Deep Sky Monitor From Curiosity to Cosmos.

User Guide & Data

Learn to explore pulsars, black holes, supernovae and spacecraft with Deep Sky Monitor, see where its space data comes from, and use its free JSON API.

User guideHow to use each page: the sky, search, images, spacecraft, settings

Getting around

  • Left menu: switches between pages. in the header (or Collapse at the bottom of the menu) shrinks it to icons; the dashboard remembers your choice. On a smaller laptop or a tablet the menu is shown as icons, and opening it slides the full menu over the page; on a phone it slides in from the left.
  • Header: click the clock to switch between UTC and your local time; this changes every date and time on the site. Full screen hides the browser's own toolbars.

Scheduled jobs & Status and Settings

  • Scheduled jobs & Status shows whether the daily refresh jobs ran, how fresh each spacecraft's data is, and any errors. Each job's panel shows when it runs (by default most run once a day at 09:00 UTC, and the pulsar catalogue and the search box's name list once a week), so the computer running the scheduler needs to be awake then. Times there follow your Settings (UTC or local time). While the ADMIN_ACTIONS and JOB_SCHEDULE_EDIT toggles are on, each panel can also change its job's time and frequency, and Add New Job adds another run of one of the data tasks, with its own options (e.g. solar flares with --days=30) and schedule; an added job can be removed again.
  • Settings sets the time zone and clock format, the default page and spacecraft, how the star maps look and how many images the carousel shows. Those are saved in your browser; the image cache settings there apply to everyone.

