How Bright are Manticore A & B?

I was wondering if any posters who know more astronomy than I do could satisfy my curiosity?

I'm was wondering how bright Manticore A would be in the night sky of Gryphon and how bright Manticore B would be in the night skies of Manticore and Sphinx.

If anyone could answer these questions it would be greatly appreciated.

Thanks

Rowbi wrote:I was wondering if any posters who know more astronomy than I do could satisfy my curiosity?

I'm was wondering how bright Manticore A would be in the night sky of Gryphon and how bright Manticore B would be in the night skies of Manticore and Sphinx.

If anyone could answer these questions it would be greatly appreciated.

Thanks

I took my google powered totally amateur best at it. (Now this is at best an average, HoS says

House of Steel wrote:The Manticore System consists of a G0 star of 1.12 solar masses with a G2 binary companion of 0.92 solar masses. Both stars orbit a common center of gravity 333 light-minutes from the A component
and 406 light-minutes from the B component. The apparent eccentricity of the pair approaches twelve percent, and results in distances between the stars that range from 650 light-minutes at periastron to 827 light-minutes at apastron.

So I used the average distance of 738 light-minutes. A G2 star like the sun, or Manticore-B should be about 8,500 times dimmer at the distance of of 738 LM than it is at Earth's orbit of 8 LM. That's actually, if I didn't utter screw things up, about 46 times brighter than moonlight; or equivalent to pretty late twilight.

Going the other way a G0 star is about 20% brighter than a G2, so Manticore A will appear a bit brighter from Gryphon that Manticore B did from Manticore or Sphynx. (Of course assuming it's the correct part of each planet's yearly orbit to actually see the companion star after sunset. (What, maybe around 1/3rd of its orbit? When it's mostly between them)

Still the companion star is probably the brightest thing in their night sky (except, maybe, the multi-km long orbital stations)

Rowbi wrote:I was wondering if any posters who know more astronomy than I do could satisfy my curiosity?

I'm was wondering how bright Manticore A would be in the night sky of Gryphon and how bright Manticore B would be in the night skies of Manticore and Sphinx.

If anyone could answer these questions it would be greatly appreciated.

Thanks

v interesting question - had not thought about this!

I won't make any estimates, or add anything to Jonathans excellent answer, but will just add a little which helped me grasp the scales

Being about 12 light hours apart, they are three times the distance of Neptune from the sun and about 1/3100 of the distance to Proxima Centauri - our nearest neighbour. PC is a red dwarf not vis to naked eye.

By contrast Alpha Centauri [fractionally further at present] is one of the brightest stars in the sky with a mag of zero.

Jonathan_S wrote:So I used the average distance of 738 light-minutes. A G2 star like the sun, or Manticore-B should be about 8,500 times dimmer at the distance of of 738 LM than it is at Earth's orbit of 8 LM. That's actually, if I didn't utter screw things up, about 46 times brighter than moonlight; or equivalent to pretty late twilight.

Going the other way a G0 star is about 20% brighter than a G2, so Manticore A will appear a bit brighter from Gryphon that Manticore B did from Manticore or Sphynx. (Of course assuming it's the correct part of each planet's yearly orbit to actually see the companion star after sunset. (What, maybe around 1/3rd of its orbit? When it's mostly between them)

Still the companion star is probably the brightest thing in their night sky (except, maybe, the multi-km long orbital stations)

We can calculate the apparent magnitude and compare to Venus and the full Moon on Earth from their absolute magnitudes.

Using the formula from Wikipedia, we have M = m - log_5(d) + 5 or that m = M + log_5(d) - 5 where M is the absolute magnitude, m is the apparent magnitude and d is the distance, in parsecs. 738 light minutes is 430 microparsrecs (µpc).

If we say that Manticore-B, a G2 dwarf, has the same absolute magnitude as the Sun, that is 4.83. Putting that number in the formula, we get m = 4.83 + log_5(430e-6) - 5 = -4.99. Comparing that to the tables on Wikipedia, we find that Venus as seen from Earth has an apparent magnitude of -4.92 at maximum, -4.14 mean. So Manticore-B as seen from Manticore or Sphinx would appear slightly brighter than Venus does (at maximum).

