A look at the highlights on this day April 21
2009: European researchers say they not only found the smallest planet ever, Gliese 5810 e, but also realise that a neighbouring planet discovered earlier, Gliese 581 d, was in the prime habital zone for potential life.
1960 –Brasilia becomes capital of Brazil
1983 –1 pound coin introduced in United Kingdom
1898 – The Spanish-American War began.
1930 – Prisoners left to burn in Ohio fire. A fire at an Ohio prison kills 320 inmates, some of whom burn to death when they are not unlocked from their cells. It is one of the worst prison disasters in American history.