Voyage
Press Voyage at the top (or V) to ride as an astronaut from world to world. It starts today, above your city, and follows real transfer orbits to where each planet really is; time runs fast while crossing, and the line at the bottom says by how much. Fresh picks the stops from what is notable today; Today’s events goes where things are happening (the Sun after a strong flare, planets near opposition); Grand Tour visits Jupiter, Saturn, Uranus and Neptune; Home ends in lunar orbit watching Earth; Inner Worlds ends close to the Sun; Mars (ending at its moon Phobos) and Asteroid Belt (Ceres and Vesta, at their true size with NASA Dawn’s maps) do what they say. Photo (P) saves a 4K still stamped with where and when. Move the mouse or tap to choose the tour and where to look: Wander (the astronaut looks around), Destination or Free (drag). On arrival you can choose the next stop. Slow–Fast sets the pace; time slows to a calm rate near each world, so planets turn at an honest speed. Close / Medium / Far sets how low the orbit passes (Medium keeps the maps sharp). 2.39:1 adds cinema bars. Rear view (B) shows what you left behind, like a mirror at the top. Each orbit is timed so you arrive over the night side and watch the Sun rise over the limb; when a world hides the Sun, its faint corona appears. I switches the display between off, a quiet HUD and full instruments (trajectory, transfer Δv, navigation, sunlight and temperature, radio delay and which Deep Space Network dish can see you, and a route map), all calculated from the real trajectory. Space pauses, Esc leaves. The address #voyage or #voyage=grand-tour starts it directly; add &kiosk for an exhibit screen (no exit control, back to its tour after 3 minutes untouched) and &span=2 for two screens side by side. Add &fps (or #fps on its own) to show a frame-rate counter.
Following objects
Picking a spacecraft, asteroid or comet flies to where it is right now and follows it (Go there on its card, or G, does it again). Stars and deep-sky objects turn the view toward them; Go there centres one and zooms to frame it until you drag the view (Stop holding lets go). On a moving object’s card, Keep centred (K) holds it in the middle of the view; switch it off to let it move across the view in real time. Chase view (T) rides behind it along its direction of travel. Layers → Camera speed sets how fast the camera flies, turns and follows (Slow, Normal, Fast); it never changes time or positions.
Look around
Drag to turn the view. Scroll or pinch to zoom in close. Reset view takes you back to the starting view. Use Go to at the top right of the view, tap a name in the view, or type in Search the sky at the top to fly somewhere. A card with live facts opens on the right; close it with ✕ or Esc.
Travel in time
The time controls float at the bottom of the view: pause, step an hour at a time, choose a speed from half speed up to a year per second, run time backward, or pick any date and time. Everything follows: the Sun, the Moon, day and night, and eclipses. Now brings you back to the present.
Real stars
Every star in the view is a real star from the Yale Bright Star Catalogue, about 9,100 of them, at its true position, brightness and colour. Search for a star by name (“Vega”), by its catalogue label (“α Ori”), or by constellation (“Orion”). Its card shows when it rises, reaches its highest point and sets for you. Star names can be switched off in Layers.
Deep sky
All 110 Messier objects, the best-known galaxies, star clusters and nebulae, are marked among the stars with quiet outlines at their true size and tilt (at least 0.3° across, so small ones stay findable): pink ellipses for galaxies, dashed gold circles for open clusters, a circle with a cross for globular clusters, green squares for nebulae and blue ringed circles for planetary nebulae. Layers → Deep sky adds about 600 more from the NGC and IC catalogues (brighter than magnitude 10.5). Search by number or name (“M31”, “Orion Nebula”, “NGC 7000”), or click an outline, for its card: type, size, brightness, where it is in your sky tonight and when it is best (deep-sky objects need a fully dark sky away from the Moon), the telescope coordinates, and a Hubble photo where NASA’s Hubble Messier Catalog has one. Go there (G) puts the object in the middle of the view and zooms to frame it; scroll to zoom further, drag to let go. Each object glows softly at its true size and brightness, and for Messier objects inside the DESI Legacy Surveys’ sky coverage the view shows the real survey photo of the whole object at its true size and orientation. Galaxy distances come from their redshift, so they are shown only for galaxies well beyond our own neighbourhood. Layers → Deep sky → Brightest quasars adds the 100 brightest quasars (violet diamonds), the blazing cores of galaxies billions of light-years away; their cards give the redshift, how long ago the light left (3C 273: about 2 billion years) and how far away they are now.
