Updated stars.dat including Gaia DR2 data (update 2020-11-30)

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Art Blos M
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Post #21by Art Blos » 17.02.2020, 06:18

ajtribick wrote:It would also require changing Celestia's identifier handling: currently the HIP/encoded TYC identifier (which incidentally originated with the Pascal Hartmann catalogue) is treated as fundamental but that's not going to work with the larger catalogue as the additional stars will not be HIP/TYC stars.
Clear. Then another question. In your database has all HIP/TYC stars?
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Post #22by jujuapapa » 17.02.2020, 06:30

TY for your returns. :wink:

@ArtBlos: It would be correct if we knew exactly the number of celestia's users.
In this number, how do they use :
1 - stars.dat (original 1.6.1 2011 ?)
2 - stars_ext v 2.1c (GrantHutchinson's catalog - updt 2009 with 2,072,867 stars)
3 - stars_gaia v 0.1.2-alpha (fev 2020).
Because, they have several impacts to use one of the three catalogs... :eh:

@ajtribick : again Bravo for your work. :clap:
Do you know when your catalog will be given in v 1.0 ?
I understand (and I hope too all other users) the problem to update old celestia 1.6.1 32 bits to accept gaia 64 bits.
One day, it will be perhaps for celestia 1.8 !?! :eek:
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Post #23by Art Blos » 17.02.2020, 06:49

jujuapapa wrote:It would be correct if we knew exactly the number of celestia's users.
In any case, I will add stars.dat by ajtribick in the CO v.11. Obviously, this is the best variant. :smile:
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Post #24by LukeCEL » 17.02.2020, 15:53

Is this stars.dat missing any bright stars? I know in previous versions all the bright stars have made it onto revised.stc.

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Post #25by ajtribick » 17.02.2020, 20:56

Art Blos wrote:In your database has all HIP/TYC stars?
Unfortunately not. The main reason for this are that the cross-matches to Gaia DR2 are incomplete. In the case of HIP2 stars I can fall back to XHIP for distance information but this is not possible for TYC2. There are also some stars in Gaia DR2 that do not have parallax information.

LukeCEL wrote:Is this stars.dat missing any bright stars? I know in previous versions all the bright stars have made it onto revised.stc.
The stars.dat file contains all 117955 XHIP (HIP2) stars, but there are 118218 entries in the original HIP catalogue. Of the stars missing in HIP2, three are brighter than V=6:

HIP 55203 (ξ UMa), V=3.79
HIP 78727 (ξ Sco), V=4.16
HIP 115125 (94 Aqr B), V=5.19

These are multiple star systems which likely resulted in confusion in the data processing. Taking a quick look in SIMBAD for these three, they do have Gaia DR2 entries (in the case of the first two, the A and B components have their own separate entries) but since they are not HIP2 stars they are not present in the cross-match and therefore not in the stars.dat file.

Art Blos wrote:Do you know when your catalog will be given in v 1.0 ?
The cross-match issues are the main reason I'm treating this as an alpha. It may well be possible to use SIMBAD's query interface to resolve this, but when it comes to dealing with multiple stars this gets messy.
Last edited by ajtribick on 19.02.2020, 21:04, edited 1 time in total.

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Post #26by Fafers_br » 19.02.2020, 20:59

It is a great work indeed, ajtribick.
Congratulations and thank you for that!

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Post #27by john71 » 20.02.2020, 17:33

Thank you ajtribick!

Very nice work!!! :clap:

It would be nice to have at least a database of 10 million stars in Celestia...That's a 200MB stars.dat file...

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Post #28by jujuapapa » 20.02.2020, 19:53

@ajtribick : Few errors in the datas. :fie:

Example : Gliese 86 A (HD 13445 A) , a 'nearstar' at 35 LY given in your file at 3.0659 KPc !!! :insane:

NB : SIMBAD (2018) gives 10.787 pc or 35.18 LY.

=> Perhaps another anomalies like this ??? :think:
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Post #29by SevenSpheres » 20.02.2020, 22:30

jujuapapa, ajtribick's star database puts Gliese 86 at the correct distance of 35.172 light-years.
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Post #30by jujuapapa » 21.02.2020, 06:18

SevenSpheres wrote:jujuapapa, ajtribick's star database puts Gliese 86 at the correct distance of 35.172 light-years.
OK, TY for your return. :wink:

Perhaps, I have to look after a forgotten stc file in any subdirectory...
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Post #31by pedro_jg » 27.02.2020, 22:28

While looking through the star browser, I came across two examples of potentially spurious stars: HIP 114110 and HIP 114176. Both are within a distance of 25 ly of the Sun.
SIMBAD, for both objects, notes them as:
Non-existing star (scattered light from a nearby bright star).

