Seeing Stars during the day

[tjoneslo]

I've been slowly working through the Deneb sector worlds. One of the interesting things was seeing how bright Deneb (the star) really is. At an Absolute Magnitude of -8.73, it is one of the brightest stars known.

Now the Deneb star on the Charted Space map isn't the real Deneb star. The real one should be about 1000 parsecs from Terra, whereas the one on the map is about 200 or so.

I asked Josua to add a circle overlay to the Traveller Map API, and found the six brightest stars in charted space. The are (in order) Deneb, Helix, Yurm, Troutiyka, Antares, and Sargas.

The link shows these six stars, and a calculated distance where you can, in theory, see the star during daylight hours. By definition this is having the star's apparent magnitude of -4 or brighter

https://travellermap.com/?options=5...19&ocy4=59&ocr4=16&ocx5=33.332&ocy5=81&ocr5=5

So as background for people running campaigns in the Spinward Marches, Deneb is, by far, the brightest star in the night sky. It is almost always visible in even in daylight, a bright point of light. In some cases it will be brighter than the far companions of some systems. And bright enough to cast shadows. On the trailing edge (and throughout the Deneb sector) Deneb will be brighter than most moons. In the Usani Subsector, the Deneb is brighter than a full moon.

 

[Enoki]

Makes you wonder what other super bright stars would be visible outside of "charted" space doesn't it? If there were a few more even partially as bright as Deneb within a dozen subsectors that'd be something to consider.

 

[G. Kashkanun Anderson]

Hmmm... Looks like we need to get the old Hubble recalibrated again. If there's an F-Type supergiant less than 100 parsecs from Sol, I think we should have noticed it by now!

Troutiyka is almost in the correct position to be a stand-in for Canopus, though. Especially if, theoretically, we were to suddenly discover that our estimations of Canopus's luminosity were just enough to drop it down a type and roll it closer in a few dozen light years or so.

Also, being quite visible from Vland, I personally decided (IMTU, that is) that Deneb has a certain amount of religious significance to the Vilani, which is why I gave it the name Sudrehiirushu on my Ziru Sirka map. If I recall correctly, it means either 'Valiant Defender' or 'Last/Sole Defender' in Old High Vilani.

 

[Garnfellow]

That's pretty darned cool. Of course, when considering Troutiyka we also ought to consider the dark nebula in Dark Nebula sector. Is there actually a nebula there, or is it just some sort of poetic device? The boardgame strongly suggests that it is a real astronomical object, but then again almost nothing about the boardgame actually lines up with canon.

The existence of a nebula might explain why we can't see Troutiyka from Terra. It might also explain why first contact between Terrans and Aslan didn't occur until -1980 (wink wink), even though by -2204 Terran colonists had established colonies all around Kusyu, in Magyar, Dark Nebula, Ustral Quadrant, Iwahfuah, and even in Dark Nebula spinward of the Aslan homeworld.

 

[G. Kashkanun Anderson]

That's pretty darned cool. Of course, when considering Troutiyka we also ought to consider the dark nebula in Dark Nebula sector. Is there actually a nebula there, or is it just some sort of poetic device? The boardgame strongly suggests that it is a real astronomical object, but then again almost nothing about the boardgame actually lines up with canon.

Well, there's the Cygnus Rift, a huge dust cloud standing between us and the Sagittarius Arm, but it's a bit further away and more in the direction of Spin-Coreward than Dark Nebula Sector. It's also known as the Great Rift, so you can probably guess that, as far as canon is concerned, it's already taken anyway.

A cloud of dust and gas thick enough to obscure a supergiant barely 100 parsecs from Earth is unlikely to have gone unnoticed by us by now. Even the ancients would have probably figured out something was up, as that would likely create a rather suspiciously underpopulated looking region of the sky. And Canopus would probably have been obscured too, since it's in the same general area.

