Halloween is a big night for astronomers

http://science.nasa.gov/science-news/science-at-nasa/2005/27oct_halloween/

1. When was this programme originally broadcast?
2. What were the most popular costumes for Halloween the year before?
3. Why is Halloween an astronomical holiday?
4. According to folklore, what happened on the 31st of October?
5. Why did people become afraid of that date?