Play A Brief History of the Universe: Crash Course Astronomy #44

Thanks to the wonders of physics, astronomers can map a timeline of the universe’s history. Today, Phil’s going to give you an overview of those first few minutes (yes, MINUTES) of the universe’s life. It started with a Big Bang, when the Universe was incredibly dense and hot.

Play Dark Energy, Cosmology part 2: Crash Course Astronomy #43

The majority of the universe is made up of a currently mysterious entity that pervades space: dark energy. We don’t know exactly what it is, but we do know that dark energy accelerates the expansion of space. We think this means the Universe will expand forever, even as our view of it shrinks while space expands faster all the time.

Play The Big Bang, Cosmology part 1: Crash Course Astronomy #42

Thanks to observations of galaxy redshifts, we can tell that the universe is EXPANDING! Knowing that the universe is expanding and how quickly its expanding also allows us to run the clock backwards 14 billion years to the way the universe began - with a bang.

Play Dark Matter: Crash Course Astronomy #41

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.

Play Galaxies, part 2: Crash Course Astronomy #39

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.

Play Galaxies, part 1: Crash Course Astronomy #38

Galaxies contain gas, dust, and billions of stars or more. They come in four main shapes: elliptical, spiral, peculiar, and irregular. Galaxies can collide, and grow in size by eating each other.

Play The Milky Way: Crash Course Astronomy #37

Today we’re talking about our galactic neighborhood: The Milky Way. It’s a disk galaxy, a collection of dust, gas, and hundreds of billions of stars, with the Sun located about halfway out from the center.

Play Nebulae: Crash Course Astronomy #36

Astronomers study a lot of gorgeous things, but nebulae might be the most breathtakingly beautiful of them all. Nebulae are clouds of gas and dust in space. Some nebulae are small and dense, others can be dozens or hundreds of light years across.

Play Binary and Multiple Stars: Crash Course Astronomy #34

Double stars are stars that appear to be near each other in the sky, but if they’re gravitationally bound together we call them binary stars. Many stars are actually part of binary or multiple systems. In some close binaries matter can flow from one star to the other, changing the way it ages.

Play Black Holes: Crash Course Astronomy #33

Stellar mass black holes form when a very massive star dies, and its core collapses. Black holes come in different sizes, but for all of them, the escape velocity is greater than the speed of light, so nothing can escape, not matter or light.

Play Neutron Stars: Crash Course Astronomy #32

In the aftermath of a 8 – 20 solar mass star’s demise we find a weird little object known as a neutron star. Neutrons stars are incredibly dense, spin rapidly, and have very strong magnetic fields. Neutrons stars with the strongest magnetic fields are called magnetars, and are capable of colossal bursts of energy that can be detected over vast distances.

Play High Mass Stars: Crash Course Astronomy #31

Massive stars fuse heavier elements in their cores than lower mass stars. This leads to the creation of heavier elements up to iron. Iron robs critical energy from the core, causing it to collapse. The resulting supernova creates even more heavy elements, scattering them through space.

Play White Dwarfs & Planetary Nebulae: Crash Course Astronomy #30

Today Phil follows up last week's look at the death of low mass stars with what comes next: a white dwarf. White dwarfs are incredibly hot and dense objects roughly the size of Earth. They also can form planetary nebulae: huge, intricately detailed objects created when the wind blown from the dying stars is lit up by the central white dwarf.

Play Low Mass Stars: Crash Course Astronomy #29

Today we are talking about the life -- and death -- of stars. Low mass stars live a long time, fusing all their hydrogen into helium over a trillion years. More massive stars like the Sun live shorter lives. They fuse hydrogen into helium, and eventually helium into carbon. When this happens they expand, get brighter, and cool off, becoming red giants.

Play Brown Dwarfs: Crash Course Astronomy #28

While Jupiter is nowhere near massive enough to initiate fusion in its core, there are even more massive objects out there that fall just short of that achievement as well called brown dwarfs. Brown dwarfs, have a mass that places them between giant planets and small stars.

Play Exoplanets: Crash Course Astronomy #27

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. Exoplanets appear to orbit nearly every kind of star, and weÕve even found planets that are the same size as Earth. We think there may be many billions of Earth-like planets in our galaxy.

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