銀河For iPhone
Astrelia
A pocket galaxy.
- Real ephemeris math
- Moon-accurate
- 109k stars in 3D
What it is
You raise your phone toward the sky and it shows you what's actually there. Every star, planet, the Sun and the Moon, computed for your exact spot on Earth at this exact second, with real astronomical math.
Tap anything and it tells you everything it knows.
It has a sister app, Selenia. Same engine, same real sky, a different way of reading it.
Try it: constellations in 3D
A constellation only holds its shape from here.
These are the actual stars at their actual distances, from the HYG catalog, same as the app. Drag to orbit and watch the familiar shape fall apart into deep space.
Fig. 1Drag to orbit. Pinch or scroll to zoom. The real thing runs on the phone, with every constellation.
Try it: the galaxy map
A small version of the app's free-fly mode. These are the 7,000 brightest stars around the Sun, each at its true 3D position, with a stylized Milky Way behind them.
The real app renders about 109k in Metal, plus nebulae baked from telescope photos, and the black hole. Zoom all the way out. That little pink ring is home.
Fig. 2Drag to orbit. Scroll or pinch to zoom. Hover a bright star to name it. The stars are real and the spiral is art, same rule as the app.
Try it: bend spacetime
The heaviest thing in the galaxy map is Sgr A*, the galaxy's central black hole. Fly close and it gravitationally lenses the whole rendered galaxy behind it. On the phone this is a real Schwarzschild geodesic march, on the GPU.
This toy is the pocket version: the classic weak-field lens equation, live, on the same real stars, looking toward the actual galactic centre. Watch stars split into double images and smear into an Einstein ring as they pass behind it.
Fig. 3Move your cursor, or drag, and the hole follows. Scroll or pinch to change its mass.
Try it: a nebula, point by point
The app's nebulae aren't textures. Each one is baked from a real telescope photo into about 60,000 particles. The photo never ships, only the points.
Here are 7,000 of them, with the same trick the app uses: face-on you see the photograph, orbit and it becomes a volume.
Fig. 4Drag to orbit. Scroll or pinch to zoom. The source photos are public domain or CC BY telescope images, credited in the app.
What it does
- Sky mode
- Hold your phone up. About 8,900 naked-eye stars, constellation lines, the Sun and Moon, all pinned to the real sky. Tap a star to identify it. Pinch to zoom. There's even a time scrubber to run the sky forward and back.
- Galaxy map
- Leave Earth and free-fly through about 109,000 real stars at their true 3D positions, past nebulae baked from telescope photos, all rendered in Metal. Fly far enough in and you'll find Sgr A*, the galaxy's black hole, bending the whole rendered galaxy behind it. You can get very, very close.
- Exoplanets
- Fly to a star and see its known planets from the NASA archive, orbits and all.
- Tonight
- What's up right now from where you're standing: moon phase, visible planets, meteor showers, upcoming events.
- Constellations in 3D
- Rotate a constellation and watch the familiar flat shape fall apart into stars hundreds of light-years deep.
- Looking for the astrology?
- That's the sister app, Selenia, with natal charts, transits and a glowing celestial sphere.
Status
Version 1.0, on the App Store. It took four names: Astrolabe, Stellaria, Citlali, Astrelia. Astrelia is from aster, star.
- Swift 6
- SwiftUI + Metal
- HYG catalog
- Meeus math
- iOS only (for now)
- Done: Astronomy engine, unit-tested against the textbooks.
- Done: AR sky view, verified against the actual sky.
Get it