Stargazer
The Stargazer panel lists what is best to observe tonight from your location, with the time window and a 0–100 score. The score combines how high it is, how dark the sky is, moonlight and the forecast clouds (low cloud counts most, thin high cloud least). The bars above the list rate the sky for each hour tonight; the line under them gives the best hours, cloud, how steady the air is (from the jet-stream wind: turbulent air blurs planets at high magnification) and the aurora chance where you are. Open your sky chart (or Your sky chart on a card) shows the whole sky from where you are, like a planisphere: horizon at the edge, overhead in the centre, north up and east left, with a time slider for the next 12 hours and the chosen object ringed with its path tonight. A card for the Moon, a planet or a star shows its altitude and azimuth now, airmass, angle from the Sun, the same verdict, whether you need binoculars or a telescope, and its RA/Dec for a GoTo telescope mount.
Satellites over you
Under Stargazer, Satellites over you lists the visible passes of the next 24 hours: the ISS, China’s Tiangong station, Hubble and fresh Starlink “trains”, with the time, how high they climb, the direction they cross, and an estimated brightness (lower is brighter). A pass counts only when the satellite is sunlit while your sky is dark. If an official re-entry prediction may cross your sky, it is listed first. Switch it off in Layers → Satellites → Visible passes.
Launch windows
Launch windows (in the Observer panel) shows when a spacecraft can leave for Mars, Venus, Mercury or Jupiter. Each square is one trip: launch date across, days of travel down; blue means little energy is needed, so the blue islands are the launch windows (for Mars about every 26 months). Point at a square for its dates, the energy to leave Earth (C3), the speed change needed from low orbit and the arrival speed; click one and Fly this trip in Voyage to ride it at its real dates.
On a phone
iPhones only allow videos to go full screen, not web pages. To use Meridian without the browser bars, add it to your home screen: in Safari or Chrome, tap Share → Add to Home Screen, then open Orbit from its icon.
Your layout
Layers → Labels has separate switches for planets and moons, star names, spacecraft, asteroids and comets (the brightest few in view are named), and deep-sky objects (Messier numbers). Layers → Interface shows or hides each panel, the Voyage button and a frame-rate readout; your choices are kept in this browser.
The planets
All eight planets and Pluto are at their true positions for the date shown, on their true orbits, turned the way they really face (official IAU rotation). Fly to one with Go to or the number keys (1 Mercury to 9 Pluto, 0 Sun, 3 Earth). Tonight shows which planets are up for you now. In Compressed scale the planets are spaced so they all fit; True shows real distances and sizes.
Your sky
Meridian guesses your city from your network. For an exact position, tap Use my location, or search for a city or postal code; once set, the panel shrinks to your place (Change to pick another). Tonight shows where the Sun, Moon and planets are for you, and when they rise and set.
Real views from NASA satellites
Open Layers to switch on yesterday’s real clouds, last night’s clouds over the city lights, active wildfires, smoke and dust, and tonight’s aurora at the latest measured geomagnetic activity. Pick a past date (from 2000) to see that day’s real clouds on Earth. See your area from space in the Observer panel shows a satellite photo of where you are, and Whole Earth today shows photos of the whole sunlit Earth from 1.5 million km; drag the slider to watch it turn.
Asteroids and comets
About 95,000 real asteroids and comets from NASA/JPL are drawn at their computed positions: amber for near-Earth asteroids, grey-blue for the main belt, green for Jupiter’s Trojans, violet for bodies farther out, cyan for comets. Point at any dot to see its name, and click it for its card; or search one by name or number (“Ceres”, “Bennu”, “Halley”), then Go there. Each family can be switched on or off under Layers. The set is every known near-Earth asteroid, every asteroid brighter than magnitude 14.5 (roughly 5 km or larger in the main belt) and every numbered comet, not all 1.4 million known small bodies.