Explore Deep Sky page

  • Background: by default the chart is the realistic sky, real photographs of the whole sky stitched into one panorama (the Mellinger colour mosaic, switching to the sharper DSS colour survey as you zoom in), with the real Milky Way, nebulae and star colours. The / button under the zoom controls (or Settings) switches to the lighter drawn star chart, which is also used automatically if the photos can't load. Either way every object is where it really is in the sky, and right ascension increases to the left, as when you look up.
  • Pulsars: the purple circles. Magnetars are purple squares, and fast radio bursts are outlined squares.
  • Zoom: scroll the mouse wheel or pinch on a touch screen (the realistic sky zooms from the whole sky down to a few arcminutes; the star chart up to 12×); double-click to zoom in. Pan: drag. The buttons zoom in, zoom out and reset.
  • Select a source: click its dot or its name, or type its name in the search box. The chart flies to it, and the Details panel shows its type, pulse period, sky position, constellation, distance, discovery and why it matters. Links like /deep-sky?src=crab open with a source already selected.
  • Image carousel: up to three images of the selected object: the best real photo (a curated NASA image, a matching photo from the NASA Image Library, or the object's Wikipedia photo), a sharp telescope survey view zoomed to the object's size (Pan-STARRS colour where it covers the sky, DSS2 colour elsewhere; the amber ring marks the position), and a second photo or an infrared view (2MASS), where dust becomes transparent. Use the arrows, the dots, swipe, or the arrow keys; click an image (or ) for a large view. Each image shows its source and credit. Photos are only used when they name the object, and images are kept on the server (90 days by default), so the second view is instant. Choose how many images to show (1–5) and how long images are kept in Settings. For a gravitational-wave event the card shows the official sky map instead, because its position is too uncertain for a single telescope image.
  • Search: type any object name in the box above the chart (e.g. M87, Cyg X-1, Andromeda). Our own sources are matched first; anything else is looked up in the SIMBAD database, marked with an amber crosshair, and shown with its type, position and a survey image. Suggestions appear as you type (use the arrow keys and Enter, or click): objects on the chart, and when you type a catalogue name such as Abell, NGC, Ton or HIP, what that catalogue is and some of its best-known objects. A catalogue name alone isn't an object, so add the number (Abell 1201).
  • Supernova candidates: the small orange four-point stars. Select one to see its class (Ia, Ib/c, II or superluminous), the classifier's confidence, when it was first and last detected, a survey image of its host galaxy region, and a link to its page in the ALeRCE Explorer. Names appear when you zoom in.
  • Black holes and jets: the dark discs with an amber ring. Select one for its mass (or, for blazars, its redshift), distance and story; M87*, Sagittarius A*, Centaurus A and 3C 279 also have a NASA featured image.
  • Gamma-ray bursts: the small pink crosses. Select one for its date, its precise X-ray position (and how precise), and links to astronomers' reports about it.
  • Gravitational-wave events: the teal rings. Their positions are uncertain, often by hundreds of square degrees, so selecting one shades its 90% probability region on the chart and zooms to fit it. The panel shows what probably merged (black holes or neutron stars, with probabilities), when, which detectors saw it, how unlikely it is to be noise (false alarm rate), and the official LIGO/Virgo/KAGRA sky map.
  • SETI signals: the lime diamonds mark famous "is it aliens?" radio signals: the 1977 Wow! signal (two diamonds, one dashed, because the telescope had two receiving horns and nobody knows which one caught it), SHGb02+14a, HD 164595, Ross 128, BLC1 and the eight 2023 machine-learning signals. Perytons have no sky position, so find them with the search box. Select one to see what was detected, how it was checked and the verdict (interference, noise, unconfirmed or unexplained). Press Listen to hear a sonification, a sound built from the signal's real properties (its frequency in MHz played as the same number in Hz, its drift, duration and shape) with a moving cursor on the chart. For the Wow! signal the chart shows the six measured strengths ("6EQUJ5" decoded) against the shape expected from the telescope's beam, playable in 12 seconds or in real time (72 s).
  • Filters: the chips under the chart show or hide each type (pulsars, black holes and jets, magnetars, fast radio bursts, gamma-ray bursts, supernova candidates, gravitational waves, SETI signals). Milky Way shows or hides the band of our galaxy, where most pulsars lie.
  • Up in my sky now? Set your location (in Settings, or with the link in the panel) and each source shows whether it is above your horizon, how high, and when it next rises or sets. Your location stays in your browser.
  • Galaxies: the pale gold dots are the ~10,800 galaxies of the NGC and IC catalogues (OpenNGC): the brightest at a wide view, fainter ones as you zoom in, and their real outline (size and tilt) once they're big enough on screen. Hover for a name, click to open one (type, size, brightness, how fast it's receding and how far away it is), or search by number or name (NGC 4565, IC 1101, Sombrero); clusters and nebulae from the same catalogues are found by search too.
  • Every known pulsar: the small blue dots are the ~4,500 pulsars of the ATNF Pulsar Catalogue (violet: millisecond pulsars, teal: in binaries, amber: magnetars), refreshed weekly. Hover for a name, click to open one, or search by name (PSR J0437-4715, B1919+21).
  • Chart tools (below the zoom buttons): wavelength shows the sky in radio, hydrogen gas, microwave, infrared, hydrogen-alpha, ultraviolet, X-ray or gamma-ray light, blended with the photographs (realistic sky only); ruler measures the angle between two points or objects; what's here? opens any point you click; copies a link to this exact view (position, zoom, object, wavelength, filters). The position under the pointer (RA/Dec, galactic coordinates, constellation) shows at the top left.
  • Explore cards under each object's details (open or fold them; the page remembers): light curve (supernovae, gamma-ray burst afterglows, blazars), pulsar numbers with Listen (one click per rotation at the real rate) and the P–Ṗ diagram of all pulsars, facts from SIMBAD and Wikipedia, what's around here? (or, for a gravitational-wave event, its likeliest host galaxies), tonight from your location (best time, darkness, the Moon) and where is it, how old is its light?
  • Timeline of transients (under the filter chips): the events on a time strip; drag the slider to see only those up to a date, press Play to watch them appear in order, or jump to a date.

Space Observatories: the spacecraft behind this site's data

  • Every number on the site comes from a spacecraft: Swift pins down gamma-ray bursts, and Hubble, JWST and Chandra took many of the photos. This page shows where each one is right now, what it measures, and links to where its data appears.
  • Around Earth: a world map with today's day and night and the point where the Sun is overhead. Dots are Earth-orbiting craft, recalculated every 2 seconds from their orbital elements, with their last 45 minutes of track (the selected one also shows its next orbit, dotted). Diamonds mark the spot beneath the craft 1.5 million km away. The coloured chips hide or show a group. How far up? puts them all on one scale, from the space stations at about 400 km to the L1 and L2 craft four times farther than the Moon.
  • Deep space: the craft around the L1 and L2 points, drawn along the Earth–Sun line (seen from above or from the side), and Parker Solar Probe and Solar Orbiter around the Sun with the inner planets. Trails show yesterday and the next two weeks.
  • What each one does: how long each has been in space, and a card per spacecraft with its picture, what it measures and buttons to its data on this site.
  • Click any dot, bar or card to select a spacecraft: the panel on the right shows its picture, a live figure (altitude, or distance from Earth or the Sun), its speed, a chart of its altitude around one orbit (or its distance over the coming days), its story and links. The two chips under the title show how old the orbital data is (TLEs drift after 1–2 weeks) and how far ahead the deep-space positions go.
  • Hubble is selected when the page opens. Change this under Settings, or open a link such as /observatories?sat=iss to start on a particular one.
Studying the radio signals from deep-sky sourcesFrom a source on the chart to its real recorded signal

