Posts by granthutchison

by granthutchison
21.10.2013, 10:48
Forum: Bugs
Topic: Alcor Double?
Replies: 8
Views: 4455

Re: Alcor Double?

Ah, I thought so. :) For some reason, Pascal's data extraction generated some strange, long Hipparcos codes for multiple stars. These are interpreted by Celestia as being short Tycho codes. Hence the terminal "0", which isn't standard for Tycho. Although I converted Pascal's original stars...
by granthutchison
20.10.2013, 23:58
Forum: Bugs
Topic: Alcor Double?
Replies: 8
Views: 4455

Re: Alcor Double?

TYC 4242-6717-0 doesn't exist in a clean installation of Celestia 1.6.1.
Do you both have Pascal Hartmann's Tycho catalogue add-on installed, by any chance?

Grant
by granthutchison
28.05.2013, 01:16
Forum: Development
Topic: No more file updates from me
Replies: 12
Views: 5896

No more file updates from me

SourceForge has evolved again, and I've no plans to evolve with it. So it seems I've already made my last update to the SVN tree. The most obvious impact (which I judge won't bother many people anyway) is that I'll be making no more updates to the extrasolar planet files. For the small number of peo...
by granthutchison
01.04.2013, 14:29
Forum: Physics and Astronomy
Topic: Questions about the Alpha Centauri Star System
Replies: 30
Views: 12444

Re: Re:

While the distribution is indeed different, it does give some hard constraints. ... We therefore get a hard upper bound on the luminance of zenith sky with Sun under horizon. Not more than 1/50 the daytime value, and can be less. No, there's no such bound, because of the complex nature of sky lumin...
by granthutchison
28.03.2013, 23:56
Forum: Physics and Astronomy
Topic: Questions about the Alpha Centauri Star System
Replies: 30
Views: 12444

Re: Re:

To the contrary - this demonstrates the error in your calculations. Seriously? You resuscitate a decade-old thread for this? My "calculation" involved nothing more complex than dividing by 500, and you haven't demonstrated an error. In fact, you have the logic completely reversed - you sh...
by granthutchison
16.03.2013, 16:02
Forum: Physics and Astronomy
Topic: Brown dwarf binary discovered at 2 parsecs
Replies: 3
Views: 2217

Re: Brown dwarf binary discovered at 2 parsecs

Do you have other examples ? If you have a current version of nearstars.stc , you can find a lot of isolated brown dwarfs in the vicinity of the sun. For example, look at WISE 1506+7027, DENIS 0817-6155, LP 944-20, DENIS 0255-4700 (just a few I pulled out while scrolling through the database). We'v...
by granthutchison
15.03.2013, 19:17
Forum: Physics and Astronomy
Topic: Brown dwarf binary discovered at 2 parsecs
Replies: 3
Views: 2217

Re: Brown dwarf binary discovered at 2 parsecs

It's an isolated pair of brown dwarfs, orbiting each other. That's not unusual.
The pair is in the southern constellation Vela. If the distance and proper motion in the discovery paper are correct, they're moving across our line of sight at about 27km/s.

Grant
by granthutchison
14.03.2013, 09:02
Forum: Physics and Astronomy
Topic: Brown dwarf binary discovered at 2 parsecs
Replies: 3
Views: 2217

Brown dwarf binary discovered at 2 parsecs

A very nearby pair of brown dwarfs:
http://arxiv.org/abs/1303.2401

I've added a provisional entry to nearstars.stc:
http://celestia.svn.sourceforge.net/vie ... threv=5225

Grant
by granthutchison
20.12.2012, 18:48
Forum: Physics and Astronomy
Topic: 5 planets detected orbiting Tau Ceti
Replies: 14
Views: 6156

Re: 5 planets detected orbiting Tau Ceti

john Van Vliet wrote:Thanks Grant
Pleasure. Thanks for taking the time to say thanks. :)

olyv wrote:But i think that 4.3 times the terrestrial mass is too heavy for chemical reactions for life is done because gravity would be too high ... no ?
Can't think why. Chemistry's pretty much immune to gravity.

Grant
by granthutchison
19.12.2012, 23:35
Forum: Physics and Astronomy
Topic: 5 planets detected orbiting Tau Ceti
Replies: 14
Views: 6156

Re: 5 planets detected orbiting Tau Ceti

I've already posted a link to the original arxiv paper, and notification that I've added these planets to Celestia's SVN tree.
See here: http://www.shatters.net/forum/viewtopic.php?f=7&t=17180
Not sure why we needed another thread on the same topic.

