Sub giant stars are one kind of stars in the spectral classification. They are brighter than ordinary main sequence stars (dwarf stars), but they do not reach the true brightness of giant stars. They are considered to be stars whose core hydrogen fusion is about to end or has ended.A star whose mass is about the mass of a sun will increase its core temperature due to the contraction of its core. When the temperature is high enough to allow the hydrogen shell surrounding the core to conduct nuclear reaction, the star will expand to become a real giant star.At the beginning of the sub giant stage (likeNanhe IIIA），SiderealdiameterAnd brightness increase, but the temperature of the star will drop or the color will change significantly, and then the sub giant star will become closer to the real giant star, larger and brighter than the star with similar mass in the main sequence belt.In the stage of sub giant, the overall luminosity changes littleGlobular clusterOfHerotuCan highlight this feature.SiderealYork spectral classificationTheir luminosity is IV.
In the West, its name derives from the Greek πρ ο κ ον (prok ú on),Nanhe IIIProcyon originally means "in front of the dog", because it is located in the northeast of Sirius——Sirius15-20 minutes earlier, it rose from the horizon due north by east, and then sank to the west 2-3 hours later than Sirius.In ancient times, the Egyptians worshipped Sirius very much, because whenever it appeared on the eastern horizon at dawn, it was the annual flood season of the Nile, and the first omen of the arrival of this season was Nanhesan, which appeared before Sirius.Nanhe SanyaWinter TriangleAnd the other two areCanis MajorOfSiriusAndOrionOfBetelgeuse。Nanhesan is also a star near the solar system and the Earth. In the Close Star Table, the distance listed is 11.44 light-years (3.5 seconds difference) (ranking 13th in distance).Like Sirius, it is also a binary star - the main star (Nanhe 3A) also has a dim white dwarf as the companion star (Nanhe 3B), 1.11 light-years (0.34 seconds) away from another Luyten's star (ranking 22nd).
Nanhe I
Nanheyi is also a star far away from the solar system and the Earth. In the Close Star List, the distance listed is 990 light-years (87.5 seconds).It is also a binary star - the main star (Nanhe-A) also has a dim star as the companion star (Nanhe-B).
Nanheyi is also a beautiful star, with an apparent magnitude of 4.99 and an absolute magnitude of -2.04. It is about 990 light-years away from the Earth, much farther than Sirius, and is a G6.5IIb sub giant star.Its luminosity is 20 times that of the sun, and its surface temperature is about 5000 ℃. Compared with Nanhe Three Phase, its color is slightly red.
