There exists a swarm of ice and rocks 1 light year form the sun held together by gravity. These remains are the preserved reminiscence form the birth of the solar system. This cloud was named after him and now known as the 'Oort Cloud'. Jan Oort foretold its existence back in 1950. He was doing research about comets, how they die and their origin. Many astronomers at that time were curious about where all the comets come from. Oort calculated the rate at which the comets appeared and concluded that there must be a vast spherical swam of them few light years across surround a sun. He was right even after all the discovery about the solar system and the comets. Not only this, he was also able to calculate the distance between the center of our galaxy and our sun. This was one of the big steps we made while figuring out our place in the universe. Our star, the sun, is about 30,000 light years away form the center. Imagine what might lurk in 30,000 light years of space. Fascinating stuff!
He was also a pioneer in radio astronomy. Oort used a radio telescope to map the galaxy's spiral structure. He also discovered that the center of out galaxy was a place of giant explosions indicating the presence of a super massive black hole.
Why should I feel lonely? Is not our planet in the Milky Way? -Henry David Thoreau