Is Pluto a planet?
Pluto is officially no longer classed as a planet, and here's why. The International Astronomical Union defined three rules in 2005 that a celestial body (an object observable within space) must follow to be classed as a planet:
1. The planet must orbit the sun.
2. The planet must be large enough that its gravity can smooth it into a nice spherical shape.
3. It must have cleared up the surrounding objects around it.
Pluto fails number three as it simply isn't massive enough to pull the surrounding objects into it's orbit. This is really hard for Pluto as it lives in the Kuiper Belt, a belt of other large rocky objects.
Fortunately for Pluto it matches the first two rules, so it can be classed as a dwarf planet instead!
CG
Related Physics A Level answers
All answers ▸An aeroplane lands on the runway with a velocity of 50 m/s and decelerates at 10 m/s^2 to a velocity of 20 m/s. Calculate the distance travelled on the runway.
What is Olbers' Paradox?
A ball is kicked off a cliff at a height of 20m above ground and an angle of 30 degree from the horizontal, it follows projectile motion and lands after a time t. Its velocity at the maximum height it reaches is 20m/s, how long does it take it to land?
An electron is traveling at a velocity of 500m/s perpendicular to a uniform magnetic field. A force of magnitude 4.32 x10^(-16) N is acting on the electron, what is the magnetic flux density of the field?