Astronomy 101 Flashcards
What is astrology?
- the idea that the positions of the sun, moon, and planets exert an influence on events on Earth
- unlike astronomy, astrology lacks any scientific basis
What is an astronomical unit (AU)?
- 149.6 million km
- approximately equal tothe distance from the Earth to the sun
What is the big bang theory?
- a cosmological theory that posits a universal expansion starting from an explosion in a very dense and compact stage
- some big bang theories predict continued expansion
- others predict a slowing expansion to be followed by a reversal leading to a contraction
What is the center of masses?
- mean position of the masses that comprise a system or larger body
- for two bodies, the center of mass is a point on the line joining their respective centers of mass
What does conjunction mean?
the closest apparent approach of two celestial objects.
What is a coronagraph?
an instrument that blocks out the bright light from the solar photosphere and so makes it possible to observe the chromosphere and corona
What does the term cosmogony mean?
- (usually) refers to the origin of the solar system
- sometimes used to describe the study of the origin of the universe
What does the term cosmology mean?
the study of the origin and large-scale features of the universe
What is density?
- a measure of compactness
- mass of an object divided by its volume
What is an emission line?
- a bright line in a radiation spectrum
- line’s wavelength defined by the energy levels of the atoms or molecule from which the radiation is emitted
What is the emission spectrum?
an electromagnetic spectrum that consists of emission lines
What is escape velocity?
the minimum speed at which a body must move in order not to be restrained by gravity
What are Fraunhofer lines?
(dark) absorption lines observed in solar or stellar spectra
What is the Hertzsprung-Russel diagram?
- a graph showing absolute magnitude or luminosity plotted against temperature (sometimes with a color index) for individual stars
- shows a “main sequence” that describes a direct relationship between luminosity and temperature characteristic of a majority of known stars
What is an inferior planet?
- those planets whose orbits lie between the Earth’s orbit and the sun
- i.e., Mercury and Venus
What is interstellar reddening?
- the relative reduction of the intensity of the shorter (blue) wavelengths of a spectrum, compared to the longer (red) wavelengths
- caused by absorption and scattering of light by interstellar dust
What is ionization?
- the process of adding or removing one or more electrons from an atom or molecule
- changes the charge on the atom or molecule
What is latitude?
the coordinate used to measure (in degrees) the angular distance of a point or celestial object above or below an equator
What is a light year?
- the distance that light travels in 1 year
- approximately 1013kilometers
- often mistaken for a measure of time
What is longitude?
the coordinate used to specify the position of a point or direction around a celestial body’s axis of rotation
What is a magnetic field?
- the region surrounding a magnet or electric current in which magnetic force can be detected
- in this region, high-speed electrically charged particles will generally move along curved paths and radiate energy
What is a magnetosphere?
region surrounding star or planet (including Earth) in which a magnetic field exists
What is the minor axis of an ellipse?
the smallest diameter of an ellipse
What is a Newtonian telescope?
- the first invention of a reflecting telescope
- devised by Sir Isaac Newton in 1668
- a small flat mirror deflects the light from the primary concave mirror, focusing it outside the telescope tube