This dashboard shows where the sources are and what they are; it doesn't receive or record their radio signals. Those are recorded by large radio telescopes, and much of that data is public. A practical path from "what is this source?" to analysing its real signal:

  1. Look up the source's numbers. Search its catalogue name from the Explore Deep Sky page (e.g. B1919+21, J0437-4715) in the ATNF Pulsar Catalogue : pulse period, how fast it is slowing down, dispersion measure (how much the signal is smeared by gas on its way to us), and brightness.
  2. See what its pulses look like. The EPN Database of Pulsar Profiles holds published average pulse shapes for hundreds of pulsars at many radio frequencies, which you can plot or download.
  3. Hear them. Jodrell Bank's Pulsar Sounds turns real pulsar recordings into audio: slow pulsars tick, fast ones hum.
  4. Download real data.
  5. Analyse it. The two key steps are de-dispersion (lower radio frequencies arrive later, so the signal is shifted back into line using the dispersion measure) and folding (adding up thousands of rotations at the known period until the faint pulse rises out of the noise). The free tools astronomers use are PRESTO (searching, de-dispersion and folding) and PSRCHIVE (processing folded pulsar data).
  6. Observe one yourself. Amateur radio astronomers have detected the brightest pulsars, such as PSR B0329+54 and Vela, using dishes a few metres across, a low-noise amplifier and a software-defined radio, then folding many minutes of data at the known period. It's challenging, but possible.
Going further with black holes and transient eventsPublic archives with the real measurements

The chart marks where these objects are; the real measurements live in public archives:

About the dataWhere every dataset comes from, and how fresh it is
Why "not for operational use"? Everything here is real data, made for learning and exploring, but it isn't guaranteed: it refreshes on a schedule (most of it once a day), so it can be hours old; when an outside service such as CDS or NASA is down, parts of it fall back to mirrors or are missing for a while; and spacecraft positions and event regions are approximations. Don't use it for decisions that matter, such as satellite operations or space-weather warnings: use the official sources instead (NOAA SWPC for space weather, Space-Track for orbits, GraceDB for gravitational-wave alerts).
  • Space Observatories: real orbital elements (TLEs) for 9 Earth-orbiting spacecraft from CelesTrak , refreshed daily (last refresh: ). Positions are computed live every 2 seconds with standard SGP4 orbital propagation (satellite.js ) and your device's clock. Element sets drift after a week or two, so accuracy depends on the refresh job running. Craft at the Sun–Earth L1 and L2 points (SOHO, IMAP, DSCOVR, ACE, JWST) and around the Sun (Parker Solar Probe, Solar Orbiter) are too far for TLEs; their positions come from NASA JPL's Horizons ephemeris (last refresh: ).
  • Deep-sky radio sources: a hand-curated reference catalog of well-known pulsars, a magnetar and a fast radio burst source, with published coordinates, distances and periods. There is no simple public live feed of raw pulsar signals, so this catalog changes only when the database is edited.
  • Galaxies, clusters and nebulae (NGC/IC): the OpenNGC catalogue (Mattia Verga, CC-BY-SA 4.0): all ~14,000 objects of the New General Catalogue and Index Catalogue, ~10,800 of them galaxies, with positions, sizes, brightness, Hubble types and redshifts. Checked weekly and imported again only when it has changed. Distances shown are estimated from the redshift (Hubble law), so they are rough for nearby galaxies, whose own motion adds to the expansion. It is also the fallback name lookup while SIMBAD is down.
  • All known pulsars: the ATNF Pulsar Catalogue (CSIRO; Manchester et al. 2005), imported every week (last import: ): position, period, spin-down, dispersion measure, distance, magnetic field and age.
  • Explore cards and wavelengths: optical light curves from the ZTF survey (via the ALeRCE broker) and the Swift-XRT light curves ; facts and nearby objects from SIMBAD; gravitational-wave host galaxies from GLADE+ ; constellation boundaries from Roman (1987); wavelength maps (Haslam 408 MHz, NVSS, HI4PI, Planck, AllWISE, Finkbeiner Hα, GALEX, ROSAT, Fermi) through CDS HiPS. Tonight's plan, the Sun and Moon, and light travel times (Planck 2018 cosmology) are calculated in your browser. If CDS (Strasbourg) isn't responding, the sky photos come from the DSS colour mirrors at NASA IRSA or ESA ESASky , survey views from NASA SkyView (black and white), and SIMBAD lookups from its Harvard mirror.
  • Supernova candidates: recent objects that the ALeRCE broker classifies as supernovae (types Ia, Ib/c, II and superluminous) from their brightness changes in the Zwicky Transient Facility (ZTF) survey, refreshed daily (last import: ). These are machine classifications with a confidence score, not confirmed supernovae. ZTF observes from California, so they cluster in the northern and equatorial sky.
  • Gravitational-wave events: the most recent significant public alerts from the LIGO, Virgo and KAGRA detectors, via GraceDB (last import: ). For each we read the alert's own sky map to find the most probable point and the 90% probability region. Alerts are issued only while the detectors are in an observing run.
  • Gamma-ray bursts: bursts from the last two years with X-ray afterglow positions measured by NASA's Swift satellite, from the UK Swift Science Data Centre (last import: ).
  • Black holes and jets: seven hand-curated objects (M87*, Sagittarius A*, Centaurus A, Cygnus X-1, the ultramassive black hole in the galaxy cluster Abell 1201, and the blazars 3C 279 and TXS 0506+056) with published positions, distances and masses.
  • SETI signals: a hand-curated list of famous candidate signals from the search for extraterrestrial intelligence, from the published record: the Wow! signal (Big Ear, 1977) and the later candidates, with the eight 2023 signals of interest from Ma et al. 2023 (Breakthrough Listen) and star positions from SIMBAD. None has turned out to be a confirmed alien signal. The sounds are sonifications built in your browser from each signal's properties, not recordings.
  • Stars and constellations: 5,044 real stars down to magnitude 6 (about what the eye sees on a dark night) and the 88 constellation figures, from d3-celestial (HYG database, BSD licence). Realistic sky: the Mellinger colour mosaic and DSS2 colour survey, shown with Aladin Lite (CDS, Strasbourg).

