For standard candles, the team used Cepheid variable stars
, which pulsate at a rate that is correlated with their brightness, and type la supernovas, whose brightness properties are well-understood.
The distances to all other galaxies, hence their deduced physical sizes, would double in the 7950s following Walter Baade's landmark reevaluation of how Cepheid variable stars
are used as distance indicators.
Oscillations occur not only in mechanical systems but also in dynamic systems in virtually every area of science: for example the beating human heart, business cycles in economics, predator-prey population cycles in ecology, geothermal geysers in geology, vibrating strings in musical instruments, periodic firing of nerve cells in the brain, and the periodic swelling of Cepheid variable stars
This portion of the electromagnetic spectrum has numerous advantages, especially when observing Cepheid variable stars
, the so-called "standard candles" that are used to determine distances to distant galaxies.
We present analysis of two double model Cepheid variable stars
, BQ Serpens and VX Puppis.
Since the launch of NASA's Hubble Space Telescope in 1990, the team has observed 18 galaxies up to 65 million light years away and discovered almost 800 Cepheid variable stars
, a special class of pulsating star used for accurate distance measurement.
This was, more or less, how Tom Osypowski introduced me to V42 and V84, M5's two Type II Cepheid variable stars
, at the 2013 Golden State Star Party.
Caption: Astronomers measure distance to faraway galaxies--a key to the Hubble constant--by recording the brightness of supernovas and Cepheid variable stars
All Cepheid variable stars
of a given type that vary at a specific rate have the same inherent brightness.
In the "local" universe, they use standard candles such as exploding white dwarfs or Cepheid variable stars
The stable of standard candles already houses phenomena known as type la supernovas and Cepheid variable stars
, which have predictable luminosities but are good for measuring distances only to objects present when the universe was nearly 4 billion years old.
Double stars, Cepheid variable stars
, Viewing galaxies, Black holes, Main-sequence stars, Globular clusters, Discovery of Proxima, Extra-solar planets, Open star clusters, Sub-giant stars, Nebulae, Yellow-dwarf star, Barred spiral galaxies, Galaxies and time, Close double stars, Coloured double stars, Super galaxy clusters, Mira variable stars, Giant stars, Carbon stars, Observing double stars, Solar type stars, Nicolas Louis de Lacaille, Astrophotography, Light year, Sub-dwarf stars, Venial equinox, Hot Jupiters, Delta-Scuti variable star, Apparent brightness.