CT Was the Death Star I or II bigger than any Solar System Moons?

Was the Death Star I or II bigger than any Solar System Moons?
I found this that kind of answers my own question.


What do others think?

 

Using either the Legends or the newcanon figures, both DSs are slightly smaller than the smallest spherical moons like Mimas, but a lot bigger than the more irregular moons like Phobos and Deimos.

Legends figures: 120 km diameter DS1, 160 km diameter DS2
Newcanon: 160km diameter DS1, 200 km diameter DS2.

The only time a DS was bigger than, say, Mimas, was during the period when the Incredible Cross Sections/Complete Locations books were published. when the figures were 160km diameter DS1, 900km diameter DS2. These figures got retconned back to the original figures late in the Legends era with the Death Star Owner's Workshop Manual.

 

I remember at some point it was decided that the DSII's laser dish was bigger than the first DS and I'm like... that doesn't sound right, but I don't enough about Death Star's to dispute it.

 

A moon can theoretically be any size. I'm not sure how large the DS is actually supposed to be, but I think it's quite possible that some of the minor moons in this solar system are actually smaller than the DS. Hard to say for certain though, without hard data from Lucas or someone working on the movies. Not sure if Lucas ever mentioned the DS's actual size in Earth units.

 

Not him - but one of the SFX guys:

Bantha Tracks [DS1]
Bantha Tracks #6 [Autumn 1979] : Grant McCune, Chief Model Maker for the movie:

"The scale on the models ranged from 1:8 on the life pod and Lifepod Bay to 1:16 for most of the space vehicles to an incredible 1:180,000 for the Death Star (making the full size Death Star 102+ miles in diameter)"

 

True, but I always assumed that there was a specific parameter of what made a moon a moon, Any bigger and it’d be either a dwarf planet, or, well, a planet. Like if our actual moon was as big as Earth or bigger, well, it wouldn’t be a moon right? We would be its moon, presuming of course its gravity didn’t sent our planet crashing into it billions of years ago.

 

I'm not an astronomer but I don't think so. What makes a moon a moon is that it's a planet's satellite, like our moon, regardless of size. It orbits around Earth. While a planet has its independent orbit around a star/sun, like Earth, Mars, Jupiter etc. If our moon were detached from Earth and had its own path directly around the sun, it wouldn't be a moon anymore, but either a planet/planetoid or asteroid. E.g. Pluto: it used to be the 9th planet but has been "demoted" to asteroid due to its small size. Still it's not a moon as it doesn't revolve around another planet.

I guess so. Due to mass, the smaller object will orbit around the larger one, but only seemingly so. In fact the Earth's path is affected by the moon's gravity as well, though to a lesser degree. If Earth were significantly smaller than the moon, then yes, WE would be the moon. If Earth and moon were equal size, they would revolve around each other (twin planets?), as twin or triple suns tend to. I don't think one would crash into the other, not after trillions of years, because the orbits have become stable. If there were any crashes I think that would have happened much much earlier, during the formation of those objects, before their paths have become stabilized. If the moon were to crash into Earth some day I guess it would have to be due to outside influences, such as a large meteor hit. Otherwise it's unlikely to happen. Please someone correct me if I'm wrong.

 

Moons can be of any size, as long as they're smaller than the primary. "Dwarf planets" however, have to be (or at least have been in the past) close to hydrostatic equilibrium - the shape of a liquid body of that size, rotating at that speed, experiencing the gravity of any nearby bodies, including itself.

Our Moon is not quite in hydrostatic equilibrium - but it's close enough to it to be reasonably called a "dwarf planet". To the eye, it is very spherical, and the "not quite in equilibrium" bit doesn't make much of a difference to shape.

Phobos and Deimos are moons - but they're nowhere near hydrostatic equilibrium - because they're too small for their own gravity to "round" them into the right shape.

The DS1 and DS2 are way bigger than Phobos and Deimos, but they're also way smaller than typical "in hydrostatic equilibrium" bodies (unless you're using the 900km diameter figure for the DS2, which was retconned away).

Plenty of moons in the Solar system (all much bigger than the DS2) exist that would be dwarf planets if they were not orbiting something bigger- but were instead in a "dwarf planet belt" like the Kuiper Belt is.

 

So, you're tellin' me, in a way, it is a moon? Damn. Obi-Wan was wrong.

 

I think I've seen the phrase "Artificial moons" used for really big space stations before.

 

Or you could use "satellite" in its original meaning instead. Now most people think of the artificial type first. But originally a satellite is a natural object that orbits around planets.

 

Using the Legends figure of 120km diameter, there's a comet been discovered that's bigger than that.

https://www.bbc.co.uk/news/science-environment-61097826

 

DS2 looks a lot bigger relative to the moon than a 200 km diameter would suggest - but this is due to being a lot "closer to the viewer" than the moon is.

