The stars at night look big and bright

[Shadowdancer]

I was wondering something: For systems on the edge of the Great Rift and Lesser Rift, are there fewer stars in the sky at night, and from space, in the direction of the rifts?

I know that some light from the stars on the other side of the rifts would get through, but based on the distances, how much of that would be visable to the naked eye, and how much would only be visable with telescopes, etc.

 

[Malenfant]

Well, realistically there aren't any "rifts" (as in places where there are no stars at all), at least not in those positions - they're not the gaps between the spiral arms, but even if they were there would still be stars present in them, they'd just be very dim ones. The spiral arms are just those areas where the big, bright OB stars are concentrated, which is what makes them look bright relative to the gaps between them that are filled with older, smaller, dimmer stars.

Even if the Traveller rifts did exist, I don't think you'd notice much of a difference in the stellar density in the night sky. It would just mean that most of the bright stars you can see with the naked eye are far away (heck, most of the stars that we can see in our night sky are far away - we can only see our brightest neighbours with the naked eye)

I think you'd notice a difference at the very edge of the galactic disk, where you'd look to corewards and see lots of stars, and look rimwards and you'd only see a few distant galaxies. But that's very far to rimward of Sol and Charted Space.

 

[kafka47]

Rifts are also where there is high concentrations of interstellar dust. So it possible to have a situation akin to Nightfall or Pitch Black.

I would imagine when one looks up at the sky it would also matter what is the magnitude of the nearby stars for if there a rift created from simply low star density would not distant stars appear like the Milky Way in the Northern Hemisphere or the Magellian Clouds in the Southern? Because of the amount of material the light must travel through before reaching the observer?

 

[Malenfant]

Bear in mind that even if you're smack bang in the the middle of the Great Rift (assuming they are places that literally contain very few stars) - say in the Faoheiroi'iyhao sector off in the bottom left corner of the Charted Space map, you still have the entire galaxy around you that's full of stars. All you'd be missing would be stars that are nearby, but by comparison most of the bright stars we can see in our own night sky are those that are far away anyway.

If the rifts are just big dust clouds (and by golly they're big) - then yes, they'd definitely block off the light from outside them. That said, they'd be illuminated from inside by any stars within them, but that light may not be able to get out to be visible to those outside the "rift".

But I don't think that's what Rifts are supposed to be (and besides, they wouldn't be that big or that dense either)

 

[marvo]

Someone with a lot of time on their hands could possibly make a visual based on the stellar types of the stars around the great rift. It would be nice to have a program that takes the UWP data for the stella data and displays a map with the stars as colored dots representing their size, color and brightness. This would probably fall down at the extreme ends of the scale, but it would be worth a try.

I think you will find that there are very few really bright stars. These would be 'landmarks' just like the brighter stars in our sky, and would be visible across the rift. That is, assuming there are no clouds of dust in the way.

 

[Malenfant]

Yeah, I suspect that the bright stars you'd see would be ones that are beyond the rift.

And remember that even if you're surrounded by tons of M dwarfs in the rift, chances are that you're not even going to see most of them from a few lightyears away with the naked eye. Hell, you can't even see Proxima Centauri with the naked eye from here.

 

[marvo]

Something else just occured to me. From earth (given a good dark spot to observe from) there is a noticable difference between looking in the plane of the galaxy, and looking perpendicular to it. So from somewhere near the great rift there might be a noticable difference depending which direction you looked. Overall though, even the great rift, is not that far across so it might be insignificant.
As Malenfant pointed out, clouds of dust would make more of an impact than distance alone. IMTU there are large clouds of dust in the Reft Sector. But they are only there to hide some systems that I created there.

 

[Malenfant]

Depends how far the "rift" extends in the vertical plane. If it's really just an elongated bubble that's a few hundred parsecs long by a few tens of parsecs wide and high, then above and below it there will still be plenty of stars (up to the top and bottom edges of the galactic disk). In which case, you'd see what you just described - the plane of the milky way as a band of stars, and less stars above and below (but still quite a lot of stars).

If, for some reason, it's something that cuts right through the entire thickness of the disk, then you'll see lots of stars in the plane of the galaxy, and hardly any if you look directly "up" or "down". But that is almost certainly not the case here.

 

[Tarondor]

The vast majority of the stars we see at night from Earth are hundreds or thousands of light-years away. An observer in a star-poor region of the galaxy (but still within the spiral arms), would likely see a sky very much like our own. The bright stars would still be at a similar distance. Heck, most of them would be the -same- bright stars observable from Earth.

Remember that although the Great Rift is big on the scale of Known Space, it's a tiny speck on the scale of the galaxy, or even of a sprial arm.

