About Jupit

News and explainers about Jupiter, its moons and the spacecraft sent to study them, alongside pieces on the rest of the solar system and on the stars past it.

We keep reference pages on Jupiter, its four large moons and the missions there, a sky calendar computed from the planets’ orbits, and a set of instruments: the Moon, Saturn and the other planets as they look right now, maps of the solar system and the sky, an eclipse map, a black hole you can walk around, pulsars you can hear, and tools for getting a feel for size and distance. Every drawing is computed from real positions and follows the one clock at the bottom of the page. A page on the deep sky follows stars from birth to what they leave behind.

We carry no advertising and no sponsored posts.

Articles are researched from primary material: space agency releases, mission pages, conference abstracts and published papers. Each article ends with the sources it relied on.

Dates for future events are the planned dates at the time of writing. Missions slip, and we update articles when they do.

Articles are told in the voice of Otto Perihelion and checked by the Jupit editorial desk before they go out.

Nobody. We made him up.

Professor Otto Perihelion is the voice this site is written in, because the sky deserves better than a manual. He says “I” and we let him. He has no degree, no telescope and no employer, and any adventure he claims to have had did not happen.

The numbers he quotes are real. Each one is either calculated on the page or has a source listed under it, and when one is wrong we fix it and say so. Otto is made up. The facts are not.

Otto’s words are drafted with the help of an AI language model. Every figure in them is checked against the source listed with it, the calculations are tested against published values, and a person decides what is published. If something still reads wrong, the corrections address is the place to say so.

Every photograph on this site is real data from a spacecraft or a telescope, shown with its caption and its source. Where a picture is something else (an artist’s concept, a composite, a scan of a book) the caption says so. Many are in colours the eye would not see, because the light was infrared, ultraviolet or X-rays; the caption says that too.

No picture here was made by an image generator. If we ever use one it will be labelled “Illustration”. The globes on the instruments are drawn by this site from published maps, and each page says what is real in them and what is simplified.

When we get a fact wrong we fix the article and add a dated note at the end saying what changed. We do not edit errors away quietly.

If you find a mistake, or a picture credited wrongly, write to [email protected].

This site sets no cookies, runs no analytics and loads nothing from other companies. All the calculations happen in your browser.

If you set a place on Planets tonight or The whole sky tonight, it is remembered in your browser’s own storage on your device, so it is there next time, and it appears in the address bar so that a link you copy shows the same sky. If you press “Use my location”, your browser asks you first and the position is rounded to half a degree. None of this is sent to us. A date of birth typed into the birth-sky or other-worlds instruments is not stored at all.

Like any web server, the one that sends you these pages keeps a short log of requests: the address they came from, the time and the page asked for. A link that carries a place carries it into that log too. We use the log only to keep the site running.

The positions of the planets and moons are computed in your browser with Astronomy Engine, an open source library by Don Cross. Sizes, orbital periods and gravity come from NASA’s planetary fact sheets.

