THE SOUTHWORTH PLANETARIUM
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Altitude:  10 feet below sea level
Founded January 1970
Julian Date: 2459104.16
2020-2021:  IX


THE DAILY ASTRONOMER
Friday, September 11, 2020
Remote Planetarium 87:  Week 19 Quiz and Skywatch

We're finishing a truncated week due to the Labor Day holiday.   So, the
quiz consists of fifteen questions instead of twenty.      Ten of those
questions are based on answers we provided to the questions subscribers
sent us, so it all seems a bit circular.     We're looking forward to a
full week starting on Monday.

Enjoy your weekend-after Labor Day weekend, which probably isn't referred
to that way.


*1.  What is actually happening when a planet goes "retrograde?"*
a.  it starts moving backward in its orbit
b. from our perspective, it appears to be moving backward in its orbit
c. it is moving behind the Sun from our perspective
d.  none of the above

*2.  A superior planet will begin a retrograde loop prior to reaching
____________.*
a. superior conjunction
b. inferior conjunction
c. opposition
d. none of the above

*3.   What is "dark matter?"*
a.  matter that only emits radiation in the UV section of the
electromagnetic spectrum.
b.  matter that does not emit any radiation that we can detect
c.   matter inside a black hole
d.  all of the above

*4.  What is "dark energy?"*
a. gravitational potential energy
b. the energy that powers black holes
c. the force believed to be responsible for the acceleration of the cosmic
expansion
d. none of the above

*5.  Dark energy is believed to comprise _______ of the Universe.*
a. 45%
b. 59%
c. 68%
d. 79%

*6.  Approximately ___________ years from now we will enter the "galaxy
isolation" phase of the Universe.*
a. 10
b. 300 million
c.  15 billion
d. 200 billion

*7.  The last stars should perish in about ________________ years.*
a. 30
b. 100 million
c. 100 billion
d. 100 trillion

*8. "Heat Death" is considered the triumph of entropy.  What is entropy?*
a.  the tendency of the Universe toward a state of greater disorder
b.  the tendency of the Universe to become smaller
c.  the tendency of the Universe to become hotter
d.  all of the above

*9.  Can the Sun ever be seen at the North Pole and South Pole
simultaneously?*
a.  no
b.  yes
c.  not for the last 30 million years
d.  not until 30 million years in the future

*10. The atmospheric refraction is maximum at _______________.*
a. the zenith
b. the horizon
c. the eastern horizon
d. the northern horizon

*11.  How is the Magellanic Stream different from the other stellar
streams?*
a.  it is much longer than all the others
b.  it consists of gas, not stars
c.  it is less massive than all the others
d.  none of the above
e. all of the above

*12.  The Fimbulthal Stream is named for a ____________ from __________
mythology.*
a. river; Norse
b. sea god; Greek
c  lake; Inuit
d. volcano; Hindu

*13.  ______________ is the Milky Way Galaxy's largest globular cluster.*
a.  Palomar 5
b. Omega Centauri
c.  47 Tucanae
d.  Pyxis Globular Cluster

*14.  The Sagittarius Stream originates from _______________________.*
a.  the constellation Sagittarius
b.  the Sagittarius Galactic Cluster
c.  the Sagittarius Dwarf Spheroidal Galaxy
d. stars from every constellation in the ecliptic (zodiac).

*15. In approximately ____________ years, the Milky Way will collide with
the Andromeda Galaxy.*
a.  3 - 9
b. 100 - 400 million
c.  4 - 5 billion
d.  60 - 75 billion

ANSWERS
*1.  What is actually happening when a planet goes "retrograde?"*
b. from our perspective, it appears to be moving backward in its orbit
All planets move in the same direction.   However, when Earth approaches
and then passes a superior planet (one farther from the Sun relative to
Earth),  that planet will appear to reverse course relative to the
background stars.   We recall that Earth always moves more quickly than any
of the superior planets.   Inferior planets can also exhibit retrograde
motion.      These planets appear to go from prograde to retrograde or
retrograde to prograde motion when they change direction as they travel
around their orbits.