Taking your number that a G0 is 20% brighter (1.2x) and knowing that absolute magnitudes are logarithmic gives us Manticore-A's absolute magnitude is - 2.5 log_10 (1.2) = -0.19 more than the Sun/Manticore-B. That is, 4.83 - 0.197 = 4.63. The apparent magnitude of Manticore-A from Gryphon would be around -5.19. That is over 2.5x brighter than the Venus mean.

Venus is the brightest, natural point-like object on the Earth night sky, so both of those stars would most likely be the brightest night-sky natural objects. But unlike Venus, which as an inner planet is never far from sunset or sunrise, the two stars could appear at full night. The only thing that could rival them are inner planets on the same system, but unlikely.

The brightest point-like object in our current night sky is the ISS, at -5.9 (at perigee and fully illuminated).

ThinksMarkedly wrote:

Jonathan_S wrote:So I used the average distance of 738 light-minutes. A G2 star like the sun, or Manticore-B should be about 8,500 times dimmer at the distance of of 738 LM than it is at Earth's orbit of 8 LM. That's actually, if I didn't utter screw things up, about 46 times brighter than moonlight; or equivalent to pretty late twilight.

Going the other way a G0 star is about 20% brighter than a G2, so Manticore A will appear a bit brighter from Gryphon that Manticore B did from Manticore or Sphynx. (Of course assuming it's the correct part of each planet's yearly orbit to actually see the companion star after sunset. (What, maybe around 1/3rd of its orbit? When it's mostly between them)

Still the companion star is probably the brightest thing in their night sky (except, maybe, the multi-km long orbital stations)

We can calculate the apparent magnitude and compare to Venus and the full Moon on Earth from their absolute magnitudes.

Using the formula from Wikipedia, we have M = m - log_5(d) + 5 or that m = M + log_5(d) - 5 where M is the absolute magnitude, m is the apparent magnitude and d is the distance, in parsecs. 738 light minutes is 430 microparsrecs (µpc).

If we say that Manticore-B, a G2 dwarf, has the same absolute magnitude as the Sun, that is 4.83. Putting that number in the formula, we get m = 4.83 + log_5(430e-6) - 5 = -4.99. Comparing that to the tables on Wikipedia, we find that Venus as seen from Earth has an apparent magnitude of -4.92 at maximum, -4.14 mean. So Manticore-B as seen from Manticore or Sphinx would appear slightly brighter than Venus does (at maximum).

Taking your number that a G0 is 20% brighter (1.2x) and knowing that absolute magnitudes are logarithmic gives us Manticore-A's absolute magnitude is - 2.5 log_10 (1.2) = -0.19 more than the Sun/Manticore-B. That is, 4.83 - 0.197 = 4.63. The apparent magnitude of Manticore-A from Gryphon would be around -5.19. That is over 2.5x brighter than the Venus mean.

Venus is the brightest, natural point-like object on the Earth night sky, so both of those stars would most likely be the brightest night-sky natural objects. But unlike Venus, which as an inner planet is never far from sunset or sunrise, the two stars could appear at full night. The only thing that could rival them are inner planets on the same system, but unlikely.

The brightest point-like object in our current night sky is the ISS, at -5.9 (at perigee and fully illuminated).

hmmmmm - I don't dispute the calcs [saw them myself] but somehow that feels a lot less bright than I would imagine!

I therefore wondered about actual photos of the sun taken from Voyager etc looking back from Neptune or Pluto to give some sort of impression.

Whilst looking [without much success] I came across this quote from Wikipedia

From Pluto, the Sun is point-like to human eyes, but still very bright, giving roughly 150 to 450 times the light of the full Moon from Earth (the variability being due to the fact that Pluto's orbit is highly elliptical, stretching from just 4.4 billion km to over 7.3 billion km from the Sun).[28] Nonetheless, human observers would find a large decrease in available light: the solar illuminance at Pluto’s average distance is about 85 lx, which is equivalent to an office building hallway’s illuminance or a toilet’s lighting.

https://en.wikipedia.org/wiki/Extraterrestrial_sky#Neptune

I don't know how reliable that is!!

Isaac, what is missing from that quote... Brightness is not exactly defined properly...

What one cares about in VERY crude terms without proper equations; Quantity = area x temperature effectively gives Magnitude.

Why the Sun is "brighter" at Pluto. Starts at ~5800K, the moon? Yea, no, but due to distance has a vastly larger quantity and thus its MAGNITUDE is enormous as it is not a point source as the Sun is in regards to Pluto.

