Chapter 14 Flashcards
(20 cards)
Galaxy
Gravitationally bound collection of a large number of stars. The Sun is a star in the Milky Way Galaxy.
Milky Way Galaxy
The spiral galaxy in which the Sun resides. The disk of our Galaxy is visible in the night sky as the faint band of light known as the Milky Way.
Galactic disk/galactic disk
An immense, circular, flattened region containing most of a Galaxy’s luminous stars and interstellar matter.
Galactic bulge
Thick distribution of warm gas and stars around the galactic center.
Galactic halo
Region of a galaxy extending far above and below the galactic disk, where globular clusters and other old stars reside.
Variable stars
A star whose luminosity changes with time.
Pulsating variable stars
A star whose luminosity varies in a predictable, periodic way.
RR Lyrae
Variable star whose luminosity changes in a characteristic way. All RR Lyrae stars have more or less the same average luminosity.
Cepheid
Star whose luminosity varies in a characteristics way, with a rapid rise in brightness followed by a slower decline. The period of a Cepheid variable star is related to its luminosity, so a determination of this period can be used to obtain an estimate of the star’s distance.
Period–luminosity relationship
A relation between the population period of a Cepheid variable and its absolute brightness. Measurement of the pulsation period allows the distance or the star to be determined.
Galactic center
The center of the Milky Way or any other galaxy. The point about which the disk of a spiral galaxy rotates.
Note:
upper right (blue-shifted)
Spiral arm
Distribution of material in a galaxy forming a pinwheel-shaped design, beginning near the galactic center.
Spiral density wave
A wave of matter formed in the plane of planetary rings, similar to ripples on the surface of a pond, that wraps around the rings, forming spiral patterns similar to grooves in a record disk. Spiral density waves can lead to the appearance of ringlets.
Self-propagating star formation.
Mode of star formation in which shock waves produced by the formation and evolution of one generation of stars triggers the formation of the next.
Rotation curve
Plot of the orbital speed of a disk material in a galaxy against its distance from the galactic center. Analysis of rotation curves of spiral galaxies indicates the existence of dark matter.
Dark halo
Region of a galaxy beyond the visible halo where dark matter is believed to reside.
Dark matter
Terms used to describe the mass in galaxies and clusters other techniques, but that has not been confirmed by observations at any electromagnetic wavelength.
Gravitational lensing
The effect induced on the image of a distant object by a massive foreground object. Light from the distant object is bent into two or more separate images.
Galactic nucleus
Small, central, high-density region of a galaxy. Many galactic nuclei are thought to contain supermassive black holes, and almost all the radiation from active galaxies is generated within the nucleus.
