Transient Explorer

What am I looking at?

Every night the Rubin (LSST) and ZTF telescopes image the sky and flag anything that changed since last time: a supernova going off, a star flaring, an asteroid passing through. Each flag is an alert. The Fink broker classifies them, and this site shows what they are and where. Transients the two surveys miss, reported by others to the Transient Name Server, are here too.

Sources

  • ZTF and Rubin: objects the surveys alerted on. Each detection is an alert, with the broker's classification, a reliability score and three image cutouts.
  • TNS: transients reported to the Transient Name Server that neither survey alerted on, among them nearly every bright one south of −30°, which ZTF cannot see. Each detection is a report: the magnitudes reported to TNS (the discovery, and any later ones), each in its reporter's filter, then ATLAS's measurements (c and o bands) for two months while it is brighter than 19. Reported by names the surveys (ATLAS, GOTO, Pan-STARRS, …). When ZTF or Rubin later alerts on one, it becomes their object.
  • CBAT: reports on the Central Bureau's Transient Object Confirmation Page that neither the surveys nor TNS have, mostly bright Galactic novae (PNV J…) and dwarf novae in outburst (TCP J…). An object that matches a TOCP entry shows its designation.
  • A TNS type (SN Ia, Nova, AGN, …) decides an object's class whoever saw it; without one, the broker's label does.
  • An object is active while it has detections in the window. A TNS or CBAT object ATLAS does not measure (fainter than 19, older than two months, or not yet measured) is active only while the window holds its last report, so it leaves the short windows a week later.

Pages

  • Dashboard: how many alerts and objects arrived in a window, what kinds, where on the sky, and the brightest new supernova candidates.
  • Sky: the map. Most of what follows is about it.
  • Objects: the same objects as a table you can sort, filter by the broker's label or TNS type, and page through; click one for its light curve and images.
  • Tonight: a planner for your telescope. Pick your site and telescope, and it lists the supernovae, novae and new objects seen this week that are above your horizon while it is dark and bright enough to see, sorted by when each is best placed, with finder charts, a CSV export and a printable list.

Search

  • An object id (ZTF26abvkmbu, a Rubin id, or the first few characters), a TNS name (SN 2026abc), coordinates (35.71 -4.75 or 02:22:50 -04:45:00, add r=10' for a radius), a deep-drilling field (COSMOS), a class (SN Ia, EclBin) or any name astronomers use (M31).

On the map: zoom to go deeper

  • Whole sky (wider than 20°): a heatmap of how many objects were seen in each patch of sky.
  • Region (1°–20°): a finer heatmap plus numbered badges. The number is the count of objects, the color is their most common class, and a white ring means something new in the last night.
  • Objects (under 1°): one dot per object. A white ring means it was seen last night, and a white center means it has been detected only once so far. Click a dot for its light curve, classification and images.

Drag to pan, scroll or pinch to zoom, or click a badge to zoom into it.

Filters

  • Window: how far back to look, from last night to a year.
  • Active / new: objects detected in the window, or only those first seen in it.
  • Class: most alerts are solar-system objects (asteroids). Pick Non-Solar System to hide them and see what else is out there.
  • Brightness (≤ 20, ≤ 18, ≤ 16): only objects at least that bright. Smaller magnitudes are brighter. An object marked faded was last seen fainter than in the survey's reference image, so it has no brightness of its own and counts only under any mag.
  • History (2+ nights, …): only objects seen on several nights, which filters out one-off artifacts.

Observing from your site

  • Your site: an observatory from the list, or your latitude and longitude (typed, or Use my location). A position is rounded to half a degree, and the site is remembered in this browser only.
  • Object panel: when the object is up tonight, its altitude through the night with the moon, the next 60 nights, and a Finder chart with a link to AAVSO's comparison stars.
  • Objects: Visible from… keeps what is above your limit in tonight's dark window, with when and how high.
  • Sky: Observer… shades what is below your horizon at a time you pick; the counts do not change.
  • Tonight: Subscribe gives an RSS feed of your setup, one item a night with the picks, once the data through the night before are in (or three hours before dark). A condition (novae, rare types, something brighter than a magnitude) leaves nights without a match out, so a feed-to-email service mails only those. The plan is also JSON, for scripts and robotic telescopes. A feed's address holds your rounded site and setup: a reader or email service you give it to keeps it.
  • Where your data count: the surveys measure their own objects every few nights, but a TNS or CBAT object gets only ATLAS's photometry, and only while it is brighter than 19. Unconfirmed marks one reported on a single night in the last two weeks: a detection confirms it, and a deep non-detection is news too. No recent data marks one seen on two or more nights that nothing has measured for four nights or more: a magnitude fills the gap in its light curve.

Dark means the sun more than 12° below the horizon (18° if you choose). Positions ignore refraction and precession, a few tenths of a degree: enough to plan, not to point.

Classes

  • SN candidate
  • AGN / nuclear
  • Variable star
  • Solar system
  • Cataloged
  • Unknown
  • Low reliability
  • Other

Data credits

Fink: ZTF and Rubin alerts: classifications, light curves and cutouts
Möller et al. 2021, MNRAS 501, 3272; ZTF (Bellm et al. 2019) and the Vera C. Rubin Observatory LSST.
Transient Name Server (TNS): names, types and discovery reports of transients from every survey
The IAU Transient Name Server, operated by the Weizmann Institute of Science; reports by the surveys named on each object.
CBAT: the Transient Object Confirmation Page: bright novae and other transients reported to the Central Bureau
Central Bureau for Astronomical Telegrams, Transient Object Confirmation Page (TOCP).
ATLAS: forced photometry of TNS objects, from the ATLAS forced-photometry server
Tonry et al. 2018, PASP 130, 064505; Smith et al. 2020, PASP 132, 085002; Shingles et al. 2021, TNS AstroNote 2021-7.
CDS, Strasbourg: sky imagery (HiPS), finder charts (hips2fits) and name resolution (Sesame)
This research has made use of the CDS services, Strasbourg Astronomical Observatory, France.