How accurate is it?
No position in the view is made up. Measured and refreshed: the orbits of the space station and satellites (CelesTrak and Space-Track, every few hours; positions calculated with SGP4 in your browser, good to about a kilometre), asteroid flybys (JPL, every 6 hours), space weather, the Earth photos and the cloud, fire, smoke and night maps (NASA satellites, from the last day), and your weather forecast. Computed for the time shown: the Sun, Moon, planets and Jupiter’s moons come from astronomy-engine’s models of their orbits, good to about an arcminute (1/30 of the Moon’s width); stars are their catalogue positions. Computed from a fixed orbit: the 95,000 asteroids and comets start from JPL orbits refreshed on the 1st of each month and follow them without the pull of the planets, so most are within a small fraction of a degree, but a near-Earth asteroid that passes close to a planet, or a comet near the Sun, can drift further; the Asteroid flybys list uses fresh orbits instead. Not to scale: in Compressed scale sizes and distances are shrunk so everything fits; each body’s direction from the Sun, and all timing, stay true. The Sun’s surface is drawn, not photographed. Choose True for real sizes and distances.
Space weather and asteroids
Space weather shows the latest solar flare, any solar storm on its way to Earth, the solar wind measured 1.5 million km upstream (speed, density and Bz; a southward Bz brightens the aurora in the view), and a rough guide to seeing the aurora where you are. A recent flare also glints on the Sun in the view. Tap an asteroid under Asteroid flybys to see where it is now and its path past Earth; tap it again to hide it.
Satellites: shadow, re-entries, close approaches, storm drag
Earth orbit has three tabs. Nearby shows the space station and satellites; a gold dot means the satellite is in sunlight, a hollow dot that it is in Earth’s shadow. Its card says when that changes and gives the beta angle, the Sun’s angle above the orbit plane, which decides how much of each orbit is in sunlight. Re-entries lists objects about to fall back into the atmosphere: tap one to see the orange path where it could come down (the ± time), then Show at predicted time. Close approaches lists public warnings of two objects passing close: tap one, then Go to closest approach to see both orbits. In Space weather, Satellite drag shows how fast the ISS and Starlink satellites are sinking; storms heat the upper air and speed it up. Tap it for a 30-day chart. Each of the four can be switched off in Layers. Positions are calculated with SGP4 from public orbit data and are good to a few kilometres; the official numbers come from the U.S. Space Force via Space-Track.org.
Reading the panels
Where to look shows the Sun and Moon from your location: the compass is which way to face, the arc is how high to look above the horizon. Ground track is a world map of day and night and of where the Sun, Moon and spacecraft are directly overhead; tap it to enlarge. Earth orbit lists the space station and satellites, and asteroids passing close; 1 LD is the distance to the Moon, about 384,400 km. The Next 24 hours strip adds your local weather: shading for clouds, blue ticks for likely rain, and temperatures.
Two ways to watch
Console shows every panel. Viewport keeps just the view, a clock and the time controls. The eye button hides everything.
