View Full Version : Fate of Smith´s Cloud?

2010-Apr-13, 03:19 PM
What does Smith´s Cloud consist of? How much does it contain hydrogen ions, hydrogen atoms, hydrogen molecules and dark matter respectively?

What is the metallicity of Smith´s Cloud? How does it compare to metallicity of Magellanic Clouds?

What are the present observational constraints on the proper motion of the Cloud?

What is the time when the Cloud is due to collide with Milky Way disc?

What are the observational limits on the distance between impact point of the Cloud, and the then position of the Sun? And shall the Sun then be at the same side of the Milky Way disc or at the opposite side?

2010-Apr-13, 09:43 PM
Did you check wiki (http://en.wikipedia.org/wiki/Smith%27s_Cloud)? It won't (re-)load for me know, but it answers at least one of your questions (collision time) and has some references.

John Jaksich
2010-Apr-13, 10:56 PM
Interesting post--here is what I pseudo-randomly got from Google:

"EMBARGOED For Release: 10:00 a.m., CST, Friday, January 11, 2008"

""The leading edge of this cloud is already interacting with gas from our Galaxy," said Felix J. Lockman, of the National Radio Astronomy Observatory (NRAO), leader of a team of astronomers who used the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) to study the object. The scientists presented their findings to the American Astronomical Society's meeting in Austin, Texas."

Here is the link: http://www.nrao.edu/pr/2008/smithscloud/

John Jaksich
2010-Apr-13, 11:05 PM
Here's another link from Astronomy Magazine:


It may be scarier than it should be??? :neutral:

2010-Apr-13, 11:22 PM
I'm confused:

So, where did the cloud come from? "This has such a low total velocity that it's absolutely bound to the galaxy. There's no question of it being some intergalactic object," Lockman explained. "One of the most attractive theories of high-velocity clouds is that they're the remnants of galaxy formation." Smith's Cloud, he suggests, is a straggler from the Milky Way's early days that only now is reaching the construction site.

He appears to be saying it's origen is the early formation of the Milky way, that it's "absolutely bound to the galaxy," then calls it an "intergalactic object." Perhaps miswording?

John Jaksich
2010-Apr-13, 11:30 PM
For me -it is hard to say---> but there are dwarf ellipticals in orbit around the Milky Way---I will continue to search through Google and my personal library -- on hand . . .

You are not the only one confused . . .

John Jaksich
2010-Apr-14, 12:24 AM
I searched Physics preprint archiver server:

Title: Smith’s Cloud: a High-velocity Cloud Colliding with the Milky
Authors: Felix J. Lockman, Robert A. Benjamin & A.J. Heroux, Glen I. Langston

Smith’s Cloud (Smith 1963) is a large, coherent H I feature also called the Galactic
Center Positive (GCP) complex (Wakker & van Woerden 1997). Its velocity of +100 km s−1
is only slightly larger than permitted by Galactic rotation at its location ( , b ≈ 39◦ , −13◦ ),
and Smith concluded that it was most likely part of the Milky Way disk. In recent years,
however, it has been classified as a high-velocity cloud because it lies far beyond the main
H I layer (Lockman 1984; Wakker & van Woerden 1997). It has been interpreted variously
as a cloud expelled from the disk (Sofue et al. 2004), or the gaseous component of the Sgr
dwarf spheroidal galaxy (Bland-Hawthorn et al. 1998). We have made an extensive survey
of Smith’s Cloud in the 21cm H I line using the Green Bank Telescope, whose angular
resolution and sensitivity promised new insights into this system. In particular, we hoped
that because of its large angular size we might be able to measure its transverse velocity
(e.g., Br ̈ ns et al. (2001); Lockman (2003)). A complete discussion of the observations will
appear elsewhere. Here we present the initial results on the Cloud’s physical properties and

Pardon the lack of quality!

John Jaksich
2010-Apr-14, 01:13 AM
The following is also from the Physics Preprint Server:

Title: The Smith Cloud: high-velocity accretion and dark-matter confinement

Authors: M. Nichols, J. Bland-Hawthorn

Journal-ref: Astrophysical Journal 707 (2009) 1642-1649

Although I am no expert it states that the cloud is of a low- metallicity type----mainly hydrogen.

2010-Apr-14, 02:12 AM
I would like to see a 'parts per thousand' number... because this 'Smiths Clod.'--Oops cloud is a defuse gas nebular... and talking of it like this makes it into more than it is.. How much mass and over what area is it spread or concentrated ? As it is entwined into and through this galaxy, will we even notice.

John Jaksich
2010-Apr-14, 02:58 AM
It is slated to be within the Milky Way long after all of us have passed on some 27 Million years from now. . . It is of interest to those who study the chemical evolution and accretion of gases into galaxies.

Hey! ... it is in our galactic backyard . . . it is good fodder for a advanced undergraduate and graduate students.

The way I see it . . . if someone can do something productive with it ----> where i can not ---> then more power to them!

2010-Apr-14, 07:24 AM
Did you check wiki (http://en.wikipedia.org/wiki/Smith%27s_Cloud)? It won't (re-)load for me know, but it answers at least one of your questions (collision time) and has some references.

The article caused the questions.

It gives the speed, with huge error bars - and then goes on to quote collision time without any error bars.