How Big Is the Sun? From the Moon to Giant Stars at the Same Scale | Scale Side by Side #02
Short answer
- The Sun is far larger than any planet — yet some stars spread out beyond Jupiter's orbit.
- Of the 372 stars within about 32.6 light-years of the Sun, about 75% are red dwarfs.
- Proxima Centauri has about 0.12 solar masses (about 130 Jupiters); about 80 Jupiter masses is the rough guide for sustained hydrogen fusion.
Video
Pressing play loads the YouTube player on this page. Watch on YouTube
Explained
In the video
- 0:00Is the Sun big or small?
- 0:18Moon and Earth: what's the difference between a moon and a planet?
- 0:45How big are the giant planets?
- 0:59How big is the Sun?
- 1:31Proxima Centauri: how big is the nearest star?
- 2:20How big is Sirius?
- 2:34How big is Aldebaran? What about Earth's path?
- 2:59How big is Betelgeuse?
- 3:34How big is VY Canis Majoris?
- 3:58How many stars are near the Sun?
- 4:46What if we line everyone up at the same scale? (Orion)
Is the Sun a big star or a small one? We line up the Moon, Earth, Jupiter, the Sun, and other stars in 3D at the same scale.
Comparison data
We compare diameter: the width from one side to the other. Solar System objects are listed in kilometers (km); other stars use the same diameter ratios shown in the video.
| Object | Diameter (width) | Type of value |
|---|---|---|
| Moon | 3,475 km | From NASA tables |
| Mercury | 4,879 km | From NASA tables |
| Ganymede (a moon of Jupiter) | 5,262 km | From NASA tables |
| Mars | 6,779 km | From NASA tables |
| Venus | 12,104 km | From NASA tables |
| Earth | 12,742 km | From NASA tables |
| Neptune | 49,244 km | From NASA tables |
| Uranus | 50,724 km | From NASA tables |
| Saturn (body only, excluding rings) | 116,464 km | From NASA tables |
| Jupiter | 139,822 km | From NASA tables |
| Proxima Centauri | About 1.5 × Jupiter's diameter | Published value |
| Sun | About 1.39 million km | From NASA tables |
| Sirius A (the brighter star of the pair) | About 1.7 × the Sun's diameter | Published value |
| Aldebaran | About 45 × the Sun's diameter | Published value; measurements vary |
| Betelgeuse | About 760 × the Sun's diameter (estimate) | Published estimate |
| VY Canis Majoris | About 1,400 × the Sun's diameter (estimate) | Published estimate |
The kilometer values are mean diameters: the diameter of a sphere with the same volume as the object. Values are rounded as in the video. Estimates of Betelgeuse's and VY Canis Majoris's sizes vary between studies. The red rings are circles drawn at the planets' average distances from the Sun; they compare only how far a star would reach if placed where the Sun is.
What this episode shows
- The Sun is about 109 times as wide as Earth.
- Placed where the Sun is, Betelgeuse would contain Earth's entire orbit, while VY Canis Majoris would contain even Jupiter's orbit.
- The Sun is small beside giant stars, but large among its neighbors. About three in four nearby stars in the video's census are red dwarfs: small, reddish stars.
Shorts
Sources
Where the facts and numbers in the video and on this page come from.