Keyboard
/ search · Space pause · ← → step an hour (Shift a day) · [ ] slower, faster · \ reverse · N now
0 Sun · 1–9 Mercury to Pluto (3 Earth) · M Moon · G fly to and follow the selection · K keep it centred · T chase view · V Voyage · F full screen · R reset view · S true scale · O orbits · Shift+L labels
C Console or Viewport · H hide controls · ? this guide · Esc close
Software
Three.js r147MIT3D rendering and camera controls · three.js authors · license
astronomy-engine 2.1.19MITPositions of the Sun, Moon, planets and Pluto, their rotation, rise and set times, eclipses, oppositions and elongations · Don Cross · license
IBM Plex Mono and IBM Plex Sans CondensedSIL OFL 1.1Typography · IBM Corp. · served from this site · license
Imagery and data
Earth surface · Blue MarblePublic domainNASA Goddard Space Flight Center, Visible Earth
City lights · Black MarblePublic domainNASA Earth Observatory, Visible Earth
Close-up Earth detail · Blue Marble Next Generation (500 m) via GIBSPublic domainNASA Earth Observatory / NASA GIBS, part of NASA’s ESDIS
Clouds and topography · Blue MarblePublic domainNASA Goddard Space Flight Center, Visible Earth
Moon surface and relief · CGI Moon KitPublic domainNASA Scientific Visualization Studio, from Lunar Reconnaissance Orbiter LROC and LOLA data
Jupiter mapPublic domainNASA/JPL/Space Science Institute, Cassini cylindrical map of Jupiter (PIA07782). Jupiter’s clouds drift, so feature longitudes are approximate.
Mars mapPublic domainNASA/JPL/USGS, Viking MDIM 2.1 colorized global mosaic, via USGS Astrogeology
Mercury mapPublic domainNASA/Johns Hopkins APL/Carnegie Institution of Washington, MESSENGER MDIS global mosaic via USGS Astrogeology; brightness from the mosaic, colour set to Mercury’s natural tone
Pluto mapPublic domainNASA/Johns Hopkins APL/SwRI, New Horizons global mosaic via USGS Astrogeology; areas New Horizons did not see are filled with average brightness
Sun surface, planet shading and Saturn’s ringsOriginalGenerated in the browser by this site’s own code; ring boundaries from published measurements of Saturn’s rings
Stars · Yale Bright Star CatalogueCatalogue dataHoffleit, D. & Warren, W. H. Jr. (1991), The Bright Star Catalogue, 5th Revised Ed., Yale University Observatory; via the CDS, Strasbourg (catalogue V/50). Positions, magnitudes, colours and spectral types of about 9,100 stars.
Star namesCatalogue dataIAU Working Group on Star Names (WGSN), list of approved star names, machine-readable version by E. Mamajek.
Exact NASA source files are listed in tex/SOURCES.txt. NASA imagery is used without implying NASA endorsement.
Satellite imagery · GIBSPublic domainWe acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System (ESDIS). Products used: VIIRS (NOAA-20, Suomi NPP) and MODIS (Terra) Corrected Reflectance true color; VIIRS NOAA-20 Day/Night Band; VIIRS NOAA-20 Fires and Thermal Anomalies; OMPS Aerosol Index.
Asteroid close approachesPublic domainNASA/JPL Center for Near Earth Object Studies (CNEOS), SBDB Close Approach Data API
Asteroids and cometsPublic domainNASA/JPL-Caltech Solar System Dynamics, Small-Body Database Query API: every near-Earth asteroid, asteroids brighter than absolute magnitude 14.5, and numbered comets (about 95,000 bodies); positions computed by this site from the orbital elements
Asteroid orbitsPublic domainNASA/JPL Solar System Dynamics, Small-Body Database (SBDB) API; positions computed by this site from the published orbital elements
Phobos and Deimos orbitsPublic domainNASA/JPL Solar System Dynamics, planetary satellite mean elements
Ceres and Vesta mapsPublic domainNASA / JPL-Caltech / UCLA / MPS / DLR / IDA, Dawn Framing Camera global mosaics via USGS Astrogeology; rotation from the IAU WGCCRE 2015 report
Today’s sunspotsPublic domainNASA Solar Dynamics Observatory (SDO) and the HMI science team: latest flattened intensitygram, downloaded by this site’s server
Saturn's ring structurePublic domainCassini Radio Science ring occultation (NASA/JPL; Rev 7, X band), from the NASA Planetary Data System Ring-Moon Systems Node; binned by this site into tex/saturn_rings.png
Deep-sky photos in cards · HubblePublic domain / CC BY 4.0Images from NASA’s Hubble Messier Catalog, credited on each card (NASA, ESA and the teams named there). NASA imagery is public domain; ESA/Hubble imagery is shared under CC BY 4.0. Resized by this site. No endorsement by NASA or ESA is implied.
