17. The Earth and our solar system are currently traveling through in an area with only 5% of the average density of the Milky Way Galaxy. It was likely blasted clear by a supernova 300,000 years ago.
18. In 2011, scientists estimated that there are at least 50 billion planets in the Milky Way, of which at least 500 million are in the “habitable zone” of their star. As of January 2013, the number of estimated planets in the Milky Way has more than doubled.
19. Supernovae explode on an average once every 100 years in a galaxy. Assuming there are 170 billion galaxies in the universe, there are 53 supernovae exploding every single second.
20. The last time a star went supernova in our galaxy was in 1604, and we’re overdue for another one.