Sky Puzzle

Every piece in this puzzle is a real galaxy.

Sky Puzzle is built from two telescopes. Herschel mapped huge patches of the sky in far-infrared light and found thousands of dusty galaxies from when the Universe was young — but it saw them as blurry blobs. ALMA then zoomed in on the brightest of them and found that many are gravitationally lensed: bent into rings, arcs and multiple images by a galaxy sitting in front.

Your job is to put each ALMA snapshot back where it belongs on the Herschel sky. Each unfound galaxy shows as a faint preview at its true position; match the shape, drag the piece there, and it snaps home.

POINT IT AT THE SKY Hold your phone up and the screen shows the real sky in that direction — stars, constellations, the Milky Way, and the six Herschel survey fields drawn where they truly are above you, right now. The circle shows honestly how sure the compass is; drag the sky with a finger to correct it against a star you can see, and pinch to zoom in on a field.

OR PLAY ON THE MAP Prefer the sofa? Switch to the flat map of the whole sky, or to the compact board with all six fields side by side.

FEEL THE SNAP Every placement, near miss and streak has its own haptic, so the moment a galaxy clicks home is something you feel even with the sound off. On iPad, squeeze an Apple Pencil Pro to show or hide the previews.

LEARN AS YOU GO Some of these galaxies have papers of their own. Place one and a short note tells you what was discovered about it, with a link to the research.

• 86 hand-picked stand-out galaxies to start, or all 297 for the full survey • Streaks, an arcade score and a local high-score table with three-letter initials • RA/Dec grid for anyone who wants to navigate like an astronomer • Works fully offline. No account, no ads, no tracking — the app makes no network connections at all

Made by an astronomer who works on these galaxies, as a way to show what the telescopes actually see.

Discovery signals