News from the universe
Do you remember this date? The 24th August? Didn’t you feel different? Didn’t you feel the world had changed and nothing would be the same again anymore? If you did, you were right. Something had changed. Pluto stopped to be a planet.
Did it vanish into thin air, full of stars? Was it swallowed by one of the black holes? Did it die? Was there an explosion changing it into a cloud of dust? No. Pluto was as fit as a fiddle. Pluto didn’t change during this special August night. And even if it did, nobody could see it. It was like in the joke about a man and his beautiful wife. “I want to have a beautiful wife” – the man dreamed. One day he said “Hurray! I have a beautiful wife!” Everybody was curious what had happened. “What happened with your old wife?” – they asked. “Nothing” – he answered. “I simply redefined my concept of beauty.”
The point was that some objects newly discovered appeared to be similar to planets. There were dwarf planets already, like Eris (called Xena) and Ceres. When it was discovered that there was an object bigger and further away than Pluto, everybody started to worry that it might be called a planet. The distinction between planets and dwarf planets was blurred.
On 24th August 2006 scientists from the International Astronomical Union met in Prague trying to solve the problem. The result was redefining the concept of planet!
To be a planet, an object must fulfil the following three criteria:
1) It must orbit the sun.
2) It must be massive enough to have its own gravity which makes it round in shape.
3) It must be dominant enough to clear away objects in its neighbourhood.
For dwarf planets it is enough to fulfil the first two conditions.
What does the third criterion mean? Real planets are strong enough to clear the neighbourhood around their orbits – to remove smaller bodies, which could cause collision or disturbance. Poor Pluto appeared to be too weak for this, which means that we have eight planets – again. And the world will never be the same…
Improve your vocabulary!
black holes – czarne dziury
cloud of dust – chmura kurzu
as fit as a fiddle – zdrowy jak ryba
redefine – zdefiniować coś ponownie, od początku
distinction – różnica
dwarf planets – planety karłowate
blurr – zamazany