While that shot suggests a 1-10 size ratio between the two, other shots suggest 1-30 or even more. 200 km to 4900 km size ratio is possibly something of a compromise between various visual shots.

The Endor Moon's diameter, at least in newcanon and Legends reference books, is fairly low considering it manages to hang onto an oxygen-nitrogen atmosphere - 4900 km diameter, comparable to the planet Mercury or the large moon Callisto.

 

Dang, I guess I didn't realize that the size of the Death Stars have changed from the old timelines to the new one. I know in the early years there was a lot of discrepancies, but eventually I think a standard was established. Didn't realize that standard no longer applied to the new 'cannon' timeline.

 

Your math question for today: if DSII is 200 km in diameter, how long should it take Our Heroes to traverse the interior flying at the velocity shown in the movie? (They're moving at a respectable clip for being inside a cramped and obstruction-lined shaft, but certainly not fast enough to cover 200 km in a couple of minutes.)

Bonus non-math question: what in blazes did the Executor hit, just below the DS's surface, to cause a gout of flame larger than the vessel to appear almost instantly?

 

100 km per minute is 6000 km/hour - a bit on the fast side compared to what we actually see. Perhaps the cutting back and forth allows for a bit of extra time to pass, allowing the trip out to take a bit more than 1 minute? (I'm not as concerned about the trip in - I can believe that the film allows for it taking longer than 1 minute).

It's also interesting to think about just how far Luke's taken Vader's injured body after Vader dropped Palpatine down the lift shaft - they appear to be flying out of one of the hangar bays in the equatorial trench, some 157 km away from the tower on the North Pole.

Must be a very fast hovertrain at the bottom of the shaft, in the surface hull, that can take Luke and Vader all the way to the equator in a matter of a few minutes.

 

Unfortunately there ISN'T a specific parameter of what makes a moon a moon. And don't hold your breath about getting one, either - it took 100s of years between it was widely accepted what a planet was to getting a proper definition of what makes a planet a planet.
It would seem straightforward to define a moon as an object that revolves around a planet (or dwarf planet, minor solar system body, etc.), but orbits are a little more complicated than that. Objects don't revolve around each other at all, they revolve around a common point in between each other (barycenter). This barycenter will be closer to the center of the more massive object. When there is a huge mass differential with respect to the distance between the objects (say Earth and the Sun), the barycenter is very close to the center of the more massive object - the smaller object nearly revolves around the center of the larger object, and the larger object seems to slightly "wobble". When the mass difference is a little less (say Earth and its moon), the barycenter is closer to the surface of the larger object - the moon causes the Earth to nearly revolve around itself. When the mass if even less (say Pluto and its moon Charon), both objects revolve around a common point in space. Furthermore, multiple objects will have significant impacts on an objects orbit. The moon goes around the sun as much or more because of the barycenter it shares with the sun as it does because it is "chasing the Earth". The sun is simultaneously revolving around countless barycenters due to all the object around it. Orbits are impacted by every other object, even if they do not cause them to revolve either around the other (sometimes they can cause the orbits to be in resonance depending on size and proximity - say object A travels x times around the sun for every y times that object B does).
Some popular ideas of when a planet-moon (read "planet" generically to include dwarf planets and lesser objects) system becomes a double planet system:
1. A planet-moon occurs where the barycenter they orbit is located beneath the surface of one object or another. Pluto-Charon would be double dwarf planets, Earth-Luna would be a planet-moon system.
2. A double planet occurs where both objects are always "concave in" towards the sun. In other words, if you traced a moons trajectory through space (relative to the sun) it would sometimes bend towards the sun, and sometimes away. If both objects only bend towards the sun, they are a double planet. Pluto-Charon would be a planet-moon system, Earth-Luna would be double planets.
3. Some relative mass criteria - usually requiring the mass to be close to equal. I would say this is the de facto criteria, but there is no definition of how close to 1 the ratio needs to be. Don't expect one until we discover something that makes us need a definition.
There is also no definition of what the minimum criteria for an object to be considered a moon is. Arguably you could define all the particles in a planetary ring as moons.

 

Holy cow, you're absolutely right! I never thought about that before. Must have been an anxious ride (not that the trip up would have been very fun, either).

 

Well the Emperors observatory only has executive shuttles, which was explained in the Death Star's Owner Manual book.

 

It's still going to be a trip; to do 157 km in, say, five minutes puts the Emperor Express at an average speed of 1884 km/hr. (It would of course peak higher because it's going to be slower at the beginning and end. Those Death Star contractors know a thing or two about compact inertial dampeners!) Lord Vader should have parked closer.