• Cassini's Best Maps of Jupiter (Cylindrical Map), PIA07782. Credit: NASA/JPL/Space Science Institute. Observed 11 and 12 December 2000. Resized from 3601 x 1801 pixels and converted to WebP. Nothing was retouched. Colour is close to natural, built from near-infrared and blue images. The clouds have moved since 2000, so the map shows how Jupiter turns but not its weather today.
• The Milky Way panorama, eso0932a. Credit: ESO/S. Brunier. Released 14 September 2009. Resized from 4000 x 2000 pixels and converted to WebP. Used as the sky behind the ray-traced black hole, where its light is bent by the calculation.
• Juno 3D Model. Credit: NASA Visualization Technology Applications and Development (VTAD). Published by NASA on 22 April 2019. Textures reduced to 1024 pixels; mesh compressed with Draco. Shape unchanged.
• Europa Clipper 3D Model. Credit: NASA Visualization Technology Applications and Development (VTAD). Published by NASA on 15 January 2022. Reduced from about 204,000 triangles to 60,000 with Blender's Decimate modifier; textures reduced to 1024 pixels; mesh compressed with Draco. The model predates launch and may differ in detail from the spacecraft as flown.
• CGI Moon Kit: LROC colour map and LOLA elevation map. Credit: NASA's Scientific Visualization Studio; data from the Lunar Reconnaissance Orbiter (LROC and LOLA teams). Released in 2019, from data gathered since 2009. Colour map resized and converted to WebP. The elevation map was turned into a map of surface slopes (scripts/moon-normal.py) at its real height scale, then resized. Used to draw the Moon on the Moon instrument. Slopes shade the surface but cast no shadows.
• Jupiter Marble, PIA22946. Credit: NASA/JPL-Caltech/SwRI/MSSS; image processing by Kevin M. Gill. 12 February 2019. Resized and converted to WebP. Nothing was retouched. Colour enhanced by the processor.
• Southern Storms, PIA21641. Credit: NASA/JPL-Caltech/SwRI/MSSS; image processing by Betsy Asher Hall and Gervasio Robles. Combined from three Juno orbits; released 25 May 2017. Resized and converted to WebP. Nothing was retouched. Enhanced colour, stereographic projection, every area shown in daylight.
• Close-up of Jupiter's Great Red Spot, PIA21772. Credit: NASA/JPL-Caltech/SwRI/MSSS; image processing by Jason Major. 10 July 2017, 7:10 p.m. PDT (11 July, 02:10 UTC). Resized and converted to WebP. Nothing was retouched. Colour enhanced by the processor.
• Global image of Io (true color), PIA02308. Credit: NASA/JPL/University of Arizona. Galileo spacecraft; released 27 August 1999. Resized and converted to WebP. Nothing was retouched.
• Europa's Stunning Surface, PIA19048. Credit: NASA/JPL-Caltech/SETI Institute. Galileo spacecraft, late 1990s; reprocessed and released 21 November 2014. Resized and converted to WebP. Nothing was retouched. Colour approximates what the eye would see.
• Juno's Ganymede Close-up, PIA24681. Credit: NASA/JPL-Caltech/SwRI/MSSS. 7 June 2021. Resized and converted to WebP. Nothing was retouched. Preliminary image through one (green) filter, so not in colour.
• Global Callisto in Color, PIA03456. Credit: NASA/JPL/DLR. Galileo spacecraft; released 22 August 2001. Converted to WebP. Nothing was retouched.
• Juno on Jupiter's Doorstep, PIA20701. Credit: NASA/JPL-Caltech/SwRI/MSSS. 21 June 2016. Converted to WebP. Nothing was retouched.
• Family Portrait of Jupiter's Great Red Spot and the Galilean Satellites, PIA00600. Credit: NASA/JPL/DLR. Galileo images from June and September 1996; Callisto from Voyager, 1979. Converted to WebP. Nothing was retouched. A composite arranged for the picture. The moons are not in their real positions.
• Europa Clipper Captures Infrared Image of Mars (Color Added), PIA26566. Credit: NASA/JPL-Caltech/ASU. 1 March 2025. Converted to WebP. Nothing was retouched. False colour showing temperature.
• Europa Clipper Artist's Concept, PIA26068. Credit: NASA/JPL-Caltech. Released 27 August 2024. Resized and converted to WebP. Nothing was retouched. An artist's concept, not a photograph. Labelled as such wherever it appears.
• An artist's concept depicting a Voyager spacecraft. Credit: NASA/JPL-Caltech. Published by NASA on 10 November 2026. Resized from 2048 x 1152 pixels and converted to WebP. Nothing was retouched. An artist's concept, not a photograph. Labelled as such wherever it appears.
• Position of Voyager 1 and Voyager 2 outside the heliosphere, PIA22835. Credit: NASA/JPL-Caltech. Read on 11 November 2026. Resized from NASA's 2048 x 1152 pixel JPEG rendition and converted to WebP. Nothing was retouched. A drawing, not a photograph or a plot of data. The source page does not say it is to scale.
• Hera's first close-up of Didymos. Credit: ESA. Released by ESA on 5 November 2026. Read on 12 November 2026. Converted from ESA's 1020 x 1020 pixel PNG to WebP. Nothing was retouched. Monochrome camera image. ESA's article gives the distance as 60 km and its image page says 600 km.
• Gemini South captures supernova SN 2026ahvu, noirlab2628a. Credit: International Gemini Observatory/​NOIRLab/​NSF/​AURA. Acknowledgments: PI: S. Dahm (NSF NOIRLab/Gemini). Image processing: J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), D. de Martin & M. Zamani (NSF NOIRLab). Released by NOIRLab on 12 November 2026. Read on 13 November 2026. Resized from NOIRLab's 2018 x 1759 pixel JPEG and converted to WebP. Nothing was retouched. The source page does not give the date the picture was taken.
• DECam observations before/after supernova SN 2026ahvu, noirlab2628c. Credit: Dark Energy Survey/​DOE/​FNAL/​DECam/​CTIO/​NOIRLab/​NSF/​AURA. Acknowledgment: PIs: G. Narayan & T. Murphey (University of Illinois at Urbana-Champaign). Image processing: M. Zamani & D. de Martin (NSF NOIRLab). Released by NOIRLab on 12 November 2026. Labels in the picture: 18 November 2018 and 5 November 2026. Read on 13 November 2026. Resized from NOIRLab's 3309 x 4648 pixel JPEG and converted to WebP. Nothing was retouched; the labels are NOIRLab's. A collage of two pictures. NOIRLab says the final composite also includes observations taken between 2013 and 2018.
