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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.
The most innovative area of human motion lies not on Earth, but with the exploration of space. Meet the private space entrepreneurs jostling to offer the tantalizing prospect of cheap, frequent travel beyond the atmosphere into Earth orbit.
This is the story of how our solar system will be transformed by the aging sun before coming to a spectacular end in about eight billion years. Astronomers can peer into the far future to predict how it will happen by analysing distant galaxies, stars and even planets in their final moments. In this film, Horizon brings these predictions to life in a peaceful midwestern town that has a giant scale model of the solar system spread out all over the city. As it ages, the sun will bloat into a red giant star, swallowing planets... as well as half the town. The fate of the Earth itself hangs in the balance. How will the solar system end?
Today Phil helps keep you from ticking off an astronomer in your life by making sure you know the difference between a meteor, meteorite, and meteoroid. When the Earth plows through the stream emitted by a comet we get a meteor shower. Meteors burn up about 100 km above the Earth, but some survive to hit the ground. Most of these meteorites are rocky, some are metallic, and a few are a mix of the two. Very big meteorites can be a very big problem, but there are plans in the works to prevent us from going the way of the dinosaurs.
23 • Crash Course Astronomy • 2015 • Astronomy
Last week we covered multiple star systems, but what if we added thousands or even millions of stars to the mix? A star cluster. There are different kinds of clusters, though. Open clusters contain hundreds or thousands of stars held together by gravity. They’re young, and evaporate over time, their stars let loose to roam space freely. Globular clusters, on the other hand, are larger, have hundreds of thousands of stars, and are more spherical. They’re very old, a significant fraction of the age of the Universe itself, and that means their stars have less heavy elements in them, are redder, and probably don’t have planets (though we’re not really sure).
35 • Crash Course Astronomy • 2015 • Astronomy
Today Phil explains that YES, there are other planets out there and astonomers have a lot of methods for detecting them. Nearly 2000 have been found so far. The most successful method is using transits, where a planet physically passes in front of its parent star, producing a measurable dip in the star’s light. Another is to measuring the Doppler shift in a star’s light due to reflexive motion as the planet orbits. Exoplanets appear to orbit nearly every kind of star, and we’ve even found planets that are the same size as Earth. We think there may be many billions of Earth-like planets in our galaxy.
27 • Crash Course Astronomy • 2015 • Astronomy