|Saxena, Ajay K. Principles of Modern Physics. Oxford: Alpha Science, 2005.||"The sunspots are found to move across the disc from day-to-day; from this it is inferred that the Sun rotates with a period of about 25 days at its equator."||25 days|
|"Sun." The Columbia Encyclopedia, Sixth Edition. 2008.||"Observations of sunspots and studies of the solar spectrum indicate that the sun rotates on its axis from east to west; because of its gaseous nature its rate of rotation varies somewhat with latitude, the speed being greatest (a period of almost 25 days) in the equatorial region and least at the poles (a period of almost 35 days."||25-35 days|
|Stallo Bernhard, John. The Concepts and Theories of Modern Physics. New York: Adamant, 2000.||"We are able to test this question mathematically, by calculating from the sun's actual period of rotation, which is twenty-five and three tenths days, what would be the velocity of rotation if, conserving the sum of the areas described by all its material points, it were expanded so that its radius, which is now equal to one hundred and twelve times the equatorial radius of the earth, became equal to the distance from the earth to the sun, or from Neptune to the sun."||25.3 days|
|White, Charles Joyce. The Elements of Theoretical and Descriptive Astronomy for Use of Colleges and Academics. New York: Wiley, 1890: 100.||"The period of rotation is about 25 days, and the plane of rotation is inclined 7° to the ecliptic."||25 days|
|Hamilton, Calvin J. Sun. Views of the Solar System, 1997-2007.||"The Sun's period of rotation at the surface varies from approximately 25 days at the equator to 36 days at the poles. Deep down, below the convective zone, everything appears to rotate with a period of 27 days."||25-36 days|
The period of rotation of the sun is determined by use of sunspots. Sunspots which are cyclonic disturbances in the photosphere of the sun are found to move across the solar disk from day to day.They differ widely in duration, sometimes lasting for several months and sometimes disappearing in the course of a few hours. The plane of rotation of these sunspots are inclined seven degrees to the ecliptic. The motion of sunspots determine the rate of rotation at a particular latitude. The sun doesn't rotate as a solid body, but rather varies its rotation period from the equator to the poles. The various rotation periods may also vary with time. Sunspots move by small amounts over the surface of the sun, but these movements are small enough that they may be ignored and therefore sunspots may be used to determine the rotation of the sun.
The sun rotates on its axis from east to west. The sun as a whole has no single period of rotation, but different portions of its surface perform their revolutions in different times. The equatorial regions move more rapidly than the rest of the solar surface, and as a result they also complete the entire rotation in shorter time. The period of rotation of the sun varies somewhat with latitude, (at higher latitudes the sun tends to rotate more slowly), but it is estimated that the sun's period of rotation at the surface varies from about 25 days at the equator to about 35 days at the poles.
Chelsea Edobor -- 2008
|Ebbinghausen, E. G. Astronomy. 5th ed. Merrill, 1985.||"The sun's roational period is about 25 days at the equator,
27 days at 35 degrees latitude,
33 days at 75 degrees latitude, and about 35 days near the poles."
|Handbook of Chemistry and Physics. 61st ed. Florida: CRC Press, 1980.||"Physical data: (period of rotation sidereal days) sun 24.66225±.00003"||24.66225 days|
|Gutsch, William A. 1001 Things Everyone Should Know About the Universe. New York: Doubleday, 1998.||"At the equator, the sun turns around once in about 25 earth days."||25 days|
|Pananides, Nicholas A. Introductory Astronomy. Massachusetts: Addison Wesley, 1979.||"The rotation period at the equator is 25 days and increases to 27½ days at latitude 30 degrees. The period increses to 35 days at latitude 75 degrees."||25–35 days|
|Goth, George. The Magnitude of Physics. The Physics Teacher. December 1996.||"… period of rotation of sun: 2.125 × 106"||24.59 days|
The movement of solar surface features (sunspots) show that the sun is in rotation about its axis. Observations also reveal that the sun's equator is inclined about seven degrees to the plane of the ecliptic. The sun rotates from west to east in the same direction as the earth. However unlike the earth, the sun does not rotate as a solid body.
The motion of sunspots determine the rate of rotation at a particular latitude. Sunspots are fairly circular structures that contain two well-defined parts. The spots occur in pairs or in groups, however with two main spots. The line that joins the centers of a pair is almost parallel to the sun's equator. At the equator the sun's rotational period is twenty-five days while at higher latitudes the sun tends to rotate more slowly. The rotational period near the poles it is thirty-five days. In contrast to the earth, the position of a place on the sun changes as the places closer to the equator speed ahead. The surface of the sun is not solid but fluid.
Radhika Kapoor -- 1999