Halo's star?

[sudnadja]

According to TravellerMap , Halo (Solomani Rim 0726, Albadawi Subsector) is hosted by an F0 II star. II is a "bright giant", and an F0 II should have a luminosity of about 1000x of the sun.

As it's only 11-12 parsec away from us, it should be around -2.26 apparent magnitude to us, significantly brighter than Sirius and the brightest star in our night sky.

Is there any Traveller lore about what this star is, and why it was placed so close to Terra as to be so visibly bright? The name "Halo" is suggestive, too.

Another star, Troutiyka, a F8 Ia supergiant which would have a luminosity >50,000 solar luminosities, is about 60 parsec from Terra and would have a apparent magnitude of -3.0. Even brighter than Halo in our sky.

 

[whulorigan]

According to TravellerMap , Halo (Solomani Rim 0726, Albadawi Subsector) is hosted by an F0 II star. II is a "bright giant", and an F0 II should have a luminosity of about 1000x of the sun.

As it's only 11-12 parsec away from us, it should be around -2.26 apparent magnitude to us, significantly brighter than Sirius and the brightest star in our night sky.

Is there any Traveller lore about what this star is, and why it was placed so close to Terra as to be so visibly bright? The name "Halo" is suggestive, too.

I am not aware that Halo's central star has ever been canonically identified, and I am aware of most such identifications (I think). Those stars were probably assigned randomly, and may even be legacy form earlier rulesets. The T5SS project was notionally taking care of such anomalies; perhaps it was an oversight, or perhaps a deliberate choice that I am unaware of.

Another star, Troutiyka, a F8 Ia supergiant which would have a luminosity >50,000 solar luminosities, is about 60 parsec from Terra and would have a apparent magnitude of -3.0. Even brighter than Halo in our sky.

I believe that this star (as well as one or two others) have been brought up before in other threads.
http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=36848
http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=33826

The fact that it is in the Sector named the "Dark Nebula" might account for some of the dimming in apparent magnitude. The Dark Nebula might be one of the nearer absorption nebulae components associated with the Cygnus Rift.

 

[G. Kashkanun Anderson]

According to TravellerMap , Halo (Solomani Rim 0726, Albadawi Subsector) is hosted by an F0 II star. II is a "bright giant", and an F0 II should have a luminosity of about 1000x of the sun.

As it's only 11-12 parsec away from us, it should be around -2.26 apparent magnitude to us, significantly brighter than Sirius and the brightest star in our night sky.

I think you're actually underestimating the problem with this star a little. My calculations indicate that Halo's star should be about 3200 times the luminosity of Sol, with an absolute magnitude of just under -4.0. This would give it an apparent luminosity of -3.7 at 12 parsecs, which places it in roughly the same luminosity category as Venus.

Is there any Traveller lore about what this star is, and why it was placed so close to Terra as to be so visibly bright? The name "Halo" is suggestive, too.

Another star, Troutiyka, a F8 Ia supergiant which would have a luminosity >50,000 solar luminosities, is about 60 parsec from Terra and would have a apparent magnitude of -3.0. Even brighter than Halo in our sky.

Troutiyka got passing mention a few years back in a discussion of bright stars in Dark Nebula sector. Mostly, I think it was waved off by suggesting that the eponymous 'dark nebula' in the region was dimming any stars in the region as seen from Terra.

As far Halo, I suspect its existence is most likely an artifact of LBB Book 6's star system generator, which is waaaaaaaaay overweighted towards the creation of Bright Giant stars. Going by the plain vanilla LBB6 system generator (and assuming standard regional stellar density), you will produce on average about 17-18 Bright Giants per sector, when realistically you should be able to crank out at least 2 full sectors of stellar data before you even come across one.

 

[sudnadja]

I think you're actually underestimating the problem with this star a little. My calculations indicate that Halo's star should be about 3200 times the luminosity of Sol, with an absolute magnitude of just under -4.0. This would give it an apparent luminosity of -3.7 at 12 parsecs, which places it in roughly the same luminosity category as Venus.

I used the luminosity curves from an H-R diagram, do you have a better mapping or table for spectral type <-> luminosity that you could share a reference to? (and thanks!). As we go up in spectral class I do know that more of the luminosity is emitted in non-visible light and that might explain some of it, but an F type star should still have the majority of its flux in the visible bands, right?

