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🌌 Astronomy & Cosmic Scale Converter

Convert astronomical distances, masses, and explore the cosmic scale

Common Astronomical Distances

1 AU = 149.6 million km
Earth-Sun distance
4.37 ly = 1.34 pc
Proxima Centauri
8.3 light-minutes = 1 AU
Light travel time to Sun
26,000 ly = 8 kpc
Distance to galactic center
2.5 million ly = 0.77 Mpc
Andromeda Galaxy
384,400 km = 0.0026 AU
Earth-Moon distance

Celestial Body Masses

1 Solar Mass = 333,000 Earth Masses
Our Sun
318 Earth Masses = 1 Jupiter Mass
Jupiter comparison
95 Earth Masses = 0.000285 Solar Masses
Saturn
81.3 Lunar Masses = 1 Earth Mass
Earth-Moon system
0.815 Earth Masses = 4.87×10²⁴ kg
Venus
0.107 Earth Masses = 6.42×10²³ kg
Mars

Cosmic Time Scales

13.8 billion years = 13,800 million years
Age of the Universe
4.54 billion years = 4,540 million years
Age of Earth
225 million years = 1 galactic year
Solar system orbit around galaxy
65 million years = 65,000 thousand years
Dinosaur extinction
200 thousand years = 200,000 years
Modern humans emergence
1 cosmic year = 13.8 billion years
Universe age unit

Astronomical Angular Measurements

0.5° = 30 arcminutes
Full Moon angular size
0.25 arcsec = 250 milliarcseconds
Stellar parallax threshold
1° = 3,600 arcseconds
Basic conversion
90° = π/2 radians
Quarter circle
1 arcmin = 60 arcseconds
Basic subdivision
0.76 arcsec = 760 mas
Proxima Centauri parallax

Stellar Brightness Examples

Sun: -26.7 apparent, +4.8 absolute
Our nearest star
Sirius: -1.46 magnitude
Brightest star in night sky
Vega: 0 magnitude (reference)
Magnitude system reference
6th magnitude = naked eye limit
Faintest visible stars
Full Moon: -12.6 magnitude
Brightest natural night object
30th magnitude = Hubble limit
Space telescope capability

Cosmic Distance Scale

Explore the vast scales of the universe, from our solar system to the observable universe

🌙
Earth-Moon
384,400 km • 0.0026 AU
1.3 light-seconds
☀️
Earth-Sun (1 AU)
149.6 million km
8.3 light-minutes
🪐
Solar System Edge
~40 AU • 6 billion km
5.5 light-hours
⭐
Nearest Star (Proxima)
4.37 light-years • 1.34 parsecs
268,000 AU
🌟
Galactic Center
26,000 light-years • 8 kpc
Center of Milky Way
🌌
Milky Way Diameter
100,000 light-years • 30 kpc
Our galaxy's span
🌠
Andromeda Galaxy
2.5 million light-years • 0.77 Mpc
Nearest major galaxy
🔭
Observable Universe
46.5 billion light-years • 14.3 Gpc
Current cosmic horizon

Stellar Parallax Calculator

Distance (parsecs) = 1 / Parallax (arcseconds)   |   1 parsec = 3.26 light-years
Enter either parallax angle or distance to calculate the other values

Magnitude & Distance Calculator

m - M = 5 × log₁₀(d) - 5   |   m = apparent magnitude, M = absolute magnitude, d = distance (pc)
Enter any two values to calculate the third (and light-year conversion)

Astronomical Constants & Reference Values

📏 Fundamental Distances
1 Astronomical Unit 149,597,870.7 km
1 Light-year 9.461 × 10¹² km
1 Parsec 3.086 × 10¹³ km
1 Parsec 3.26 light-years
1 Parsec 206,265 AU
⚖️ Celestial Masses
Solar Mass 1.989 × 10³⁰ kg
Earth Mass 5.972 × 10²⁴ kg
Jupiter Mass 1.898 × 10²⁷ kg
Lunar Mass 7.342 × 10²² kg
Sun vs Earth 333,000 × Earth
⏰ Cosmic Time Scales
Age of Universe 13.8 billion years
Age of Earth 4.54 billion years
Age of Solar System 4.6 billion years
Galactic Year 225 million years
Sun's Lifetime ~10 billion years
💫 Notable Objects
Proxima Centauri 4.37 light-years
Andromeda Galaxy 2.5 million ly
Galactic Center 26,000 light-years
Betelgeuse ~650 light-years
Observable Universe 46.5 billion ly radius

Astronomical Units Quick Reference

Unit Symbol Equivalent Used For Examples
Astronomical Unit AU 149.6 million km Solar system distances Planetary orbits, asteroid distances
Light-year ly 9.46 trillion km Interstellar distances Nearby stars, stellar neighborhoods
Parsec pc 3.26 light-years Professional astronomy Stellar distances, parallax measurements
Kiloparsec kpc 1,000 parsecs Galactic distances Star clusters, galactic structure
Megaparsec Mpc 1 million parsecs Intergalactic distances Nearby galaxies, galaxy clusters
Gigaparsec Gpc 1 billion parsecs Cosmological distances Distant galaxies, universe structure