This is the third of a series of five (Introduction, I, II, III, IV) posts about the astrography of the Mass Effect galaxy.
The Normandy Reborn
Mass Effect the First had us in the shoes of Commander Shepard, recently made into a Spectre, one of the most notorious positions in Citadel Space, and interacting on the regular with the big wigs of the Citadel as well as different Megacorporations and larger-than-life techno-cephalopoidal eldritch abominations (as one does). Mass Effect 2 flips this on its head by driving Shepard underground, forced to interact with the shadier elements of the galaxy as they and their crew navigate its criminal underbelly, all under the ever-present gaze of Cerberus, the shady human supremacist corporation/group/entity/cult introduced in one of the first game's sidequests.
Mass Effect the Second is very much a more mature game than the first, eschewing a bit of its squeaky clean (but by no means morally pure, in the slightest) ascetic aesthetic and leaning hard into 'DARKER AND EDGIER!!1!' aspects – sometimes, I feel, to its own detriment. When it works, it really works, but there are times where I feel it veers into it not because it is interesting for the narrative to do so, but because it was a mandate from corporate. But I digress.
Mass Effect 2 brings back a lot of fan favourites – Joker, Tali, Garrus – and introduces us to many new faces that would themselves win over our hearts. The gorgeous Normandy SR-2, the eccentric charm of Dr. Mordin Solus, a genuinely cool guy who is rather unfortunately eminently puncheable due to looking exactly like Kanye West... but what truly matters for us here is that this game introduces us to a new, revamped galaxy map! This time, instead of just selecting where we want to go with a cursor, we get to fly a teeny tiny Normandy across the map! Now ain't that just swell?
Furthermore, the planetary information boxes now regularly feature the 'Orbital Distance' at which planets orbit their stars, unlike its predecessor! This makes it possible to calculate the stellar mass for all systems in the game... in theory (ooOOOoooOOoooh, foreshaaaadowing!).
Beyond that, I've also noticed a few interesting differences in trends when it comes to planets in Mass Effect 2 compared to 1; for starters, the inclusion of a few Hot Jupiters in the planet pool – which is only natural, as at the time the game was made they had come to the forefront of the exoplanetology world as many early exoplanet detections were of this type, due to observational biases favouring large, close-in worlds over smaller terrestrial worlds farther out from their star.
Another thing I noticed is a shift away from the remarks on planetary composition I mentioned in the previous post. In fact, whereas the entries in the first game felt like the work of a single person, I get the impression that this time around more than one individual might have been responsible for writing the planet entries, as the Vibes™ (a very scientific and quantifiable measure, I assure you) between some of the new ones do seem quite different. And I have to say, rather unfortunately, that the disconnect between Codex and gameplay has wormed its way into the planetary descriptions too this time around, as we will see...
A Rude Awakening
One of the things that most jumped out to me after compiling all the data, and a big part of why I took so long to write this post, is that a surprising number of planets in Mass Effect 2 have ludicrously high density values – take for example the world of Partholon, in the Balor system on the Caleston Rift; it has a density of a whopping 19.42 g/cm³. That's nearly as dense as the densest element in the periodic table, Osmium, which comes up to 22.59 g/cm³!
This is highly unusual, to say the least. Rocky planets are composed of varying fractions of silicates and iron, as they are vastly more abundant across the universe than elements of atomic numbers 27+ as well as the fact that they are not 'volatiles' – i.e.: they remain solid even under a quite significant degree of stellar bakeage, instead of evaporating/sublimating off into space – they are 'refractory,' as we call'em. Logic thus dictates, if you'll allow me the Spockism, that the mass of a rocky, terrestrial planet of a given radius should be bound at an upper limit by the density of iron, which comes up to no more than 7.87 g/cm³...
... except that's not entirely true. See, the funny thing thing about planets is that they're made out of a lot of stuff. Stuff on a planet, being subject to its gravity, has weight. And when you pile stuff on top of stuff, the aforementioned stuff does a stu(ff)pendous job of putting the stuff beneath it under lots of pressure. This means that the deeper you go into a planet, the greater the pressure and the greater the compression of the stuff the planet's made off – the stuff's being stuffed harder, if you will.
