Pisces, the knowledge of this constellation in astronomy

Every year from June 5438+00 to February 12, residents in the northern hemisphere face the southern sky and look up at around 8 pm. They can see that four bright stars form a huge square-Pegasus. In the southeast of Pegasus, several small stars (ω, λK, γ, 8 stars) form an irregular polygon, which is Pisces. Several dark stars (σ, τ, π, φ, X, etc. ) Another irregular polygon is formed near Andromeda, which is another part of Pisces and is called "Northern Fish". The western fish and the northern fish in Pisces are arranged in a huge V-shape, which seems to be a ribbon connecting the tails of the two fish. Each side of the V symbolizes a fish, and the connection point is the alpha star at the tip of the V.

The equatorial plane of the earth extends infinitely, and the great circle intersecting with the celestial sphere is the celestial equator. The equatorial plane and the ecliptic plane do not overlap, and there is an included angle of about 23.5 degrees between them, commonly known as "the intersection angle of the ecliptic". In addition, the celestial equator and the ecliptic have two intersections, namely the vernal equinox and the autumnal equinox. The intersection of the sun from the southern hemisphere to the northern hemisphere along the ecliptic is called the vernal equinox, and the intersection of the sun from the northern hemisphere to the southern hemisphere is called the vernal equinox. The sun passes the vernal equinox on March 2 1 day every year. On this day, the sun shines directly at the equator of the earth, and day and night around the world are almost equal in length, which is customarily called equal division of day and night. Astronomy stipulates that this day is the beginning of spring in the northern hemisphere.

More than 2000 years ago, the vernal equinox was located in Aries. Ancient astronomers identified the vernal equinox as the first sign of the zodiac, namely Aries. In fact, because the earth is like a swinging top, its swinging motion causes vernal equinox to slowly move westward along the ecliptic for about 50 seconds every year. So the vernal equinox is no longer in Aries, and now he is near the east of λ star in Pisces. As the vernal equinox continues to move westward, it will enter Aquarius more than 400 years later.

There are many binary stars in Pisces, but they are all dark and must be observed with a small astronomical telescope. Alpha Pisces is a binary star with an orbital period of 930 years. The magnitudes of the two satellites are 4.33 and 5.23, respectively, with a difference of 1.8 arc seconds. Pisces ψ is a pair of binary stars far apart. The brightness of the two sub-stars is equal to 5, with a difference of 30 seconds. The TX star in Pisces is an irregular variable star with a magnitude ranging from 5.5 to 6. From the perspective of starry sky observation, Pisces belongs to the autumn constellation. In the autumn starry sky, readers may wish to try to find and observe this beautiful legendary zodiac sign. NGC488 is a bright NGC in Pisces.

The representative of a galaxy, which looks like a north-south beam, has a bright core with brightness of 1 1.2, etc. NGC524 is a bright elliptical galaxy with clear boundary and bright core, and the brightness is 1 1.5. If you have a small telescope, search near the belt of Pisces "Northern Fish", where there is a famous celestial body that looks like a nebula. /kloc-in the 8th century, messier, a French comet hunter, first discovered it and named it M74. Because it was dark and limited by the conditions at that time, messier didn't know what celestial body it belonged to. Later, the British astronomer Earl Ross discovered through a large telescope that there was a faint halo around the bright part in the center of M74. It turns out that it is a spiral extragalactic galaxy. M74 is 30 million light-years away and consists of about 1000 billion stars. It is classified as Sc in the classification of galaxies. It looks very spectacular because it is facing us. Its spiral arms are covered with blue clusters and dark dust belts. In short, it is very similar to the Milky Way.