CSET Science Subtest 1: Astronomy Flashcards

Terms Definitions
Organization of Solar System
Sun, Mercury, Venus, Earth, Mars, Asteroid Belt and Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto and Charon, Eres
Kuiper belt
A vast cloud of small icy and rocky bodies, on the outer edges of the solar system much larger than the asteroid belt.
Pluto's Orbit
Inclined and highly eccentric
Dwarf Planet
orbits the Sun; sphere shape; has not cleared the region of its orbit; not a moon
Prograde Rotation
the counterclock wise spin of a planet or moon as seen from above the planets's North Pole; rotation in the same direction as the sun's rotation
Retrograde Rotation
the rotation of a planet opposite to its direction of revolution around the sun. Pluto and Venus' rotation. Also: apparent backward orbit from Earth.
Inner Solar System
Dense, rocky, metallic planets close to the sun and too hot for ice and gas.
Outer Solar System
Gas and Ice giants
Nebula
an immense cloud of gas (mainly hydrogen) and dust in interstellar space
Nebular Hypothesis
our sun along with the planets and other members of the solar system began forming nearly 5 billion years ago, some 9 billion years after the big bang,from supernova explosions. gravitational energy caused the nebula to contract and, in so doing, it began to rotate and flatten. inside the smaller concentrations of matter began condensing to form planets. at the center of the nebula there was sufficient pressure and heat to initiate hydrogen nuclear fusion, and our sun was born
Protoplanet
The embryonic stage of a planet when it is growing because of the collisions with planetesimals.
Planetesimals
An object formed by the accretion of dust grains. Those that keep growing form protoplanets.
Accretion
The formation of a celestial object by the effect of gravity pulling together surrounding objects and gases
Astronomical Unit (au)
A unit of distance used in astronomy. The average Earth-Sun distance, or 150 million km, or 93 million miles.
Exoplanets
planets outside our solar system
Planetary Transit Method
Astronomers look for the drop in brightness of a star as an orbiting planet transits or passes in front of it in our line of sight. The mass and radius of an orbiting planet may be determined from the transit data.
Astrometric Wobble Method
detecting the back-and-forth wobble of a star against a backdrop of background stars
Radial Velocity
velocity along the line of sight toward or away from the observer
Doppler
The change in wavelength or frequency of a wave as seen by an observer who is moving with respect to the source of the waves.
Doppler Wobble Method
This method detects the star's wobble through subtle red- and blue-shifts in its spectral lines
Gravitational Lensing
the gravity of the star with the planetary system can bend light from a background star that happens to be in the line of sight. It makes the background star appear brighter. The lensing happens by chance as the foreground star moves through space.
Dark Matter
Emits no electromagnetic radiation. Its presence is inferred from the fact that it has a gravitational effect on "normal" luminous matter. Dark matter is widely believed to account for some 90% of all matter in the universe.
Globular Clusters
A spherical agglomeration of hundreds of thousands of stars. Hundreds of them orbit the core of the Milky Way galaxy.
Open Cluster
A group of stars loosely held together by gravity. The Pleiades cluster in Taurus is the most famous.
Interstellar Cloud
An accumulation of dust and gas (mainly hydrogen and helium). They may come in a wide range of sizes, densities, and temperatures.
Emission nebula
A cloud of ionized gas emitting light in certain discrete wavelengths.
Spiral Galaxy
flat and disk-shaped, rotating, with two or more curving arms that appear to emerge from a central bulge or from a bar. A large, sparsely populated halo of stars and globular clusters surrounds the disk. The arms are the site of star formation and appear brighter than the rest of the disk.
Elliptical Galaxy
may be very large, with hundreds of millions or even trillions of stars. They may be spherical, or like "squashed" spheres — ellipsoidal. They exhibit no arms or other structures, and have much less star formation than spirals. Elliptical galaxies are thought to have formed from collisions and mergers of spirals.
