exit the galaxy...

Although the majority of visible matter is concentrated in the galactic plane, the halo contains a lot of matter too, including halo stars, which stand out because their tangental motion relative to the Sun is about 200 km/s rather than 20 km/s for the disk stars. The galactic halo also contains many globular clusters, filled with hundreds of thousands to millions of stars each. Most of these clusters are on orbits highly inclined to the galactic plane. So it would probably be a safer assumption to consider the galaxy as a sphere.

 

[tony873004]

Wikipedia has a nice description: http://en.wikipedia.org/wiki/Milky_Way#Halo

The galactic disk is surrounded by a spheroid halo of old stars and globular clusters, of which 90% lie within 100,000 light-years,[20] suggesting a stellar halo diameter of 200,000 light-years. However, a few globular clusters have been found farther, such as PAL 4 and AM1 at more than 200,000 light-years away from the galactic center. While the disk contains gas and dust obscuring the view in some wavelengths, the spheroid component does not. Active star formation takes place in the disk (especially in the spiral arms, which represent areas of high density), but not in the halo. Open clusters also occur primarily in the disk.