Recording Star Reverberations

Stars have been a common subject over the last year primarily because there are many parts of astrophysics that are still a mystery. The brilliant thing about astronomy is that it is a part of physics that anyone can take part in. Even the most amateur astronomer can use basic photometry to  learn something about an observed object. Photometry is just recording the brightness of an object over a period of time. If an object dims it is probably because something is moving across it and blocking out some of the light. If a star is being observed its probably an exoplanet and if it is another planet in our solar system dimming it must be one of their moons. Professional photometry isn’t performed from the ground (and when it is its normally done on top of mountains in the Bahamas or the like) it is usually done from telescopes positioned in space. The most famous of these, The Kepler Space Telescope, has been recording the brightness of a white dwarf for three months (exactly 78.7 days).

This star has only half the mass of The Sun but five times the surface temperature and has an almost complete helium atmosphere. This means that it is actually a variable star with a constantly changing luminosity, the hottest white dwarf that has ever been recorded to pulsate. By observing a change in luminosity, probably brought about by a solar spot, the rotation of the white dwarf was also calculated to be about 10.2 hours. This star also demonstrates some unique astroseismology, the equivalent to earthquakes for a star. Standing waves form inside the star’s plasma and these oscillating modes can reveal details about the star’s internal structure. This white dwarf, however, contained eleven completely independent modes which allow researchers check on their rotation estimate. This information goes into a growing database focused on answering the questions of stellar evolution one of the many things that astrophysics still needs to work out.


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