The intensity of starlight varies mainly due to phenomena such as binary eclipses, stellar pulsations, star spots, and the Doppler effect. These variations can be observed from Earth depending on various physical factors influencing the brightness of the stars.
Stars can vary in brightness due to their rotation on themselves. This phenomenon is observed when certain parts of the star's surface are brighter than others, depending on their orientation relative to our line of sight. When a star rotates on its axis, the brighter regions can be successively hidden from our view, causing regular variations in brightness. This process, known as rotational modulation, can influence the amount of light we perceive coming from the star. Rotating variable stars are an example of this phenomenon, where variations in brightness are due to their rotation and not to other external factors.
Binary stars are stellar systems composed of two stars orbiting around each other. When one of the stars passes in front of the other, from our point of view on Earth, an eclipse occurs.
The intensity of the light we perceive from binary stars varies during these eclipses. Indeed, when the foreground star passes in front of the background star, some of the light from the latter is blocked, resulting in a temporary decrease in the total luminous intensity emitted by the binary system.
Binary eclipses allow astronomers to study the stars composing these systems in a detailed manner. By analyzing the variations in luminous intensity during the eclipses, scientists can determine important information about the stars themselves, such as their sizes, masses, and temperatures.
These observations help enrich our understanding of stellar physics and improve our models of formation and evolution of binary stars.
Pulsating variable stars are stars whose luminosity varies regularly due to variations in their size, temperature, and intrinsic brightness. These changes in brightness are caused by periodic pulsations that modify the amount of light emitted by the star. Pulsating variable stars are classified into several categories based on the duration and amplitude of their pulsations, ranging from Cepheid variable stars to Mira variable stars. These pulsations can be caused by instabilities in the outer layers of the star, leading to periodic expansions and contractions that affect the amount of light emitted. Observations of pulsating variable stars are essential for better understanding stellar evolution and the physics of stars.
Cepheid variable stars are stars whose brightness fluctuates regularly depending on their pulsation period, allowing for the measurement of large distances in the Universe.
Some variable stars, called eruptive stars, can undergo spectacular stellar eruptions that result in rapid and intense variations in their brightness.
Binary stars are star systems that orbit around a common center of mass. When one star passes in front of the other, it can cause eclipses and variations in brightness as observed from Earth.
The brightness of stars can vary due to various factors such as their rotation, binary eclipses, or internal pulsations.
When a star rotates on itself, some parts of its surface can be brighter than others, resulting in variations in light intensity observable from Earth.
A binary eclipse occurs when two stars orbiting around each other pass in front of or behind each other, creating periodic variations in brightness.
Some stars undergo variations in size or internal temperature that result in regular luminous pulsations, causing observable changes in intensity.
The variations in luminosity of stars can be predicted in some cases, especially for known variable stars, but unexpected events can also occur.
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