Pulsar/FRB data: published positions and distances (Wikipedia, ATNF Pulsar Catalogue, Chatterjee et al. 2017, Tendulkar et al. 2017). Black hole and jet data: published positions, distances and masses (Event Horizon Telescope, Wikipedia). Supernova candidates: ALeRCE broker, ZTF survey. Gravitational-wave alerts and sky maps: LIGO/Virgo/KAGRA via GraceDB. Gamma-ray burst positions: Swift XRT, UK Swift Science Data Centre. Survey images: DSS2 colour, Pan-STARRS1 and 2MASS via CDS hips2fits ; object photos also from Wikipedia / Wikimedia Commons (each with its author and licence); object sizes from SIMBAD; name search: CDS Sesame (SIMBAD, NED, VizieR); star-name suggestions: IAU Catalog of Star Names (WGSN, 2022 edition, CC BY); featured images: NASA Image and Video Library . A demo built on real data: not for operational satellite tracking or space-weather forecasting.

For DevelopersA free, open JSON API for pulsars, galaxies, transients and spacecraft

Build with real space data

Every number on Deep Sky Monitor comes from a free, open astronomy JSON API: the full ATNF pulsar catalogue, every NGC/IC galaxy, black holes and jets, supernova candidates, gravitational-wave events, gamma-ray bursts, live spacecraft positions, plus look-ups for any object in the sky. No sign-up and no API key; it answers from any website (CORS), and it's described in OpenAPI 3, so you can try every call in the browser or generate a client in your language.

Open the API documentation Download openapi.json

Deep-sky sources

The curated pulsars, black holes, magnetars and fast radio bursts on the Explore Deep Sky map: position, distance, period, discovery and a featured image.

  • GET /api/sources
  • GET /api/gw/{id}/region

Star catalogues

About 4,500 pulsars with period, spin-down, magnetic field and age; about 10,800 galaxies with size and brightness; name search and full NGC/IC records.

  • GET /api/pulsars
  • GET /api/galaxies
  • GET /api/catalog/search
  • GET /api/catalog/object/{name}

Object look-ups

Find any object by name, get its facts (type, distance, magnitudes, newest papers), what's around it, telescope images and light curves.

  • GET /api/resolve
  • GET /api/object-facts
  • GET /api/nearby
  • GET /api/object-images
  • GET /api/lightcurve

Spacecraft

Hubble, JWST, GOES, SOHO and the other observatories behind the data: what each one measures, its orbital elements or upcoming positions from NASA JPL Horizons.

  • GET /api/satellites

Sky images & status

Survey images (DSS2 colour, Pan-STARRS, 2MASS infrared) of any position, and which outside data services are answering right now.

  • GET /sky-image/survey
  • GET /api/service-health

Coordinates are J2000 degrees. Calls that ask outside services are rate-limited per visitor and cached, so please cache answers on your side too. The data belongs to its providers (listed under About the data): please credit them when you use it.