A new 4 planet system

[chris]

Another planet has been found orbiting Mu Ara, making that system the second one with 4 planets. Here's a paper describing the discovery:
http://fr.arxiv.org/abs/astro-ph/0608396

One of the interesting things in the paper is that one of the models that fit the radial velocity data had two of the planets sharing in orbit as a Trojan pair. However, they rejected this solution after a stability analysis showed that starting from the Trojan configuration, the system would be destroyed in less than a century.

Grant has already checked an updated extrasolar.ssc into CVS.

--Chris

[granthutchison]

I've now committed a further update, revising the whole mu Ara system using the Pepe et al paper Chris links to. The orbits of the outer planets were never good, and the advent of this fourth planet in the analysis tightens up the parameters for the others, making the whole system look a lot neater.
Pepe et al also propose and use a different lettering system. Sigh.

Grant

[chris]

Oops. Look what I posted to this thread:

http://www.celestiaproject.net/forum/viewtopic.php?t=9985

while you were committing your update.

Thanks!

--Chris

[granthutchison]

Ha.
I noticed the same awkward orbits Cham did, and realized only after I'd committed the first update that there must be new orbits for the other three planets, too, even though the Extrasolar Planets Encyclopaedia hadn't updated them.

Grant

[Malenfant]

How do we get these updates if we can't compile Celestia ourselves?

I think it'd be useful to compile and make available a patch that contains new and refined systems every now and then, that we can download and add to the existing 1.4.1 distributions that we already have installed. I'm sure the patch wouldn't be all that big. Not all of us are developers .

[chris]

You can get updates to Celestia's default data files without having to install a CVS client:

http://celestia.cvs.sourceforge.net/cel ... stia/data/

Click on the version number to view (or download) the most recent version.

--Chris

[selden]

All of the updated files, SSC, STC and DSC catalogs as well as source code, can be downloaded by anyone from SorceForge. You can browse the CVS tree at
http://celestia.cvs.sourceforge.net/celestia/celestia/

[Malenfant]

Yes, but I was thinking more along the lines of making a zip file or something available maybe once a month that contains all the new files, so people don't have to wade through the CVS files to figure out which ones are newer than the ones they have. Heck, I could just find them and put a zip file on the motherlode or something, it's just a more convenient way to get up to date than figuring out which files you have or don't have and downloading them individually.

Also, it's not entirely obvious which files there have been updated from the ones packaged with 1.4.1. Is 1.4.1 less than six months old, or more? I can't even remember when it came out. I'm guessing that if you list the files by age on the link you posted, the top five (down to 4 months old) are the ones that aren't in the 1.4.1 windows release?

EDIT: looking at the installer file at http://www.celestiaproject.net/~claurel/celestia/files/ , 1.4.1 (windows) was released on Feb 14 2006, which means it's 6.5 months old. But does that mean files listed as being 6 months old are already included in it or were they included later that month? The age is a bit inexact.

[selden]

Often enough there are incompatible changes in the files, unfortunately, as new features are added to the code and, for example, new entries are made in catalogs which make use of them.

I suspect the amount of someone's time spent trying to gather together only those files that are compatible with the previous release would actually be more than the time required to create a complete new release.

It seems unlikely to me that you'll ever see an "official" collection like what you describe. Presumably someone ambitious could put together an unoffical collection of updates, though.

[Malenfant]

well, one could just go through the folders on the CVS, locate the ones updated within say the past 6 months, put them all in a zip file in the right folders and then make that available?

I don't think there'd be any compatibility problems with just taking the latest versions of the data files and putting them in a package for people to install over the existing files in 1.4.1, would there?

[tony873004]

In table 1 of the journal paper, does anyone know what K and lambda[sub]0[/sub] are?

My guess is that K is the observed velocity of the star at time T. And since the star's velocity will be sinusoidally oscillating between 0 and its maximum value, lambda[sub]0[/sub] is the planet's position in the orbit that would yield velocity K.

[ajtribick]

I'll just link here the Gozdziewski et al. paper which seems to be an independent announcement of the fourth planet.

They use a designation system compatible with the previous designations, where the 370-day planet is designated "e"...

This is a bit of a mess.

[symaski62]

I'll just link here the Gozdziewski et al. paper which seems to be an independent announcement of the fourth planet.

They use a designation system compatible with the previous designations, where the 370-day planet is designated "e"...

This is a bit of a mess.

yes

http://exoplanet.eu/star.php?st=HD+160691