rubin observatory · lsst alert stream
ten million alerts a night, and one question worth asking of each of them.
find me things that look like this
Rubin photographs the whole southern sky every few nights, six times over, through six filters. Anything that moved or changed since the last pass becomes an alert. There are far too many of them for anyone to look at.
paralx embeds every one of those light curves into a single vector space, so the question stops being “what is this?” and starts being “what else has ever done this?” — which is a question a computer can answer before the night is over.
six ways to see the same night
colour is a measurement, not a decoration.
Every object is photographed through six pieces of coated glass, ultraviolet out to near-infrared. How its brightness differs between them is how you tell a dying star from a passing rock — so a light curve is never one curve. It is six, and the shape of the set is the fingerprint.
- u365 nmhot young stars
- g477 nmsupernova rise
- r623 nmthe workhorse
- i762 nmthrough the dust
- z913 nmcool and distant
- y1000 nmthe deepest red
the chart
you can watch something explode before the night is over.
Every alert is plotted the moment it lands. A transient rises over days and fades over weeks, and the bluer bands do both first — so the gap between the curves is telling you how fast the thing is cooling, which is most of what you need to know about what it was.
- cadence
- every 3 nights
- to plot
- under 60 seconds
- depth
- 24.5 mag per visit
the comparator
nothing here is a map of the sky.
Every light curve is embedded into one 256-dimensional space. Two objects sit close together in it when they brightened and faded the same way — which has nothing at all to do with where they are. The nearest neighbour to tonight's transient might be a supernova recorded in 2014 on the other side of the sky.
So the search is not “what is near this?” It is “what has ever behaved like this?” — asked against every night the survey has ever recorded, and answered in the time it takes to draw the plot.
- embedding
- 256-d
- corpus
- every night since first light
- top match
- cosine 0.98
- returned in
- under 200 ms
the footprint
eighteen thousand square degrees, every three nights, for ten years.
The band running through the middle is our own galaxy, and the survey steps around it on purpose — the disc of the Milky Way is so crowded and so dusty that almost nothing behind it can be measured cleanly. The five ringed fields are the opposite bargain: almost no sky at all, revisited constantly, and therefore far deeper than anywhere else.
the instrument
an uncountable number in, four answers out.
Ingest, embed, index — the whole pipeline reports itself, because an instrument is only as good as the stream behind it. Nothing is dropped quietly.
- the chartthe live sky, plotted as it landslight curves
- the comparatorfind me things that look like thisneighbours
- the circularthe night's anomalies, digesteda digest
- the systempipeline health, always in viewtelemetry
point it at your night
bring a transient. leave with everything that ever looked like it.
The comparator is live over the whole Rubin stream. There is nothing to install and nothing to configure — the index is already built, and it has been running since first light.