Solar System Debris

1. Comets have played an important role in the history and evolution of astronomical thought.
    To the Greeks, they were "hairy stars," a phenomenon occurring in the earth's
    _______________. Tycho Brahe (1546-1601) showed that comets belonged to the realm
    of the _________________. Isaac Newton (1643-1727) explained their
    __________________ based upon the universal law of gravitation, while Edmund Halley
    (1656-1742) proved that comets could make repeated returns to the ________________.

2. A comet has been called the closest thing to nothing that anything can be and still be
    considered something. Although not a good definition for a comet, it is a true statement.
    Why?
    ___________________________________________________________________
    ________________________________________________________________________

3. Comets may represent the best example of the original, undifferentiated material left over from
    the formation of the solar system. In those early days these bodies may have been catapulted
    into the outer fringes of the solar system from the gravitational effects of the planets
    _______________ and _______________ working in concert with U     and N      . These
    latter planets drove the cometary bodies inward towards the sun.

4. Supposedly, in the outer reaches of our solar system there is a large region of billions and
billions of comets known as the _______________ cloud.

5. _______________ moving near this cloud can cause some of these comets to fall in towards
the _______________ where the major planets eventually expel or modify their long period
orbits into orbits of shorter duration.

6. New comets entering the solar system for the first time have random inclinations to the plane of
the ecliptic indicating that the shape of the Oort cloud is _______________.

7. Comets which have orbital periods greater than 200 years are termed _______________
period comets, while comets with orbital periods of 200 years or less are called
_______________ period comets.

8. As a class of objects in the solar system, comets with periods of 200 years or less are unique in
    that their orbital eccentricities and inclinations are, on average, much larger than the
    _______________. However, almost all of these comets revolve around the sun in the same
    _______________ as the planets, indicating the profound influence which the planets have had
    on these objects. Halley's Comet is one of two exceptions to this rule.

9. Comets with orbital motions which were originally clockwise were either _______________
    from the solar system by the Jovian planets or were gravitationally perturbed to orbit the sun in a
    _______________ direction.

MORPHOLOGY OF A COMET

10. A comet approaching the sun can be likened to a dirty _______________. It is mainly
composed of water _______________ mixed with _______________. Other constituents
include frozen m______________, a_______________, and c_________ d_________. .

11. The smallest part of the comet, described in the preceding question as the dirty snowball, is
    called the _______________. A typical diameter may be _______________ miles. Comet
    Hyakutake, which appeared in the spring of 1996 had a nucleus less than two miles (1-3 km) in
    diameter. Hale-Bopp, which will be even more prominent during the spring of 1997 has a
    nucleus as great as 25 miles (40 km) in diameter

12. As sunlight heats the comet, the ices _______________, (change directly into a gas). Pockets     of gas form underneath the comet's surface due to solar warming. When these areas "pop," the
    escaping gasses drag the dust and other gritty substances away from the nucleus to form the
    _______________, the veiled region surrounding the solid center.

13. This region around the nucleus, which may be hundreds of thousands of miles in diameter, is
composed of neutral gases, some p_______________ and d_______________. Collectively,
the coma and nucleus of a comet are called the _______________.

14. Surrounding the coma and even part of the tail is a larger invisible cloud or halo of excited
    _______________ gas which can be millions of miles in extent. This cloud also suggests that
    one of the primary constituents of a comet's nucleus is a very common compound called
    _______________. This was confirmed by the Halley flybys of 1986.

15. As a comet approaches the sun _______________ (type of energy) radiation excites the
    gases in the coma until they begin to glow or f_______________. In this process, energy of a
    shorter wavelength, which is invisible to the human eye, is absorbed by the gases of the comet
    and emitted as longer wavelengths, which can be seen. Comets generate their own light.

16. The mechanism which creates one of the two types of tails a comet may possess involves the
    solar wind and the magnetic field of the sun. The solar wind (plasma) slams into the plasma
    surrounding the coma. This produces a shock front (a region of higher density) because the
    velocity of the solar wind is reduced. The result is a pileup of other solar wind particles in the
    region. This forces the magnetic field lines of the sun which are in the vicinity of the coma to also
    slow wrap themselves around the coma and sweeping in back of it to form the
    I_______________ tail. This tail is usually STRAIGHT/CURVED (circle one) and
    YELLOW/BLUE (circle one) in color.