So, yes, Manticore B from A would be bright, but would give very little MAGNITUDE compared to a moon, or space station in orbit.

Thanks Everyone for the interesting replies.

I was trying to visualize what land navigation would be like say in the Copperwall Mountains on Sphinx with a second star.

If we assume that the stars orbit one another in close to the same plane as the their planetary systems. Wouldn't that mean that for at least part of the year the other Star would rise and set during planetary night.

Relax wrote:Isaac, what is missing from that quote... Brightness is not exactly defined properly...

What one cares about in VERY crude terms without proper equations; Quantity = area x temperature effectively gives Magnitude.

Why the Sun is "brighter" at Pluto. Starts at ~5800K, the moon? Yea, no, but due to distance has a vastly larger quantity and thus its MAGNITUDE is enormous as it is not a point source as the Sun is in regards to Pluto.

So, yes, Manticore B from A would be bright, but would give very little MAGNITUDE compared to a moon, or space station in orbit.

Rowbi wrote:If we assume that the stars orbit one another in close to the same plane as the their planetary systems. Wouldn't that mean that for at least part of the year the other Star would rise and set during planetary night.

They usually do, since they're usually formed from the same molecular cloud and retained the angular momentum that the cloud possessed. Binary systems due to capture are possible, but a G2 / G0 pair capture is anywhere between unlikely to impossible. One of the two stars would need to be far more massive than the other -- capturing red dwarfs, for example.

So yes, there's a day in the year when both stars rise at the same time and there's another in which one rises when the other sets. The time between those two events is not exactly half a year because the two stars are moving relative to one another.

And because it's going to be very close to the ecliptic on either system, it's not very useful for land-based navigation. And it does move relative to background stars, albeit very slowly.

isaac_newton wrote:hmmmmm - I don't dispute the calcs [saw them myself] but somehow that feels a lot less bright than I would imagine!

I was surprised by the result too. I was expecting a couple of magnitudes brighter.

Whilst looking [without much success] I came across this quote from Wikipedia

From Pluto, the Sun is point-like to human eyes, but still very bright, giving roughly 150 to 450 times the light of the full Moon from Earth (the variability being due to the fact that Pluto's orbit is highly elliptical, stretching from just 4.4 billion km to over 7.3 billion km from the Sun).[28] Nonetheless, human observers would find a large decrease in available light: the solar illuminance at Pluto’s average distance is about 85 lx, which is equivalent to an office building hallway’s illuminance or a toilet’s lighting.

https://en.wikipedia.org/wiki/Extraterrestrial_sky#Neptune

I don't know how reliable that is!!

We can check our math. We have the Sun's absolute magnitude of 4.83. At perihelion, Pluto is 4.4 billion km from the Sun, which is 244.6 light-minutes or 142.6 µpc. Putting it in the same equation as before gives us an apparent magnitude m = 4.83 + log₅(142.6e-6) - 5 = -5.67.

The table at Wikipedia lists the Sun at aphelion (not perihelion!) from Pluto at -18.20.

Conclusion: my results are wrong. If someone can spot the error, please point it out.

The same table lists the Sun at Eris' aphelion as -16.70. Eridian aphelion is 97.457 AU = 472 µpc = 810 light-minutes. That's very close to the apoastron we were given between the two components (within 2%). So this value is a very good approximation for how bright Manticore-B would be from Manticore or Sphinx.

That's about 33x more than the full moon on Earth, which in turn is enough to cast shadows.

Another tidbit: on Earth, the minimum brightness for something to be seen during the day is about -4. While the exact value for Manticore, Sphinx, and Gryphon depend on their atmospheres, we're talking about 12 magnitudes of difference. So either star is visible in any of the planets any time it has risen, even during daytime.

Absolute magnitude is the brightness at 10 parsecs (32.6 light years). Thus, the Sun with its absolute magnitude of 4.83 would be 100 times brighter (which by the way is 5 magnitudes) at 1 parsec (i.e., -.07 apparent). At .326 light years (3.0843X10^14 meters), it would have an apparent magnitude of -5.07. According to the data in _House of Steel_, the distances between Manticore-A and Manticore-B ranges from 650 to 827 light minutes. Let's use the 827 number and assume the distance is the same for the planet Manticore. That is about 1/12440 of the .326 light years. That means a magnitude increase of just over 10. The number I calculate for Manticore B (assuming it is as bright as the Sun), when viewed the Landing sky, is -15.57.