Astrophysics
Astrophysics
Calculators & Tools
Light Year Calculator
The Light Year Calculator converts any distance (km, miles, AU, ly, parsecs, Mpc, Gly) into all five light-time units simultaneously: light-seconds, light-minutes, light-hours, light-days, and light-years. Includes 15 famous presets (Solar System, Nearby Stars, Deep Space), a communication delay panel showing one-way and round-trip signal time, and a travel time comparison table with Parker Solar Probe, Voyager 1, New Horizons, and hypothetical 1%, 10%, 20% c spacecraft.
Schwarzschild Radius Calculator
The Schwarzschild Radius Calculator works out the event horizon size of any mass using r_s = 2GM/c². Enter a mass in kilograms, Earth, Jupiter, solar, or billion solar masses and it returns the Schwarzschild radius, photon sphere, innermost stable orbit, surface gravity, and average density inside the horizon. It also computes the tidal stretch a body would feel at the horizon with a survival verdict, revealing why small black holes spaghettify you while supermassive ones can be crossed unharmed. Presets run from a proton to the ultramassive quasar TON 618.
Luminosity Calculator
Computes stellar luminosity from radius and temperature using the Stefan-Boltzmann law (L = 4πR²σT⁴). Returns luminosity in watts and L☉, absolute magnitude, OBAFGKM spectral type with color, habitable zone boundaries (Kopparapu 2013), implied main-sequence mass, optional apparent magnitude at a given distance, and optional main sequence lifetime from mass input. Six famous star presets: Proxima Centauri, Sun, Vega, Sirius A, Rigel, Betelgeuse.
Black Hole Temperature Calculator
The Black Hole Temperature Calculator computes the Hawking temperature of any black hole from its mass using T = hbar x c^3 / (8 x pi x G x M x k_B). Enter a mass in solar masses or kilograms to get Hawking temperature, Schwarzschild radius, evaporation time, radiation power, peak emission wavelength, and CMB status. Bidirectional: also converts from a known temperature back to mass.
Redshift Calculator
The Redshift Calculator converts between redshift z, wavelength, and velocity using z = (λ_obs − λ_em)/λ_em. Enter a redshift, a pair of wavelengths, or a velocity, and it returns z, the wavelength stretch factor, the cosmological scale factor, and two velocity readings: the naive cz and the relativistic Doppler velocity that stays below light speed. It handles blueshift, shows where real spectral lines land at any redshift, and includes a gravitational redshift explorer for compact objects. Presets range from the approaching Andromeda Galaxy to the cosmic microwave background at z = 1089.
Black Hole Collision Calculator
The Black Hole Collision Calculator computes the outcome of two black holes merging. Enter both masses in solar masses to get the Schwarzschild radius of each, estimated gravitational wave radiation efficiency, final merged mass, final event horizon radius, total GW energy released, and peak gravitational wave frequency. Based on LIGO GW150914 merger physics and the symmetric mass ratio approximation.
Parallax Calculator
The Parallax Calculator converts a star’s parallax angle into distance and back using d(pc) = 1/p(arcsec). Enter parallax in arcseconds, milliarcseconds, or microarcseconds to get distance in light-years, parsecs, AU, and km, or enter a distance to get the parallax angle. It adds an asymmetric distance uncertainty band from a measurement error, an instrument-reach verdict comparing naked eye, Hipparcos, and Gaia precision, and optional tangential velocity from proper motion. Six presets use real Gaia and Hipparcos parallaxes.
Universe Expansion Calculator
The Universe Expansion Calculator computes the age of the universe at any redshift by integrating the Friedmann equation of the Lambda Cold Dark Matter model. Enter a redshift and a cosmology to get the current age, the age at that redshift, the lookback time, the scale factor, the Hubble rate then, and the dominant expansion era (radiation, matter, or dark energy). It lets you build your own universe with adjustable H0, matter, and dark energy densities, and projects its ultimate fate from eternal de Sitter acceleration to a Big Crunch. Planck 2018 returns the accepted age of 13.79 billion years.
Hubble Law Distance Calculator
The Hubble Law Distance Calculator computes comoving distance, recession velocity, and lookback time from redshift, distance, or velocity input using FLRW flat LCDM numerical integration. Includes an H0 selector (Planck 67.4, DESI 68.5, SH0ES 73.0, custom), famous object presets (Virgo Cluster, Coma Cluster, 3C 273, GN-z11), a superluminal recession flag with GR explanation, and a unique H0 Tension panel comparing Planck vs SH0ES results side by side.
Olbers' Paradox Calculator
The Olbers' Paradox Calculator works out how bright the night sky should be from the star density, average stellar luminosity and radius, and the age of the universe. It returns the integrated night-sky flux compared to daylight and full moonlight, the look-out limit, the fraction of sky covered by stellar disks, and a dark, twilight, or blazing verdict. Use it to see quantitatively why a finite universe age keeps the night sky dark and how redshift turned the predicted bright sky into the cosmic microwave background.
Drake Equation Calculator
The Drake Equation Calculator estimates the number of communicating civilizations currently present in the Milky Way galaxy by multiplying seven factors: star formation rate, planet formation rate, habitability, emergence of life, emergence of intelligence, development of technology, and civilization lifespan. Adjust all seven variables or choose from four famous presets including Frank Drake's original 1961 values and Carl Sagan's optimistic estimate. The result includes N, the average distance to the nearest civilization, and a Fermi Paradox interpretation of your output.
Radiation Pressure Calculator
The Radiation Pressure Calculator computes the pressure, force, and acceleration that light exerts on a surface using P = (1+r)I cos²θ/c. It works from sunlight at any distance, a custom intensity, or a laser beam power, and handles absorbing or reflecting surfaces. Beyond the basic force, it returns the lightness number β, the distance-independent ratio of radiation force to solar gravity that decides whether a solar sail can escape the Sun, along with areal density versus the 1.53 g/m² critical threshold. Real mission presets include IKAROS, LightSail 2, and Breakthrough Starshot.