That is huge. Just reference for those who don't feel "astronomical units": One astronomical unit (AU) is (roughly) the Earth-Sun distance.
Distances to compare with: Pluto is ~39 AU away from the sun. Voyager 1, the furthest probe of humanity right now, is ~160 AU away from the sun.
So in other words: that is mind-bogglingly large.
(If you want to read more about astronomical units: https://en.wikipedia.org/wiki/Astronomical_unit )
Nah. It is comparing a distance with a distance.
Besides I assume more people reading my comment are familiar with the concepts of radius/diameter than the meaning of astronomical units. But now, thanks for your clarification, even the geometrically challenged will have the correct mental model. You never know.
> On the same scale, Pluto is 78 AU and Voyager is 320 AU.
Have to disagree. You take your pocket tape measure, carefully hook the end of the tape on the Sun and slowly walk to Pluto. You read what it says. That is a distance.
Then you walk to the disk, hook one end of the tape on one side (carefully, since it is made of dust) and walk to the other side. That is a distance.
Where do I hook my tape measure to measure 78 AU for Pluto? Orbits are not real. You cannot kick them, you cannot lick them, you cannot hook a tape measure on them.
“See where that planet is? Now imagine how far it will be in 124[1] years in a sun fixed coordinate system!” does not quite have the same impact on me as “See that blob? It is huuuge!”
Doubling the number with Voyager makes even less sense. You cannot even say that you are measuring the antipodal points of its orbit, since it is not orbiting the Sun. So the “diameter” of what are you even talking about there?
1: half of Pluto’s orbital period.
FTFA, quoted by you above: “The outer ring is about 240 astronomical units in diameter.”
Pluto’s orbit is 60-98 AU in diameter. Voyager 1, if it were orbiting the sun, would have an orbital diameter of 320 AU.
By that measure then, you carefully hook your tape measure to Fomalhaut and slowly walk out to the outer ring, whereupon your ancient eyes perceive the distance to be 120 AU, not 240 AU (since 240 AU is the diameter). A given rock in the outer ring is therefore less distant from Fomalhaut than Voyager is from the Sun.
That's all the parent is saying, and I agree with them - I, too, know the difference between radius and diameter but a quick read of your comment left me thinking that Fomalhaut's outer ring is orbiting further away from Fomalhaut than Voyager is from the Sun.
It's clearer to compare a radius to a radius, is all.
The OP wasn't comparing a diameter to a radius, he was comparing one line to another line: the diameter of the outer ring (line going from one end to the other passing through the middle) and the distance between Pluto and the Sun (line between two points). The fact that Pluto orbits the Sun is just a coincidence for the purposes of this comparison.
OP was mathematically correct, just a bit unclear. We really don't need to spend so much time on this.
Though out of fashion, the various power laws of Bragg, Richardson, Armellini building on the Titius–Bode rule come to mind, namely that there may be physical reasons to see orbital patterns emerge consistent with some sort of power law.
Below data includes candidate planets/disks still being verified.
Our Sun: - Mass 1 M - Inner Planets: 0.39 AU to 1.52 AU - Inner Disk (Asteroid Belt): 2.1-3.2 AU - Gas Giants: 5.2 AU to 30.06 AU - Outer Disk (Kuiper Belt): 30-55 AU
Formalhaut: - Mass: 1.92 M - Hot Disks: 0.21 AU to 1.08 AU - Inner Disk: Around 8-12 AU - Outer Disk: Previously around 133-158 AU but now suggesting around 120 AU? (Surrounded by a larger halo)
Vega - Mass: 2.135 M - Planet: 0.05 AU - Inner Disk: Around 8 AU - Outer Disk: Around 80-120 AU (Surrounded by a larger dust halo)
Epsilon Eridani: - Mass: 0.82 M - Inner Disk: Around 3 AU - Planet: 3.48 AU - Potential Additional Disk: Around 8-20 AU (and may revise inner disk & planet) - Planet: 40 AU - Outer Disk: Around 35-75 AU
Proxima Centauri - Mass: 0.1221 M - Planets: 0.03 - 0.05 AU - Hot Disk: 0.4 AU - Inner Disk: 1-4 AU - Planet: 1.5 AU - Outer Disk: 30 AU
HR 8799 - Mass: 1.43 M - Inner Disk: Less than 16 AU - Planets: 16.25 AU, 26.67 AU, 41.39 AU, 71.6 AU - Outer Disk: 135-360 AU
Beta Pictoris - Mass: 1.75 M - Planet: 2.7 AU - Inner Disk: 6.4 AU - Planet: 10 AU + Potential Planetary Belts: 14/16, 28/30, 52, 82 AU - Outer Disk: 130 AU (Surrounded by a larger disk/halo)
55 Cancri - Mass: 0.905 M - Planets: 0.01-0.7 AU - Speculated Planets: 0.9-3.8 AU - Planet: 5.9 AU - Disk: Around 40 AU (Would be interesting if a second disk around 4 AU)
Tau Ceti - Mass: 0.783 M - Planets: 0.1-1.334 AU - Planet: 3-20 AU - Disk: 35-50 AU (Would be interesting if a second disk around 3-5 AU)
(240 AU is 32 light hours)
I guess that's just one of those cosmic coincidences.