Celestia Forums

I've done a search on this and cannot find VY Canis Majoris in my Celestia 1.6.0

I have tried Navigation Goto Object: VY Canis Majoris, HIP 35793 with 1 space and with 2 spaces, and with SAO 173591 and it still does not show up.

I have looked for several other stars in the same way and have had no problems finding others that I have looked for.

Am I doing something incorrectly?

I'd love some help on this.

Thanks,

Glen

glen4cindy wrote:I've done a search on this and cannot find VY Canis Majoris in my Celestia 1.6.0

I have tried Navigation Goto Object: VY Canis Majoris, HIP 35793 with 1 space and with 2 spaces, and with SAO 173591 and it still does not show up.

I have looked for several other stars in the same way and have had no problems finding others that I have looked for.

Am I doing something incorrectly?

I'd love some help on this.

Thanks,

Glen

Have you tried pressing the ENTER key, and then typing in HIP 35793?
This works on my system, but I also have the 2.5 million stars DB which is available from the
Motherlode.

Hope that helps, Brain-Dead Bob

VY Canis Majoris is not in the default Celestia 1.6.0 star database.

The 1.6.0 star database is based on the revised Hipparcos catalog (van Leeuwen 2007). You can look this catalogue up at the VizieR service. The record for VY Canis Majoris is here. As you can see, the value for the parallax is negative. This value is unphysical and thus the star was rejected from the database.

BobHegwood wrote:
Have you tried pressing the ENTER key, and then typing in HIP 35793?
This works on my system, but I also have the 2.5 million stars DB which is available from the
Motherlode.

Hope that helps, Brain-Dead Bob

Thanks Bob. I've been to the Motherlode. If you could provide a pointer as to where on there to look and how to load the star database from there, I would be most appreciative.

Thanks!

Glen

--- edit ---

See John's reply above.

Thanks, Brain-Dead

This did it.

Thank you all so very much!

Canis Majoris beautiful!

Bear in mind that the larger star databases use data from an earlier revision of the Hipparcos catalogue and also incorporate code that generated spurious binary systems out of line-of-sight doubles. Getting rid of these fake binaries, which occasionally placed a nearby star at a distance of thousands of light years, was the main motivation for the upgraded database in Celestia 1.6.0.

ajtribick wrote:Bear in mind that the larger star databases use data from an earlier revision of the Hipparcos catalogue and also incorporate code that generated spurious binary systems out of line-of-sight doubles. Getting rid of these fake binaries, which occasionally placed a nearby star at a distance of thousands of light years, was the main motivation for the upgraded database in Celestia 1.6.0.

So does this mean that using this larger star database is not really a good idea? If this is the case, I may have to revert to the 1.6.0 database. I want this to be as accurate as possible.

Thanks!

I suppose you were referring to the 2.07 million stars (2.1C) originally prepared by Pascal Hartman and updated to work with Celestia >=1.5.1 by Grant Hutchison.

Celestia represents a 3D visualization, and thus besides 2D angular information, sufficiently accurate distance values are required for every star! In general, the distances are derived from measured parallaxes (Hipparcos, Tycho). Unfortunately the latter become too small (compared to the measurement uncertainties) very rapidly, which limits stongly the number of acceptable stars according to Celestia scientific standards.

The 2 million star database may be suitable as "glittering" background for some nice Celestia screenshots, but really the respective star distances have been estimated by means of a highly uncertain method. An empirical statistical correlation between star color (B-V) and absolute magnitude is exploited along with further uncertain assumptions about the luminosity classes involved. See e.g. http://pascal.hartman.free.fr/newcat.html
As you can see from the included diagrams, the deviations from a best fit "color-magnitude" correlation are expected to be large for individual star distances.

So if you want to have accurate stars, by all means, use the official Celestia 1.6.x database!

Fridger

john Van Vliet wrote:from here
http://celestiamotherlode.net/

on the left is
"extrasolar "
and from that menu go to " stars"
the "c" is here
http://celestiamotherlode.net/catalog/s ... on_id=1114

Thanks for that information . . . ! I had to replace my hard-drive on one of my computers (the one that can actually run Celestia without locking up), & I couldn't find those files on the eighty-gazillion back-up disks that I have . . . ! Sometimes if I have trouble finding a star, I shuffle over to Wikipedia to find all the other designations that stars frequently have . . .

