The planets are about the same size and orbit a star in a harmonious way. Researchers describe this galaxy as the "perfect solar system".
The study was published Nov. 29 in the British journal Nature.
The galaxy number is HD110067 and it is located in the constellation Horae, one of the northern celestial constellations. The stars in the galaxy are as bright as the sun, and the six planets are numbered by the letters b, c, d, e, f, and g according to their proximity to the stars.
Unlike the solar system, which had violent impacts during its formation, the galaxy formed planets of various sizes. The planets in the HD110067 galaxy are similar in size and have a rare phenomenon of orbital resonance, in which there is a simple mathematical proportional relationship between the orbital periods of two or more planets. In the HD110067 galaxy, the four planets B, C, D, and E have an orbital resonance rate of 3 to 2, that is, the planet closer to the star makes 3 revolutions, and the planet immediately outside it makes 2 revolutions. The orbital resonance rate of e, f, and g is 4 to 3, i.e., for every 4 revolutions of the inner planet, 3 revolutions of the outer planet immediately adjacent to it.
According to CNN, most of the known planetary systems do not have orbital resonance. Astronomers believe that planetary systems usually have orbital resonances in the early stages of formation, but this state is difficult to maintain because many factors such as the gravitational pull of a giant planet, the close passage of a star, and the collision of a planet with other celestial bodies can break this state.
Raphael Luke, an astronomer at the University of Chicago in the United States who led the study, said that only about one percent of the planetary systems maintain orbital resonance, and HD110067 is like a "rare fossil" that has not experienced "the chaos of the early days of the formation of our solar system", but has preserved the original structure of a planetary system intact, which can be called a "perfect solar system" and is an ideal object for studying the birth of planets.
The planets in the HD110067 galaxy are larger than Earth and smaller than Neptune, and belong to sub-Neptune. Such planets are widespread in the Milky Way, but not in the solar system. Astronomers have different views on how the planet formed and what makes it, and that a planetary system with all planets as sub-Neptune could help scientists explore the planet's origins, Luke said.
*: Xinhua News Agency Editor-in-Charge, Yang Xue.