We were taught in school lessons that there are 9 planets but a Caltech astronomer Michael Brown lately announced that there are actually ten planets. A new planet is added to the Solar family. It is a bit smaller than Pluto. Scientists have no good rational to have a new planet included in the Solar system. Even Pluto should be excluded, too.

Among the nine planets, four planets including Earth, Venus, Mars and Mercury are terrestrial objects while others being gaseous, except for Pluto that is composed of ice. The so called “new planet” is actually of ice. Scientists have no scientific rational to define it as a planet.

Pluto is too far away from the Sun and its orbit is more eccentric than others and tilts in a different plane. For 75 years it has been habitually defined as a planet. Based on this precedence, now that a ice ball has been called planet, a newly-discovered icy ball, at three-fourths the size of Pluto, should be defined as a planet. But, it is too numb to remember so many planets.

I agree with the editorial of the New York Times that we can drop Pluto from the planetary ranks, let alone the new discovered ice ball. Dr Brown should withdraw his proposal.