What was the purpose of the "booby-trapped" solar system in the Expanse novels?

Question

Warning: no idea how to word my question without being one giant spoiler for book 8, so proceed with caution ;-)

A major plot point revolves around Tecoma system, which the ringbuilders (*) had apparently rigged as a sort of booby trap: the system contains only a single neutron star on the verge of gravitational collapse, and absolutely nothing else. Also, the ring gate is above the plane of the ecliptic, in line with the spin axis of the star, and when the star later does collapse, it sends a relativistic gas jet through the gate and basically nukes the entire ring space.

What I'm not getting is how this would have made any sense to the ringbuilders - they more or less pointed their booby trap right at themselves. I guess the idea is that when the "Others" try some of their physics-altering shenanigans, then one of them will sooner or later trigger the trap and let the star go nova - but the only ones to get hurt will be the physical beings using the ring space...?

P.S. I haven't finished book 9 yet, so if this is answered somewhere there, I'll put my question on hold ;-)

Answer 1

The events of Leviathan Falls provide more information which allows you to think about Tecoma, but the explanation below is based solely on information from Book 1-8.

Remember how Duarte decided to do a counterstrike against the Goths. He transited warships through the ring until the next one would go Dutchman, then send through a ship laden with antimatter. His logic is that since the Goths attack human ships after they transit through the gates, the gate transit must in some way hurt them, otherwise they wouldn't care. Thus, throwing an antimatter laden ship through must hurt a lot more.

Tecoma is the same thing, but on a grander scale. Rather than a single warship, it pumps an entire supernova through not one but two gates. And sure, whatever stuff happened to be present in the Ringspace gets destroyed, but the Hub is bulletproof and everything else can be rebuild. It's not a serious loss to the Romans, who were otherwise willing to obliterate entire solar systems.

Answer 2

To understand the purpose of the booby-trapped solar system we should recall what it is. The system is described as follows:

That star [in the Tecoma system] wasn’t natural, it was created. And it was created from a system that looked like Sol. It was manufactured and it was pointed at the ring gate. They aimed it like tying a shotgun trigger to a doorknob. Our bomb ship did something to activate it. Maybe it got something to come look at us, and that’s what set it off. I don’t know. But it was built to be a booby trap... It fired off the largest gun that it’s possible to make given the physical laws of the universe. And what’s more? The [Ring] station was built to withstand it. It took a gamma burst from a collapsing neutron star, and it’s not dead.
_{Elvi Okoye, Tiamat's Wrath, p. 212}

While it's true in some sense that the Ringbuilders

pointed "the largest gun that's possible" at themselves, it's not really a danger to them because the Ring station was built to withstand it (as is apparent from when the booby-trap actually went off).

The reason why the Ringbuilders pointed it at the system's ring is hinted at by books 3-8, and especially once

ships transiting through the rings started "going dutchman".

Recall that Naomi figured out that this problem can be avoided by staying in the "safety curve", and that the

safety curve was based on the amount of matter and energy making transits though the gate network.
_{Tiamat's Wrath, p. 213}

Up to and including book 8, multiple characters theorized that

the creatures that killed the Ringbuilders -- the unknown aggressors / Goths / "dark gods" -- are harmed or don't like the movement of ships through the rings, and that these enemies attacked the Ringbuilders to get them to stop using the rings. Furthermore, these enemies apparently attack through the rings -- hence the design of Duarte's attempt to attack them.

This turns out to be true. Leviathan Falls (book 9) reveals

It's where the power comes from. [The Ringbuilders] cracked the universe open, pushed their way in here, and it pushed back. A whole other universe trying to smash this place flat, and it powers the gates, the artifacts. That magnetic ray gun Duarte was playing with. They built stars with it. Broke rules that you can’t break without a different set of physics to strain it through.
_{The Investigator, Leviathan Falls, p. 453}

In other words

the Ringbuilders forced open a space (the ring space) which is powered by another universe (where the Goths are from), and the use of this power from the Goths' universe is what angers them. Furthermore, this confirms that the Goths enter our universe from the rings / ring space, so in effect the Tecoma system booby-trap is also pointed at the Goths. Moreover, the Ringbuilders also knew or theorized that energy (and matter) passing through the rings harmed the Goths, so they pointed "the largest gun" they could at a ring gate. As a real-world analogy, this would be like the Roman army deploying catapults aimed at the roads they built (leading into their territory) to defend against invading barbarians (Goths) -- the weapon is pointed at the road the Romans built, but only because that's where the enemy will be coming from.