*2.  A superior planet will begin a retrograde loop prior to reaching
____________,*
c. opposition
When Earth passes between the Sun and a superior planet, that planet is
said to be in "opposition."  As Earth approaches the planet, it will appear
to begin a retrograde loop.    Only after opposition will the planet resume
prograde motion.

*3.   What is "dark matter?"*
b.  matter that does not emit any radiation that we can detect
"Dark matter" is so named because it doesn't emit any radiation that
astronomers can detect.    We believe dark matter exists because of the
gravitational influence it exerts on visible matter.

*4.  What is "dark energy?"*
c. the force believed to be responsible for the acceleration of the cosmic
expansion
Cosmologists have determined that the cosmic expansion is accelerating with
time, as opposed to being impeded, as was one believed.    They ascribe
this acceleration to "dark energy," a force that remains mysterious.
 In this instance the "dark" refers to our ignorance of its nature.

*5.  Dark energy is believed to comprise _______ of the Universe.*
c. 68%
According to the most recent estimates, dark energy makes up about 68% of
the Universe;  dark matter comprises 27%.   The remaining five percent
consists of the visible matter that we once believed to have encompassed
the entire Universe.

*6.  Approximately ___________ years from now we will enter the "galaxy
isolation" phase of the Universe.*
d. 200 billion
The Universal expansion should reach a point at which all the other
galaxies will be outside out of view, making it appear as though the galaxy
is alone.  Now, that time span is enormous!   Our species will most
assuredly not be around by that time. In fact, humans will likely have gone
extinct more than 199 billion years before.

*7.  The last stars should perish in about ________________ years.*
d. 100 trillion
Current stellar models suggest that the last stars should finally perish in
about 100 trillion years!       To give you an idea of this time span, the
Universe is only 13.8 billion years old!

*8. "Heat Death" is considered the triumph of entropy.  What is entropy?*
a.  the tendency of the Universe toward a state of greater disorder
As the Universe expands and stars perish, the Universe will become colder
and less energetic according to the Second Law of Thermodynamics.    Heat
death will be the ultimate triumph of entropy.

*9.  Can the Sun ever be seen at the North Pole and South Pole
simultaneously?*
b.  yes
The atmosphere "projects" images just below the horizon into our view.
 For this reason, the Sun first rises at the South Pole a few days before
the September equinox and sets at the North Pole a few days after the
September equinox.        Also, the Sun will rise a few days before the
March equinox at the North Pole and set a few days after the March equinox
at the South Pole.  So, for about ten days a year, the Sun will be
simultaneously visible at the North and South Poles.

*10. The atmospheric refraction is maximum at _______________.*
b. the horizon
The refraction amount is about 1/2 a degree, about equal to the Sun's
angular diameter.    The Sun will therefore appear to rise just before it
has actually risen.

*11.  How is the Magellanic Stream different from the other stellar
streams?*
b.  it consists of gas, not stars
The Magellanic Stream is a million light year long stream of gases taken
from the Large and Small Magellanic Clouds, two satellite galaxies to the
Milky Way.

*12.  The Fimbulthal Stream is named for a ____________ from __________
mythology.*
a. river; Norse


*13.  ______________ is the Milky Way Galaxy's largest globular cluster.*
b. Omega Centauri
Omega Centauri was once classified as a star in Centaurus, hence the name
"Omega Centauri," from the Bayer Nomenclature System.    Consisting of more
than one million stars distributed over a spherical region nearly 200 light
years in diameter, Omega Centauri  is such a rich cluster it is thought to
be the nucleus of an extinct dwarf galaxy.      [Note:   FSR 1758, located
on the other side of the galactic bulge, might well be larger than Omega
Centauri.  However, FSR 1758's size and stellar population value remains
uncertain.]

*14.  The Sagittarius Stream originates from _______________________.*
c.  the Sagittarius Dwarf Spheroidal Galaxy
The stellar stream consists of stars stripped away from this dwarf galaxy.
Over the next billion years the Milky Way will entirely absorb this dwarf
galaxy.

*15. In approximately ____________ years, the Milky Way will collide with
the Andromeda Galaxy.*
c.  4 - 5 billion
Through a series of collisions, the Milky Way and Andromeda Galaxies will
merge to form one mega-galaxy,

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