Cepheid variables
Cosmic distance candles
Cepheid variables are stars that pulsate in a regular cycle, brightening and dimming over periods of days to months.
Their importance to astronomy lies in a predictable relationship between pulsation period and luminosity—longer periods mean brighter stars.
This allows astronomers to calculate distances to far-off galaxies by comparing observed brightness to actual brightness: Hubble used Cepheid variables to prove galaxies existed beyond the Milky Way.
Huge luminous evolved star
- F-typeJaguar sports car
- PolarisCelestial north marker
- giant starMassive evolved stellar body
- instabilityTendency toward unpredictable change
Calibrated sequence of astronomical measurements
- extragalacticBeyond any galaxy's bounds
- AndromedaNearest spiral galaxy
- Magellanic CloudsNearby dwarf galaxies visible south
- galaxiesGravitationally bound stellar assemblies
redshift · cosmological · parallax · megaparsec · Hubble · Edwin Hubble · observable universe · distance measurement
Measuring light intensity
- magnitudeSize or scale
- luminosityIntrinsic brightness of source
- spectroscopyStudy of light-matter interaction
- telescopeInstrument magnifying faraway objects
observatory · time series · monitoring · survey · detection · measurement · calibration · data analysis
Repeated back-and-forth movement
- periodicityRecurring at regular intervals
- expansionIncrease in scope
- contractionReduction in size
- cycleRepeating sequence of events
amplitude · ionization · shockwave · phase · envelope · opacity · rhythmic
supergiant
Huge luminous evolved star
- F-typeJaguar sports car
- PolarisCelestial north marker
- giant starMassive evolved stellar body
distance ladder
Calibrated sequence of astronomical measurements
- extragalacticBeyond any galaxy's bounds
- AndromedaNearest spiral galaxy
- Magellanic CloudsNearby dwarf galaxies visible south
galaxies · redshift · cosmological · parallax · megaparsec · Hubble · Edwin Hubble · observable universe · distance measurement
photometry
Measuring light intensity
- magnitudeSize or scale
- luminosityIntrinsic brightness of source
- spectroscopyStudy of light-matter interaction
telescope · observatory · time series · monitoring · survey · detection · measurement · calibration · data analysis · Gaia
oscillation
Repeated back-and-forth movement
- periodicityRecurring at regular intervals
- expansionIncrease in scope
- contractionReduction in size
cycle · amplitude · ionization · shockwave · phase · envelope · opacity · rhythmic
- Celestial Objectsstars, planets, moons, comets, galaxies
- starsstars, Sirius, Polaris, sol, sun
- Stellar Astronomystellar populations, red giants, white dwarfs, dwarf stars, giant stars
- Variable StarsMira, Betelgeuse, Polaris, nova, novae
- Galaxiesgalaxy, galaxies, Milky Way, spiral galaxy, Andromeda
- galaxy partsgalactic core, spiral arms, galactic center, spiral arm, nucleus