 

[flykiller]

So as background for people running campaigns in the Spinward Marches, Deneb is, by far, the brightest star in the night sky.

imtu deneb is the navigation benchmark for the spinward marches. mentioned it in my recovery story.

 

[flg]

The link shows these six stars, and a calculated distance where you can, in theory, see the star during daylight hours. By definition this is having the star's apparent magnitude of -4 or brighter

Note that apparent magnitude of -4 is only about as bright as Venus from Earth. And "visible in daylight" and "bright enough to cast shadows" are situations that very much depend on local conditions (is there an atmosphere to scatter light? Is it only visible in daylight if you know exactly where to look? etc etc).

If you want Deneb to be as bright as the full moon in the sky (bright enough to cast shadows at night on a world with earthlike atmosphere), then it has to be around app mag -12.5, and assuming a luminosity of 200,000 Sols, that's at a considerably smaller radius of 5 lightyears - less than 2 pc. (app mag -4 is at a distance of 250 lightyears, or ~75pc radius).

 

[shaunhilburn]

The link shows these six stars, and a calculated distance where you can, in theory, see the star during daylight hours. By definition this is having the star's apparent magnitude of -4 or brighter

A main sequence host star of spectral class M6 or M7 will produce fainter daytime skyglow, so an earthlike planet at UV Ceti or Wolf 359 will have a much higher background contrast in broad daylight, allowing stars of around -0.75 to -1 to be seen. This is similar to dusk when Sirius or Canopus can first be seen; not standing out clearly and somewhat difficult to reacquire when you look away, yet plainly visible if you know where to look.

 

[G. Kashkanun Anderson]

A main sequence host star of spectral class M6 or M7 will produce fainter daytime skyglow, so an earthlike planet at UV Ceti or Wolf 359 will have a much higher background contrast in broad daylight, allowing stars of around -0.75 to -1 to be seen. This is similar to dusk when Sirius or Canopus can first be seen; not standing out clearly and somewhat difficult to reacquire when you look away, yet plainly visible if you know where to look.

Also, as you move through the late K-Type stars and beyond, the type of radiation emitted moves increasingly over to the infrared spectrum, to the point where late M-Types like M6 or M7 stars are nearly entirely in the infrared, as far as the human eye can tell. The skies of worlds orbiting those skies will tend to range from early twilight (for the late K and early M-Type stars) to deep dusk (for late M-Types). Still brighter than moonlight (after all, they are stars), but definitely not like a Terran sky.

 

[sudnadja]

I've been slowly working through the Deneb sector worlds. One of the interesting things was seeing how bright Deneb (the star) really is. At an Absolute Magnitude of -8.73, it is one of the brightest stars known.

Now the Deneb star on the Charted Space map isn't the real Deneb star. The real one should be about 1000 parsecs from Terra, whereas the one on the map is about 200 or so.

This is about a year and a half late to the conversation, but Deneb is somewhere around 450 parsec from sol in reality. If you take Simbad data and compute it it works out to 432.9 parsec (2.31 mas parallax according to Simbad), wolfram curated data is at 474.447 parsec from sol.

I've used both Deneb and Antares along with Sol and the travel distances between the three of those and Capital to estimate the location of Captial in the real sky. It is, unfortunately, completely unworkable and the traveller map has very little resemblance to the real sky. (for example, the game map has Deneb more coreward than spinward, in reality it is much more spinward than coreward, not to mention a 15 parsec offset from Sol in the +z (vs the galactic plane) vs sol.

Incidentally, I got a radius of 42.16 parsec for for visible apparent magnitude brighter than -4, I'm not sure if that's what you got for your map as well.

 

[sudnadja]

Also incidentally, I have Deneb listed at an absolute magnitude of -7.13 (possibly that's relative to visible flux?) but also interesting is another very bright star is real-world nearby - Sadr (Gamma Cygni) is 58 parsecs away almost direct coreward at absolute magnitude of -6.12.