Bending the Universe

2026-07-09 / Rob Spearman / Software / Blog

When people hear that we've added black holes to our Nightshade universe simulator, they might imagine that we created a couple of new 3D models.

In reality, we did something much more fundamental: we changed how light travels through the Nightshade universe.

That new capability allows black holes to bend the apparent paths of light from surrounding objects in real time.

That distinction may seem subtle, but it completely changes how black holes can be explored in a live planetarium program.

More Than a Model

Many black hole simulations are designed to reproduce familiar scientific imagery or cinematic effects.

Our goal was different.

Rather than treating a black hole as just another model in the scene, we changed how light propagates through the Nightshade universe. As light from distant objects passes through the intense gravitational field surrounding a black hole, its path bends before reaching the observer.

The result is that the view changes in real time as you move around the black hole.

Many black hole visualizations distort a rendered background image, where each star is represented by an extended blob of pixels rather than an ideal point source. Warping those pixels can produce misleading results. Nightshade instead computes each star's apparent position independently as its light is bent by gravity.

Why Does It Look Different?

One of the first things people notice is that our simulation doesn't look like the familiar orange images from the Event Horizon Telescope.

That's intentional.

Those remarkable images answer a different question. They were never intended to show what the human eye would see. They combine radio observations with image reconstruction and false color to reveal structures that are otherwise invisible.

We asked a different question.

If you could safely observe the supermassive black hole at the center of our galaxy with your own eyes, what might it actually look like?

That question guided nearly every design decision behind the simulation, from the appearance of the accretion structure to the way light is rendered.

Real-Time Astronomy

Building a convincing black hole is one challenge.

Building one that can be explored interactively during a live planetarium presentation is another.

The simulation balances current astrophysical understanding with the practical requirements of real-time rendering. The result is an interactive experience that lets presenters explore gravitational lensing while maintaining the responsiveness required during a live show.

Not Everything Should Bend

Interestingly, changing how light behaves introduced another challenge.

Planetarium software doesn't render only stars. It also displays labels, images, videos, fulldome media, overlays, and educational content.

Those shouldn't all be gravitationally lensed just because a black hole is nearby.

Teaching Nightshade what to bend—and what not to—became just as important as teaching it how.

Two Very Different Black Holes

This release introduces two black holes.

Sagittarius A* is the supermassive black hole at the center of the Milky Way. It includes gravitational lensing, a three-dimensional accretion structure, and relativistic effects.

The second is Gaia18ajz, a stellar-mass black hole candidate without an accretion disk. It serves as a reminder that many black holes don't announce themselves with spectacular glowing rings. It is a great way to explore gravitational lensing.

Together, they illustrate that black holes are not all alike.

Resources for Presenters

We have published a technical white paper describing the visual design decisions behind the Sagittarius A* model.

We have also published a black hole Augmented Lesson to help presenters use these simulations in live programs.

We are hosting group meetings for Digitarium users who want a walkthrough of the new black hole features and time for questions.

For us, this release isn't just about adding black holes.

It's about making the Nightshade universe behave even more like the real one.