 

[flykiller]

deneb is a class A supergiant. if it were ten parsecs away from earth it would be as bright as the full moon - so I've read. up in the spinward marches it would be the brightest object in the sky after the local star and any moon, and be very prominent religiously and culturally and technically. a competent navigator could probably get a good idea of where he was just by looking at deneb and the orientation of its nearby companions.

 

[marvo]

Originally posted by flykiller:
deneb is a class A supergiant. if it were ten parsecs away from earth it would be as bright as the full moon - so I've read. up in the spinward marches it would be the brightest object in the sky after the local star and any moon, and be very prominent religiously and culturally and technically. a competent navigator could probably get a good idea of where he was just by looking at deneb and the orientation of its nearby companions.

Really good point!

Based on this I did some research and came up with the following:

The distance of Deneb seems to be in dispute. Various sources put the distance between 1,600 and 3,200 ly. The luminosity varies between 60,000 and 250,000 times that of the sun. The free program 'Celestia' (see link at the end of this post) uses the high end figures and this makes Deneb VERY bright indeed. By zooming around in the Celestia program I found that Deneb would have a magnitude of -12 (full moon) at a distance of about 5.5 ly! Even at 100 ly, about 33 parsecs or Traveller hex's, it would have a magnitude of -6.25. So yes, from anywhere in the Spinward Marches Deneb would be by far the brightest star in the sky.

Now for the bad news. I did some calculations of distance based on the OTU. Deneb to Terra is about 209 hex's, or 209 parsecs. 209 x 3.262 = 681.75 ly. This is about 1,000 ly off the nearest real world estimate. Not really a surprise but just an interesting sidenote.

Anyone who want's a free 3D astronomy simulator should check out Celestia. It's a free, open source program with lot's of options. It's main feature is that it lets you move around the galaxy and view from anywhere. If you download some of the free plugins you will find it is far better than a lot of commercial products. Plus you can save screenshots or movies from it. Great for Traveller background.

Celestia 3D Space Simulator - home page

 

[Malenfant]

Celestia is a great program. I used it a lot to reality check my realistic near star co-ordinates

Also, I found that Deneb is in the wrong place in Traveller (as are most stars). I was using the 3227 ly distance (derived from HIPPARCOS parallax data), which put it at a distance of 990pc from Sol - 98.54 pc directly to rimward, 984.58 pc to spinward, and 34.51 pc "above" the plane of the map relative to Sol. That would put it very far the spinward end of the Charted Space map - it'd be 35 sectors to spinward of Massila.

Even if it was at 1630 ly (500 pc), it'd be about 50pc to rimward, 497pc to spinward, and 17.4pc above Sol. That would put it 17.75 sectors to spinward of the Diaspora sector, way off the map.

 

[Malenfant]

BTW, next time you're out late at night sky-watching, find the star Altair and move your gaze a bit east (I think) of it - you'll be looking roughly at the Spinward Marches - they're located around the border of the constellations of Aquila and Scutum (assuming they're in the galactic plane). They're about 200 pc from Sol.

If you have Celestia, find the star HD 176468 - that's roughly in the middle of the Spinward Marches sector.

 

[mike wightman]

That would be Arba C-200200-C NI then???

 

[Malenfant]

I have no idea

. I'd imagine the real stars don't tally with any of the ones shown in the Spinward Marches sector anyway.

Actually, I'm not convinced that HD 176468 is in the *middle* of the SM sector, but I'm pretty sure it must be in the sector somewhere.

 

[mike wightman]

Do you know what the Traveller stats for HD 176468 star would be?

 

[Malenfant]

There are a few bright stars in the vicinity, the brightest is probably 21 Aql, which apparently is a B8 II Bright Giant (and therefore very young and very massive). That definitely would be in the Marches.

 

[Malenfant]

Celestia appears to be rather confused about HD 176468 - it claims it's a K2 V, but it has a luminosity that is 23 Sols.

HIPPARCOS claims it's a K2... so it's probably more likely to be a K2 III. If the luminosity is correct, then at a guess I'd say it's an 6-8 billion year old (low metallicity) 1 solar mass star that's just left its subgiant phase and is on its way up the Red Giant Branch.

 

[marvo]

Originally posted by Sigg Oddra:
That would be Arba C-200200-C NI then???

Hmm... the spectral type matches. According to my Spinward Marches datasheet Arba's sun has a spectral type of K2 V. In Celestia, star HD 176468 has a spectral type of K2 V.
Coincidence? Or is malenfant just messing with our heads?

 

[Malenfant]

probably coincidence, especially given that the Size in Celestia is most likely wrong.