Cowherd and weaver star

The fairy tale of the Cowherd and the Weaver Girl crossing the river on the seventh day of the seventh lunar month is probably a household name in China. Altair and Vega are located on both sides of the Tianhe River, which are particularly conspicuous in summer nights. Can Altair and Vega really meet once a year?

Altair and Vega are two stars like the sun, and they can also glow by themselves. The official name of Altair in China is Heguji; It combines with several other stars to form a constellation called Skyhawk. The official name of Vega in China is Vega I; It and several other stars form a constellation called Lyra. The names and divisions of constellations were introduced from the west.

Altair and Vega are far away from us! Altair 16 light years, Vega 27 light years. The distance between them is also very far, which is 16 light years. That is to say, the fastest light and electricity, from Altair to Vega, have to run nonstop 16 years, not to mention other means of transportation. Suppose the Cowherd and the Weaver Girl really live on these two stars, and they want to make a phone call or send a telegram to say hello to each other. This long-distance call will take 16 years one way! It can be seen that two stars in the sky can't "meet".

In addition, the surface temperature of Altair reaches 8000 degrees Celsius, while Vega is even higher, reaching 1 1000 degrees Celsius. Vega is bigger than Altair in size. The diameter of Vega is three times that of our sun, while the diameter of Altair is 1.6 times. How can two such big stars "meet"? =

= = = = = = = = = There is an obvious bright star above us in the summer evening, that is Vega. Across the Tianhe River, the weaver girl facing the southeast of the sky is Altair. There are two little stars on both sides of Altair, which are said to be their children.

Altair is twice as big as the sun, the temperature is 2000 degrees higher than the sun, and the light is 8 times stronger than the sun. Vega, on the other hand, is bigger, 10 times of the sun, with a temperature of 4000 degrees higher and a light intensity of 50 times stronger than the sun. No wonder we see Vega's light on such a hot planet, slightly blue.

Vega, or Alpha Lyra, is called Vega for short in China folk and astronomical circles. It is the brightest star in the northern hemisphere, second only to the large focal length, and also the brightest early star in the northern hemisphere. Although it has been the standard star for photoelectric photometry and MK spectral classification since 1953, many years of photometric research show that it is a variable star, and the difference between blue and yellow bands is 0.08 magnitude. However, the classification and darkening law of its variable stars need further discussion. In addition, its apparent speed has also changed significantly. The spectral classification of Vega is that A0V is earlier than Sirius A's A 1V, but its surface effective temperature of 9660K is lower than the latter's 9970K, and its radius is slightly larger than that of typical A0V star. It can be seen that the evolution of Vega seems to have been divorced from the original main sequence. Soft X-rays from Vega have been discovered by the probe rocket and the high-energy observatory-1 satellite. The research published in 1979 shows that the X-ray luminosity of 0. 15 ~ 0.8 kev is about 0.3× 1029 erg per second (the luminosity of the sun in the same wave band is less than 0.0 1× 65429 erg per second).