PDA

View Full Version : xplns -- why so many galaxies in Virgo?



themusk
2004-Apr-03, 02:22 AM
I was just amusing myself, on this overcast day, with xplns (http://www.astroarts.com/products/xplns/). I normally have it configured to match what I could see with my naked eye in the immediate vicinity of where I live (i.e., configured for my real-world conditions). But tonight I flipped on the switch for deep space objects and looked around.

Why are there so many galaxies in and about Virgo? Is it just because of the Virgo cluster, or is there another reason as well?

Brady Yoon
2004-Apr-03, 02:31 AM
Yeah, it's because of the Virgo Cluster. And that's also the direction of the center of the Virgo supercluster. Galaxies aren't evenly distributed throughout the universe. They are organized in clusters and superclusters, and between them, lie voids stretching hundreds of megaparsecs across.

Normandy6644
2004-Apr-03, 06:26 PM
Yeah, it's because of the Virgo Cluster. And that's also the direction of the center of the Virgo supercluster. Galaxies aren't evenly distributed throughout the universe. They are organized in clusters and superclusters, and between them, lie voids stretching hundreds of megaparsecs across.

There are 3d representative models of this around, and it's really cool to look at. The structure of the universe is more "stringy" and clumped in places, as opposed to evenly distributed.

dakini
2004-Apr-03, 07:22 PM
isn't our galaxy headed towards a supercluster now? perhaps it was the virgo one, but my astronomy prof said that the milky way was headed for a supercluster now.

ngc3314
2004-Apr-03, 07:54 PM
isn't our galaxy headed towards a supercluster now? perhaps it was the virgo one, but my astronomy prof said that the milky way was headed for a supercluster now.

We're headed in the general direction of the Virgo cluster (which is pretty much the center of the Local Supercluster). It used to look pretty certain that we'd eventually get there (another 15 billion years or so), but what with the accelarating cosmic expansion, that is no longer so clear. The superclusyer's gravity has certainly slowed down the expansion between here and there (as mass concentrations are wont to do), but the amount may or may not be enough for the Local Group galaxies (Andromeda, us, M33, and a host of dwarfs) to get there.

If we do and the Milky Way still has enough gas, there could be interesting fireworks of the kind that fits such movie titles as Gone with the Wind or Left Behind. Here's an example:
http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/02/
and
http://www.astr.ua.edu/keel/c153

Describing events over these spans and seen at such distances turns into an exercise in verb tenses - like the "English for Time Travellers" essay by (IIRC) Larry Niven.

Kevinito
2004-Apr-03, 08:29 PM
I was just amusing myself, on this overcast day, with xplns (http://www.astroarts.com/products/xplns/). I normally have it configured to match what I could see with my naked eye in the immediate vicinity of where I live (i.e., configured for my real-world conditions). But tonight I flipped on the switch for deep space objects and looked around.


I just needed to ask you a question about xplns. I have a linux-based system at home and I use K-Stars. Is this compatible with SuSE 9.0? I just tried to download it from the products page but there is not a link to download. Any help?

Thanks,

Kevin

JohnOwens
2004-Apr-03, 11:00 PM
Describing events over these spans and seen at such distances turns into an exercise in verb tenses - like the "English for Time Travellers" essay by (IIRC) Larry Niven.
I don't recall any such by Niven, and I've read darn near everything by him. Perhaps you're thinking of the book mentioned by Douglas Adams in one of the Hitchhiker's Guide books? :-k

ChesleyFan
2004-Apr-04, 03:39 AM
[quote="ngc3314"]We're headed in the general direction of the Virgo cluster (which is pretty much the center of the Local Supercluster). It used to look pretty certain that we'd eventually get there (another 15 billion years or so), but what with the accelarating cosmic expansion, that is no longer so clear. The superclusyer's gravity has certainly slowed down the expansion between here and there (as mass concentrations are wont to do), but the amount may or may not be enough for the Local Group galaxies (Andromeda, us, M33, and a host of dwarfs) to get there. quote]

And (IIRC) isn't the Virgo cluster in turn moving toward the Great Attractor, along with a bunch of other superclusters?

themusk
2004-Apr-04, 04:35 AM
I just needed to ask you a question about xplns. I have a linux-based system at home and I use K-Stars. Is this compatible with SuSE 9.0? I just tried to download it from the products page but there is not a link to download. Any help?

I'm running Mandrake 9.2 (and very seriously thinking about building a Linux from scratch system), so I can't say for certain what it will take to get xplns running on SuSE. It should run: the real question is how much fiddling with libraries and the like it would take to get it running.

The download page for xplns is

http://www.astroarts.com/products/xplns/download.html

I don't think Red Hat rpms are compatable with SuSE systems (unless this has changed since I last needed to deal with the question -- anyone know?). You could always install the slackware executable in /usr/local or /opt (depending on what SuSE's convention is.