A consequence of this is that the materials that make up a planet might actually be compacted way more densely than when subject to Standard Temperature and Pressure* conditions. Take as an example Earth's core: it is believed to be made of an Iron-Nickel alloy at a roughly 9:1 ratio. As such, we might expect its density to be between Iron and Nickel's at 7.97 g/cm³, but no! Because it is being compressed by an entire freaking PLANET's worth of stuff, Earth's core has a density of around 12.9 g/cm³, ish.
*ISO 5011, for the sticklers in the room
Modelling all of this computationally is possible using steady-state models (no, not that one, get outta here cosmologists!) of planetary interiors, which use the known physical properties of materials and differential equations to figure out the planet's interior temperature and pressure profiles, and how all its constituent stuff will settle down without further collapsing in on itself. In fact, a freely available one anyone can use is ExoPlex, available on GitHub!
So because so many planets in Mass Effect 2 had densities higher than I felt plausible, I decided to learn how to use ExoPlex to try and test their plausibility. That's all swell GAB, but uh, slight problem: you're pursuing a degree, working, and getting embroiled in Random Assorted Shenanigans™ with an alarming regularity. How, exactly, do you wish to find the time to learn how to use a whole new tool for a blog post, you obtuse nincompoop?
Why, you've raised an excellent point, voices in my head. And indeed, I've completely given up on it in the name of getting this post done with. Hooray! So instead of using ExoPlex myself, I've turned to good ol' Universe Sandbox instead, which a few updates back has actually implemented exactly this, the simulation of planetary interior pressure/temperature curves and the usage of that information to drive planetary bulk density. I will also be referring to this paper by Unterborn et al. (2023) which actually introduced ExoPlex, as a way to sidestep learning how to use it myself and instead relying on work done by people smarter than me.
New Worlds
Mass Effect 2 features the following 23 individual Clusters:
- Caleston Rift — 5 Systems
- Crescent Nebula — 4 Systems
- Eagle Nebula — 5 Systems
- Far Rim — 2 Systems
- Hades Nexus — 4 Systems
- Hawking Eta† — 5 Systems
- Hourglass Nebula — 4 Systems
- Ismar Frontier — 3 Systems
- Krogan DMZ — 3 Systems
- Local Cluster† — 1 System
- Minos Wasteland — 2 Systems
- Nubian Expanse — 3 Systems
- Omega Nebula — 6 Systems
- Pylos Nebula — 4 Systems
- Rosetta Nebula — 3 Systems
- Serpent Nebula† — 2 Systems
- Shadows Sea — 1 System
- Sigurd's Cradle — 2 Systems
- The Phoenix Massing — 5 Systems
- The Shrike Abyssal — 2 Systems
- Titan Nebula — 1 System
- Vallhallan Threshold — 3 Systems
- Viper Nebula — 1 System
Totalling up to 71 individual star systems. Clusters marked with † have previously appeared in Mass Effect.
Much like in the first game, which featured the real Horsehead [sic] Nebula (Barnard 33) as one of its clusters, Mass Effect 2 has quite a few real locations among its roster: the Crescent Nebula (NGC 6888), the Eagle Nebula (M16), the Hourglass Nebula (MyCn18)†, and somewhat surprisingly, given its rather 'extra' name, the Omega Nebula (M17).
†There is another 'Hourglass Nebula' within the Lagoon Nebula, but the one showcased in ME2 is MyCn18, a picture of which is used as the cluster's background art.
Also possibly real is the 'Rosetta Nebula' – there is actually a Rosette Nebula (Caldwell 49), but single-letter difference aside, as the Mass Effect wiki itself notes the cluster's in-game art seems to be using a flipped image of the Orion Nebula instead. I will have quite a few things to say about this cluster still...
As previously mentioned, this time around we've actually had the planets' orbital radii as a rule rather than the exception, which allows us to have a cursory understanding of each system's central star. A fun fact about Kepler's Third Law of Planetary Motion? If you use as units Earth's orbital radius and orbital period (i.e.: AU and Sidereal Year), the resulting Keplerian constant is spat out as the multiple of the Sun's mass required for that radius-period relationship to hold – i.e.: for all intents and purposes, Solar Mass (M⨀). This means that by calculating the Keplerian ratios of the different planets (with error margins) we can find out the parent star's mass!
