Eakhoi (Dark Nebula 2123)

[Garnfellow]

Eakhoi is a high-population Aslan garden world in Khtoiakta subsector (K) of Dark Nebula, 9 parsecs trailing from Kusyu, about 4 parsecs from the Solomani Confederation border, and roughly 61 parsecs spinward of Terra.

What's really notable about this system is that the mainworld orbits a yellow supergiant, spectral type F8 Ia -- the same as Delta Canis Majoris. It's a busy little system, with 4 gas giants, 1 asteroid belt, and 9 other worlds.

It looks like T5 allows a habitable zone for even F8 Ia stars -- way out in orbit 12. But can the rest of the system details be reconciled with this star? I'm fine with implausible, I'm just curious where the impossible line lies.

Shouldn't a star like this be visible to the naked eye from Earth? It seems like it would be one of the most remarkable astrographic features in this part of Charted Space.

 

[tjoneslo]

There was, many years ago, a long discussion on the JTAS boards about Antares, which is another supergiant star with several billion people on a habitable world.

From what I remember about that discussion here were the problems raised:

1) the 100D limit for the star is somewhere about 2-4 week out from orbit 12 even assuming a 1G or 2G drive on the ships. This makes trade with the system hugely difficult. There is probably a trade station somewhere in the outer system (say orbit 18) (or several).

2) There isn't enough time for world to (depending upon the which research papers you have read) have formed, cooled to the point where they have a solid surface, or have any kind of atmosphere. The solution to this problem for Antares was to add a third (brown dwarf) companion star where the world was orbited. This put it outside the 100D limit for the primary, and gives enough time to have the world form a real garden worlds (with life and everything). I could also see using a captured deep space wandering planet, now warmed and aggressively terraformed.

3) The star will go supernova. Probably not in the timescale of anyone currently living in the system, but on a stellar lifespan scale, real soon now. There will be essentially no warning, and what little warning there will be (if people are paying attention) there is no way to get everyone off the planet.

Yes, you should be able to see the star with a naked eye from Terra during daylight hours. The same effect should be true in the Spinward Marches and Deneb sectors with regard to the Deneb system. And the Antares sector and Antares star.

 

[whulorigan]

Eakhoi is a high-population Aslan garden world in Khtoiakta subsector (K) of Dark Nebula, 9 parsecs trailing from Kusyu, about 4 parsecs from the Solomani Confederation border, and roughly 61 parsecs spinward of Terra.

What's really notable about this system is that the mainworld orbits a yellow supergiant, spectral type F8 Ia -- the same as Delta Canis Majoris. It's a busy little system, with 4 gas giants, 1 asteroid belt, and 9 other worlds.

It looks like T5 allows a habitable zone for even F8 Ia stars -- way out in orbit 12. But can the rest of the system details be reconciled with this star? I'm fine with implausible, I'm just curious where the impossible line lies.

Shouldn't a star like this be visible to the naked eye from Earth? It seems like it would be one of the most remarkable astrographic features in this part of Charted Space.

Note that down in the left corner of TravellerMap, Dark Nebula Sector is noted as being "Unreviewed", meaninig that some of the data of Dark Nebula is likely to change when it gets the full T5 treatment (it will say "Traveller 5 Second Survey" instead of "Unreviewed" when this is done).

But to your point: Delta Canis Majoris lies a little under 500pc from Earth in a generally Rimward direction, and as you mentioned, Eakhoi's Star lies at a distance of a little under 70pc to Spinward. So yes, an F8Ia star in Dark Nebula Sector would be quite bright in Terra's sky if it were at that distance, unless it were obscured by intervening dust clouds (remember, this Sector is called the "Dark Nebula").

NOTE:
I was able to locate the following stars along a Spinward/RimSpinward bearing that could possibly fit with a little tweaking (keeping in mind that the distances on TravellerMap are projections/compressions of 3D space onto a 2D plane, and that the hexes really have to do with the distance thru Jumpspace, and generally approximate 1pc distances as transformed from NormalSpace):

1) HD 199290: Type F2Ib / Distance ~160pc
2) HD 203918: Type F8 (Luminosity unspecified) / Distance ~ 90pc
3) HD 15000: Type F5II / Distance ~ 80pc
4) EM* CDS 283: Type F6Iab / Distance unspecified ^*
5) V* VY Persei: Type F7.5Ib / Distance unspecified ^*
6) IRAS 02143+5852: Type F7I / Distance unspecified <sup>*

*</sup> - Note that this probably means that an accurate parallax measuremneant cannot be obtained (i.e. it might be very far away).
​

 

[rancke]

[...] (keeping in mind that the distances on TravellerMap are projections/compressions of 3D space onto a 2D plane, and that the hexes really have to do with the distance thru Jumpspace, and generally approximate 1pc distances as transformed from NormalSpace):

Unfortunately, Traveller maps show accurate realspace distances that can be traversed with SLT and are transitive (if that's the term I want). So that handwave makes no more sense than the flat galaxy does.