• Hubble Takes Mars Portrait Near Close Approach. Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), J. Bell (ASU) and M. Wolff (Space Science Institute). 12 May 2016. Resized and converted to WebP. Nothing was retouched.
• First image of a black hole, eso1907a. Credit: EHT Collaboration. Observed April 2017; released 10 April 2019. Resized and converted to WebP. Nothing was retouched. Built from radio observations at a wavelength of 1.3 mm; the colour is chosen, not seen.
• Sample of Sidereus Nuncius drawings of Jupiter and the Medicean Stars. Credit: History of Science Collections, University of Oklahoma Libraries. Printed in Venice, March 1610. Resized and converted to WebP. Nothing was retouched.
• “Cosmic Cliffs” in the Carina Nebula (NIRCam image). Credit: NASA, ESA, CSA, STScI. Released 12 July 2022. Resized and converted to WebP. Nothing was retouched. Infrared light shown in visible colours.
• Global mosaics of Io (Galileo SSI and Voyager, colour merged, 1 km), Europa (Voyager and Galileo SSI, 500 m), Ganymede (Voyager and Galileo SSI, colour, 1.4 km) and Callisto (Voyager and Galileo SSI, 1 km). Credit: USGS Astrogeology Science Center; image data NASA/JPL. Voyager 1 and 2 (1979) and Galileo (1995 to 2003). Resized from the full mosaics and converted to WebP. Nothing was retouched. On the home page the black-and-white Europa and Callisto maps are tinted with the site's colour for each moon. Europa and Callisto have no global colour map here. Blurred and black areas are gaps in coverage.
• Panoramic Rings, PIA06175. Credit: NASA/JPL/Space Science Institute. Cassini natural-colour mosaic; released 11 February 2005. One line across the picture was sampled and stretched to real distances from Saturn using seven ring features with known radii (scripts/ring-profile.py). Opacity was estimated from brightness. The opacity is an estimate, not measured data. The innermost 2,000 km of the C ring is outside the photograph and repeats the nearest colour.
• Mars Viking colour global mosaic (925 m) and Mercury MESSENGER MDIS enhanced-colour global mosaic (665 m). Credit: USGS Astrogeology Science Center; image data NASA/JPL (Viking) and NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington (MESSENGER). Viking Orbiters (1976 to 1980); MESSENGER (2011 to 2015). Resized from the full mosaics and converted to WebP. Nothing was retouched. Mercury's map is in enhanced colour, which exaggerates differences the eye would not see.
• Hubble Goes High Def to Revisit the Iconic 'Pillars of Creation' (near-infrared view). Credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA). Hubble Space Telescope. Resized and converted to WebP. Nothing was retouched. Near-infrared light shown in visible colours.
• Southern Ring Nebula (NIRCam and MIRI images side by side). Credit: NASA, ESA, CSA, STScI. Released 12 July 2022. Resized and converted to WebP. Nothing was retouched. Infrared light shown in visible colours.
• The Helix Nebula: Unraveling at the Seams, PIA15817. Credit: NASA/JPL-Caltech. Released 3 October 2012. Resized and converted to WebP. Nothing was retouched. Infrared and ultraviolet light shown in visible colours.
• Most Detailed Image of the Crab Nebula, PIA03606. Credit: NASA/ESA/JPL/Arizona State University. Released 1 December 2005. Resized and converted to WebP. Nothing was retouched.
• NASA's Hubble Captures the Beating Heart of the Crab Nebula. Credit: NASA and ESA. Hubble Space Telescope. Resized and converted to WebP. Nothing was retouched.
• Cassiopeia A: Death Becomes Her, PIA03519. Credit: NASA/JPL-Caltech/STScI/CXC/SAO. Released 10 June 2005. Resized and converted to WebP. Nothing was retouched. False colour: infrared, visible light and X-rays.
• A Change of Seasons on Saturn - October, 1997, PIA03159. Credit: NASA and The Hubble Heritage Team (STScI/AURA); acknowledgment: R.G. French (Wellesley College), J. Cuzzi (NASA/Ames), L. Dones (SwRI) and J. Lissauer (NASA/Ames). Hubble Space Telescope, October 1997. One line down the middle of the disc was read and turned into colour by latitude, with the darkening toward the edge removed (scripts/saturn-bands.py). Latitudes behind the rings, in their shadow or too near the edge were copied from the same latitude in the other hemisphere. Belts only: the same at every longitude, no storms or spots, and as they were in 1997.
• Voyager 3D model, used in the film "Voyager 1, one light-day". Credit: NASA/JPL-Caltech.
• Blue Marble Next Generation, December 2004, topography and bathymetry, used in the same film. Credit: NASA Earth Observatory (Reto Stöckli).
• The Sun in extreme ultraviolet (AIA 304), 11 November 2026, used in the same film. Credit: Courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.
• Natural Earth, 1:110m land. Credit: Made with Natural Earth. Coordinates rounded to a hundredth of a degree.
• The Bright Star Catalogue, 5th Revised Edition (Preliminary Version). Credit: D. Hoffleit and W. H. Warren Jr, Astronomical Data Center, NSSDC/ADC (1991), via CDS catalogue V/50. Stars of visual magnitude 5.0 and brighter only: position, magnitude and B-V colour.
• IAU Catalog of Star Names. Credit: International Astronomical Union, Working Group on Star Names. Names matched to catalogue stars by HR number. Version of 4 April 2022.
• Paths of Juno, Juice and Europa Clipper. Credit: JPL Horizons, NASA Jet Propulsion Laboratory (Juice trajectory supplied to JPL by ESA). One position every two days, in the ecliptic plane, rounded to 0.0001 au. Refreshed with scripts/fetch-horizons.mjs; the fetch date is shown on the pages.
• Draco geometry decoder. Credit: Google, distributed with three.js. Unmodified.

The full list, with terms of use, is in credits.json.