How do cepheid variables form

Delta Cephei, for which this class of star is named, was discovered a few months later by amateur English astronomer John Goodricke. In , during an investigation of variable stars in the Magellanic Clouds, American astronomer Henrietta Swan Leavitt discovered the relationship between the period and luminosity of Classical Cepheids.

After recording the periods of 25 different variables stars , she published her findings in In the following years, several more astronomers would conduct research on Cepheids. By , Edwin Hubble was able to establish the distance between the Milky Way and the Andromeda Galaxy based on Cepheid variables within the latter.

These findings were pivotal, in that they settled the Great Debate , where astronomers sought to established whether or not the Milky Way was unique, or one of many galaxies in the Universe.

In short, they were able to prove that the Universe is in a state of expansion, something that had been suggested years prior. Further developments during the 20th century included dividing Cepheids into different classes, which helped resolve issues in determining astronomical distances. This was done largely by Walter Baade, who in the s recognized the difference between Classical and Type II Cepheids based on their size, age and luminosities.

Despite their value in determining astronomical distances, there are some limitations with this method. Chief among them is the fact that with Type II Cepheids, the relationship between period and luminosity can be effected by their lower metallicity, photometric contamination, and the changing and unknown effect that gas and dust have on the light they emit stellar extinction. Resolving this discrepancy is one of the largest problems in modern cosmology, since the true size and rate of expansion of the Universe are linked.

However, improvements in instrumentation and methodology are increasing the accuracy with which Cepheid Variables are observed. In time, it is hoped that observations of these curious and unique stars will yield truly accurate values, thus removing a key source of doubt about our understanding of the Universe. We have written many interesting articles about Cepheid Variables here at Universe Today. They can then use the distance modulus to calculate the distance to the supernova, and the galaxy that it is in.

Type Ia supernovae can be used to measure distances from about 1 Mpc to over Mpc. A Cepheid variable star has a period of 3. Its apparent magnitude is 5. How far away is this Cepheid variable star? Magnitude and Color What is distance modulus? Calculations and questions based on distance modulus Comparing the magnitudes of different objects.

Both teams independently arrived at the the conclusion that not only is our Universe expanding but it is actually accelerating, a result that the prestigious American magazine Science announced was the research advance of One of its major initial observational programs, dubbed the Hubble Key Project, was aimed at refining and calibrating the extragalactic distance scale by observing Cepheids in other galaxies.

The goal was to use the recalibrated scale to calculate a more precise value for the Hubble Constant, H 0 which at that time was measured as somewhere between 50 and km s -1 Mpc -1 kilometres per second per megaparsec depending on the method used. The international team of astronomers discovered many new cepheids in the 18 galaxies they studied. In the giant spiral M81, for instance they found 32 Cepheids to add to only two that had been found previously using ground-based telescopes.

Using the HST they made 22 twenty-minute exposures of each of two fields in M 81containing the Cepheids. Once the data from these was reduced they were able to calculate a distance to M 81 of 3. This value was based on the results of the Cepheid studies which were then combined with other techniques such as observations of Type Ia supernovae, Type II supernovae, the Tully-Fisher relation and the surface brightness of galaxies. Skip to main content.

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Discovery of the Period - Luminosity Relationship. HST images of Cepheids in M