Hans

 

[Garnfellow]

1) the 100D limit for the star is somewhere about 2-4 week out from orbit 12 even assuming a 1G or 2G drive on the ships. This makes trade with the system hugely difficult. There is probably a trade station somewhere in the outer system (say orbit 18) (or several).

I was a little surprised to find that when I checked the T5 book, the 100-diameter limit for a both a F5 Ia and a G0 Ia was within orbit 11. I was expecting it to be well outside the habitable zone.

Is this right? Or am I maybe misreading the chart?

 

[Garnfellow]

Note that down in the left corner of TravellerMap, Dark Nebula Sector is noted as being "Unreviewed", meaninig that some of the data of Dark Nebula is likely to change when it gets the full T5 treatment (it will say "Traveller 5 Second Survey" instead of "Unreviewed" when this is done).

And that's exactly why I'm looking at the data. I guess my ultimate question here is, should we recommend that Marc chuck this supergiant, or can we find a reasonable way to make it work?

So yes, an F81a star in Dark Nebula Sector would be quite bright in Terra's sky if it were at that distance, unless it were obscured by intervening dust clouds (remember, this Sector is called the "Dark Nebula").

And that's one of the other questions I have in the back of my mind as I'm reviewing the data: if there really is a dark nebula in this Sector, where would it be and what would it look like? The boardgame -- which of course has only the most tenuous of connection to the canonical UWP data -- features a nebula maybe 2 parsecs in width, with some six stars within it.

Could you have some kind of dust cloud that large 50-80 parsecs from Terra that we haven't yet detected, or is that just too close? Maybe not a true nebula, but something smaller and closer.

I am fine with the sector name being just some sort of poetical or marketing device like "Greenland," but if one could shoehorn a reasonable astronomical explanation, that seems far more preferential.

 

[whulorigan]

And that's one of the other questions I have in the back of my mind as I'm reviewing the data: if there really is a dark nebula in this Sector, where would it be and what would it look like? The boardgame -- which of course has only the most tenuous of connection to the canonical UWP data -- features a nebula maybe 2 parsecs in width, with some six stars within it.

Could you have some kind of dust cloud that large 50-80 parsecs from Terra that we haven't yet detected, or is that just too close? Maybe not a true nebula, but something smaller and closer.

I am fine with the sector name being just some sort of poetical or marketing device like "Greenland," but if one could shoehorn a reasonable astronomical explanation, that seems far more preferential.

There actually is a massive set of dust clouds called the Great Rift (or sometimes the Cygnus Rift) that lies at about the distance (~ 80pc -100pc) of the Great Rift on Traveller Map, although it begins at a bearing somewhat counter-clockwise from Deneb's bearing, and continues over toward the Lesser Rift and 2000 Worlds, as seen from Earth ^*. Note that this is a rift in terms of visibility, not in terms of low stellar density. Perhaps there could be some outlying pockets of these clouds in the Dark Nebula.

^* - Note that this is not a single continuous formation, but are overlapping bands and pockets of nebular formations at varying distances that merely look like a continuous band from Earth. It is called a rift because it is black and you cannot see any stars through it.
​

http://en.wikipedia.org/wiki/Great_Rift_%28astronomy%29

P.S. And I am all for placing an actual "Dark Nebula" of some sort (perhaps 1-3pc wide) somewhere in the Dark Nebula Sector. ISTR somewhere once seeing a map of Charted Space that located the rough position of the nebula, but I do not remember where (and I do not think it was the Dark Nebula boardgame).

 

[inexorabletash]

Note that down in the left corner of TravellerMap, Dark Nebula Sector is noted as being "Unreviewed", meaninig that some of the data of Dark Nebula is likely to change when it gets the full T5 treatment (it will say "Traveller 5 Second Survey" instead of "Unreviewed" when this is done).

"Unreviewed" is a bit of a misnomer in this case. It should really say "under review" and this is the sort of feedback Marc, DonM and company want before it gets the stamp of approval (and why the data is up on TM). So... paging DonM!

 

[inexorabletash]

"Unreviewed" is a bit of a misnomer in this case. It should really say "under review" and this is the sort of feedback Marc, DonM and company want before it gets the stamp of approval (and why the data is up on TM). So... paging DonM!

FYI, to clarify this, I've split out "In Review" from "Unreviewed" on the map site. Sorry for the confusion.

