Pulsars

[selden]

Cham,

Sorry: yes.

[granthutchison]

Even rapidly spinning pulsars are going to be spherical, because the "centrifugal" force is trivial compared to their gravitation. But look at this thread for information on creating a star with a custom oblateness and rotation period.

Grant

[Cormoran]

Thanks for the advice folks.

Oh well, I guess tomorrow's project is generating data for overlay planets.

I'll keep you informed

Cormoran

[Cham]

I may have found a soilution.

Just make a new .ssc file, with entries like this (the first pulsar in your .stc file) :

"PSR 0006+1834" "PSR 0006+1834"
{
Emissive true
Texture "WhiteDwarf.jpg"
Radius 750
Oblateness 0.07

EllipticalOrbit {
Period 1000
SemiMajorAxis 0.0
Eccentricity 0.0
Inclination 0.0
}
RotationPeriod 0.01
Albedo 1
}

[Cormoran]

Okay, version 1.1 is now available.

It makes use of a Pulsar model created by Rassilon, slightly modified to change the axis of the emission jets (Rassilon is credited in the Zip file, but if he minds me using the model, I will remove the zip immediately). It is included in the Zip file.

http://homepage.ntlworld.com/jdchapman66/Pulsars.zip

Hope this is more to your liking Cham. You will note that I have had to ad the Pulsar itself as a planet. Unfortunately, the rotation periods are so small that they show up as 0 on the celestia data display.

As always, comments and observations welcome.

Cheers,

Cormoran

[Cham]

Is there a problem in the RA of your new version ? It doesn't match the old version !

And the mesh doesn't work, by the way.

[Cormoran]

Oops

Terribly sorry Cham. Forgot to add the texture files into the zip. I blame the lateness of the hour and a lack of caffeine.

If you do the download again and just drop the .jpg files into celestia/textures/medres it should be okay.... if not, let me know.

The RA data in the old version was calculated from Hours/minutes/seconds of arc, and my Math may have been a bit off. The new data is extracted in degrees directly from the source site and merely reformatted, and thus the new version should be more accurate.

Cheers,

Cormoran

[Cham]

I don't like much the mesh. So I edited your new Pulsars.ssc like this :

"PSR" "PSR J0006+1834"
{

Emissive true
Texture "WhiteDwarf.jpg"
Radius 10
Oblateness 0.07

EllipticalOrbit {
Period 1e10
SemiMajorAxis 1e-10
Eccentricity 0.00
Inclination 0.00
}

RotationPeriod 0.000192708
Obliquity 0.00
Albedo 1

Atmosphere {
Height 30
Lower [ 0.8 0.9 1 ]
Upper [ 0.26 0.47 0.84 ]
}
}

Try it, and tell me what you think.

But there's something strange. After selecting a pulsar, I get 0 km radius and Planetary companion present. Most pulsars have a radius of about 10 km.

[Cormoran]

The Planetary companion is the pulsar model itself.

The radius of zero you get on the Pulsar is because Celestia displays the radius in terms of solar radii, and a teeny weeny pulsar is way to small to register without going down to a large number of decimal places.

As for the model, while its not ideal, its the best out there so far as I know. It also shows the rotation rate really well visually.

If anyone wants my data source files let me know. I'd be interested to see how other folks deal with the issue of displaying pulsars.

Regards,

Cormoran

[Cham]

I need to be sure about the rotation periods listed in your Pulsars.ssc file. For example, I checked for the pulsar PSR J1047-6709 on those sites :

http://www.gae.ucm.es/~emma/protons/ms- ... r_data.dat

http://www.gae.ucm.es/~emma/protons/ms- ... ta.dat.old

They gives a period of 0.1984514505627 sec.

In your .ssc file, there is RotationPeriod 0.000055125.

If it's in sec, then it doesn't fit at all. If it's in days, it gives 4,7628 sec, which isn't right. If it's in hours, then it gives the right number : 0,19845 sec.

But in what units does Celestia shows the period ? When I go to that pulsar, Celestia gives 1 sec, which was explained before. When I click on the pulsar model, I get 0.00 hours, which should be the right unit. Is Celestia showing the right rotation on screen ? When I use my watch for about 60 rotations, I get about 1 sec approximately .

Opinion ?

[Cormoran]

The rotation period is in hours.

As I said before, Celestia can't display such small rotation periods.

Cormoran

[Cham]

Such small rotation periods ? It's only about 0.1 sec up to few seconds. I understand it can't show the number in the up-left corner, but is it showing it "live", on screen ?

[Cham]

I have modified your Pulsars.ssc to have a better representation of a pulsar (even if I never talked to one in person ). For example, the first pulsar in the list is now like this :

"PSR" "PSR J0006+1834"
{
Emissive true
Texture "Pulsar.jpg"
Radius 30
Oblateness 0.07

EllipticalOrbit {
Period 1e10
SemiMajorAxis 1e-10
Eccentricity 0.00
Inclination 0.00
}

RotationPeriod 0.000192708
Obliquity 0.00
Albedo 1

Atmosphere {
Height 30
Lower [ 0.8 0.9 1 ]
Upper [ 0.2 0.2 0.2 ]
}
}

Try it, and tell me your opinion.

[Cham]

Sorry, I forgot to mention that my Pulsar.jpg is the texture from the original pulsar model with jets, that I have resampled to a bigger size (2k) and changed the colors and contrast. I made it to a light blue texture.

I visited the slowest pulsars in the list :

PSR J2144-3933 (period of about 0.002 hour = 8.5 seconds)
PSR J0528+2200 (period of about 0.001 hour = 5 sec or so)
PSR J1741-2019
PSR J1848-1952

Celestia runs them correctly.

This addon should be standard. t's very cool !

Can you imagine an ordinary asteroid of, says, 200 km, falling directly into a pulsar of about 10 km radius !? Celestia isn't able to show this, why not ? LOL

[Cham]

Funny, I just found an interesting article on the first pulsar I talked about in my previous post :

http://arxiv.org/abs/astro-ph/0010603

This pulsar has a "very long" period of 8.5 seconds = 0.002 hours and is called "extremal" in the above article.