In ancient Chinese mythology, there are love stories of cowherds and weavers, and I believe many people know them. Because the Queen Mother's mother did not allow it, the cowherd weaver girl was forced to separate, across the river, and could only meet on the Queqiao Bridge every Tanabata.
The river in the mythological story is the Milky Way, which can be seen in the clear night sky.
It should be noted here that the Milky Way is a barred spiral galaxy, very large, about 100,000 to 180,000 light-years in diameter, containing about 100 billion to 400 billion stars, and the solar system is only a member of the Milky Way, so the milky white bright band of stars that we see in the night sky is only part of the Milky Way, not all, and the star density of that bright band region is extremely high, containing about 100 billion stars.
The Cowherd Weaver Girl corresponds to the Cowherd Star and the Vega Star on both sides of the Silver Belt in the night sky, respectively, both of which are relatively close to Earth and are members of the hundreds of billions of stars in the Milky Way. From the earth, altair and Vega are indeed distributed on both sides of the Milky Way, the so-called one-leaf barrier, this is just an illusion, you know, the thickness of the Milky Way is thousands of light years.
Also known as Altair, or Aquila α star and River Drum II, the star in the constellation of Aquila is the brightest star in the constellation of Aquila, on the eastern shore of the Milky Way. It is also the twelfth brightest star in the night sky.
Altair is a star in the main sequence stage, located 16.7 light-years from Earth, with a mass greater than the Sun, about 1.8 times the mass of the Sun. The actual brightness of Altair is 10.6 times that of the Sun, with a surface temperature of about 7,000 degrees Celsius, while the Surface Temperature of the Sun is about 5,500 degrees Celsius.
Altair 's equatorial rotation is very fast , at 286 km/s , and the rotation takes only 8.9 hours a week. In contrast, the Sun rotates much more slowly, with a rotation period of about 25 days at the equator. The excessive centrifugal force causes the altair's equator to bulge outward, ellipsoidal in shape, and its equatorial diameter is 1.14 times the diameter of the pole.
Vega, also known as Vega I or Lyra α, is on the west coast of the Milky Way, 25 light-years from Earth. Vega is not only the brightest star in the constellation Lyra, but also the fifth brightest in the night sky. In the Northern Hemisphere , it is the second brightest star in the night sky , after Arcturus.
Vega is farther from Earth and looks brighter than Altair because it has 2.1 times the mass of the Sun. Because of the greater mass, the nuclear fusion reaction inside the star is more intense, producing more light and looking naturally brighter.
Like Altair, Vega is relatively flattened , with rotational speeds of up to 274 km/s at the equator , rotating every 12.5 hours.
Due to precession (precession refers to the long-term precession of the Earth's axis of rotation), Vega was a North Star about 14,000 years ago and will become a North Star again in 12,000 years.
How far away The Star and Vega are from Earth, respectively, has already been mentioned above. Connecting Altair, Vega and Earth as three points, knowing the side length and angle size of the two sides, it is easy to know how far away Morning Glory and Vega are using the cosine theorem.
The results show that the two stars are in a straight line distance of 16.4 light-years in the universe.
Looking at the whole universe, this distance is not much. But for human beings, this is an insurmountable gap. It will take tens of thousands of years for the fastest probe to fly humanity's fastest probe to Proxima Centauri, the star outside the solar system closest to Earth. Even if the two meet at the fastest speed in the universe, "at the speed of light," they can only meet about once every 16.4 years. Judging from the life span of human beings, they can only meet each other a few times in a lifetime.
Both Altair and Vega are younger stars than the Sun (4.6 billion years old), but Vega will age faster because Vega is more massive than Altair.
In addition, Vega in Lyra, Altair in Aquittus, and Tianjin IV in Cygnus, a large triangle formed in the sky by these three stars is also known as the Summer Triangle. Since there are not many brighter stars near the Great Triangle in summer, it stands out in the northern sky.