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Astronomy Study Guide Ptolemy's Zodiac Constellation Meaning Major Stars Aries

Astronomy Study Guide Ptolemy's Zodiac Constellation Meaning Major Stars Aries Ram Taurus Bull Aldebaran Gemini Twins Pollux, Castor Cancer Crab Leo Lion Regulus Virgo Virgin Spica Libra Balance Scorpius Scorpion Antares Sagittarius Archer Capricornus Sea-goat Aquarius Water-bearer Pisces Fishes Other Constellations Constellation Meaning Major Stars Aquila Eagle Altair Auriga Charioteer Capella Bootes Herdsman Arcturus Canis Major Greater Dog Sirius Canis Minor Smaller Dog Procyon Centaurus Centaur Alpha, Beta Cepheus King Delta Cephei (pulsating variable) Cetus Whale Mira Ceti (long period variable) Cygnus Swan Northern Cross; Deneb Eridanus River god Achernar Lyra Lyre Vega : M57 Ring Nebulae Orion Hunter Rigel : Betelgeuse Pegasus Winged horse Great Square Perseus Perseus Algol (eclipsing variable) Piscis Austrinus Southern fish Fomalhaut Ursa Minor Lesser bear Polaris (Northern star) Big Dipper is part of Ursa Major; Sickle is the head and mane of Leo; Alpha Andromedae is northeast star of the Great Square of Pegasus Brightest Stars Sirius (Canus Major) Canopus (Carina) Alpha Centauri (Centaurus) Vega (Lyra) Arcturus (Bootes) Rigel (Orion) Capella (Auriga) Procyon (Canis Minor) Achernar (Eridanus) Beta Centauri (Centaurus) Nearest Stars Alpha Centauri (Centaurus) Barnard's Star (Ophiuchus) Wolf 359 (Leo) Lalande 21185 (Ursa Major) Sirius (Canis Major) Absolute magnitude = V + 5 - 5 log(d) V = apparent magnitude d = distance in parsecs Classes of stars O : about 25000 K; bluest B : 23000 - 12000 K; includes Beta Centauri A : 11000 - 8000 K; includes Sirius F : 7500 - 6000 K G : 6000 - 5000 K; has line for ionized calcium; includes the sun and Capella K : 4000 - 3200 K; has line for neutral calcium M : < 3000 K; has line for titanium oxide d = distance in parsecs Hertzsprung-Russell Diagram Plots spectral class (OBAFGKM) on horizontal axis and absolute magnitude on vertical axis Most stars are on top-left to bottom-right diagonal; called Main Sequence; those at bottom right are dwarfs White dwarfs are on diagonal parallel to but below Main Sequence; very dense; includes Sirius B Giants are at center right Supergiants are at top Stefan's law says energy output varies as fourth power of temperature Variable stars do not have constant luminosity Eclipsing variable stars are binary stars that pass in front of each other Pulsating variable stars may be of cepheid (like Delta Cephei), RR Lyrae (like RR Lyrae), or long-period (like Mira Ceti) Erupting variable stars are novas or supernovas Life cycle of medium-sized stars Protostars : collection of interstellar gas and dust (from dark nebulas or globules); T Tauri is a prototype protostar HR Main Sequence Red giant White dwarf : much mass compressed in small volume, making it harder for energy to escape End of life for large stars Supernovas : use up last of energy in a big explosion Neutron star / pulsar : remaining mass becomes super-compressed; examples include Crab Nebula and Gum Nebula; really big stars may collapse into black holes, which can only be observed by their gravitational effects on nearby stars since no electromagnetic radiation can escape from them Most abundant elements Hydrogen 109, Helium 6.3*107, Oxygen 800,000, Carbon 500,000, Nitrogen 100,000, Neon 93,000 Random terms Conjunction - two bodies due north and south of each other (same latitude); inferior if inner planet is between Earth and Sun; superior if inner planet is on far side of Sun; right ascension (N celestial pole) or celestial longitude (N eclipic pole) Opposition - right ascensions differ by 12 hours or celestial longitudes differ by 1800 Perihelion - point of orbit nearest Sun Aphelion - point of orbit farthest from Sun Perigee - point of orbit nearest Earth Apogee - point of orbit farthest from Earth Equinox - length of day and night is equal everywhere on the planet Meteor - ice or rock that burns up entering Earth's atmosphere; called a meteoroid in space and a meteorite if a remnant makes it to the ground Synodic Period - The time interval between two successive occurrences of a specific type of alignment of a planet (or the moon) with the sun and the earth Foucault Pendulum - first proved that Earth rotates on its axis Ecliptic - the path in the sky that the sun appears to traverse over the course of a year Zeeman Effect - Spectral line splitting due to the influence of magnetic fields Syzygy - name given to the configuration when three celestial bodies are in a line Baily’s Beads - Beads of light visible around the rim of the moon at the beginning and end of a total solar eclipse Albedo - the reflecting power of an object (how much light a planet reflects) Heliopause - outer boundary of the sun's magnetic field Elongation - the position of an inferior planet by the angle it makes with the sun as seen from the earth Van Allen Belts - two main radiation belts that surround the earth Bishop’s Ring – occurs around Sun after volcanic eruption Sun Dogs- two bright spots of light on opposite sides of a halo around the sun Tidal Friction - phenomenon that causes the Moon's rotation about its own axis to be equal to the Moon's period of revolution about the Earth Azimuth - angular position of an object measured from a fixed point along the horizon Precession - change in orientation of the Earth's axis Solar Declination Angle - angular position of the sun at solar noon with respect to the plane of the equator Retrograde – motion when a planet seems to be moving westward in the sky Famous People Hipparchus - first man to classify stars according to their brightness Aristarchus - Greek astronomer who first proposed a model of the solar system with the Sun at the center Copernicus - wrote the book "On the Revolutions of the Heavenly Spheres"; first theorized the heliocentric system in modern times. Eratosthenes - first measured the radius of the Earth Tycho Brahe - Danish astronomer who built the largest naked eye astronomical observatory in modern Europe. He made countless observations of the position of Mars and other celestial bodies. Kepler - realized that planets follow elliptical, rather than circular, orbits around the Sun O. Roemer - Danish astronomer who calculated an accurate value for the speed of light in 1676. Galileo Galilei - Italian astronomer and physicist who first utilized the telescope for astronomical observations. Isaac Newton - wrote law of gravity Meteor Showers : Perseids August 12, Orionids October 21, Geminids December 13 Aurora Borealis and Aurora Australis are caused by collisions between atoms from solar flares along Van Allen belts and terrestrial atoms Arno Penzias and Robert Wilson of Bell Labs found cosmic background radiation predicted by George Gamov from Big Bang Theory Largest telescopes Refracting : Yerkes Observatory, Williams Bay WI Reflecting : Keck, Mauna Kea, HI Space : Hubble Single Radio Dish : Arecibo Observatory, Puerto Rico Radio Interferometer : Very Long Baseline Array, HI to Virgin Islands Kepler's Law: planets revolve in ellipse with Sun at one focus; line joining the Sun to a planet sweeps out equal areas in equal times; the square of the period of revolution of a planet is proportional to the cube of the length of the major axis of the orbit. Planets Mercury : fastest orbiting; longest day; no moons; visited by Mariner 10 1974-1975; Caloris Basin impact crater 800 miles in diameter; hydrogen- helium atmosphere Venus : most circular orbit; hottest; no moons; dense, white atmosphere mainly of carbon dioxide, possibly with sulfuric acid clouds; visited by Mariner 2 1962; Mariner 5 and Venera 4 arrived on same day in 1967; visited by Mariner 10 1974; mapped by Magellan in 1989-1994 Mars : Olympus Mons is solar system's tallest mountain; atmosphere of carbon dioxide; polar caps of water and carbon dioxide; visited by Mariner 4 1964; orbited by Mariner 9 1971; visited by Vikings 1976, Mars Pathfinder (with Sojourner) and Mars Global Surveyer 1996; Albert Hall discovered outer Deimos and inner Phobos moons Jupiter : largest and most massive; shortest day; deepest oceans; atmosphere 90% hydrogen, 10% helium; visited by Pioneer 10 and 11 1973-1974; 17 known moons; Galileo discovered Ganymede (largest moon in solar system), Callisto (oldest, most crater moon surface), Io (volcanic), and Europa in 1610; visited by Voyager 1 and 2 in 1979; Great Red Spot has counterclockwise rotation; Shoemaker-Levy 9 collided with Jupiter 1994; orbited by Galileo 1995 Saturn : lowest average density; second largest; 18 moons (tied with Uranus for most); atmosphere 75% hydrogen, 25% helium; visited by Pioneer 11 in 1979, also by Voyager 1 and 2 1981; Cassini to visit in 2004 Uranus : discovered by William Herschel in 1781; visited by Voyager 2 1986; 18-21 moons including Miranda, Ariel, Umbriel, Titania, and Oberon; atmosphere 83% hydrogen, 15% helium, 2% methane Neptune : has Great Dark Spot; atmosphere 80% hydrogen, 19% helium, 1% methane; visited by Voyager 2 in 1989; 8 moons including Triton (largest) and Nereid (most eccentric in solar system) Pluto : smallest and uploads/Geographie/ astronomy-study-guide.pdf