Spoiler: it's a mess. For one, there are a few systems where different planets will have completely different Keplerian ratios, which should not be possible. Minute variations? Yeah, sure, that happens because the planet's own mass should technically be factored in as well when running the calculation, but it's a whole other thing entirely to have one planet orbiting around a star of 0.3 M⨀ and the other 1.7 M⨀. Furthermore, I've found that pretty much every single system where the star is of a given spectral type seems to have the exact same mass.
Am I completely sure about the above? Admittedly, no. The error margins on the calculated Keplerian ratios don't allow us to beat the gavel and make a ruling on it, but, like... consider the Aysur system, in the Caleston Rift. It has six planets, and the Keplerian ratio with the smallest relative uncertainty is that for the outermost planet, Tamgauta: (0.99302±0.00355) AU³/Yr². Hm.
Consider, too, the Relic system, Eagle Nebula; lowest relative uncertainty? Beach Thunder, (0.99339±0.00455)AU³/Yr². Hmmmmmm.
What's more, for every planet in these two systems? The value 1 is safely within the error margin for every single one of its planets' Keplerian ratios. This also holds true for other systems, and for different mass values too. It seems to me that, when cooking up the different systems for Mass Effect 2, whomever was responsible always used the same mass value for a given star type. As far as I've been able to divine, the values used seem to be: 0.3 M⨀ for M-type stars; 0.8 M⨀ for K-type stars; 1.0 M⨀ for G-type stars (which make up the vast majority of the game's systems); 1.7 M⨀ for F-type stars.
Three stars are noteworthy for breaking this mould: Nith (Krogan DMZ), stated in-game to be a B-type star in the description of its planet Mantun, has a most likely mass of about 14.87 M⨀; Dirada (Pylos Nebula) has a most likely mass of 3.17 M⨀, which assuming it to be a main sequence star, would also make it a B-type. And finally, we have Qertassi in the Nubian Expanse, sitting at an utterly chonkular 40.8 solar masses as derived from the Keplerian ratio of its single planet, Norehsa, in the description of which the game remarks the star to be “an elderly, metal-poor Population II star, broadly similar to Arcturus.” Even though Arcturus is thought to have a mass similar to the Sun's, but hey, I digress.
Finding out that the same star classes seem to have the exact same masses was a bit of a letdown to me, I do have to admit, but on the flip side this regularity opens up the possibility of our examining planetary properties that we would not have been able otherwise; namely planetary temperatures, as we'll be able to make reasonably good guesses on stellar luminosity and from that we can calculate blackbody equilibrium temperatures, infer the different planets' albedo values, and even possibly their atmospheric greenhouse effect values too, though this all vastly exceeds the scope of today's post.
And finally addressing that whole planetary density thing I alluded to at the start of the post; Partholon, the worst offender in the game, has a mass of (23.07660±0.17483) M⨁ and a calculated density of (19.42125±0.14713) g/cm³. This is the Balor system's (Caleston Rift) outermost planet, far beyond the system's frost line. As such, considering its sheer mass, it's borderline unthinkable that this planet is somehow terrestrial – it has exceeded by far what is necessary to start slurping up Helium and Hydrogen from the surrounding proto-planetary nebula and grow into a gas giant via core accretion, as goes our modern understanding of planetary formation, and yet in-game its atmosphere is simply given as 'trace'.
Be that as it may, in using Universe Sandbox to try and figure out what sort of physical composition would be required to get this sort of bulk density, I was somewhat surprised to find that it is, in fact, physically possible through the magic of gravitational compression. It would require, however, that the planet have a frankly ludicrous 75:25 Fe:Si ratio, or in other words, the planet'd have to be three quarters pure iron. This is... very unlikely, to say the least – doubly so when considering just where in the system the planet is. I'd love to cross-reference this value with Unterborn's paper too, but the planet's mass is such a ludicrously high value that Unterborn doesn't have such high-mass planets listed in his tables as possible 'terrestrial' planets, so...
The End Run
Before we wrap up this post, I must first remark on two other things that jumped to me while compiling all this data, the first being the codex-gameplay disconnect I alluded to earlier in the post.
I've always been rather chagrined by the fact Mass Effect, as a franchise, seems to largely ignore the Codex except when convenient. In many ways, Mass Effect as presented in the games feels like a poor Netflix adaptation of an excellent sci-fi novel which would have been its Codex, keeping the same recognisable shape but feeling rather... pasteurised for general audiences, and it pains me a bit.
