Collisions and Explosions in the Universe – Science, Astronomy for Children

Looking up into the night sky, you could be forgiven for thinking our Universe is a calm and peaceful place. Many of our ancient ancestors thought that the Universe was eternal and unchanging. But nothing could be further from the truth! Our Universe is constantly active, full of collisions and explosions! And you don’t have to look far to see evidence of that. Many of the objects in our own solar system are covered in craters, the result of rocks from space smashing into the surface. One of the largest craters on our own planet, the Chicxulub crater, is the result of the asteroid that wiped out the dinosaurs. Our Moon is visibly covered in craters. The large dark areas on the Moon, the maria or seas, are cooled magma released from under the surface of the Moon during heavy bombardment from space. In fact the Moon itself is the result of a Mars sized object smashing into the early Earth while it was still forming. The material left behind formed into the Moon we see today. On much larger scales, galaxies can collide and merge in space. With so much distance between the stars in these galaxies, it’s quite rare for stars to smash into one another during these mergers. Instead they harmlessly pass by one another. However, massive clouds of gas in each galaxy can be squashed into each other, heating up and forming new stars. Some of these stars will be huge, many times the mass of our own Sun. When these giant stars die, they explode in extremely bright supernovae, producing as much light in the brief explosion as the Sun will throughout its entire life. Some even larger stars produce giant flashes of gamma-radiation when they die, known as gamma-ray bursts. These explosions act like torches, producing narrow beams of intense light that can be seen almost back to the beginning of the Universe; almost as far as the largest explosion of them all, the Big Bang which formed our Universe. Sometimes collisions and explosions can even happen together. The leftover cores of two stars that exploded billions of years ago can smash into one another, producing another huge explosion. Collisions on this scale causes space and time to wobble, an effect known as a gravitational wave. By watching the light from explosions with telescopes and detecting collisions through gravitational waves, scientists can learn even more about our ever-changing Universe.


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