Gravitational waves from NGC 4993

[Cham]

I may create an addon to show the source located in NGC 4993 :

Suggestions ?

Original scientific paper : https://arxiv.org/pdf/1710.05833.pdf

Wikipedia : https://en.wikipedia.org/wiki/GW170817

More to follow...

Added after 3 hours 53 minutes:
I'm currently unable to find the exact coordinates of the source located in NGC 4993, that was seen in the optical band. Surely that could be found somewhere.

Added after 5 minutes 35 seconds:
This event is a major landmark, and it could be important to show it in Celestia. It's the first neutron stars collision that have been identified, combined with gravitational waves detected with both LIGO and Virgo, and there's also an electromagnetic signal associated to the event, on the whole electromagnetic spectrum. This is the real start of multi-messenger astronomy ! It's only missing (?) the neutrinos ! Thus, this event is well worth showing in Celestia !

[Fenerit]

The image within Wiki page shows the galaxy as it seen from Earth; that is: correctly oriented, neither upside-down refracted nor left-right mirror reflected. So the coordinates of the source should be tuneable since the galaxy RA Dec.

[LukeCEL]

Cham,

Page 5 of the paper (Abbott et al. 2016) contains the coordinates of the source:
α(J2000) = 13h 09m 48.085s ± 0.01
δ(J2000) = -23° 22' 53.343" ± 0.218

Luke

[Cham]

I don't think these coordinates are in the proper frame for a Celestia DSC object. We need a conversion tool.

[CM1215]

There are plenty of converters on the internet.

Look at this one: https://www.swift.psu.edu/secure/toop/convert.htm

[Cham]

Ok, I got it right !

Here's a very preliminary addon displaying something weird at the proper location, near NGC 4993. (turn on nebulae, then get close and personal)

I should replace the current sprite model (a simple nebula) with a billboard displaying some usefull information about the historical event.

Any suggestion for a billboard ?

Code: Select all

Nebula "GW170817"
{
   Mesh "LMC1.cmod"
   Radius 100
   RA 13.1633569  # Galaxy : 13.1631
   Dec -23.3814842  # Galaxy : -23.3839
   Distance 1.435E8  # method: V_cmb
   Axis    [ -0.8032  -0.0119  -0.5956]
        Angle     83.0961
        InfoURL "http://en.wikipedia.org/wiki/GW170817"
}


Here's the small (unfinished) addon :

GW170817.zip

(220.74 KiB) Downloaded 256 times

(229 KB zip file)

Here's a preview of the location :

[Fenerit]

Some scripted behaviour with timeline? Timeline showing the merger; then what is it now, whether a quark star or whatelse, will be fictional...

[Cham]

A spacetime location in Celestia would be... lost in spacetime ! Without a script, it would be difficult to find.

I prefer a permanent location billboard, using a single sprite. I'll test a proof of concept later.

Added after 15 minutes 43 seconds:
Here's another version, with a sprite billboard. The picture could be changed very easily.

GW170817.zip

(385.58 KiB) Downloaded 238 times

(397 KB zip file)

Added after 12 minutes 8 seconds:
I found a nice picture to use as a landmark billboard, from this place : http://i2.wp.com/www.gw.iucaa.in/wp-content/uploads/2017/10/GW170817_infographic.png.

Just edit the CMOD file as this, and download the PNG file given below, and place it into the textures/medres folder :

Code: Select all

#celmodel__ascii

material  # 1 Billboard
  emissive 1 1 1
  diffuse 1 1 1
  opacity 1
  texture0 "GW170817_infographic.png"
end_material

mesh
vertexdesc position f3 pointsize f1 end_vertexdesc

vertices 1
0 0 0 1

sprites 0 1
0

end_mesh


In Celestia, type GW, then complete its name, then go ! I think it is pretty nice !

Here's a preview :