Eagle Eagle and Lyra

Altair is aquila. The official name of Altair in China is Hegu II. It and several other stars form a constellation, commonly known as the eagle. Altair is the alpha constellation of the eagle. Altair is a bright star slightly darker than Vega, located on the east bank of the Milky Way, also known as Altair.

In summer and autumn, Altair is one of the brightest stars in the sky. Its luminous ability is very strong, about 9 times that of the sun, and its whole body is silvery white. The equatorial region of Altair, the star with the twelfth brightness in the whole day, runs at a speed of 26 km/s and its rotation speed is as high as 1027000km/h, which is about 60 times that of the sun!

Its surface temperature is 2000℃ higher than that of the sun. Therefore, Altair is not a nearly perfect sphere like the sun, and its "waist circumference" is obviously enlarged and becomes a flat ellipsoid.

Niu Langxing explained.

Altair is a star slightly larger than the sun, with a diameter of about 3.26, a radius of 1.7 times that of the sun, and a distance of 16.7 light years from the earth (one light year is about 10 trillion kilometers), which means that the light emitted by Altair now is the light emitted by Altair 16.7 years ago. Vega is 26.4 light years away. Astronomers calculated by triangulation that the distance between Altair and Vega was 16 light years.

The apparent magnitude of Altair is 0.77m, which is the twelfth bright star in the whole day. Its connection with the beta and gamma stars of Aquila points to Vega. In ancient China, the beta star and the gamma star were regarded as two children carried by a cowherd on a pole, and he was struggling to catch up with Vega.

Unfortunately, the cruel queen mother tore off the golden hairpin on her head and welcomed the sky with one move. In an instant, a Tianhe fell from the sky, which almost separated the two lovers forever. Legend has it that their experience touched God, and they were allowed to meet once a year on the seventh day of July. Every day, all the magpies in the world come to the edge of the Milky Way and build a magpie bridge for the couple to cross the river.

According to ancient legends, the seventh day of July is the day when the Cowherd and the Weaver Girl meet, but in fact, it will take a long time to meet at the distance of Cowherd and Weaver Girl 16 light years. On July 7th every year, half a moon floats near the Milky Way, and the moonlight and the Milky Way merge into one, so that we can't see the Milky Way. People thought that the Tianhe disappeared at this time and the cowherd and the weaver girl met!

Reference to the above content: Baidu Encyclopedia-Altair