Astronomy

Major Stars by Constellation

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

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

General terms

Conjunction : two bodies due north and south of each other; 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

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

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 least massive; slowest orbiting; coldest; most eccentric orbit; discovered by

Clyde Tombaugh at Lowell Observatory in Flagstaff; James Christy discovered moon Charon; Kuiper

Belt of asteroids nearby

Sun : 865,000 mile diameter; 93 million miles from Earth; 499 seconds (8 minutes) for light to reach Earth;

surface 5778 K; core 28 million F; photosphere - chromosphere - corona

Three planets believed to exist near Upsilon Andromedae

Earth's atmosphere : troposphere - stratosphere - mesosphere - thermosphere - ionosphere

Twilight : civil (center of Sun 0 to 6 degrees below horizon), nautical (6 to 12 degrees), astronomical (12 to 18 degrees)

Space Exploration

               First animal in space - Laika (dog, 1957)

               First satellite - Sputnik I (1957)

               First American satellite - Explorer I (1958)

               First man in space - Yuri Gagarin (1961, Vostok I)

               First American in space - Alan Shepard (1961)

               First American in orbit - John Glenn (1962)

               First spacewalk - Alexi Leonov

               First American spacewalk - Ed White

               First woman in space - Valentina Tereshkova (1963)

               First American woman in space - Sally Ride

               First black person in space - Guion Bluford

               First men on moon - Neil Armstrong, Edwin Buzz Aldrin (1969, Apollo 11), Michael Collins in command module

               American manned space programs - Mercury, Gemini, Apollo, Skylab, Space Shuttle

               Russian manned space programs - Vostok, Voskhod, Soyuz, Salyut

               Died in Apollo flash fire in 1967 - Grissom, Chaffee, and White

               First space shuttles - Enterprise (trainer), Columbia, Challenger, Discovery, Atlantis