We reveal the planetary enigmas on our doorstep and embark on the New Horizons voyage to photograph Pluto. Will our encounter with this tiny ball of ice and rock and the trillions of icy objects beyond it paint a clearer picture of how the planets came to be?
Scientists have started looking to the heavens and wondering what the weather might be like on other planets. Today, we are witnessing the birth of extra-terrestrial meteorology. They began with our solar system, sending spacecraft to explore its furthest reaches, and now the latest telescopes are enabling astronomers to study planets further afield. Our exploration of the universe is revealing alien worlds with gigantic storm systems that encircle entire planets, supersonic winds and extreme temperatures. On some planets, temperatures are so hot that the clouds and rain are believed to be made of liquid lava droplets, and on other planets it is thought to rain precious stones. We thought we had extreme weather on Earth, but it turns out that it is nothing compared to what's out there.
Active galaxies pour out lots of energy, due to their central supermassive black holes gobbling down matter. Galaxies tend not to be loners, but instead exist in smaller groups and larger clusters. Our Milky Way is part of the Local Group, and will one day collide with the Andromeda galaxy. Clusters of galaxies also clump together to form superclusters, the largest structures in the Universe. In total, there are hundreds of billions of galaxies in the Universe.
How do astronomers make sense out of the vastness of space? How do they study things so far away? Today Phil talks about distances, going back to early astronomy. Ancient Greeks were able to find the size of the Earth, and from that the distance to and the sizes of the Moon and Sun. Once the Earth/Sun distance was found, parallax was used to find the distance to nearby stars, and that was bootstrapped using brightness to determine the distances to much farther stars.
Today on Crash Course Astronomy, Phil dives into some very dark matters. The stuff we can actually observe in the universe isn’t all there is. Galaxies and other large structures in the universe are created and shifted by a force we detect mostly indirectly, by observing its impact: DARK MATTER.