aroundPrimary starThe moving stars are called companion stars, which are actually two stars rotating around each other.SiriusThe companion star B ofWhite dwarf。It is small, almost the same size as the earth, and invisible to the naked eye;But the density is extremely high, 30000 times higher than the density of watersunlightalmost.This star was predicted by astronomers in 1834 due to the irregular motion track of Sirius, and was directly observed in 1862. Its "white dwarf" identity was determined in 1915, which attracted great attention from the astronomical community.However, at least 1200 years ago, many tribes in Mali, Africa, began to sacrifice this star, and knew its volume, density, orbital shape (ellipse) and its cycle around Sirius (49 Earth years). They recorded these in the original woodcut,muralAnd textiles.
mentionSiriusThe companion star B has to tell the story of what happened to it, because many major discoveries often start with some small "deviations"
In the eighth century AD, the Chinese astronomers of the Tang Dynasty compared their observations with the records of ancient times and found that the positions of stars had changed.More than a thousand years later, in the 18th century, the BritishHarleyWe also saw the same phenomenon independently.Originally, the so-called immovable and unchanging“fixed star"People call it wrong. The stars in the sky are moving and changing.
In 1834, an astronomer noticed thatfixed star——SiriusIts motion is strange, and its path is undulating, unlike ordinaryfixed starAlways move evenly along a straight line.The astronomer thus asserted that Sirius was not a single star, but abinary star The other star is an "invisible" companion star;The undulating route is exactlySiriusThe result of moving while circling. Later, some astronomers studiedSiriusAnd according toLaw of universal gravitation, predictedSirius B After 28 years, in 1862, the "invisible" Sirius companion star was finally found in the telescope.This "invisible" companion star is too dark compared with Sirius. In the telescope, it looks like the illusion caused by the defect of the telescope. However, when observing other objects, this "defect" is gone, so everyone believes that they have found Sirius's "invisible" companion star.
The two stars that make up a binary star are called binaryChild starThe brighter one is calledPrimary star；The darker one is called the companion star.Some of the brightness differences between the primary star and the companion star are small, while others are large.So, as mentioned above, you can use a telescope to put twoChild starThe distinguished binary stars are correspondingly calledVisual binary。
There is a kind of "double star"celestial sphereThe angular distance between them is very close, but they have no mutual gravitational effect. They are called geometric binary stars orOptical binaryIt is not a real double star, such as Kaiyang and Fu.
stayGalaxyThe number of binary stars is very large, estimated to be no less thanSingle star。Studying binary stars is not only for understandingStar formationAnd the diversity of evolution process is of great significance, and it is also an indispensable aspect for understanding the formation and evolution of the Milky Way.
Visual binary
It can be distinguished directly by eyes or cameraPrimary starAnd companion stars are calledVisual binary。Sirius、Vega II, Virgo gamma, etc. are included.
The light variation curve of the five eclipsing binaries of Daling is characterized by obvious major minima (darkest) and minor minima (darker), while the light variation curve outside the eclipse is relatively smooth, the light variation period is as short as several hours, and as long as several decades, the light variation amplitude is also large and small.[1]Its prototype isFive Tombs。
It is roughly the same as the former, but in the light variation curve of the latter, there is a curve between the primary minimum and the secondary minimum.This is caused by the irregular shape of the main star affected by the companion star.[1]
The maximum of the light curve of the eclipsing binary is circular, and the depth of the major and minor minima are roughly equal.This feature reflects that the two stars are deformed due to tidal action, have a common shell, and have continuous material flow, and are intimate.[1]Its prototype isUrsa Major WKonductra.
Spectroscopic binary
There are many binary stars that are very close to each other. Even with the largest telescope in modern times, their two sub stars cannot be distinguished.However, astronomers obtainedspectrumIt can be found that they are composed of two stars.Such a binary star is calledSpectroscopic binary。
