Name:___________________________________________________ Date:__________________________
1. The radio frequency static Karl Jansky observed in 1931 with his rudimentary radio frequency
antenna peaked 4 minutes ________________ each day, confirming for him that the source could not
be the sun.
2. Radio frequency radiation induces a weak __________________ in a radio telescope antenna.
3. Electromagnetic radiation travels through space at approximately ______________ km per second.
4. The frequency of electromagnetic waves is given in units called ______________.
5. Wavelength of electromagnetic energy is given in _____________ or some decimal fraction thereof.
6. As electromagnetic radiation spreads out from a source, the area it covers is proportional to the
________________ of the distance the radiation has traveled.
7. The property that primarily determines the effects of electromagnetic energy, and therefore how we
categorize it, is its ___________________.
8. Electromagnetic radiation in the frequency range just higher than x-rays is called
__________________ _______.
9. The radio range includes the ________________ (longest/shortest) wavelengths in the electromagnetic spectrum.
10. The range of electromagnetic radiation with wavelengths slightly shorter than visible light is called
_______________________.
11. The range of electromagnetic radiation with wavelengths slightly longer than visible light is called
____________________.
12. The GAVRT is currently capable of receiving radio waves in the _______ and _______ bands.
13. Electromagnetic waves include both a(n) __________________ and a(n) ________________ vector at right angles to each other and to the direction of wave propagation.
14. The direction of the electric vector describes an electromagnetic wave’s
______________________.
15. The most important property of objects in determining the frequency of the radiation they emit is
___________________.
16. In the case of thermal radiation, the higher the temperature of an emitting object, the
______________ energy is contained in its radiation.
17. An object that absorbs and re-emits all the energy that hits it is called a(n)
_____________________.
18. Wien’s Law states that the peak amount of energy is emitted at ____________ wavelengths for higher temperatures.
19. ___________ ______________ is defined as the energy received per unit area per unit of frequency bandwidth.
20. A plot of a brightness spectrum shows the brightness of radiation from a source plotted against the
discrete _______________ comprising that radiation.
21. Emissions due to temperature of an object, ionization of a gas, and line emissions from atoms are
all examples of _______________ radiation.
22. Neutral hydrogen emits radiation at a characteristic wavelength of ________ cm .
23. A region of interstellar space containing neutral hydrogen gas is called a(n) _____ region, while a
region containing ionized hydrogen is called a(n) _______ region.
24. Synchrotron radiation is produced when charged particles spiral about within
__________________ field lines.
25. Unlike thermal radiation, the intensity of non-thermal radiation often ________________ with frequency.
26. A dense molecular cloud that greatly amplifies and focuses radiation passing
through it is called a ______________.
27. The wavelengths of radiation that we can observe from the ground are limited by Earth’s
________________.
28. Radiation that has passed through a cloud of gas produces a spectrum with a characteristic set of
dark _________________ _________.
29. Complex organic molecules have been detected in space using the discipline of
_______________ __________________.
30. The angle at which an electromagnetic wave is _____________ from a surface equals the angle at which it impinged on that surface.
31. The ratio of the speed of electromagnetic energy in a vacuum to its speed in a given medium is that
medium’s ____________ ____ ___________________.
32. Extraterrestrial objects seen near the horizon are actually (lower or higher) _____________ than they appear.
33. ___________________ is caused by electromagnetic waves from a source becoming out of phase as they pass through a dynamic medium such as Earth’s atmosphere.
34. _________________ _____________ is the effect produced when electromagnetic waves become circularly polarized in opposite directions as they pass through magnetic lines of force moving in the same direction as the waves.
35. Gravitational lensing is caused by the ________________ of space around large masses.
36. Doppler effect causes the frequency of waves from a receding object to appear (lower or higher)
_____________.
37. ___________________ ___________ is the apparent faster-than-light motion of a discrete source within a quasar.
38. Occultations provide astronomers good opportunities to study any existing _________________ of the occulting object.
39. A source of radiation whose direction can be identified is said to be a ________________ source.
40. The origin of cosmic background radiation is believed to be _______ _______ ________.
41. Cepheid variable stars with longer regular periods are more ________________ than those with shorter regular periods.
42. The activity of the sun varies over about a(n) _____-year cycle.
43. Sunspots are (cooler or hotter) ____________ than the surrounding surface of the sun.
44. The aurora that sometime appears in Earth’s upper atmosphere are associated with solar
____________.
45. A _______________ is a rapidly spinning neutron star.
46. The predominant mechanism producing radiation from a radio galaxy is _______________
______________________.
47. The most distant objects so far discovered are ______________.
48. The radio energy from most planets in the solar system is (thermal or non-thermal)
__________________ radiation.
49. On Jupiter, a compass needle would point ___________.
50. The ___________________ is the region around a planet where the planet’s magnetic field dominates the interplanetary field carried by the solar wind.
51. Surrounding Jupiter at approximately the orbit of Io is a strongly radiating ______________
_____________.
52. Radio telescopes are best placed in (high or low) _____________ locations.
53. The great circle around Earth that is at every point the same distance from the north and south
poles is called ____________________.
54. Great circles that pass through Earth’s north and south poles are called ________________.
55. In Earth’s coordinate system, the north-south component of a location is called ________________ .
56. In Earth’s coordinate system, longitude is measured from the _____________ _________________ .
57. A solar day is about 4 minutes (longer or shorter) ______________ than a sidereal day.
58. The Earth’s axis precesses around a complete circle having a 23.5 degree radius relative to a fixed
point in space over a period of about _________ ___________.
59. A diagram that shows a 360º silhouette of the horizon as viewed from a particular location is called
a(n) ________________ ___________.
60. In all astronomical coordinate systems and in general usage, _____________ is directly overhead
and ____________ is directly below the observer.
61. In the horizon system of coordinates, the horizontal component of an object’s coordinates is given
by the _________________.
62. In the horizon system of coordinates, the vertical component of an object’s coordinates is given by
the _________________.
63. In the equatorial coordinate system, an object’s east-west component is given as its __________
_______________.
64. In the equatorial coordinate system, an object’s north-south component is given as its
_______________.
65. ___________ is a date of reference used in sky almanacs to take into account slight variations in the celestial coordinates of objects due to the precession of Earth’s axis.
66. The ____________ is the plane formed by the orbit of Earth around the sun.
67. The reference in the _______________ coordinate system is a plane through the sun parallel to the mean plane of the Milky Way galaxy.
68. In the Milky Way galaxy alone, the number of planetary systems could be on the order of _________________.
69. The diameter of our galaxy is around _____________ light years.
70. Astronomers estimate the age of the Universe to be on the order of 15 ___________________ years.
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