But the Sun would not remain on the Main Sequence forever.

The mass converted to energy was millions of tons per second. The Sun’s bulk was so huge that this was a tiny fraction; in all its five-billion-year history so far the Sun had burned only five percent of its hydrogen fuel…

But, relentlessly, the fuel in the core would be exhausted. Gradually an ash of helium would accumulate in the core, and the central temperature would drop. The delicate balance between gravity and radiation pressure would be lost, and the core would implode under the weight of the surrounding, cooler layers.

Paradoxically, the implosion would cause the core temperature to rise once more — so much so that new fusion processes would become possible — and the star’s overall energy output would rise.

The outer layers would expand enormously, driven out by the new-burning core. The Sun would engulf Mercury, and perhaps more of the inner planets, before reaching a new gravity-pressure equilibrium — as a red giant. This hundred million-year phase would be spectacular, with the Sun’s luminosity increasing by a factor of a thousand.

But this profligate expansion was not sustainable. Complex elements would be burned with increasing desperation in the expanding, clinker-ridden core, until at last all the available fuel was exhausted.

As the core’s temperature suddenly fell, equilibrium would be lost with sudden abandon. The Sun would implode once more, seeking a new stability. Finally, as a white dwarf, the Sun would consist of little more than its own dead core, its density a million times higher than before, with further contraction opposed by the pressure of high-speed electrons in its interior.

Slowly, the remnant would cool, at last becoming a black dwarf, surrounded — as if by betrayed children — by the charred husks of its planets.

…At least, Lieserl thought, that was the theory.

If the laws of physics were allowed to unravel, following their own logic unimpeded, the Sun’s red giant stage was still billions of years away… not mere millions of years, as Superet’s evidence suggested was the case.

Lieserl’s brief was to find out what was damaging the Sun.

Lieserl. Try to pick up the p-modes; we want to see if that sensory mechanism works…

“Absolutely. Helioseismology, here I come,” she said flippantly.

She opened her eyes once more.

A new pattern was built up by her processors, a fresh overlay on top of the images of convective cells and tangled flux tubes: gradually, she made out a structure of ghostly-blue walls and spinning planes that propagated through the convective cavern. These were p-modes: sound waves, pressure pulses fleeing through the Solar gas from explosive events like the destruction of granules on the surface. The waves were trapped in the convective layer, reflected from the vacuum beyond the photosphere and bent away from the core by the increasing sound speed in the interior. The waves canceled and reinforced each other until only standing waves survived, modes of vibration which matched the geometry of the convective cavern.

The modes filled the space around her with ghostly, spinning patterns; their character varied as she surveyed the depth of the cavern, with length scales increasing as she looked into the interior. Looking up with her enhanced vision Lieserl could see how patches — thousands of miles wide — of the Sun’s surface oscillated as the waves struck, with displacements of fifty miles and speeds of half a mile a second.

The Sun rang, like a bell.

Good… good. This is terrific data, Lieserl.

“I’m glad to oblige,” she said drily.

All right. Now let’s try putting it together. Use the neutrino flux, such as it is, and the helioseismology data, and everything else you’ve got… Let’s find out how much we can see.

Lieserl felt a thrill of excitement — subtle, but real — as she began to comply. Now she was moving to the core of her mission, even of her life: to look into the heart of the Sun, as no human had done before.

As the processors worked to integrate the data she called up from her long-term memory a template: the Standard Model of the Sun. The processors overlaid the cavern around her with yet another level of complexity, as they populated it with icons, graphics, grid lines and alphanumeric labels, showing her the basic properties of the Standard Model. The Model — refined and revised over millennia — represented humanity’s best understanding of how the Sun worked. She looked in toward the core and saw how, according to the Model, the pressure and temperature rose smoothly toward the core; the temperature graph showed as a complex three-dimensional sphere in pink and red, reaching an intensely scarlet fifteen million degrees at the very heart.

Slowly, her processors plotted the reality — as she perceived it now — against the theory; graphs and schematics blossomed over each other like clusters of multicolored flowers.

After a few minutes, her vision stabilized. She stared around at the complex imagery filling the cavern, zooming in on particular aspects, highlighting differences.

Oh, no, Scholes said. No. Something’s wrong.

“What?”

The discrepancies, Lieserl. Particularly toward the core. This simply can’t be right.

She felt amused. “You’ve gone to all the trouble of constructing me, of sending me in here like this, and now that I’m here you’re going to disbelieve what I tell you?”

But look at the divergences from the Model, Lieserl. Under a command from Scholes, the actual and predicted temperature gradients were picked out in glowing, radiant pinks. Look at this.

“Hmm…”

According to the Standard Model, the temperature should have fallen quite rapidly away from the fusion region — down by a full twenty percent from the central value after a tenth of the Sun’s radius. But in fact, the temperature drop was much more shallow… falling only a few percent, Lieserl saw, over more than a quarter of the radius.

“That’s not so surprising. Is it?” In riposte she superimposed a graphic of her own, a variant of the Standard Model. “Look at this. Here’s a model with a dark matter component — photinos, orbiting the core.” The dark matter — fast-moving, almost intangible particles kept clustered around the heart of the Sun by its gravity field — transferred energy out of the core and to the surrounding layers. “See? The photinos just leak kinetic energy — heat energy — out of the core. The central temperature is suppressed, and the core is made isothermal uniform temperature — out to about ten percent of the radius.”

Scholes sounded testy, impatient. Yes, he said, but what we’re looking at here is an isothermal region covering three times that radius — twenty-five times the volume predicted even by the widest of the Standard Model’s variants. It’s impossible, Lieserl. Something must be going wrong with —

“With what? With the eyes you’ve built for me? Or with your own expectations?”

Irritated, she canceled all the schematics. The spheres and contour lines imploded in sparkles of pixels, exposing the native panorama of the convective cavern, a complex, ghostly overlay of flux tubes, p-modes and convection cells.

Frustrated, with some analogue of nervous energy building in her, she sent her Virtual self soaring around the cavern. She chased the rotating p-wave modes, sliced through flux tubes. “Kevan. What if the effect we’re seeing is real? Maybe this divergence in the core is what you’ve sent me in here to find.”

Maybe… Lieserl, what will you do next?

“It’s early days, but I think I’ll soon have learned all I can out here.”

Out here?

“In the cavern — the convective zone. All the evidence we have is indirect, Kevan. The real action is deeper in, at the core.”