One implication of Traveller 5 is that the distances shown on the 2d maps are real space differences. Sublight travel between the stars are part of the game, thus when an object is placed 20 parsec away on the map, that's 20 real space parsec, not just jump space parsec, which, as another thread mentioned, removes that particular handwave explanation of the distances and star luminosities not making a lot of sense.

Another implication of the size of charted space (~1000 ly or so?) is that a supergiant might well appear to be late in its supergiant phase from one side of charted space and have gone supernova with a tremendous difference in luminosity from certain points within charted space and then appear to be a supernova remnant from another part of charted space.

 

[Garnfellow]

I think this must be some sort of error. Halo's primary is consistently listed as an F2 V in Solomani: Alien Module Six (1986), GURPS Traveller: Rim of Fire (2000), and The Traveller Chronicle 10 (1996). (Neither the CT nor MGT supplement have stellar data.)

I don't believe Halo is specifically mentioned in any canonical source, so I can't see why the stellar data would have intentionally been changed here.

Paging Joshua . . .

 

[esampson]

Really, if you are going to worry about issues like this then Halo is probably the least of your concerns. The map in Traveller was designed largely through random numbers and bears little to no resemblance to the stars near Earth. Just looking around Sol you are missing Epsilon Eridan (which we know has 2 planets), and Tau Ceti (which we know has 5 planets), Sirius and Barnard's Star are in the wrong position relative to one another, and Alpha Centauri (Prometheus) is too far away (unless you always round up, but then you hit the problem that Junction is too close, if you assume that Junction is either Wolf 359 or Lalande 21185. If you don't assume it is either of those you have an even bigger problem because it just doesn't exist).

I'm not saying that it is bad to be picky about details like these, but I think if you are going to do that you probably want to chuck the entire map and build a new one based off stellar data that Marc just didn't have easy access to when he drew up the maps thirty some-odd years ago.

 

[sudnadja]

Really, if you are going to worry about issues like this then Halo is probably the least of your concerns. The map in Traveller was designed largely through random numbers and bears little to no resemblance to the stars near Earth. Just looking around Sol you are missing Epsilon Eridan (which we know has 2 planets), and Tau Ceti (which we know has 5 planets), Sirius and Barnard's Star are in the wrong position relative to one another, and Alpha Centauri (Prometheus) is too far away (unless you always round up, but then you hit the problem that Junction is too close, if you assume that Junction is either Wolf 359 or Lalande 21185. If you don't assume it is either of those you have an even bigger problem because it just doesn't exist).

I'm not saying that it is bad to be picky about details like these, but I think if you are going to do that you probably want to chuck the entire map and build a new one based off stellar data that Marc just didn't have easy access to when he drew up the maps thirty some-odd years ago.

I thought that Epsilon Eridani was 1530 Shulimik, and Tau Ceti was 1429 Iilike? Junction is "canonically" Wolf 359, and Lalande 21185 is 2029 Midway, this from the "Traveller Known Stars list", but I think all of those have canonical sources.

known stars list

I'm aware of the local stellar topography and have done a fair amount of work in trying to map that in 3d (for example):



(Fomalhaut is also on the wrong side of the map, for example) and also come up with 2d representations of that, with principle component analysis or varying self-organizing maps approaches, and as I mentioned before it is a fundamentally unsolvable problem - 3d universe in a consistent 2d map. What I do want to do is come up with either plausible explanations of the inconsistencies or come up with a list of the inconsistencies that could be changed somewhat to reduce them. I do like the setting, and it's compelling to think of a vast galactic empire in the direction of Ophiuchus.

At any rate, I think the discussion isn't really intended to be nit-picking in so much as an ask for how others explain these stars, if travellermap is in error (which in this case might be the case, as the star was canonically originally G2 V?), and also as a sounding board for which mistakes to avoid if you do come up with your own maps. Placing a Ia supergiant within a sector or two of Terra should be avoided, for example, because that would be the brightest star in our sky.

 

[whulorigan]

Just looking around Sol you are missing Epsilon Eridan (which we know has 2 planets), and Tau Ceti (which we know has 5 planets), Sirius and Barnard's Star are in the wrong position relative to one another, and Alpha Centauri (Prometheus) is too far away (unless you always round up, but then you hit the problem that Junction is too close, if you assume that Junction is either Wolf 359 or Lalande 21185. If you don't assume it is either of those you have an even bigger problem because it just doesn't exist).