17. Meanwhile, the dust escaping from the nucleus is also dragged into the coma by the jetting
    action of the ______________ which are escaping from the warmed nucleus. The velocities of
    the dust particles are modified by the flow of these gases and may even be coupled to the
    magnetic field sweeping around the comet. The pressure of sunlight also pushes particles one
    micron in size or smaller in back of the nucleus to form the _______________ tail which is
    shining through the process of s_______________ (reflected) light. This tail is usually
    STRAIGHT/CURVED (circle one) and YELLOW/BLUE (circle one) in color.

18. When light is _______________, the rays which are passing the small particles of dust are
    deflected (bent) from their straight line paths. Some of this light reaches us to reveal the location
    of the dust tail. This is different from _________________ light which "bounces" off a larger
    particle allowing it to be viewed directly.

19. The beautiful blue tail that Hyakutake produced during the latter part of March 1996 was an
excellent example of an _______________ tail. Hyakutake was a dust poor comet.

20. With respect to direction, a comet's tail always points TOWARD/AWAY (circle one) from
    the sun. When a comet enters the solar system, it comes in ________________ first and
    _________________ second. However, when a comet leaves the solar system, it exits
    _________________ first and _________________ second.

DISCOVERING A COMET

21. About 5-10 / 10-20 / 20-30 (circle one) new comets are discovered each year. Because they
    are generally faint, diffuse objects when first seen, WIDE FIELD/NARROW FIELD (circle
    one) telescopes and cameras are usually employed in cometary searches. Because new comets
    can be found in any part of the sky, and searching for them can be a very time-consuming
    enterprise, AMATEUR/PROFESSIONAL (circle one) astronomers play a significant role in
    new cometary discoveries. Since most comets are brightest when near perihelion, they are
    generally discovered in the vicinity of the _______________. Therefore, a good time to go out
    and search for comets would be before _______________ or after _______________.

22. Once a comet is discovered it is named after the _______________(s) who discovered it.
The family names of as many as ONE/TWO/THREE (circle one) people can be attached to the
object. See the answer section for the new naming schemes.

23. Within several days after discovery an _______________ is calculated. This gives
astronomers the ability to describe the path of the comet within the framework of the solar
system bodies and in what part of the sky it will be seen from earth.

BRIGHTNESS OF A COMET

24. Once this is completed the brightness or _______________ of the comet at different
distances from the earth can be calculated.

25. The difference in intensity between one whole magnitude is _______________. The brighter
the comet, the more POSITIVE/NEGATIVE (circle one) the magnitude of the object.

26. Determining the brightness of a comet is a difficult task to accomplish because the comet
produces light through two processes: _______________ and _______________.

27. The change in brightness of a comet due to its distance from the _______________ varies as
the inverse square of this distance (1/d²). This means that if the distance of the comet is halved,
the brightness of the comet will increase _______________ times.

28. The change in brightness of the comet due to its distance from the _______________ is
    another matter. As this distance is halved the comet's brightness can increase by (1/d²) to
    (1/d ^ 6), or from _______________ to _______________ times. This can make a huge
    difference as to whether the comet becomes a spectacular apparition or a dud.

29. Many times comets arriving from the Oort cloud for the first time may have a layer of easily
    sublimed volatiles which cause the comet to appear abnormally _______________ for its
    distance away from the sun. One of the most overrated comets to fit this scenario was Comet
    Kohoutek of 1973-74. During the spring of 1990, Comet Austin also pulled this same stunt. On     the other hand, Hyakutake blossomed into beautiful object in 1996, and Hale-Bopp is right on
    target to give an equally fine performance in 1997.

30. The end result of a comet may be the total disintegration of the object or the exhaustion of all
volatiles and the misinterpretation of this body for an _______________.

METEORS

31. Over tens of thousands of years, the _______________ from the tails of comets gradually
    disperses as a result of the _______________ perturbations of the planets and the slowing of
    their orbital velocities due to the *Poynting-Robertson effect. In the latter situation, dust which
    absorbs energy from the sunward direction, radiates infrared energy back into space more
    effectively in the direction opposite to its orbital motion. This slows the velocity of the dust,
    causing the particles to eventually ________________ into the sun.

