+- The Orion's Arm Universe Project Forums (https://www.orionsarm.com/forum)
+-- Forum: Offtopics and Extras; Other Cool Stuff (https://www.orionsarm.com/forum/forumdisplay.php?fid=2)
+--- Forum: Real Life But OA Relevant (https://www.orionsarm.com/forum/forumdisplay.php?fid=7)
+--- Thread: Dyson Spheres around White Dwarfs (/showthread.php?tid=3559)
Dyson Spheres around White Dwarfs - selden - 05-15-2018
Dyson Spheres around White Dwarfs
Ibrahim Semiz and Salim O˘gur
https://arxiv.org/pdf/1503.04376v1.pdf
Quote:We point out that Dyson Spheres could also be built around white
dwarfs. This type would avoid the need for artificial gravity technol-
ogy, in contrast to the AU-scale Dyson Spheres. In fact, we show that
parameters can be found to build Dyson Spheres suitable –temperature-
and gravity-wise– for human habitation. This type would be much
harder to detect.
RE: Dyson Spheres around White Dwarfs - Cray - 05-17-2018
(05-15-2018, 04:41 AM)selden Wrote: Dyson Spheres around White Dwarfs
Ibrahim Semiz and Salim O˘gur
https://arxiv.org/pdf/1503.04376v1.pdf
Aww. The one problem to really solve before building one of these...
"Therefore, a rigid Dyson Sphere around a white dwarf could not be built
without some extra means of support, about which we choose not to speculate
here."
RE: Dyson Spheres around White Dwarfs - Drashner1 - 05-18-2018
Of course, in OA magmatter has more than enough strength for this, assuming you can figure out how to arrange it in a way that doesn't result in black hole collapse.
In RL or OA, dynamic compression members and orbital rings could readily provide the required support using conventional matter materials.
This class of dyson might be relatively common across the setting. Would anyone like to write up an example and possibly an addition/mod to the existing page on dyson spheres?
Todd
RE: Dyson Spheres around White Dwarfs - selden - 05-18-2018
A related paper:
Gaia Reveals Evidence for Merged White Dwarfs
Mukremin Kilic, N. C. Hambly, P. Bergeron, C. Genest-Beaulieu, N. Rowell
https://arxiv.org/abs/1805.01227
Quote:We use Gaia Data Release 2 to identify 13,928 white dwarfs within 100 pc of the Sun.
_____
If my arithmetic is right, that means that at least 2% of all stars are White Dwarfs, so there are lots of them available. Actually, the percentage probably is somewhat higher, since the efficiency of detecting stars, especially those as dim as white dwarfs, falls off with distance.
============================
Here's my arithmetic:
volume with a radius of 100pc: 4/3 *pi* 100^3 = 4 186 667 cubic pc
14000/4200000 = 0.0033 wd / cubic pc
Using the "traditional" value for the density of stars in the solar vicinity, if the average star density is 0.14 stars / cubic pc, then 0.0033/0.14 = 0.024 or 2.4% of stars are White Dwarfs.
To check that number:
if the average star density is 0.14 stars / cubic pc, then there are
0.14*4/3*pi*100^3 = 580,000 stars within 100 pc. 14000/580000 = 0.024 = 2.4%
However, Gaia yields a slightly higher stellar density within 100 pc: about 0.167 stars/cubic pc.
When I queried the Gaia archive for a list of stars with a parallax > 10 milli-arc seconds (i.e. with distances < 100 pc) it returned a row count of 700,055. (I didn't put any constraint on the parallax accuracy, though.) Gaia has been reported as detecting ~2x as many stars as were originally expected, so a count of 700,000 instead of 600,000 doesn't seem too unreasonable.
So 14000/700000 = 2%.
and 700000/4200000 = 0.167 stars / cubic pc.
RE: Dyson Spheres around White Dwarfs - ai_vin - 05-18-2018
(05-18-2018, 03:04 AM)Drashner1 Wrote: Of course, in OA magmatter has more than enough strength for this, assuming you can figure out how to arrange it in a way that doesn't result in black hole collapse.
In RL or OA, dynamic compression members and orbital rings could readily provide the required support using conventional matter materials.
This class of dyson might be relatively common across the setting. Would anyone like to write up an example and possibly an addition/mod to the existing page on dyson spheres?
Todd
I think this page; http://www.orionsarm.com/eg-article/4847416b8b0ad does the job already.
RE: Dyson Spheres around White Dwarfs - Drashner1 - 05-19-2018
Hm. Yeah - I believe you're right, at least in terms of covering the general concept.
That said, another way of highlighting this particular bit more might be a clade of sophonts that like to live around white dwarf stars in particular or the like.
Just a thought,
Todd