What is particularly annoying though is that this disconnect between gameplay and the games' written material now seems to extend to the planetary descriptions too; the planets Sinmara (Solveig system, Caleston Rift), Taitus (Talava system, Caleston Rift), Haestrom (Dholen system, Far Rim), and especially Gei Hinnom (Sheol system, Hades Nexus) are all listed as having 'trace' atmospheres or a surface pressure of 0.0 atmospheres, and yet when going down to their surfaces they all clearly possess atmospheres. On Taitus and Haestrom both, your party struts around with no helmets nor respirators just fine. But worst of all is Gei Hinnom, which is supposed to be – and I goddamn quote – “A nearly atmosphere-less, tidally-locked planet orbiting a red dwarf star,” and yet has, I kid you not, an entire freaking JUNGLE down there!
I– Wha–...? ... C'mon guys, you're better than this...
Another disconnect between description and what's actually on-screen is Helyme (Zelene system, Crescent Nebula), where “(...) a global extinction occurred, wiping out all native animal life forms more complex than zooplankton.” And yet, down on the surface we see them little roly-poly beetle-buggy fellas that crop up every now and again in Mass Effect's worlds, as well as bird-like critters flying at certain points of the map. Why, that sure is some darn weird zooplankton, huh?
But the thing that really, really rustled my jimmies – nay, outright crinkled my Jameses – is a single star system in the accursed cluster that is Rosetta Nebula (remember that? Told you we had unfinished business with it...). Not only is the cluster itself named sufficiently closely to a real nebula for us to be tempted to connect the two, to add insult to injury, one of its systems is named 'Alpha Draconis'.
'Well, so what, Gab?' So what, dear reader, is that Alpha Draconis is a real star, 'α Draconis' being the Bayer Designation of the star traditionally known as Thuban, in the constellation of Draco, the Dragon. Small problem: it's not anywhere near close to any nebulae, and everywhere too close for us to not know of any nebula near it, at a measly 303 light-years away from Earth, give or take a handful. What's more, neither of the two nebulae (Caldwell 49 & Sharpless 2-170) this stupid cluster could be mapped to are ANYWHERE close to Thuban in the night sky! At all!
If you're not going to bother even trying, WHY would you name a system after a real star!??
ₐₐₐₐₐₐₐₐaaaaaaaaaaaaaaaaAAAAAAAA̷̝͝Ȁ̴̰A̶̛̮À̶͜A̴̝͑A̶̙͂Ȁ̷̜A̸͇̤̣̱͛̆Ä̸̧̧͔́̊̌̽Á̵͜A̸͚̞̎̂A̸͔̒̅̏̓A̷͚̫̐̒A̶̡̢͔͈̒̆̏̚A̴͙̰͝Ạ̸͇͘A̸̲̠͑ͅA̶͚̼̠͋̃͑A̵͚̬͉͒A̶͖͚̲͕͋͐͘͝——Why, sorry about that – I seem to have briefly lost my composure. I'm sure this little hitch won't be any trouble for us down the line when we try to map out the Mass Effect world unto the real Milky Way galaxy, haha, ha...
... ah, damn it.
Reflections
With all that out of the way then, without further ado, here's the link to the compiled data for Mass Effect 2's star systems, all dully transcribed and noted down as per last time: https://docs.google.com/document/d/1vMPPk_9lLT05nuq0lXWV6OgP_Hj4FRHep8m6Hl6Jvlo/edit?usp=sharing
As of the time of posting, the Appendix section of the above doc has been transcribed directly from the first one's, and will thus see some small revisions to properly reflect this new document, as well as the inclusion of a few more formulae. That and one little last check to see if a typo was actually present in-game or I made a mistake is all that's needed before I can call this one truly well and done, and then move on to finish compiling the Mass Effect 3 document.
As per last time, comments are disabled on the document itself, but if you have any remarks, questions or comments, feel free to drop me a line down in the post's comments section!
⬢⬢⬢
Well then. This uh, this took a while. I guess I now know better than say that the next instalment 'won't take too long,' huh?
I really do want to start posting more here on the blog, so you can actually expect some non-Mass Effect posts this time around, for reals this time, pinky-double-swear. What I know for sure is that I'll be starting a series of posts on using the amazing Traveller Map and interpreting its many, many fields of data in ways that are useful at the gaming table.
And, well, living up to the blog's motto, there'll probably be some Random Miscellanea™ along the way as well. Until then!
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