- NASA NSSDCA — Planetary Fact Sheets (Mean diameters of the Moon, the eight planets, and the Sun, plus Earth's and Jupiter's orbital distances. Diameters are twice the tabulated radii)nssdc.gsfc.nasa.gov/planetary/factsheet
- NASA NSSDCA — Jovian Satellite Fact Sheet (Ganymede's radius, doubled to obtain its diameter)nssdc.gsfc.nasa.gov/planetary/factsheet/joviansatfact.html
- arXiv — Kervella et al. (2017) (Proxima Centauri's size. The adopted radius of 0.1542 times the Sun's is used to calculate its diameter relative to Jupiter's)arxiv.org/abs/1611.03495
- arXiv — Kervella et al. (2003) (Sirius A's diameter, 1.711 times the Sun's)arxiv.org/abs/astro-ph/0306604
- arXiv — Hatzes et al. (2015) (Aldebaran's radius. The video uses 45.1 times the Sun's radius; measurements range from 36 to 46 times)arxiv.org/abs/1505.03454
- arXiv — Joyce et al. (2020) (Betelgeuse's radius, using versions 4–5: 764 times the Sun's radius, with an estimated range of 702–880. Rounded to about 760 in the video)arxiv.org/abs/2006.09837
- arXiv — Wittkowski et al. (2012) (VY Canis Majoris's radius, 1,420 ± 120 times the Sun's, rounded to about 1,400 in the video. A radius ratio is also a diameter ratio)arxiv.org/abs/1203.5194
- CDS — Reylé et al. (2021), nearby-star catalogue (August 2023 update, covering stars within about 32.6 light-years of the Sun—the distance light travels in about 32.6 years. The video's census includes the Sun: 280 of 372 stars are counted as red dwarfs, including 34 close companions whose types are uncertain)cdsarc.cds.unistra.fr/ftp/J/A+A/650/A201
- University of Rochester — Pecaut & Mamajek, stellar types and sizes (Typical sizes used for the nearby-star lineup. Stars with measured sizes use those values; the others use sizes inferred from their types)pas.rochester.edu/~emamajek/EEM_dwarf_UBVIJHK_colors_Teff…
- Reylé et al. 2021 (the Sun's neighbors)arxiv.org/abs/2104.14972
- Saturnian Rings Fact Sheetnssdc.gsfc.nasa.gov/planetary/factsheet/satringfact.html
- NASA Space Place "How big is the Sun?"spaceplace.nasa.gov/sun-compare/en
- NASA Ganymedescience.nasa.gov/jupiter/jupiter-moons/ganymede
- NASA Jupiter Factsscience.nasa.gov/jupiter/jupiter-facts
- SIMBAD (Gaia EDR3 and Hipparcos parallaxes)simbad.cds.unistra.fr
- NASA "Hubble Solves Mystery of Monster Star's Dimming"science.nasa.gov/missions/hubble/hubble-solves-mystery-o…
- RECONSrecons.org/census.posted.htm
- IAU 2006 Resolution B5iauarchive.eso.org/static/resolutions/Resolution_GA26-5-6.…
- IAU Measuring the Universeiauarchive.eso.org/public/themes/measuring
- NASA Star Typesscience.nasa.gov/universe/stars/types
- Moonlightscience.nasa.gov/moon/facts
- Moonlightscience.nasa.gov/moon/moonlight
- NASA Sun Factsscience.nasa.gov/sun/facts
- Caltech/IPAC Cool Cosmoscoolcosmos.ipac.caltech.edu/page/low_mass_stars_brown_dwarfs
- NASA Night Sky Network "Meet the Workaholic Star Betelgeuse"science.nasa.gov/solar-system/skywatching/night-sky-netw…
- NASA SVS "CGI Moon Kit" (lroc_color_16bit_srgb_4k.tif)svs.gsfc.nasa.gov/4720
- NASA Earth Observatory "Blue Marble: Next Generation with Topography and Bathymetry" (world.topo.bathy.200407)science.nasa.gov/earth/earth-observatory/blue-marble-nex…
- USGS "Mercury MESSENGER MDIS Basemap MD3 Color Global Mosaic 665m"astrogeology.usgs.gov/search/map/mercury_messenger_mdis_basem…
- USGS "Mars Viking Colorized Global Mosaic 232m" (Mars_Viking_MDIM21_ClrMosaic_1km)astrogeology.usgs.gov/search/map/mars_viking_colorized_global…
- NASA Photojournal "Cassini's Best Maps of Jupiter (Cylindrical Map)" PIA07782science.nasa.gov/photojournal/cassinis-best-maps-of-jupi…
- USGS "Ganymede Voyager - Galileo SSI Color Global Mosaic 1.4km"astrogeology.usgs.gov/search/map/ganymede_voyager_galileo_ssi…
- NASA SVS "Growing Sunspots - A Full Disk View: February 2011" (HMIsunspot.01900.jpg)svs.gsfc.nasa.gov/3897
- ESO "SPHERE's view of Betelgeuse in January 2019" eso2003beso.org/public/images/eso2003b
- NASA "VY CMa" (Hubble Space Telescope, WFPC2)science.nasa.gov/asset/hubble/vy-cma
- ESO "Orion constellation" orion-ch17-bardon-cceso.org/public/images/orion-ch17-bardon-cc
- ESO "The Milky Way panorama" eso0932aeso.org/public/images/eso0932a
- ESO image license (CC BY 4.0)creativecommons.org/licenses/by/4.0
Voice, music, art
- Music (OpenTracks): “キューブスカイ” by かずち / “宇宙の神秘” by 田中芳典 / “星屑サラウンド-1chorus-” by 龍崎一
- Sound effects: made by Tamelabo, mixing CC0 recordings from Freesound (taiko, tape rewind, small bell)
- Voice: synthetic narration (series narrator)
