Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
40 Cards in this Set
- Front
- Back
Low-mass stars
|
Stars born with masses less than about 2M Sun; these stars end their lives by ejecting a planetary nebula and becoming a white dwarf.
|
|
High-mass stars
|
Stars born with masses above about 8M Sun; these stars will end heir lives by exploding as supernovae
|
|
Molecular Clouds
|
Cool, dense interstellar clouds in which the low temperatures allow hydrogen atoms to pair up into hydrogen molecules.
|
|
Protostar
|
A forming star that has not yet reached the point where sustained fusion can occur in its core.
|
|
Life Track
|
A track drawn on an H-R diagram to represent the changes in a star's surface temperature and luminosity during its life; also called an evolutionary track.
|
|
Main Sequence Star
|
Stars whose temperature and luminosity place them on the main sequence of the H-R diagram. Main-sequence stars are all releasing energy by fusing hydrogen into helium in their cores.
|
|
Red Giant
|
A giant star that is red in color
|
|
Hydrogen-shell burning
|
Hydrogen fusion that occurs in a shell surrounding a stellar core.
|
|
Helium Fusion
|
The fusion of three helium nuclei into one carbon nucleus.
|
|
Helium Flash
|
The event that marks the sudden onset of helium fusion in the previously inert helium core of a low-mass star.
|
|
Planetary Nebula
|
The glowing cloud of gass ejected from a low-mass star at the end of its life.
|
|
Supernova
|
The explosion of a star
|
|
The nearest supernova seen in nearly 400 years and helped astronomers refine theories of supernovae
|
Supernova 1987A
|
|
Supernova Remnants
|
A glowing, expanding cloud of debris from a supernova explosion.
|
|
White dwarfs
|
The hot, compact corpses of low-mass stars, typically with a mass similar to the Sum compressed to a colume the size of the Earth.
|
|
Chandrasekhar Limit
|
The maximum possible mass for a white dwarf, which is about 1.4M Sun
|
|
Accretion Disk
|
A rapidly rotating disk o material that gradually falls inward as it orbits a starlike object.
|
|
Nova
|
The dramatic brightening of a star that lasts for a few weeks and then subsides; occurs when a burst of hydrogen fusion ignites in a shell on the surface of an accreting white dwarf in a binary star system.
|
|
White Dwarf Supernova
|
A supernova that occurs when an accreting white dwarf reaches the white-dwarf limit, ignites runaway carbon fusion, and explodes like a bomb.
|
|
Massive Star Supernova
|
A supernova that occurs when a massive star dies, initiated by the catastrophic collapse of its iron core.
|
|
Neutron Stars
|
The compact corpse of a high-mass star left over after a supernova; typically contains a mass comparable to the mass of the Sun in a volume just a few kilometers in radius.
|
|
Pulsars
|
A neutron star from which we see rapid pulses of radiation as it rotates.
|
|
Blackhole
|
A bottomless pit in spacetime. Nothing can escape from within a black hole, and we can never again detect or observe an object that falls into a black hole.
|
|
Disk
|
The portion of the spiral galaxy that looks like a disk and contains an interstellar medium with cool gas and dust; stars of many ages are found here.
|
|
Bulge
|
The central portion of a spiral galazy that is roughly spherical (or football shaped) and bulges above and below the plane of the galactic disk.
|
|
Spiral Arms
|
The bright, prominent arms, usually in a spiral pattern, found in most spiral galaxies.
|
|
Halo
|
The spherical region surrounding the disk of a spiral galaxy.
|
|
Globular Clusters
|
A spherically shaped cluster of up to a million or more stars; globular clusters are found primarily in the halos of galaxies and contain only very old stars.
|
|
Dark Matter
|
Matter that we infer to exist from its gravitational effects but from which we have not detected any light; dark mater apparently dominates the total mass of the universe.
|
|
Our sun is located in the disk about 28,000 light-years from the galactic center-a little more than halfway out from the center to the edge of the disk.
|
The Suns location in the Milky Way
|
|
Spiral Galaxies
|
Galaxies like the Milky Way with arching structures lying in a plane and emanating from the nuclear bulge.
|
|
Barred Spiral Galaxies
|
Galaxies with a bar of stars running through the nuclear bulge
|
|
Elliptical Galaxies
|
Galaxies with an elliptical shape, no spiral arms, and little interstellar matter.
|
|
Irregular Galaxies
|
Galaxies that are asymmetrical and are sometimes just 2 or more galaxies colliding.
|
|
Hubble's Law
|
A linear relationship between the recessional velocity and the distance to the galaxies. V=HD
|
|
Big-Bang theory
|
States that all the matter in our observable universe came into being at a single moment in time as an extremely hot, dense mixture of subatomic particles and radiation.
|
|
Lookback time
|
Refers to the amount of time since the light we see from a distant object was emitted.
|
|
Cosmological Horizon
|
Marks the limits of the observable universe; a boundary int time, not space.
|
|
Messier Catalogue
|
1st catalog of nonstellar "fuzzy" objects during the 1770's. 109 such objects.
|
|
Nucleosynthesis
|
When helium is depleted, the fusion of heavier elements begins in High-Mass Stars.
|