Unusual Stars
June 28th 2011 04:10
Category: Stars
animation shows the star changing its luminosity over a period of 30 days.
HST Hubble image taken of M31_V1 the first Cepheid Variable star in M31 discovered by Edwin Hubble, some eighty odd years ago.
The stars called Cepheids are very unusual stars. Cepheid variable stars are large, the average mass of a typical cepheids is in the order of five to twenty times the mass of our Sun. Unlike supernova’s a Cepheid star’s brightness can alter and dim. Its relevant brightness can vary anywhere between bright to dull, this process may take a few months.
The star can alter its state in a cyclic manner. The star may start out to be somewhat compact in size soon large temperature and pressure gradients build up in the star. These larger pressures cause the star to expand.
When the star has fully expanded the gravity pressure gradient in the star weakens. Without the pressure gradient to support the star against gravity, the star deflates and contracts and the star returns to its compressed state. The altering states is why Cepheid star grow brighter and dimmer on a regular cycle.
Cepheid variable stars have very useful properties, they are very bright and their period of pulsation is related to their average variance in luminosity occurs in a timely manner. Because of these properties, an astronomer can determine the distance to a Cepheid variable by measuring its period and its apparent brightness.
The luminosity of a Cepheid variable star was obtained by using photographic glass plates.
Photographic plates were highly non-linear and often produced measurements that were not accurate.
The accuracy increased with the use of more modern CCD cameras the images taken with these devices the distances of these particular stars could be measured more accurately.
Other stars can exhibit variance in luminosity. Algol variables stars belong to a class of eclipsing binary stars.
These stars orbit very close to each other and can eclipse each other causing the luminosity to change over a very short period usually measured in days. Cepheids and Algol variables stars are common throughout the universe.
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Comment by S.L.
The Political Brief
Comment by CMoreStars
Astroearth
Camera Sense
For the most part Cepheids return back to their normal state. It is possible that they have some planetary bodies.