Gojira2006 wrote: Sometimes if I have trouble finding a star, I shuffle over to Wikipedia to find all the other designations that stars frequently have . . .

Wiki is definitely a suboptimal choice in this regard. Here is the (professional) link that you actually want to question for finding alternative names for any deep sky object:

http://simbad.u-strasbg.fr/simbad/

Just enter the object in question into the "by identifier" tab.

Fridger

t00fri wrote:

Gojira2006 wrote: Sometimes if I have trouble finding a star, I shuffle over to Wikipedia to find all the other designations that stars frequently have . . .

Wiki is definitely a suboptimal choice in this regard. Here is the (professional) link that you actually want to question for finding alternative names for any deep sky object:

http://simbad.u-strasbg.fr/simbad/

Just enter the object in question into the "by identifier" tab.

Fridger

Thanks . . . !

Mickey...

If you wish to use the most accurate-to-date stars database, then please
listen to Fridger's advice.

If you want more (albeit less accurate) destinations, then you can't beat
the 2.5 million stars database mentioned by John.

This is simply a matter of taste, but I'm afraid that you are talking to your
average, brain-dead, typical eye-candy kind of guy where I'm concerned.
If you know how to select and add stars via the scientific method, then
you should be able to add the stars you wish using one of the methods
listed above.

Sorry, but I'm not worth much in accuracy information. I'm just a guy
who likes to look at Celestia's eye-candy. Accuracy and completeness
are obviously important, but I have not the knowledge needed in order
to insure this approach. I just tend to rely on Fridger, John, and others
who do assure me that an add-on uses accuracy.

Thanks, Bob

Stand by for fireworks. VY Canis Majoris has been moved to 7th place, based on the currently quoted diameter (1420 solar radii) from its Wikipedia and Google detail page. The very large estimated ranges previously accepted (1800-2200 solar radii) overlapped with any number of stars and the position could legitimately have been anywhere in the top ten or more stars, so the current position is not fundamentally any different.

The top 11 largest stars are:

11. HR 5171 (1,315 solar radii). Discovered in 2014, this large yellow hypergiant star is shaped like a giant peanut.
10. IRC+10420 (1,342 solar radii)
9. VV Cephei A (1,050 to 1,900 solar radii)
8. AH Scorpii (1,411 solar radii)
7. VY Canis Majoris (1,420 solar radii)
6. KY Cygni (1,420 solar radii)
5. VX Sagittarii (1,520 solar radii)
4. Westerlund 1-26 (between 1,530 to 2,544 solar radii)
3. RW Cephei (1,535 solar radii)
2. WOH G64 (1,540 solar radii)
NML Cygni (see below)
1. UY Scuti (1,708 solar radii)

I have created an addon that includes all of these stars, based on Luke's addon on the Celestia motherlode. Here it is: https://drive.google.com/file/d/1ZAS8x8moOJuWqMgCuc1pvRwUxaHcn-uF/view?usp=sharing

A red hypergiant star called NML Cygni was made largest star in 2013 with a larger radius, but currently according to its detail page on Google and Wikipedia it now has a radius of 1,183 solar radii (possibly referencing this paper https://www.aanda.org/articles/aa/full_html/2010/15/aa13771-09/T6.html). However, the reason to it once thought to being so large is due to calculations with the Stefan-Boltzmann Law have given a radius of almost 1,650 solar radii. NML Cyg's real size still remains uncertain.

Working out NML Cyg's radius:
Square root of ( (5,772/3,250)^4 x 270,000 ) = 1,638.96 solar radii.

Thank you. - Joey P.

I just realized I erred in the installation of the addon from the Celestia Motherlode. There already seems to be a HIP 35793 (does not include the VY CMa name), and installing the addon placed a VY CMa about 1 full kiloparsec away in the same direction (lacking the HIP designation).

I suppose I may have to include a "Modify" in the .stc file?

roninwolf1981, you can use the modify command if you don't want to change the origional data files. Since you are already using an addon why not edit the addon data files directly and plug in the correct coordinates?

With "modify," I should be able to override the verbiage/nomenclature of what's already displaying on the star's entry, correct?

And to answer your question, I say sure...