About

A front page for the changing sky

Every clear night, robotic survey telescopes photograph the sky and flag everything that changed. The alerts are public — millions per night — but they flow through research tools built for astronomers. Last Night's Sky is the missing storytelling layer: the place a curious person checks in the morning to see what the universe did overnight, in plain language, with the uncertainty kept honest.

It is an educational project, not a research archive. When you outgrow it, the links on every event page lead to the real instruments — that's the site working as intended.

Data & credits

This site exists because world-class scientific infrastructure publishes its data openly. Everything you see here is built on:

ALeRCE — the Automatic Learning for the Rapid Classification of Events broker, which ingests, cross-matches, and machine-classifies the public alert stream and serves it through a free API. Our classifications and light curves are theirs, reported with their probabilities.

The Zwicky Transient Facility — the survey camera at Palomar Observatory producing tonight's alerts. ZTF is supported by the U.S. National Science Foundation and an international partnership.

CDS, Strasbourg — the sky map runs on Aladin Lite and the archival imagery (DSS2 colored) and cutouts come from their HiPS services. Decades of quiet, foundational work.

Vera C. Rubin Observatory (NSF–DOE) — whose ten-year Legacy Survey of Space and Time began in 2026 and will multiply this stream many times over. Its public broker feeds will join this site as they mature.

Classifications shown here are automated estimates from broker machine-learning pipelines and may be revised or retracted; nothing on this site is a confirmed astronomical discovery unless independently announced (e.g. on the Transient Name Server). Please credit the projects above when reusing anything you find here.

The public API

The site's own JSON endpoints are open (CORS enabled, no key) and documented in the README-level detail in llms.txt: /api/lastnight, /api/events, /api/event?id=, /api/records. Be gentle; it's a small site.

Lineage

From the maker of cmetracker.ai, which does for solar storms what this site does for the deep sky, and asteroidtracker.ai, which watches the near-Earth asteroids our homepage counts each night — the "asteroids on the move" number links there, and its data powers our nearest-pass line. Same formula throughout: live public data, real synthesis, plain language.