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Transcript
Galaxies Galaxies When we look out into the night sky what may look like a single star could be an entire galaxy. Galaxies are huge rotating collections of gas, dust, billions of stars, planets and other celestial objects. Hubble’s Extreme Deep Field Galaxies Our Galactic home is the Milky Way galaxy. The Milky Way contains more than 200 billion stars, including our Sun. Earth Zoom to the Milky Way Galaxy Galaxies You can see the Milky Way galaxy without any telescopes! All you need is a clear night sky. The Milky Way appears like an arch of light in the night sky. The Milky Way from Chile Galaxies The Milky way is very large – 100 000 light years across. Our Sun is 30 000 light years from the center of the galaxy, which is good because we want to stay far away from the supermassive black hole at the center of our galaxy. Milky Way Galaxy Map Galaxies Black holes are thought to be at the center of galaxies. These are extremely dense quantities of matter in space. They have such strong gravitational pulls that nothing – not even light – is fast enough to escape. 10 Mind-Bending Facts About Black Holes Galaxies Black holes are made when a star that is 30 times heavier than the Sun dies and leaves a core that is so massive that it collapses under its own gravity. Galaxies Galaxies also contain star clusters. Star clusters are groups of stars that develop together from the same nebula (a star nursery – full of gas). Zoom in on a Star Cluster 5500 light years away Galaxies Galaxies come in 4 different shapes: elliptical, spiral, lenticular and irregular. Galaxies Elliptical Galaxies are spherical or oval shaped. They are older with very little gas, dust or young stars. Half of the galaxies we see are elliptical. Galaxies Spiral Galaxies look like pinwheels – a flattened disk with a central bulge and spiral arms. The core is made of old stars and the arms contain the younger stars. The Milky Way is a barred spiral galaxy (has a central bar). Galaxies Lenticular galaxies have a central bulge surrounded by a flat disk of gas and dust but has no spiral arms. These are thought to be spiral galaxies that have lost their gas and dust, and so are also made up of older stars. Galaxies Irregular galaxies have irregular shapes. They have more gas and dust than other galaxies and contain 100 million – 10 billion stars.