Deep-sky photos in the view · DESI Legacy Imaging SurveysCC BY 4.0Colour images from the DESI Legacy Imaging Surveys DR10, cut out with hips2fits, a service provided by CDS, Strasbourg, resized and with the sky background darkened by this site; shared under CC BY 4.0. The Legacy Surveys consist of the DECam Legacy Survey, the Beijing–Arizona Sky Survey and the Mayall z-band Legacy Survey, with data from NSF’s NOIRLab facilities; see legacysurvey.org for the full acknowledgement.
Quasars · Milliquas v8Catalogue dataThe brightest quasars from the Million Quasars catalogue, version 8: Flesch, E. W. (2023), The Open Journal of Astrophysics; via CDS VizieR (VII/294). Distances are our calculation from redshift (Planck 2018 cosmology).
Deep-sky objects · OpenNGCCC BY-SA 4.0Messier and bright NGC/IC galaxies, clusters and nebulae (positions, sizes, magnitudes, types, redshifts) from OpenNGC by Mattia Verga, positions from the NASA/IPAC Extragalactic Database (NED). Our converted file dso/dso.json is shared under CC BY-SA 4.0 (notice). M102 is taken as NGC 5866. Galaxy distances are our estimate from redshift (Hubble constant 67.4 km/s/Mpc, Planck 2018).
Milky Way backgroundCC BY-SA 3.0 IGORendered by this site from ESA Gaia DR3 data (credit: ESA/Gaia/DPAC), queried through the Gaia archive; we summed, projected, coloured and tone-mapped the starlight. This work has made use of data from the European Space Agency (ESA) mission Gaia, processed by the Gaia Data Processing and Analysis Consortium (DPAC). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. The Milky Way images (tex/milkyway_*.jpg) are shared under CC BY-SA 3.0 IGO. No endorsement by ESA is implied.
Satellite orbits · SGP4MITsatellite.js (Shashwat Kandadai and contributors), served from this site
Satellite orbit dataFree public dataCelesTrak (Dr. T.S. Kelso), downloaded by this site’s server: space stations, weather satellites, Hubble and everything launched in the last 30 days (for Starlink trains)
Re-entry predictions and close-approach warningsU.S. Government dataSpace-Track.org, 18th and 19th Space Defense Squadrons, U.S. Space Force; downloaded by this site’s server under its own account. Not endorsed by the U.S. Space Force.
Real-time solar windPublic domainNOAA Space Weather Prediction Center, DSCOVR / ACE at the L1 point; downloaded by this site’s server
Geomagnetic activity (Kp)Public domainNOAA Space Weather Prediction Center, downloaded by this site’s server; satellite sink rates are this site’s own calculation
Space weather · DONKIPublic domainNASA Community Coordinated Modeling Center (CCMC), Space Weather Database Of Notifications, Knowledge, Information (DONKI), via api.nasa.gov; aurora guide is this site’s own estimate
Whole-Earth photos · EPICPublic domainNASA EPIC Team; Earth Polychromatic Imaging Camera on NOAA’s DSCOVR spacecraft, via api.nasa.gov and epic.gsfc.nasa.gov
Local weather · Open-MeteoCC BY 4.0Weather data by Open-Meteo.com, licensed under CC BY 4.0; used in the Next 24 hours strip
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Our server downloads recent clouds, night lights, wildfires, smoke, spacecraft positions, asteroid data, space weather and whole-Earth photos from NASA on a schedule and serves them from this site, so for these your browser does not contact NASA.
Past dates and your area
Three features load images straight from NASA’s GIBS image server: satellite imagery for a past date you choose, “See your area from space”, which you open yourself, and a sharper image of the region of Earth you zoom in on. NASA then receives your IP address, the map region around your location (for your area), or the region you are looking at (for close-ups). NASA’s own privacy policy applies to those requests. Switch off “Satellite imagery for the date” in Layers to stop past-date requests.
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