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Astronomy DTU
Chapters 5-9
| Question | Answer |
|---|---|
| Star | Self-luminous sphere of gas. Transform matter from lighter elements into heavier ones. |
| Universe | All space along with all the matter & radiation in space. About 14 billion years old, since the Big Bang, & made up of mostly hydrogen with little helium. |
| Solar System (Our) | The Sun, planets, their satellites, asteroids, comets, & related objects that orbit the Sun. About 4 million years old & contain very little hydrogen & helium. |
| Hydrogen fusion (hydrogen burning) | The thermonuclear fusion of hydrogen to produce helium. |
| Fission Theory | Theory that the Moon formed from matter flung off the Earth because the planet was rotating extremely fast |
| Young solar system | Gravity, rotation, & heart shaped |
| Solar nebula | Cloud of gas & dust from which the Sun & the rest of the solar system formed. Diameter of about 100 AU like the "Orion Nebula" |
| Angular momentum | A measure of how much energy an object has stored in its rotation and/or revolution. |
| Protosun | The Sun prior to the time when hydrogen fusion began in its core. |
| Protoplanetary disk (proplyd) | A disk of material encircling a protostar or a newborn star. |
| Heavy elements stayed in central area lighter elements are pushed out | "We are literally made of star dust" |
| Collisions in the early solar system | led to the formation of planets |
| A planet orbits a star. | A moon or natural satellites orbits a planet. |
| Order of planet formation: | Planetesimals > Protoplanets > Planets |
| Planetesimal | Primordial asteroid-like object from which the planets accreted |
| Protoplanet | Embryonic stage of a planet when it is grown because of collisions with planetesimals |
| Core-acceretion model | Traditional theory of giant planet formation that begins with terrestrial planets slowly pulling abundant amounts of water, hydrogen, & helium onto themselves. |
| Gravitational instability model | Theory of giant planet formation in which gases collapse together quickly, without the need for a seed terrestrial planet to form first. |
| Orbital inclination | Tilt or angle of an object's orbital plane around the Sun compared to the ecliptic. All less than 7 degrees. |
| Craters | Circular depression on a celestial body caused by the impact of a meteoroid, asteroid, or comet or by a volcano. Common in early solar system. |
| Radioactive dating of moon rocks | 3.8 billion years ago |
| Minor debris from the formation of the solar system | still exists. |
| Types of debris from formation of the solar system | Asteroid belts, Comets, & Meteoroids |
| Asteroid belt | A 1 1/2 AU wide region between the orbits of Mars & Jupiter in which most of the asteroids are found. |
| Comet | Small body of ice & dust in orbit about the Sun. While passion near the Sun, a comet's vaporized ices gives rise to a coma, tails, & a hydrogen envelope. |
| Meteoroid | Small rock in interplanetary space |
| KBO's (Kuiper Belt Objects) - Especially big 1s | Pluto, Eris, Quaoar & Sedna |
| Kuiper belt | Doughnut-shaped ring of space around the Sun beyond Pluto that contains many frozen comet bodies, some of which are occasionally deflected toward the inner solar system. |
| Oort cloud | Hollow spherical region of the solar system beyond the Kuiper belt where most comets are believed to spend most of their time. |
| Comparative planetology | Orbits - Size - Mass - Density - Spectra - Albedo - Moons |
| Planet | Object orbiting a star that is held together by its own gravitational force in a nearly spherical shape, that is able to clear its neighborhood of debris, & is not the moon (or satellite) of a larger orbiting body |
| dust & extrasolar planets | orbit a breathtaking variety of stars |
| Earth | unique of all planets, covered with 71% mostly liquid water |
| Atmosphere | 4 to 1 mix of nitrogen to oxygen, presently is the third to envelop our planet |
| Carbon dioxide | important because it blocks UV rays & helps form oxygen |
| Atmospheric pressure | 14.7 lbs per square inch Pressure = Force/Area |
| Pressure = | Force/Area |
| Lower layers of the Atmosphere | Troposphere & Stratosphere |
| Troposphere | lowest level of the Earth's atmosphere |
| Stratosphere | second layer in the Earth's atmosphere, directly above the troposphere |
| Ozone layer | lower stratosphere, where most of the ozone in the air exists |
| Ozone holes | |
| Upper layers of atmosphere | Mesosphere & Ionosphere (thermosphere) |
| Mesosphere | layer in the Earth's atmosphere above the stratosphere |
| Ionosphere (thermosphere) | region of Earth's atmosphere, above the mesosphere, in which sunlight ionizes many atoms |
| Carbon dioxide & Greenhouse effect | today 30 degrees centigrade warmer |
| Plate tectonics | produce major changes of Earth's surface proposed by Newton Alfred Wegener introduced idea in 1915 |
| Continental drift - Pangaea | - Volcanoes - Mountain formation - earthquakes |
| Continental drift | gradual movement of the continents over the surface of the Earth due to plate tectonics |
| Earth's interior consists of | rocky mantle & an iron-rich core |
| Planetary differentiation produces | a layered structure - core & mantle |
| Surface density | 5520 km/m3 temp 290 |
| center density | 5000 K |
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