This is the epic story of the stars, and how discovering their tale has transformed our own understanding of the universe. Once we thought the sun and stars were gods and giants. Now we know, in a way, our instincts were right. The stars do all have their own characters, histories and role in the cosmos. Not least, they played a vital part in creating us. There are old, bloated red giants, capable of gobbling up planets in their orbit; explosive deaths - supernovae - that forge the building blocks of life; and black holes, the most mysterious stellar tombstones. And, of course, stars in their prime, like our own sun. Leading astronomers reveal how the grandest drama on tonight is the one playing above our heads.
Now that we’re done with the planets, asteroid belt, and comets, we’re heading to the outskirts of the solar system. Out past Neptune are vast reservoirs of icy bodies that can become comets if they get poked into the inner solar system. The Kuiper Belt is a donut shape aligned with the plane of the solar system; the scattered disk is more eccentric and is the source of short period comets; and the Oort Cloud which surrounds the solar system out to great distances is the source of long-period comets. These bodies all probably formed closer into the Sun, and got flung out to the solar system’s suburbs by gravitational interactions with the outer planets.
As we approach the end of Crash Course Astronomy, it’s time now to acknowledge that our Universe’s days are numbered. Stars will die out after a few trillion years, protons will decay and matter will dissolve after a thousand trillion trillion trillion years, black holes will evaporate after 10^92 years, and then all will be dark. But there is still hope that a new Universe will be born from it.
Since its formation in the early 60’s, NASA has continued to be the leading power in space exploration. Working with other space agencies, it has contributed substantially to the ongoing exploration of our universe, achieving incredible firsts that span the decades.