32. If a dust particle from a comet's tail enters the atmosphere of the earth, a _______________
is the result.

33. The streak of light which is seen in the sky IS/IS NOT (circle one) a result of the glow of the
    dust particle itself.

34. The very rapid motion (7-45 miles/second or 11-72 km/sec) of the particle through the
    atmosphere causes the cylinder of air through which the particle is passing to
    _______________ revealing the location of the particle. The actual object disintegrates and/or
    is vaporized in the process. Beyond 45 miles per second (72 km/sec) the object is moving too
    fast to be a part of the solar system. Seven miles per second (11 km/sec) represents the escape
    velocity of earth and the lower limit of meteor velocities.

35. When a meteor is observed, the event is usually occurring at an altitude of 5-10 / 10-40 / 40-
70 (circle one) miles above the earth's surface.

36. At certain times of the year an observer may view, over a period of several hours, numerous
    meteors radiating from the same location in the sky. At these times the earth's orbital plane is
    intersecting the orbital plane of a _______________. These events are called
    ____________________ (two words).

37. The fact that meteors appear to be diverging from a _______________ indicates that the
    particles are traveling ________________ to each other. As they approach the observer they
    _______________, similar to what a person would expect if she/he were standing on a long,
    straight section of railroad tracks which stretched in front of the viewer to a vanishing point.

38. An extremely bright meteor is usually referred to as a _________________.

39. A dust or rock fragment in orbit about the sun is referred to as a _________________. If it is
much larger the term _________________ would apply.

40. Objects which enter the atmosphere and strike the earth or other planets or moons are called
    ________________. No fireball from a meteor shower has ever been witnessed to fall to
    earth. Therefore it is assumed that meteors originate from _________________ while the
    natural objects that fall to earth to become meteorites originate in the
    _______________________ (two words) between _________________ and
    __________________.

METEORITES

41. There are three broad classifications of meteorites which are as follows:
_________________, _________________, __________________.

42. The most common variety, called _________________, are basically composed of
    _________________ material intermixed with varying amounts of iron in the form of flecks.
    Many also have inclusions called ch_______________ composed usually of olivine and
    pyroxene, silicate minerals with higher concentrations of iron and magnesium.

43. _________________ meteorites are composed primarily of iron with up to 13 percent nickel
    mixed throughout. Although this type of meteorite is not commonly the type recovered from a
    witnessed fall, they are the predominate meteorites associated with finds because they
    _____________________________________________________________
    ________________________________________________________________________

44. The fact that stony and iron meteorites exist, indicates that the parent bodies to which these
specimens originally belonged probably had silicate crusts and iron cores. In other words, these
objects were chemically _______________.

45. The least common variety, called _______________, are composed of a mixture of silicates
and native iron which probably originated from the transition zone of a body that was
differentiated, or from a totally undifferentiated asteroid.

46. All meteorites are about _______________ years of age, indicating that they are examples of
unchanged original solar system material.

47. Meteorites as a whole are an excellent indicator of the bulk ______________ of the terrestrial bodies of the solar system. Stony meteorites give geologists insight into the bulk composition of
planetary _______________.

48. The orbital velocities of small meteorites (several yards in diameter) striking the earth's surface
are FULLY/NOT FULLY (circle one) slowed to a free fall by the earth's atmosphere. Giant
meteorites strike the earth at velocities of FEET PER SECOND/MILES PER SECOND (circle one).

49. When a large meteorite strikes the earth or another astronomical body a _______________ is     formed which is BIGGER THAN/AS BIG AS (circle one) the impacting body. The kinetic
    energy (energy of motion) of the meteorite is converted into _______________ which
    vaporizes the original meteorite and the ground in the immediate target zone. The impact event
    looks very much like a rock being tossed into a liquid.

50. The floor of the meteorite crater is always _________________ than the surrounding terrain.
The crater walls are always _________________ than the surrounding terrain.

51. The best example of a meteorite crater in the world is found near Winslow, Arizona and is
    called ________________________. The crater is PROPERLY/IMPROPERLY named
    (circle one). Winslow is about three hours southeast of the south rim of the Grand Canyon if
    your are driving. The event which formed this crater occurred about 25-50,000 years ago.