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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