There might be other such cases that I haven't spotted.
However, in my opinion, that issue doesn't detract too much from the overall quality of the data files so far.
Thank you in advance!

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Post #32by ajtribick » 27.02.2020, 22:44

Good find. I'm not making individual corrections to the various entries as this would be a lot of work. Presumably these "stars" are missing in Gaia DR2 but because the cross-match is incomplete (even beyond just missing the brightest stars that are too bright for Gaia) I can't rely on the lack of a match being a non-existent object.

Given the date of the correction (1998 according to the list of errata), I'm slightly surprised this didn't get taken into account when compiling HIP2 (2007) or XHIP (2012).

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Post #33by LukeCEL » 27.02.2020, 22:54

ajtribick wrote:I'm not making individual corrections to the various entries as this would be a lot of work.

This would be good to put in revised.stc. I just wish there was a "Remove" or "Delete" directive in Celestia, just like we have "Modify" and "Replace"...

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Post #34by Art Blos » 01.03.2020, 09:17

ajtribick < Are you planning any updates until the end of April? Is it worth adding the current version to the CO right now or wait?
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Post #35by ajtribick » 01.03.2020, 09:51

@Art Blos - I don't have any plans to do any updates on this unless someone finds a sufficiently severe bug, i.e. that something's gone wrong with correctness with respect to the input data. (Correctness with regards to external reality is another matter, which should probably be handled in revised.stc or an equivalent mechanism)

I don't think that spending time on things like trying to obtain a better DR2-HIP2 or DR2-TYC2 cross-match makes much sense given that the release of EDR3 is expected later this year, which would likely mean having to do it all over again.

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Post #36by jujuapapa » 01.03.2020, 09:58

Post #35by ajtribick » 4 minutes ago
@Art Blos - I don't have any plans to do any updates on this unless someone finds a sufficiently severe bug, i.e. that something's gone wrong with correctness with respect to the input data. (Correctness with regards to external reality is another matter, which should probably be handled in revised.stc or an equivalent mechanism)
I don't think that spending time on things like trying to obtain a better DR2-HIP2 or DR2-TYC2 cross-match makes much sense given that the release of EDR3 is expected later this year, which would likely mean having to do it all over again.

Logical : in his time, Oppenheimer didn't ensure the after sales service of his invention... :eek: :biggrin:
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Post #37by Art Blos » 03.03.2020, 19:16

I have serious suspicions that all stars in red circle belong to the Large Magellanic cloud. Can you check this moment?
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Post #38by ajtribick » 03.03.2020, 20:44

Interesting observation! I think you're probably right.

As an example, the LMC B[e] supergiant R126 (TYC 9167-518-1, HD 37974) is assigned a distance of 10.5 kpc in the Gaia geometric distance catalogue, versus a ~50 kpc distance to the LMC. I don't have a Celestia installation to hand as I'm writing this but it wouldn't surprise me if it were part of the "spike".

The measured parallax for R126 in Gaia DR2 is -0.074±0.028 mas. As the paper on which the geometric distances catalogue is based notes, it is possible to make inferences about distance from a negative parallax (even though the straightforward 1/parallax approach obviously fails). However the model used assumes that the star is part of our Galaxy, which is obviously untrue for a star that's in the LMC. Hence the nonsense distances.

So from what I can tell, this is correct with respect to the input catalogues, but not external reality :)

Judging by the picture, it looks like there might also be a similar "spike" towards the SMC. Querying Gaia again for the SMC Wolf-Rayet system HD 5980 (TYC 9138-1929-1), this is assigned a distance of 5.85 kpc based on a parallax of 0.061±0.041 mas, versus the distance to the SMC of ~60 kpc. Again the large error bars mean the assumption that the star is a member of our Galaxy becomes a factor.

If there's a catalogue listing extragalactic members of the TYC2 catalogue it'll probably be worth excluding such objects. If not, I guess it's a case of waiting to see what EDR3 looks like.

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Post #39by Art Blos » 04.03.2020, 06:16

As a result, at the moment you will not modify the base?
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Post #40by ajtribick » 07.03.2020, 14:04

Having done a few searches on VizieR, I'm not sure there's any reliable source on which TYC stars are extragalactic. It's an interesting problem, for values of "interesting" that mean "don't expect anything in the immediate future". :)


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