solar system
It seemed to move by the naked eye on a celestial sphere, but, before modern times, seven heavenly bodies, the sun, the moon, Mercury, the Venus, Mars, Jupiter, the Saturn which I could observe were counted for a planet. The earth is not a planet, and this is because it was thought that it is the Hub or a base.
Modern times began, and the earth was recognized to be the one of the planets around the sun, and it came to be recognized when the sun and the moon were not planets. In addition, Neptune was discovered in Uranus, 1846 in 1781 by development of the astrodynamics and the development of the observation technology. In addition, Ceres discovered in 1801 or Pallas discovered in the next year were treated at first as a planet, but similar small heavenly bodies were discovered in sequence between Mars and Jupiter, and the number of the planet called them from a thing beyond 20 in a mass with an asteroid in 1850's and I distinguished it from the planet and came to treat it. And Pluto was discovered in 1930 and was considered to be the ninth planet.
The heavenly bodies which you should have called have been fixed for a planet conventionally the other day. However, after 1990's, the heavenly bodies (mass is not different for wrong number of digits heavenly bodies) which the heavenly bodies around the orbit which had similar resonance relations that I was seen in the Neptune beyond between Pluto / Neptune and mass could compare with Pluto were discovered in succession, and a dispute arose whether I should have called these with a planet. and larger than the Pluto(136199) With discovery of Ellis (2,003 temporary mark UB313), the time to define something as the planet rose.
Modern times began, and the earth was recognized to be the one of the planets around the sun, and it came to be recognized when the sun and the moon were not planets. In addition, Neptune was discovered in Uranus, 1846 in 1781 by development of the astrodynamics and the development of the observation technology. In addition, Ceres discovered in 1801 or Pallas discovered in the next year were treated at first as a planet, but similar small heavenly bodies were discovered in sequence between Mars and Jupiter, and the number of the planet called them from a thing beyond 20 in a mass with an asteroid in 1850's and I distinguished it from the planet and came to treat it. And Pluto was discovered in 1930 and was considered to be the ninth planet.
The heavenly bodies which you should have called have been fixed for a planet conventionally the other day. However, after 1990's, the heavenly bodies (mass is not different for wrong number of digits heavenly bodies) which the heavenly bodies around the orbit which had similar resonance relations that I was seen in the Neptune beyond between Pluto / Neptune and mass could compare with Pluto were discovered in succession, and a dispute arose whether I should have called these with a planet. and larger than the Pluto(136199) With discovery of Ellis (2,003 temporary mark UB313), the time to define something as the planet rose.