Everything here is also JSON: Data and API has the public API, the feeds, the exports and how to cite the data.

The data is refreshed nightly. Every view is a link: on the map the URL records the position, zoom, filters and selected object, so Copy link shares exactly what you see.

Made by jgriz

Data and API

Everything the site shows is also JSON, from a public API: no key, no account, GET only, open to any origin. The data are rebuilt nightly, and run through the night of 2026-09-30.

Sources and their terms

ZTF and Rubin objects come from the Fink broker's alerts; transients neither survey alerted on come from the Transient Name Server and CBAT's Transient Object Confirmation Page, measured by ATLAS. Each provider's data stay under its own terms, and each asks to be credited as below when you use them. TNS, CBAT and ATLAS agreed to this site's use of their data with that credit; for anything beyond personal research, read their terms on their sites.

Fink: ZTF and Rubin alerts: classifications, light curves and cutouts
Möller et al. 2021, MNRAS 501, 3272; ZTF (Bellm et al. 2019) and the Vera C. Rubin Observatory LSST.
Transient Name Server (TNS): names, types and discovery reports of transients from every survey
The IAU Transient Name Server, operated by the Weizmann Institute of Science; reports by the surveys named on each object.
CBAT: the Transient Object Confirmation Page: bright novae and other transients reported to the Central Bureau
Central Bureau for Astronomical Telegrams, Transient Object Confirmation Page (TOCP).
ATLAS: forced photometry of TNS objects, from the ATLAS forced-photometry server
Tonry et al. 2018, PASP 130, 064505; Smith et al. 2020, PASP 132, 085002; Shingles et al. 2021, TNS AstroNote 2021-7.
CDS, Strasbourg: sky imagery (HiPS), finder charts (hips2fits) and name resolution (Sesame)
This research has made use of the CDS services, Strasbourg Astronomical Observatory, France.

The API

Base URL https://transients.fyi/api. The interactive documentation, with every parameter and a “Try it out” button, is at /api/docs; the schema at /api/openapi.json. A source is ztf, lsst (Rubin), tns or cbat.

PathReturns
/tablea sorted, filtered page of objects (at most 100) with the exact total: the Objects page's query
/object/{source}/{id}one object's row: position, class, TNS name and type, first and last detection, peak
/object/{source}/{id}/detectionsa TNS or CBAT object's detections (ZTF's and Rubin's are Fink's to serve)
/search/objects?q=up to 8 objects by id prefix, TNS name or TOCP designation
/objectsthe objects in a cone (up to 0.75°), brightest first: the map's markers
/density, /clustersthe map's regional counts per HEALPix pixel and its badges
/manifest, /stats, /labels, /healththe build: its nights and cuts, the dashboard's numbers, labels with counts

Every response carries X-Data-Through (the data's last night, UTC) and X-Build (when the build ran); /table also returns them in its body as data_through and generated_at, for scripts that keep the JSON. The Objects page's URL keys are close to the API's: a view's filters carry over.

curl

# supernova candidates first seen in the last 7 nights, 18 mag or brighter
curl 'https://transients.fyi/api/table?window=7d&measure=new&bucket=sn_candidate&mag=18&limit=50'

# one object, and a TNS object's photometry
curl 'https://transients.fyi/api/object/ztf/ZTF26abxkuhv'
curl 'https://transients.fyi/api/object/tns/2026yjv/detections'

Python

import time

import pandas as pd
import requests

API = "https://transients.fyi/api"
params = {"window": "1M", "tns": "any", "sort": "last_mjd", "limit": 100}
rows, offset = [], 0
while True:
    r = requests.get(f"{API}/table", params={**params, "offset": offset}, timeout=30)
    r.raise_for_status()
    page = r.json()
    rows += page["rows"]
    offset += len(page["rows"])
    if not page["rows"] or offset >= page["total"]:
        break
    time.sleep(1)  # one request a second, please

df = pd.DataFrame(rows)
print(f"{len(df)} objects, data through {page['data_through']}")

A ZTF or Rubin object's alerts, light curve and cutouts are Fink's: its API (api.ztf.fink-portal.org, api.lsst.fink-portal.org; documented for ZTF and Rubin) serves them without a key, and the object panel reads them from there.

Feeds and exports

Forced photometry of any position

The site shows what the surveys detected. To measure a position on every image, detected or not, ask the surveys' own services, each with an account of your own:

Limits and etiquette

How to cite

Name the site and the data's date: Transient Explorer, https://transients.fyi, data through 2026-09-30. Credit the providers whose data you use, with the references above: Fink for ZTF and Rubin alerts (and ZTF and Rubin themselves), the TNS and the reporting surveys for reports, CBAT for TOCP entries, ATLAS for its photometry.

Changelog

2026-09-30
Version 1.0: the documentation at /api/docs, the X-Data-Through and X-Build headers, data_through and generated_at in /table's body, and a rate limit. Today's paths are version 1.