IMO, xplns and kstars are pretty much equivalent. I use xplns solely out of habit. Of course, if you want to get really serious about star maps, the way to go is xephem. (http://www.clearskyinstitute.com/xephem/) Arming yourself with a FITS viewer (http://www.nrao.edu/software/fitsview/fvunx.html) makes for a whole lot of fun. For some mysterious reason I've never been able to get Celestia to behave properly for me (it militantly refuses to compile or install as an rpm binary), but I have seen Celestia, and it is a good thing indeed.

dakini
2004-Apr-04, 06:20 AM
man, i'm just glad that this won't happen until we're all dead. it woudl suck if the galaxy was torn apart while we were still in it.

ngc3314
2004-Apr-04, 07:32 AM
Describing events over these spans and seen at such distances turns into an exercise in verb tenses - like the "English for Time Travellers" essay by (IIRC) Larry Niven.
I don't recall any such by Niven, and I've read darn near everything by him. Perhaps you're thinking of the book mentioned by Douglas Adams in one of the Hitchhiker's Guide books? :-k

They do say memory is the first thing to go - I may have been thinking of the vintage-1938 essay "Language for Tie Tavellers" by L. Sprague de Camp. (Google first, post later...)

jt-3d
2004-Apr-04, 09:44 AM
I followed a link somebody posted here that said the Milky Way would collide/pass though Andromeda. They had a slide show thing which showed how it would look. Basically, forget anything about telescopes for a while when that baby gets close. I have no idea where I found that link though.

Was this even on topic?

Kevinito
2004-Apr-04, 01:46 PM
IMO, xplns and kstars are pretty much equivalent. I use xplns solely out of habit. Of course, if you want to get really serious about star maps, the way to go is xephem. (http://www.clearskyinstitute.com/xephem/) Arming yourself with a FITS viewer (http://www.nrao.edu/software/fitsview/fvunx.html) makes for a whole lot of fun. For some mysterious reason I've never been able to get Celestia to behave properly for me (it militantly refuses to compile or install as an rpm binary), but I have seen Celestia, and it is a good thing indeed.

Yep. I went ahead and downloaded it (XEphem). Now, I just need a good Internet primer on compiling the code. It does look pretty intense. Many thanks!


-Kevin
-Kevin

Donnie B.
2004-Apr-04, 04:08 PM
Niven has definitely made comments about language tenses and time travel, though I don't know of an entire essay on the topic. I recall it as being a short digression in his more general time travel essay -- the one that concludes time travel is impossible because it makes causality unstable, so eventually the changes wrought by time travel will result in a universe that doesn't allow time travel.

This didn't prevent him from writing time travel stories, however! 8)

dakini
2004-Apr-04, 04:50 PM
jt-3d, i think that that's supposed to happen around the same time the sun destroys this planet...

actually apparantly the milky way has already "eaten" a number of galaxies already. they're a lot smaller though, so they get torn up while our galaxy's prtty alright. andromeda is about the same size though.. so that's a little more interesting.

QuagmaPhage
2004-Apr-04, 06:28 PM
I don't think Red Hat rpms are compatable with SuSE systems (unless this has changed since I last needed to deal with the question -- anyone know?).
I think it depends on the actual rpm. Some work others don't.


For some mysterious reason I've never been able to get Celestia to behave properly for me (it militantly refuses to compile or install as an rpm binary), but I have seen Celestia, and it is a good thing indeed.
If it complains about missing dependencies remember to install liblua first. The 1.3.0 version is also available through urpmi which should install it automatically. I didn't have any significant problems when I installed it.

ngc3314
2004-Apr-04, 08:20 PM
Niven has definitely made comments about language tenses and time travel, though I don't know of an entire essay on the topic. I recall it as being a short digression in his more general time travel essay -- the one that concludes time travel is impossible because it makes causality unstable, so eventually the changes wrought by time travel will result in a universe that doesn't allow time travel.

This didn't prevent him from writing time travel stories, however! 8)

Aha! Found it - my memory wasn't completely gone. I was thinking of "The Theory and Practice of Time Travel", which I have in "All the Myriad Ways", in which Niven writes of the need for these verb tenses:
basic past, altered past, altered future, excised future, home base present, present-of-the-moment, enclosed present, future past, and
past future. For astronomical observations, we might need our past, past of object as observed, future of object as observed which does or does not lie in the current past in the "special" comoving time frame (the closest the Universe may offer to a Newtonian concept of time),
and of coure our present and a distant object's present-as-observed.

Hey, maybe there's a wry little Mercury article in all this...

Wally
2004-Apr-06, 01:53 PM
I followed a link somebody posted here that said the Milky Way would collide/pass though Andromeda. They had a slide show thing which showed how it would look. Basically, forget anything about telescopes for a while when that baby gets close. I have no idea where I found that link though.

Was this even on topic?

Why forget about telescopes at that time JT? The Milky way doesn't drown out much of the sky, and we're actually inside of it. Can't see M31 doing too much to add to light pollution when we meet.

jt-3d
2004-Apr-07, 03:42 AM
Hmm, your point is logical. I can't find the one I saw but I would think that M31 will grow larger and larger. Probably will look like these (http://hubblesite.org/newscenter/newsdesk/archive/releases/1997/34/image/) images though perhaps not as bright. The video link is a slideshow of the images. Either way, it will be some show. I'll have to stick around for it.

Kaptain K
2004-Apr-07, 10:07 AM
As M31 gets closer, it gets brighter, but it also gets larger. Halve the distance, and it is four times brighter (inverse square law), but it will also be four times larger (in terms of area). So, the brightness per unit area will not change.