Grant
by granthutchison
19.12.2012, 17:28
Forum: Physics and Astronomy
Topic: Planets for Tau Ceti - maybe
Replies: 0
Views: 1718

Planets for Tau Ceti - maybe

Tuomi et al. Signals embedded in the radial velocity noise. Periodic variations in the tau Ceti velocities. ( http://arxiv.org/abs/1212.4277 ) It just appeared on arxiv yesterday, so it's highly provisional. But given the likely interest I've added the system to extrasolar.ssc on the SVN tree. ( htt...
by granthutchison
01.12.2012, 17:29
Forum: Physics and Astronomy
Topic: Pole star Polaris much closer than thought
Replies: 7
Views: 3598

Re: Pole star Polaris much closer than thought

What a low level of writing about an important science result! The writer at space.com didn't even consider it necessary to quote the original scientific paper. Since the distance of Polaris is anyhow much larger than what is exploitable by means of standard parallax measurements, it would have bee...
by granthutchison
27.11.2012, 23:31
Forum: Physics and Astronomy
Topic: Is a black hole a perfect sphere?
Replies: 19
Views: 6436

Re: Is a black hole a perfect sphere?

In this case, time and space coordinates have the same dimension, since generally a 4D space-time vector in Minkowski space reads (x,y,z,ict), as required by the validity of special Relativity. For c=1: [x] = [y] = [z] = [t], since the components of vectors must have all the same dimensions. ;-) Th...
by granthutchison
27.11.2012, 13:03
Forum: Physics and Astronomy
Topic: Is a black hole a perfect sphere?
Replies: 19
Views: 6436

Re: Is a black hole a perfect sphere?

So maybe we should measure the radius of a black hole in seconds rather than metres! Moreover, is the use of the mass to measure the time, the fact more "funny" of the general relativity. What time is it? It's two kg o' clock. :o Thank you for pointing me to that paper. The paper uses nor...
by granthutchison
23.11.2012, 18:25
Forum: Physics and Astronomy
Topic: Is a black hole a perfect sphere?
Replies: 19
Views: 6436

Re: Is a black hole a perfect sphere?

Very interesting! Can you give us an idea of what the orbital radii of these orbits would be? (like in units of the event horizon radius for example). I may be misunderstanding what Fridger intended, but I think we're talking about ISCO - the innermost stable circular orbit. This lies at three Schw...
by granthutchison
16.11.2012, 17:21
Forum: Physics and Astronomy
Topic: Is a black hole a perfect sphere?
Replies: 19
Views: 6436

Re: Is a black hole a perfect sphere?

Perhaps the OP is thinking about the event horizon of the black hole? The event horizon is a mathematical surface, and you wouldn't necessarily notice very much as you fell through it, but it's certainly a significant surface, especially if you hoped to visit anywhere but the singularity in future. ...
by granthutchison
18.10.2012, 15:13
Forum: Physics and Astronomy
Topic: Planets in ALF Cen officially real
Replies: 27
Views: 9459

Re: Planets in ALF Cen officially real

Do not forget that the star is of type K so it must be orange Next time the sun is up, go out and look at it and note it's colour. I know it's bright but it'll be a good science lesson. Is it yellow, as you would seem to expect for a G-type star? Interestingly, a lot of people will assure you that ...
by granthutchison
18.10.2012, 08:23
Forum: Physics and Astronomy
Topic: Planets in ALF Cen officially real
Replies: 27
Views: 9459

Re: Planets in ALF Cen officially real

Alf Cen B is hotter than the filament of an incandescent light bulb, and has a pretty continuous visual spectrum (no deep dark gaps). It would therefore look white (just as the red-dwarf-temperature light bulb filament looks white) when close enough to display a disc. The only time it would appear o...
by granthutchison
17.10.2012, 23:44
Forum: Physics and Astronomy
Topic: Planets in ALF Cen officially real
Replies: 27
Views: 9459

Re: Planets in ALF Cen officially real

That has to be a record, right? ;) This is probably the earliest I've seen a new planet added to it after its discovery. :lol: There have been a few quick updates over the years. :) I generally add new systems to my local files pretty promptly, if only to prevent a backlog of work building up. But ...
by granthutchison
17.10.2012, 19:11
Forum: Physics and Astronomy
Topic: Planets in ALF Cen officially real
Replies: 27
Views: 9459

Re: Planets in ALF Cen officially real

I've added Alf Cen B b to extrasolar.ssc on the SVN tree:
http://celestia.svn.sourceforge.net/vie ... c?view=log

Grant

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