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Astronomy 101 Flashcards

1
Q

What is astrology?

A
  • 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
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2
Q

What is an astronomical unit (AU)?

A
  • 149.6 million km
  • approximately equal tothe distance from the Earth to the sun
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3
Q

What is the big bang theory?

A
  • 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
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4
Q

What is the center of masses?

A
  • 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
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5
Q

What does conjunction mean?

A

the closest apparent approach of two celestial objects.

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6
Q

What is a coronagraph?

A

an instrument that blocks out the bright light from the solar photosphere and so makes it possible to observe the chromosphere and corona

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7
Q

What does the term cosmogony mean?

A
  • (usually) refers to the origin of the solar system
  • sometimes used to describe the study of the origin of the universe
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8
Q

What does the term cosmology mean?

A

the study of the origin and large-scale features of the universe

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9
Q

What is density?

A
  • a measure of compactness
  • mass of an object divided by its volume
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10
Q

What is an emission line?

A
  • 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
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11
Q

What is the emission spectrum?

A

an electromagnetic spectrum that consists of emission lines

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12
Q

What is escape velocity?

A

the minimum speed at which a body must move in order not to be restrained by gravity

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13
Q

What are Fraunhofer lines?

A

(dark) absorption lines observed in solar or stellar spectra

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14
Q

What is the Hertzsprung-Russel diagram?

A
  • 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
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15
Q

What is an inferior planet?

A
  • those planets whose orbits lie between the Earth’s orbit and the sun
  • i.e., Mercury and Venus
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16
Q

What is interstellar reddening?

A
  • 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
17
Q

What is ionization?

A
  • the process of adding or removing one or more electrons from an atom or molecule
  • changes the charge on the atom or molecule
18
Q

What is latitude?

A

the coordinate used to measure (in degrees) the angular distance of a point or celestial object above or below an equator

19
Q

What is a light year?

A
  • the distance that light travels in 1 year
  • approximately 1013kilometers
  • often mistaken for a measure of time
20
Q

What is longitude?

A

the coordinate used to specify the position of a point or direction around a celestial body’s axis of rotation

21
Q

What is a magnetic field?

A
  • 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
22
Q

What is a magnetosphere?

A

region surrounding star or planet (including Earth) in which a magnetic field exists

23
Q

What is the minor axis of an ellipse?

A

the smallest diameter of an ellipse

24
Q

What is a Newtonian telescope?

A
  • 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
25
Q

What does “open universe” mean?

A

the cosmological model in which the universe expands forever

26
Q

What is opposition?

A

the position of a planet when it is on the opposite side of the Earth from the Sun

27
Q

What is an orbit?

A

the path traced out by one object around another under the influence of gravity

28
Q

What does reddening mean?

A
  • alteration of a spectrum of light that has passed through a dusty region
  • produced by the preferential scattering and absorption of the shorter wavelength (blue) light, leaving the red light less affected
29
Q

What is a redshift?

A
  • a shift of wavelengths to longer (redder) values
  • caused either by a relative velocity of separation of source and detector, or else by a gravitational field
30
Q

What is a reflecting telescope?

A

a type of telescope in which the objective (the component that gathers incoming light) is a concave mirror

31
Q

What does refraction mean?

A

the bending of light and other electromagnetic radiation in passing from one transparent medium to another

32
Q

What is the Roche limit?

A

the distance from a given body within which gravitational forces would break up a second body that is held together only by its own gravitational force

33
Q

What is a Schmidt telescope?

A

a type of reflecting telescope that uses a spherical primary mirror and a thin correcting lens across the full aperture

34
Q

What is a spectrograph?

A

an instrument for dispersing light into a spectrum and then photographing it

35
Q

What is spectrophotometry?

A

the measurement of the intensity of visible light in various parts of a spectrum

36
Q

What is a spectroscope?

A
  • an instrument for viewing a spectrum
  • usually contains a prism or grating that disperses the light
37
Q

What does a spectrum measure?

A
  • the spread or range of wavelengths in the radiation emitted by some body or region
  • the type of spectrum depends on the physical processes involved in the emission of the radiation
  • e.g., emission spectra vs. absorption spectra
38
Q

What is tidal force?

A
  • the difference between the gravitational force on one side of a body and the gravitational force on the other in a gravitational field
  • on the Earth, the oceans can respond to tidal forces and move relatively easily
  • on a completely solid object, the tidal force can produce a deformation that might even break the body
39
Q

What is zodiacal light?

A
  • the faint glow seen at night near the path of the sun across the sky
  • probably sunlight reflected by interplanetary dust

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