Irregular Galaxy
No regular structure. Like spirals, they have some gas and young stars
Dwarf Spheroidal Galaxy
Perhaps the most common type of galaxy in the universe. They are a suggested new class, still debated among astronomers. These galaxies are relatively small, and "fluffier" or lower in star density than ellipticals. It is thought that spiral and irregular galaxies which have interacted with other galaxies in a cluster lose their gas content and turn into dwarf spheroidals.
Black Hole
An object with such strong gravity that light cannot emerge from it, so it can't be seen.
Location of our Solar System
In the Milky Way Galaxy, near a "spur" off the so-called Perseus spiral arm — about two-thirds of the way from the center to the edge of the visible disk of the galaxy. The Sun, along with the other stars, orbits the center of the galaxy.
Orbit of Sun Around Center of Milky Way
Takes about 225 million years.
Size of the Milky Way
100,000 ly x 1000 ly with a 3,000-4,000 ly bulge in center
Luminosity
energy output from the surface of a star per second; measured in watts
Star Color
Depends on surface temperature of the star
Star Magnitude
Apparent brightness
Minimum temperature to ignite fusion
10,000K
Sun's Core Temperature
15,000K
Internal Structure of the Sun
Core-->Radiation Zone--> Convection Zone--> Photosphere --> Chromosphere --> Corona
Proton-proton Chain
The mechanism by which hydrogen is fused to helium in relatively low-mass stars such as the sun:
1. 1H+ + 1H+ --> 2H+ (D+) + Positron + Neutrino
2. D+ + 1H+ --> 3He2+ + gamma ray
3. 3He2+ + 3He2+ --> 4He2+ + 1H+ + 1H+
Sun's LIfespan
10 billion years
Neutrino
An elementary particle that is commonly given off in nuclear reactions or radioactive decays. It travels at close to the speed of light. It has no electric charge and passes through matter without interacting with it
Gamma Ray
Photons of electromagnetic radiation from the very highest energy part of the spectrum. They heat the sun.
Hertzsprung-Russell Diagram
y-axis = luminosity, or a quantity related to luminosity such as absolute magnitude.
x-axis = surface temperature of a star, or a related quantity such as color. Note that the temperature increases to the left in an H-R diagram.
Stellar Main Sequence
The phase in a star's life when it is powered by nuclear reactions in the core.
Brown Dwarf
An object that is intermediate in mass between a planet and a star. It may have enough mass to ignite fusion reactions in its core, but the reactions are not sustained. 13-75 times the mass of Jupiter
Anti-Matter
Matter with electrical charges which are the opposite of "normal" matter. When a particle of antimatter is brought into contact with an equivalent particle of normal matter, both particles are annihilated, and a considerable amount of energy is released.
Aperture
The diameter of the light-collecting opening of a telescope (e.g., the diameter of the objective lens or mirror).
Angles in the sky
60= 1 arc minute; 60 arcminute =1 degree; sky = 360 degrees
Resolution
the ability of a microscope or telescope to measure the angular separation of images that are close together
Refractors
A telescope that forms an image with a lens (as opposed to a mirror).
Reflectors
A telescope that forms an image with a mirror (as opposed to a lens).
Pulsar
a rapidly spinning neutron star that emits rapid pulses of radio and optical energy
Neutron Star
collapsed core of a supernova that can shrink to about 20 km in diameter and contains only neutrons in the dense core
Supernova
the brilliant explosion of a dying supergiant star
Solar Flare
Occur above active sunspots when loops of gas suddenly connect. Emit X-rays and ultraviolet radiation. Last a short time
Sunspot
an area of the Sun that is cooler and not as bright as surrounding areas and that is caused by the Sun's intense magnetic field
Corona
outermost, largest layer of the sun's atmosphere; extends millions of kilometers into space and has temperatures up to 2 million K
Photosphere
lowest layer of the Sun's atmosphere; gives off light and has temperatures of about 6,000K
Grazing Incidence
Shallow angle at which x-rays will reflect (x-rays pass through objects at most angles). Used to gather x-rays in space based telescopes.
Astronomical objects that emit x-rays
the Sun and other stars, white dwarf stars, supernovas and supernova remnants, neutron stars, black holes, active galaxies, and clusters of galaxies.
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