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- Imagine the Universe!
Difficulties in Using Cepheids to Determine the Size of the Universe There have been a number of difficulties associated with using Cepheids as distance indicators Until recently, astronomers used photographic plates to measure the fluxes from stars The plates were highly non-linear and often produced faulty flux measurements
- Science - Imagine the Universe!
Explore a universe of black holes, dark matter, and quasars A universe full of extremely high energies, high densities, high pressures, and extremely intense magnetic fields which allow us to test our understanding of the laws of physics
- Cosmic Times - Imagine the Universe!
Although Hubble’s work presents a tremen dous breakthrough in our understanding of the universe, one big question remains How far out into the universe does his model hold? The 100 inch telescope can resolve Cepheids in only the nearest nebulae In nebulae where Cepheids are barely visible, Hubble has identified the most luminous individual stars, some 50 to 100 times brighter than the
- Cosmic Times - Imagine the Universe!
Shapley included "Cepheids" from globular clusters in his calibration of the period-luminosity relationship, which will become important in the next issue of the Cosmic Times It was this calibration of the relationship that Hubble used when he observed Cepheid variables in the Andromeda Nebula Observing Andromeda
- Cosmic Times - Imagine the Universe!
The true brightness of the Cepheids in the nebulae Hubble studied was known from how the Cepheid changes its brightness Scientists had already known exactly how light dims over distance The distance to the star, and the nebula it is located in, can be found by comparing the apparent brightness of these stars to their true brightness
- Cosmic Times - Imagine the Universe!
Cepheids were identified as standard candles in 1912 by Henrietta Leavitt But it turns out that not all Type Ia supernovae are equal, either Scientists have discovered that they show a pattern of brightening and fading over several days and that the pattern varies a great deal
- Imagine the Universe!
The distance to the galaxy can be determined using observations of certain types of pulsating stars, called Cepheids, whose instrinsic brightness is related to the period of their brightness variation However, the accuracy of the distance measurement was hampered by how faint ground based telescopes could see
- Cosmic Times - Imagine the Universe!
Here she noticed that brighter Cepheids pulsed slower than dimmer Cepheids This was interesting, because all the stars in the Magellanic Clouds are basically the same distance from Earth, so it suggested that the rate at which those Cepheids were pulsing was a clue to their real brightness (or luminosity)
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