3.1 Astronomy

3.1 ASTRONOMY The Universe Universe - all existing matter that is considered to be spread out in a diameter of 10 billion light years; makes up space as a whole. Asteroid - a piece of rock that is similar to the material formed into planets; usually found in asteroid belts. Big Bang Theory - a theory that states that approximately 13.8 billion years ago the universe was formed with an explosion that expanded a single point. Celestial Object - any object outside or above Earth’s atmosphere. Comet - a relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit. Doppler Effect - change in the apparent frequency of a wave as the observer and source move away from each other. Eccentricity - ratio of the distance between the foci to the length of the major axis; defines the shape of a planet’s elliptical orbit. Focus/Foci - for an ellipse, one of the two points for which the sum of the distances to any point in the ellipse is a constant. A satellite orbiting the Earth moves in an ellipse that has Earth at one focus. Galaxy - a collection of star systems; the Galaxy Earth exists in the Milky Way. Gravitation - the movement downward resulting from a gravitational attraction. Impact Center - oval-shaped depression with a raised rim formed by a meteorite, asteroid, or comet colliding with a solid surface. Impact Event - the collision of comets, asteroids, and meteoroids, or any other type of celestial body. Inertia - the tendency of a body to maintain in a state of rest or uniform motion unless acted upon by an external force. Jovian Planet - planets that are huge gas giants and have a relatively low density. These include Jupiter, Saturn, Uranus, and Neptune. Terrestrial Planet - planets that are closer to the Sun and generally denser and rocky. These include Mercury, Venus, Earth, and Mars. Luminosity - Measures how bright the star will be in relation to the sun if all stars were the same distance from the observer. Meteor - any of the small solid extraterrestrial bodies that hits the Earth's atmosphere. Milky Way Galaxy - the name of galaxy; a spiral galaxy that contains about 400 billion stars. Moon - any natural satellite of a planet. Nuclear Fusion - the combination of the nuclei of small atoms to form larger nuclei; releases energy. Red Shift - the change of wavelength of light due to an object moving away from the observer. Blue Shift - the change of wavelength of light due to an object moving closer to the observer. Hierarchy of the Universe The universe is everything. It is expanding as seen by longer wavelengths of light to the red end of the spectrum. Universe Galaxies Stars Solar Systems Electromagnetic Spectrum Wavelength - the distance from one wave crest to another. crest crest Doppler Effect - when sound waves or light waves are stretched out or compressed based on whether the source is moving towards or away from an observer. Away Towards Red shift - Away LONGER wavelength SHORTER wavelength Blue shift - Towards Stars Stars - balls of gas that perform fusion (nuclear explosion); hydrogen fuses into helium H+H He . Constellation - group of stars that form a pattern in the night sky Stellar Parallax - a measure of stellar distance. Magnitude - a number given to celestial objects to express its relative brightness. Light Year - the distance light travels in one Earth year Binary Star - one of two stars revolving around a common center of mass under their mutual gravitational attraction. Visual Binaries - pairs of stars in which the members are far apart enough to be resolved telescopically. Absolute Magnitude - the apparent brightness of a star if it were to be viewed from a distance. This value is used to compare the true brightness of stars. Apparent magnitude - the brightness of a star when seen from Earth. HR Diagram - Hertzsprung-Russell Diagram that plots the temperature of stars against their luminosity. Main sequence Stars - starts in its early stage that are positioned from the upper left to lower right of an HR diagram; includes majority of the stars. Red Giant - a large, cool star with a high luminosity that occupies the upper right of an HR Diagram. Supergiant - very large, bright stars. Nova - a star that increases thousands of times in brightness before fading. Nebula - a large cloud of dust and gas in space. Bright Nebula - interstellar clouds of gas and dust where stars are born or have died; formed by ultraviolet radiation from hot stars. Emission Nebula - a gaseous nebula that derives its visible light from fluorescent or ultraviolet light. Reflection Nebula - a dense dust cloud in interstellar space that is illuminated by starlight. Interstellar Dust - dust and gas found between stars. Protostar - a cloud that contracts of gas and dust with enough mass to form a star. White Dwarf - a small, hot dim star that is the product of the center of an old star. Neutron Star - a star that has collapsed under its own gravity; composed of entirely neutrons and has extremely high density. Pulsar - a spinning neutron star that produces radio waves. Black Hole - an object in space whose gravity is so strong that light can escape through. Spiral Galaxies - a flattened, rotating galaxy with pinwheel-like arms of interstellar material and young stars winding out from its nucleus. Barred Spiral Galaxies - a galaxy that has straight arms extending from its nucleus. Elliptical Galaxies - a galaxy that is round or elliptical in it’s outline. Irregular Galaxies - a galaxy that lacks symmetry. Galactic Cluster - a system of galaxies containing several to thousands of member galaxies. Local Group - a cluster of about 20 galaxies to which our galaxy belongs. Degenerate Matter - when electrons are displaced inward from their regular orbits around an atom’s nucleus. Cepheid Variable - a star whose brightness varies periodically because it expands; a type of pulsating star. Pulsating Variables - a variable that changes/pulsates in size and luminosity. Eruptive Variable - star that can vary in brightness. I N C R E A S E I N S I Z E A Star’s Life Cycle Stage 1: Main Sequence Where 90% of all stars are found and fuse hydrogen. Gas (nebula) in space collects by gravity until fusion starts. Stage 2: Giants & Supergiants This is the intermediate state where the stars have moved off the main sequence and grown in size. Stage 3: White Dwarfs Small to medium stars; these are dead stars that have blown off their outer parts into the planetary nebula. Their carbon core is the only The Solar System Stage 3: Massive Stars these blow up in explosions called supernova leaving behind a black hole. az- Asteroid - a small, rocky body that orbits the sun or is found in asteroid belts. Comet- a small, icy body that moves around in space and has a visible tail due to gasses and dust. Meteor- a small, rocky body that enters the Atmosphere in flames and the vaporizes. Distance between foci Major axis ☆ Eccentricity is a measure of. a planet's elliptical orbit. ☆ The higher the number, the more elliptical the orbit The lower the number, the more circular the orbit is. ☆ No planet, asteroid, or comet revolves in a perfect circle. Every orbit is called an Ellipse. Distance between foci Length of major axis ☆ Eccentricity is a number between 0and 1.0 is circular and 1 is the most elliptical. Aphelion - the slowest orbit which is far from the sun and has low gravity. Perihelion - the fastest orbit point with high gravity.