Unit 4 Space Exploration Notes PDF

UNIT 4 EXAM NOTES Unit 4 Space Exploration Notes: Sun and Stars: Sun: composed of many layers of gas, includes hydrogen gas (73% by mass) and helium (25% by mass) but also small amounts of heavier elements. Estimated to be 4.5 billion years old. -​ Emits heat and light energy energy in the for...

UNIT 4 EXAM NOTES Unit 4 Space Exploration Notes: Sun and Stars: Sun: composed of many layers of gas, includes hydrogen gas (73% by mass) and helium (25% by mass) but also small amounts of heavier elements. Estimated to be 4.5 billion years old. -​ Emits heat and light energy energy in the form of radiation -​ Astronomers estimated mass of the sun by using the orbit of any planet, with the distance of the sun, we used Newtwon’s law of gravity to get 2x10 to 30kg more mass than the Earth -​ Six different layers: -​ Corona -​ Chromosphere -​ Photosphere -​ Convective zone -​ Radiative zone -​ Core Stars: a constellation is a group of stars that resemble a recognizable form from Earth. Although these stars all appear to lie at the same distance from the Earth, they vary greatly in size, distance, and brightness. The life cycle of a star allows us to determine the variation in these characteristics. -​ Nebula is a giant cloud of dust and gas -​ A nebula is a giant cloud of gas and dust in space that collapses under gravity, forming dense clumps. These clumps heat up and become protostars, which are the early stages of star formation  UNIT 4 EXAM NOTES -​ A protostar becomes denser as gravity pulls more gas and dust from its surrounding nebula toward its center. This accumulation of material increases the pressure and temperature, causing the protostar to contract and become even denser -​ Nuclear fusion is the process where hydrogen nuclei fuse together to form helium nuclei. Nuclear fusion produces huge amounts of energy which keeps the core of the protostar hot, which in turn forms a main sequence star (actual star). -​ The gas that fuels a star is hydrogen. After running out of this fuel, the star condenses and then expands again. How much a star expands and contracts depends on its initial size -​ Small to medium-sized star eventually form a red giant star, while really big stars become red supergiants -​ When a red giant star becomes unstable, it sheds its outer layers, creating a planetary nebula. The core left behind contracts and forms a white dwarf, which gradually cools and dims over time. -​ White dwarf are named because they are small and give off white light. One star releases all of its energy it can no longer emit light, and therefore becomes a black dwarf -​ Red supergiants undergo more nuclear fusion and therefore start to shine very bright again. Eventually, after much expansion and contraction, a supernova occurs which is when this star condenses. Depending on how big the red supergiant was, it will then either condense into a neutron star or a black hole. (FLOW CHART of life cycle of star)  UNIT 4 EXAM NOTES Solar system: Inner planets: Mercury, Venus, Earth, Mars (Rocky planets) ASTEROID BELT Outer planets: Jupiter, Saturn, Uranus, Neptune (Gaseous planets) Differences between: 1.​ Composition: Inner planets are rocky with solid surfaces, while outer planets are gas giants primarily composed of hydrogen and helium. 2.​ Size: Inner planets are smaller and have less mass compared to the much larger outer planets. 3.​ Moons and Rings: Inner planets have fewer moons and no rings, whereas outer planets have numerous moons and prominent ring systems. 4.​ Orbit: Inner planets orbit closer to the Sun, resulting in shorter orbital periods, while outer planets are farther away with longer orbital periods.  UNIT 4 EXAM NOTES Other Celestial Objects: Meteoroid: a small rock or particle of debris in space, usually ranging in size from a grain of sand to a boulder. Meteor: when a meteoroid enters the Earth's atmosphere and burns up due to friction with the air, it creates a bright streak of light in the sky, commonly known as a "shooting star." Meteorite: if a meteoroid survives its journey through the Earth's atmosphere and lands on the Earth's surface, it is called a meteorite. Comet: a comet is a ball of ice, rock, and dust. Originates from Kuiper Belt and Oort Cloud. A comet’s tail forms from melting in the surrounding nucleus, ion cloud, and dust cloud. Asteroids: small, irregularly shaped, rocky debris that orbits the Earth. Asteroid belt located between Mars and Jupiter. Oort Cloud: The Oort Cloud is a vast, spherical shell of icy objects and cometary nuclei that surrounds our solar system. It's believed to be the source of long-period comets that enter the inner solar system. Location: The Oort Cloud is located far beyond the orbit of Pluto, extending from about 2,000 to 100,000 astronomical units (AU) from the Sun. Kuiper Belt: The Kuiper Belt is a region of our solar system beyond the orbit of Neptune, extending from about 30 to 55 astronomical units (AU) from the Sun. It's similar to the asteroid belt but much larger and more massive. What's found there:  UNIT 4 EXAM NOTES ​ Dwarf Planets: The most famous example is Pluto, along with others like Haumea and Makemake. ​ Kuiper Belt Objects (KBOs): These are small, icy bodies made primarily of frozen volatiles such as methane, ammonia, and water. They vary in size from tiny fragments to objects over 1,000 kilometers in diameter. ​ Comets: Many short-period comets (those with orbits of less than 200 years) originate from the Kuiper Belt. Galaxies: Galaxies: composed of a large group of stars, gas, and dust held together by gravity. Orbits around a central point called a black hole. The observable universe contains around 100 billion galaxies. A small galaxy is one that has less than a billion stars. -​ Black hole: is a region in space where gravity is so strong nothing can escape -​ Dark matter: (90% of matter in universe) refers to matter in the universe that is invisible because it doesn't interact with light or radiation -​ Astronomers have proven the existence of dark matter by observing how matter in a galaxy cluster bends light rays, they were able to compute and map out where they believe the dark matter is -​ Galaxy origins: astronomers suggest they formed shortly after Big Bang. Milliseconds later, clouds of gases began to coalesce, collapse, and compress under gravity to form building blocks of galaxies  UNIT 4 EXAM NOTES -​ Types of galaxies: -​ Spiral Galaxies: Formed from rotating clouds of gas and dust, flattening into disks with spiral arms. -​ Barred Spiral Galaxies: Similar to spiral galaxies but with a central bar structure, likely due to internal dynamics. -​ Elliptical Galaxies: Formed from the merging of smaller galaxies, leading to a more rounded, random star distribution. -​ Irregular Galaxies: Lack a defined shape due to gravitational interactions or collisions, often rich in gas and dust. -​ Galaxy groupings: some galaxies occur alone or in pairs, but they are often parts of larger associations known as groups, clusters and superclusters, galaxies can interact and merge with each other -​ Milky Way: formed through merging of other galaxies over time, it has barred spiral shape, belongs to galaxy cluster ‘local group’, which contains 20 galaxies and more than 2000 billion stars -​ 100000ly in diameter and 2000ly thick -​ Andromeda galaxy closest to Milky Way Scientific Notation and Measuring Distances in Space: Astronomical Units (AU): helps us visualize vast distances by comparing them to a known standard, average distance between sun and Earth -​ 1 AU = 150 000 000km -​ Scientific notation: 1.5x10^8km Light Years (ly): measures distances to objects which are outside of our solar system, one light year equals the distance that a beam of light can travel through space in one year -​ 1 ly = 63 000 AU (DO PRACTICE QUESTIONS)