How far is Tianjin IV and Kepler -452, both cygnus?

In addition to the first discovered star black hole Cygnus X- 1, the other two stars in Cygnus are famous. One of them is one of the famous summer triangles: Tianjin. This star is about 26 15 light years away from the earth. In fact, it is a blue-and-white Supergiant star with a mass of 19 times, a radius of 200 times and a brightness of196,000 times that of the sun. Because Tianjin IV itself is very bright, although it is relatively far away (most of the stars visible to the naked eye are within 1000 light years), it still looks very bright in the night sky.

How far is Cygnus from Kepler -452? There is also an invisible one-Kepler 452. However, astronomers discovered an exoplanet named "Earth 2.0" nearby, kepler-452b, so the system attracted a lot of attention. Kepler -452, like the sun, is a yellow dwarf with a mass, radius and luminosity close to the sun. For a star as bright as our sun, more than 55 light years, it is too dark to be seen by the naked eye. Kepler -452 is at least 1400 light years away from us (according to a paper by 20 18, ARXIV: 1804.065V2), so this star is invisible to the naked eye.

Tianjin IV and Kepler 452 are both in Cygnus. What is the distance between them? Tianjin IV and Kepler 452 are closely projected on the celestial sphere, but in fact they are far apart in different spaces. As for the distance between two stars, it can be calculated by trigonometry.

Because the distance between two stars and the earth is known, you can use cosine law to calculate the angular distance between two stars-their angle with the earth. The coordinates of the celestial sphere in Tianjin are: right ascension 20h 4 1m 25.9s, declination+4516' 49 ". The right ascension of Kepler -452 is 19 hours 44m 00.886 1 s, and the declination is +44 16' 39.6438+0704 ". It can be concluded that the angular distance between two stars is 10.73, and the distance between two stars can be calculated according to cosine law (c 2 = a 2+b 2-2 abcosc).