Till 2006 there were Nine planets in the solar system. Now their are only Eight planets in the solar system. Out of these planets, which planet is not a member of solar system now ?

Question

Accepted Answer

Option 2, Pluto, is the correct answer because in 2006, the International Astronomical Union (IAU) redefined the criteria for what constitutes a planet. According to the new definition, a celestial body must meet three criteria to be considered a planet: it must orbit the Sun, it must be spherical in shape due to its own gravity, and it must have cleared its orbit of other debris. Pluto meets the first two criteria but fails the third, as it shares its orbit with other objects in the Kuiper Belt. As a result, Pluto was reclassified as a "dwarf planet," reducing the number of recognized planets in the solar system from nine to eight.

Now, let's explain why the other options are incorrect:

1. Uranus: Uranus is a gas giant and the seventh planet from the Sun. It meets all the criteria set by the IAU for being a planet. It orbits the Sun, is spherical in shape, and has cleared its orbit of other debris. Therefore, Uranus remains a recognized planet in the solar system.

3. Neptune: Neptune is the eighth planet from the Sun and, like Uranus, is a gas giant. It also meets all the IAU criteria for being a planet. Neptune orbits the Sun, is spherical, and has cleared its orbit. Thus, Neptune continues to be a recognized planet in the solar system.

4. None of these: This option is incorrect because there is indeed a planet that was reclassified and is no longer considered a full-fledged planet in the solar system. That planet is Pluto, as explained above.

In conclusion, Option 2, Pluto, is the correct answer because it was reclassified as a dwarf planet in 2006, and the other options remain recognized planets in the solar system.