The Milky Way May be 50 Percent Bigger Than Thought : Discovery News

[Panich52]

DiscoverNews
The Milky Way May be 50 Percent Bigger Than Thought : Discovery News

A ring-like filament of stars wrapping around the Milky Way may actually belong to the galaxy itself.

READ MORE (photo gallery)
http://news.discovery.com/space/galaxies/the-milky-way-may-be-50-percent-bigger-than-thought-150310.htm?utm_source=newsletter&utm_medium=email&utm_campaign=dnewsnewsletter

[DreamGypsy]

1. There has been some controversy about the connection of the Monoceros Ring to the Milky Way...

...going on for some time. Here's a comment from 2012 on some published papers in which the commenters dispute the extra-galactic nature of the ring:

Comments on the "Monoceros" affair:

(emphasis mine)

(Submitted on 5 Jul 2012)

This is a brief note to comment on some recent papers addressing the Monoceros ring. In our view, nothing new was delivered on the matter: No new evidence or arguments are presented which lead to think that the over-densities in Monoceros must not be due to the flared thick disc of the Milky Way.
Again, we restate that extrapolations are easily misleading and that a model of the Galaxy is not the Galaxy. Raising and discussing exciting possibilities is healthy. However, enthusiasm should not overtake and produce strong claims before thoroughly checking simpler and more sensible possibilities within their uncertainties. In particular, claiming that a reported structure, such as the Monoceros Ring, is not Galactic (an exciting scenario) should not be done without rejecting the possibility of being due to the well established warped and flared disc of the Milky Way (simpler).

Comments: Comments on the papers arXiv.org: arXiv:1102.2137, arXiv:1205.0807, arXiv:1205.3177, arXiv:1206.3842

What appears to be the news in the cited article is that new evidence from the Sloan Digital Sky Survey has convinced at least one astronomer, Heidi Newburg (who was a co-author of the fourth paper listed in the comment above of the Milky Way connection):

Scientists used data collected by the Sloan Digital Sky Survey to reanalyze the brightness and distance of stars at the edge of the galaxy. They found that the fringe of the disk is puckered into ridges and grooves of stars, like corrugated cardboard.

“It looks to me like maybe these patterns are following the spiral structure of the Milky Way, so they may be related,” astronomer Heidi Newberg, with Rensselaer Polytechnic Institute in New York, told Discovery News.

<snip>

Evidence that the so-called Monoceros Ring, located more than 65,000 light-years from the center of the galaxy, actually is part of the Milky Way surprised Newberg, who was on a team that discovered the ring in 2002.

“We thought it was a tidal debris stream -- a dwarf galaxy that came in and spread itself out in this big ring. For 15 years, there’s been a controversy in the field where half the astronomers think it’s a tidal stream and half the astronomers think its something in the disk. I was in the stream camp,” Newberg said.

“What I was trying to do was find more evidence that it was streams. It took a very long time to get this result, partly because I had to change my whole way of thinking. It now looks to me like it’s part of the disk,” she said.

Incorporating the ring into the map of the Milky Way expands the galaxy’s span from 100,000 light-years to 150,000 light-years, said astronomer Yan Xu, with the National Astronomical Observatories of China and a former visiting scientist at Rensselaer.

Note: since the Monoceros ring is located 65,000 LY from the center of the Milky Way, it must have a width of ~10,000 LY to increase the Milky Way's span to 150,000 LY.

Thanks for the post, Panich52. Cool stuff.