Epsilon Eridani is canonically the central star of the world Shulimik

Tau Ceti is canonically the central star of the world Iilike

Wolf 359 is canonically the central star of the world Junction

Lalande 21185 is canonically the central star of the world Midway

 

[esampson]

Epsilon Eridani is canonically the central star of the world Shulimik

Tau Ceti is canonically the central star of the world Iilike

Wolf 359 is canonically the central star of the world Junction

Lalande 21185 is canonically the central star of the world Midway

Which helps me to locate the stars but now you have issues such as Shulimik (nee Epsilon Eridani) should be about 3 parsecs away from Sirius, not right next door.

And of course these are just the inaccuracies in the extremely close vicinity. As the Spinward Marches is only about 500 lightyears away from Terra you have a massive number of stars over there that just aren't going to line up properly with Earth's sky.

I'm not complaining about a lack of accuracy; just pointing it out and saying that if the fact that a fictional star would be brighter on Earth than Sirius really concerns you there are probably much bigger fish that could use some frying.

 

[sudnadja]

I'm not complaining about a lack of accuracy; just pointing it out and saying that if the fact that a fictional star would be brighter on Earth than Sirius really concerns you there are probably much bigger fish that could use some frying.

That's one reason to focus on those fictional stars. There's no solution to the 3d-2d map problem, there is a solution to the issue of a bright giant star nearby earth - downgrade that star to something not so prominent. It's not going to be a concern for (probably) the majority of Traveller players or referees, but there does exist a minority of players and referees for whom the astronomy component of Traveller is the interesting one (opposed to trading or combat) and this thread is more for that side of the game and many people know that Sirius is the brightest star in the sky aside from the Sun, from Earth. If the star ended up 30th or 40th brightest it wouldn't matter so much, because it isn't inconsistent with grade school knowledge of the sky, but this is a star that would possibly be visible in daylight from the earth's surface.

And there's nothing wrong with that for most players, just like there's nothing wrong with the city of Gotham being on the eastern seaboard of the US in comic books, that's part of the universe there. It's just interesting for a subset of Traveller players to try to fit the Traveller universe in the context of the real one.

Since some of the canonical Traveller stars were placed near Terra as analogues for real stars, it's natural to presume that there was less randomness associated with the star types and placements with stars near Terra, thus my original question about Halo.

Anyway, I think my original post was misread if you thought I was worried about it. I'm not. I'm interested in it, was just was making the comment that "hey, there is a very bright star near Terra", and wondered if there was a specific reason for that or if the somewhat suggestive name Halo had anything to do with that.

 

[sudnadja]

I am not aware that Halo's central star has ever been canonically identified, and I am aware of most such identifications (I think).

By the way, is there a canonical "master list" of traveller stars to real stars, when those stars have been identified? I had been using "Traveller Known Stars", but I'm not sure if there's a broader list somewhere.

 

[Garnfellow]

By the way, is there a canonical "master list" of traveller stars to real stars, when those stars have been identified>? I had been using "Traveller Known Stars", but I'm not sure if there's a broader list somewhere.

I don't believe there is anything better.

 

[sudnadja]

I think you're actually underestimating the problem with this star a little. My calculations indicate that Halo's star should be about 3200 times the luminosity of Sol, with an absolute magnitude of just under -4.0. This would give it an apparent luminosity of -3.7 at 12 parsecs, which places it in roughly the same luminosity category as Venus.

Now that I've grabbed all of the sector data and munged it into a computable format, a few others popped out:

Glinde is a K8 II bright giant, 28 parsec away which would be -1.78 if the same luminosity as Halo.

Mervyn is 29.6 parsec away, K4 II, -1.66
Tura is an A4 II 32 parsec away, -1.49

the remainder of the bright giants are far enough away that if we take 3200x sol luminosity as the luminosity, they would be dimmer than Sirius.

There are a few other interesting Ia supergiants in the list too, aside from the already described Troutiyka and Deneb. Kraatiigiraki is 199 parsec away and is the same spectral category as Deneb, Muravia is an A7 Ia at 237 parsec away.

People love living around the supergiants though, Antares and Deneb have populations of 80 billion and 60 billion, respectively.

I do want to know the story behind Kraatiigiraaki. TL 0, population of 4 living around a A2 Ia supergiant. There are question marks in the UWP, but PBG is 432, so there is a population multiplier of 4. But 4 * what? I interpreted a ? to mean 0, 10^0=1 so that's 4 people. But why was the population multiplier known but the base population in the UWP unknown?