In 1501, to the great joy of the people, Katherine of Aragon and Prince Arthur were married. Soon after, they travelled to what would be their new home, Ludlow Palace to start their court, and their new lives.
Within a short amount of time, the couple fell ill. While Katherine recovered quickly, Arthur was less fortunate; and only six months after their wedding, he had died.
What exactly he died of remains unknown. Suggestions include sweating sickness, which killed a large amount of people during the Tudor period, plague, or tuberculosis.
While Henry VII and his wife, Elizabeth of York, were understandably devastated by this sudden bereavement they seem to have been very supportive of each other's grief.
Katherine became a young widow in a foreign country which she was not yet fully accustomed to and her future must have felt bleak and uncertain.