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Pulsating Stars

 Spherical degree l = 1 l = 2 l = 3 Azimuthal order m = -1 m = 0 m = +1 m = -1 m = 0 m = +1 m = -1 m = 0 m = +1 m = -2 m = -1 m = 0 m = +1 m = +2 m = -2 m = -1 m = 0 m = +1 m = +2 m = -2 m = -1 m = 0 m = +1 m = +2 m = -2 m = -1 m = 0 m = +1 m = +2 m = -2 m = -1 m = 0 m = +1 m = +2 m = -3 m = -2 m = -1 m = 0 m = +1 m = +2 m = +3 m = -3 m = -2 m = -1 m = 0 m = +1 m = +2 m = +3 m = -3 m = -2 m = -1 m = 0 m = +1 m = +2 m = +3 m = -3 m = -2 m = -1 m = 0 m = +1 m = +2 m = +3 m = -3 m = -2 m = -1 m = 0 m = +1 m = +2 m = +3 m = -3 m = -2 m = -1 m = 0 m = +1 m = +2 m = +3 m = -3 m = -2 m = -1 m = 0 m = +1 m = +2 m = +3
Images from Asteroseismology.org
All through the galaxy, we find stars that pulsate. Gravity makes stars spherically symmetric. Because of this symmetry, we can describe the pulsations with mathematical functions called spherical harmonics. The patterns of these functions depend on two numbers, usually called the spherical degree ("l") and the azimuthal order ("m").

The spherical degree changes the total number of hot and cool zones on the surface. The azimuthal order can only be between "-l" and "+l", and changes how the hot and cool zones are distributed on the surface of the star.

From a distance, we can only see the brightness of a star change when the spherical degree is small. Play with the values of "l" and "m" to see some of the different ways stars can pulsate.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information.