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Objects in Space Meteoroid A chunk of rock/dust that can be seen as a track of light in the sky as it burns up in the Earth’s atmosphere. They are too small to survive the heat of friction while travel through the Earth’s atmosphere. Meteorite a chunk of rock after it impacts on a planet or moon. More simply – a meteoroid that hits a planet or moon. Meteorites have to pass through the atmosphere to hit the Earth and therefore must be fairly large. Meteor a chunk of rock that is much smaller than an asteroid. Meteoroid that is travelling through space. The melted appearance of this specimen suggests that is actually a meteorite. Asteroids A “minor planet” or non-luminous chunk of rock that is smaller than a planet, but bigger than a meteoroid that orbits a star. A belt of asteroids can be found between Mars and Jupiter. Some asteroids have been perturbed from their orbits and travel in elliptical paths through the inner planets. Comets An object orbiting the sun, often in a very eccentric elliptical orbit. Given the nickname “dirty snowballs” as they are composed mostly of ice and loose rocky material. When comets goes close to the sun, the ice is turned into vapor and is released in a long, luminous tail. Generally originate from a region of space called the Oort Cloud. Some originate from the Kuiper Belt. When comets pass near larger objects, their orbits are disturbed and they can be directed towards the sun and form elliptical orbits. Many scientists believe that the source of water in our oceans was due to comet impacts early in our planet’s existence. The Oort Cloud Is a hypothetical region that is thought to stretch outward beyond the Kuiper Belt along the plane of the Solar System. Named after Dutch Astronomer Jan Oort who proposed this region in 1950. Its a cloud of debris left over from the formation of the Solar System and is the source of comets. Astronomer theorize that it contains over a trillion long period comets greater 0.6 km in size (some which take 50 million years to orbit the sun). Located beyond the Kuiper Belt The Oort Cloud is located from 5000 to 100000 AU from the sun. Moons A natural satellite that orbits a planet. Can travel in elliptical orbits. Only moons with sufficient mass form spheres – this is because they have sufficient gravity to form this shape. Therefore all small moons are irregular in shape. There are 4 moons larger than our moon in the Solar System, but relative to its planet, Earth’s moon is by far the largest. Planets The definition of a planet became a topic of great interest in 2006, when the Pluto debate came up! As a result, planets must meet the following criteria: 1) An object that orbits the sun. 2) An object that is large enough to be spherical in shape due to a sufficient amount of mass. 3) An object that has an orbit that is not controlled by another planet. 4) An object whose orbit has been cleared of asteroids by its gravity. 5) An object that does not emit own light (and is therefore too small to be considered a star). Many stars form binary systems in which two stars orbit each other. Stars need a sufficient mass of Hydrogen to generate enough gravity to start a nuclear fusion reaction. Dwarf Planets and the Kuiper Belt Large objects orbiting the sun that does not meet all of the criteria of a planet Discovery of dwarf planets in the Kuiper Belt started with Eris in 2003. It is believed to be larger than Pluto. It is suggested that there may be hundreds of dwarf planets in the Kuiper Belt – most of them too distant and non-luminous to be found. It is also suggested that they have icy compositions similar to comets and Pluto. The Kuiper Belt The Kuiper Belt is a doughnut-shaped ring, extending just beyond the orbit of Neptune from about 30 to 55 AU. Named for astronomer Gerard Kuiper. Short period comets originate from the Kuiper Belt (those with orbital periods less than 200 years) It is also the host of many icy dwarf planets including Pluto (also known as KBO’s (Kuiper Belt Objects) or TNO’s (trans-Neptunian Objects)) Exoplanets There are now thousands of known exoplanets. Planets that orbit other stars than the sun. The first exoplanets were only found 25 years ago. They are found when they pass in front of a star. The search is on to find an Earth-like exoplanet (especially one that might support life) Stars a self-luminous ball of gas that shines or has shone because of a nuclear fusion reaction in its interior. Extreme temperatures (several million K (kelvin) and pressures are required to ignite a fusion reaction. The sun is our closest star. The colour and size of a star can tell an astronomer a great deal about its lifespan and ultimate future. Constellations Ancient astronomers grouped these stars to form creatures and objects that we call “Constellations”. Predicting your behaviour or future based on these constellations (particularly the 12 constellations called the Zodiac) is called astrology. Astrology is NOT a science. The stars in a constellation are not necessarily located in a group or a star-cluster. Nebula Interstellar region of gas and dust If enough gas and dust are present, gravity will draw the dust together (over millions of years) and the material could pull together to form a star or a cluster of stars. (Our Solar System formed like this) Nebulas can either emit light, absorb light or reflect light. Nebulas can also result from the explosion of a star (Nova or Supernova). Gases from the star are expelled into space. Galaxy A collection of stars, gas, and dust bound together by gravity The smallest galaxies may contain only a few hundred thousand stars, while the largest galaxies have thousands of billions of stars. Galaxies can be classified based on their shape - this also gives information about their age Galaxies rotate about a central point – the Milky Way galaxy takes 220 million years to rotate. Milky Way Galaxy The Milky Way galaxy contains our solar system. Galaxies come in a variety of shapes (which are indicative of their age and size The Milky Way galaxy contains 200 - 400 billion stars and is about 120,000 light years across. Neutron Stars and Pulsars stars that have a mass of 1.5 to 3.0 times the mass of the Sun but a radius of only 10 km. It is the result of the gravitational collapse of a large star This collapse has crushed all matter into neutrons. A teaspoon of a neutron star would weigh thousands of tons. If the neutron star emits jets of matter and energy in a pulsating fashion, it is known as a pulsar. Pulsars spin rapidly and jets of material are often ejected from the poles of the pulsar. Black Hole a region in space from which, according to the general theory of relativity, neither light, radiation, nor matter can escape. Black holes have immense gravity and suck in stars and other material that get too close to their “gravity wells”. It is believed that a supermassive black hole exists in the middle of our galaxy (and the middle of most galaxies. The black holes continue to get larger as they “suck” in more and more material. Novas When a star dies, the nuclear reaction in the core stops. Since the outward force no longer exists, the star collapses onto itself due to its force of gravity. This collapse is called a Nova and can be seen from the outer layers of gas ejected from the imploding star (A nebula forms that is illuminated by the collapsed star within). When a small star “goes Nova”, it leaves behind a small star called a white dwarf and a nebula. Black Holes and Supernovas Black holes can only form from the collapse of supermassive stars. (Those with a mass of more than about 10 solar masses). The explosion will form a supernova. The energy released in a supernova is so great that the supernova will outshine every other object in the galaxy for a period of a few weeks.. The core of a supernova may become a black hole if there is sufficient mass. Supernova The explosion of a star with the resulting release of tremendous amounts of radiation (energy) and dust. They only form from the explosion of very massive stars and leave behind neutron stars or black holes. Elements heavier than iron generally only form from supernovas. A supernova will briefly outshine all other stars in a galaxy. The Crab Nebula is the remnant of a supernova recorded by Chinese astronomers in 1054. It was exceedingly bright in the night sky for years after. Quaser Quasars or quasi-stellar radio sources are the most energetic and distant members of a class of objects called active galactic nuclei. Scientists believe they are found at the centers of super-massive galaxies and surround supermassive black holes. They release so much energy, they “outshine” entire galaxies over many EM wavelengths. They are extremely distant, among the most distant objects in the universe and likely formed shortly after the Big Bang (creation of the universe)