 

[tjoneslo]

Doing some calculations, an F8 Ia star has an absolute magnitude of -5.9. For comparison the sun is 4.83. For magnitudes, smaller numbers means brighter objects. At the 61 parsecs distance, the star has an apparent magnitude of -2, which makes it brighter than Sirius (the brightest star in the sky, m=–1.47), and about the brightness of Jupiter.

That's with visible light. If there is a nebula in the way, it may dim the star some, but there would be other instruments that would see a star that bright.

 

[Garnfellow]

Thanks to tjoneslo's suggestion, I tracked down a nice recap of the Antares discussion over at the Steve Jackson games forum. (I guess the original has been lost to time and tide.) It took a lot of finagling for folks to reconcile Antares, but that effort was worth it because Antares is an important star both in the "Real World" and in Traveller canon.

Eakhoi, I'm not so sure about. The stellar data goes back at least as far as DGP's Solomani & Aslan book, but if the location of Kuzu can still be tweaked I don't think there are any sacred cows here.

The old Antares thread certainly makes it sound like the Eakhoi system as described in the current UWP would be extremely unlikely. If we were bound and determined to keep a yellow supergiant in Dark Nebula, I would suggest switching the stellar data between Eakhoi and Troutiyka (Dark Nebula 2230 B000277-E), a low population asteroid belt world in the same subsector. The Troutiyka system still has 3 gas giants to explain, but it's a lot easier to swallow than a high-population garden world. (And if we were gonna make this change I'd probably nuke the gas giants also.) Eakhoi would end up with an M1 V primary, but there are plenty of tide-locked garden worlds in Traveller canon already, so what's one more?

Switching stars, though, still leaves the problem of having such a bright star so close to Terra. I think my preference would be to just change Eakhoi's star to one that would still be very, very bright but certainly not anything brighter than Sirius!

 

[rancke]

Eakhoi, I'm not so sure about. The stellar data goes back at least as far as DGP's Solomani & Aslan book, but if the location of Kuzu can still be tweaked I don't think there are any sacred cows here.

NO!!

:rant: NO, NO, NO, NO, NO, NO!!!

<sob> Please, no...

(http://wiki.travellerrpg.com/Kuzu_(world)/meta )


Hans

 

[Garnfellow]

NO!!

:rant: NO, NO, NO, NO, NO, NO!!!

<sob> Please, no...

(http://wiki.travellerrpg.com/Kuzu_(world)/meta )


Hans

You completely missed my point: I think overriding illogical past canon is a good thing. If DGP's canonical location of Kusyu at 1919 can be amended, then by extension the much more obscure Eakhoi can also be tweaked.

 

[rancke]

You completely miss my point. I think overriding illogical past canon is a good thing. If DGP's location of Kusyu at 1919 can be fixed, then The much more obscure Eakhoi can also be, by extension.

Oh...

Carry on, then. :coffeesip: <--- tea sip



Hans

 

[tjoneslo]

Thanks to tjoneslo's suggestion, I tracked down a nice recap of the Antares discussion over at the Steve Jackson games forum. (I guess the original has been lost to time and tide.)

The original took place on the older SJGames discussion forums which got entirely deleted when the moved to the new ones. Which is too bad, we lost a lot of interesting discussions (as well as a number of flame wars).

 

[Garnfellow]

I checked the Mongoose Deneb book, to see how the Deneb system and its supergiant were handled there. The OTU Deneb is a little less than 200 parsecs from Terra, with a habitable world. The "Real World" Deneb is at least twice as distant. The T5 stellar data matches "Real World" data: an A2 Ia star.

Perhaps wisely, the Mongoose book sidesteps the issue. (The better part of valor and all that.) There's no stellar data, no connection drawn to the real Deneb: just a mention that the main world orbits a bright star.

 

[Frankymole]

Yes, you should be able to see the star with a naked eye from Terra during daylight hours.

Unless there's something in the way, blocking the light from reaching us. A dark nebula, perhaps...

 

[whulorigan]

Note that down in the left corner of TravellerMap, Dark Nebula Sector is noted as being "Unreviewed", meaninig that some of the data of Dark Nebula is likely to change when it gets the full T5 treatment (it will say "Traveller 5 Second Survey" instead of "Unreviewed" when this is done).

Just a quick follow up:

On TravellerMap, Dark Nebula is no longer "Under Review", but is now Official T5 Second Survey data. Eakhoi has kept its F8Ia primary star (obviously that "Dark Nebula" is getting in the way of Terran astronomical observers).

Note also that Kusyu is now officially located at 1226 Dark Nebula.

 

[DonM]

And I just discovered this thread. The Dark Nebula stellar data could still be reviewed...

 

[DonM]

Any comments? Is there something here we need to consider in the T5SS data for Dark Nebula?