THE SOUTHWORTH PLANETARIUM
207-780-4249   www.usm.maine.edu/planet
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70 Falmouth Street   Portland, Maine 04103
43.6667° N                   70.2667° W
Altitude:  10 feet below sea level
Founded January 1970
Julian Date: 245956.16
2019-2020:  CXXVIII

THE DAILY ASTRONOMER
Friday, April 17, 2020
Remote Planetarium 15:   Week 3  Quiz

We're ending Week 3 of the Remote Planetarium on-line course.   Thank you
for your helpful feedback and positive comments.   We certainly hope you're
continuing to enjoy these classes.     Please send us any questions and
comments you would like to share!  Our apologies if we don't respond
straight away.

Thank you also to subscriber AD who asked us to re post the questions in
the answer section.  We should have done that from the beginning.  We're
doing it now.

See you on Monday!


1.  Which of the following is NOT a terrestrial planet?
a. Earth
b. Mercury
c. Saturn
d. Mars

2. Which planet is the hottest?
a.  Mercury
b. Venus
c. Earth
d. Pluto

3.  Which planet is surrounded by the greatest number of known moons?
a.  Mars
b. Jupiter
c. Saturn
d. Neptune

4.  If you went to the planet ___________ you could visit _______________,
the highest mountain in the solar system.
a. Mars;  Verona Rupes
b. Venus; Skadi Mons
c.  Mars; Olympus Mons
d. Mercury;  Caloris Montes

5.  _____________ was the most distant planet known to antiquity.
a. Jupiter
b. Saturn
c. Uranus
d. Neptune

6. If an inferior planet is at its greatest western elongation, where will
it be visible?
a.  the eastern pre-dawn sky
b.  the western evening sky
c.  the eastern western sky
d.  it won't be visible at all

7.  After Venus passes through inferior conjunction, where would you expect
to find it in our sky?
a.  the western evening sky
b.  the eastern predawn sky
c.  rising at sunrise
d.  none of the above

8.  Jupiter was last at opposition on June 10, 2019.    When should it be
at opposition again?
a.  July 14, 2020
b.  August 31, 2020
c.  January 9, 2021
d.  September 1, 2021

9.  One can find Venus in the western evening sky.    Based on this one
piece of information, what conclusions can we draw?
a.  the next time Venus is in conjunction with the Sun, it will be between
the Sun and Earth
b.  the next time Venus is in conjunction with the Sun, it will be on the
far side of the Sun relative to Earth
c.  Venus will be closest to Earth now
d.  One can draw no conclusions from that one piece of information.

10. How many times a year will Mercury generally be in inferior conjunction?
a. once
b. twice
c.  three times
d.  five times

11. Force equals mass times ____________
a. volume
b. velocity
c.  acceleration
d.  momentum

12.  How can the Voyager 1 spacecraft continue to travel at a speed of more
than 35,000 miles per hour?
a.  the craft contains an ion propulsion drive
b.  the craft's speed is maintained by the radioisotopic
thermalelectric generator
c.  it is moving at this speed because it is traveling on its own volition
through the vacuum of outer space
d. it expels gases in one direction which propels it in the opposite
direction

13.  Let's say you had two asteroids separated by one million miles.    If
you reduce their separation distance to half a million miles, their mutual
gravitational attraction ______________
a.  doubles
b.  becomes four times greater
c.  is reduced by half
d.  remains unchanged

14.  The range of gravity is _________________
a. infinite
b.  limited to the boundaries of the object's host galaxy
c.  limited to 100 light years
d.  limited to a distance equal to 11,314 times the radius of the massive
object

15.  The "Fundamental Theorem of Astrophysics" states that
a.  the chemical composition of stars is unknowable
b.  the laws of physics governing Earth are applicable throughout the
Universe
c.  the Big Bang cannot be precisely modeled
d.  other Universes must exist

16.  What is the Sun's right ascension on the first day of spring (northern
hemisphere)?
a. 0 hours
b. 6 hours
c. 12 hours
d.  18 hours

17. The declination of Regulus, the brightest star in Leo the Lion, is
almost +12 degrees.  Which of the following statements about Regulus is/are
true
a. it is visible everywhere in the northern hemisphere
b. it is directly overhead for observers at latitude 12 degrees N
c. it isn't visible to observers south of 78 degrees S latitude
d. it is circumpolar above latitude 78 degrees N

18.  What will the Celestial Equator's maximum height be for an observer at
60 degrees N?
a.  60 degrees
b.  45 degrees
c. 30 degrees
d.  15 degrees

19.  Alpha Centauri's declination is approximately -60 degrees.   Can we
see it here in Portland (ME)?
a.  no
b. yes
c.  yes, but only in the autumn
d.  yes but only in the spring and winter

20.  Sirius' declination is - 17.  Which of the following statements about
Sirius is/are true?
a.  it is visible everywhere in the northern hemisphere
b. it passes directly overhead at latitude 17 degrees S
c. it is only visible in the summer
d. it is circumpolar at the South Pole

ANSWERS

*1 Which of the following is NOT a terrestrial planet? *
c. Saturn
A terrestrial planet is comparatively small, dense and is enshrouded in a
thin atmosphere.   A gas giant or Jovian planet is large, consists
largely of lighter elements and has thick atmospheres.   Saturn is a Jovian
planet.    The others are terrestrial.
Review
*TERRESTRIALS*
Mercury, Venus, Earth and Mars
*JOVIANS*
Jupiter, Saturn, Uranus and Neptune

*2. Which planet is the hottest? *
b. Venus
 Surprise!   Yes, even though Mercury is millions of miles closer to the
Sun than Venus, the second planet is still the hottest.   Although Mercury
is much closer, it lacks any atmosphere.  Venus is covered by a thick
atmosphere consisting of the greenhouse gas carbon dioxide.    Whereas
Mercury's daytime surface temperature averages 700 degrees, Venus'
temperature slightly exceeds 900 degrees F.

*3.  Which planet is surrounded by the greatest number of known moons? *
  b. Jupiter
As of now, astronomers have detected 79 known moons around Jupiter.     The
following is a list of each planet and the number of known moons
MERCURY - 0
VENUS - 0
EARTH - 1
MARS - 2
JUPITER - 79
SATURN -  76
URANUS -  27
NEPTUNE - 14
PLUTO -  5

4. .  *If you went to the planet ___________ you could visit
_______________,*
*the highest mountain in the solar system.*
  c.  Mars; Olympus Mons
Mars might be smaller than Earth, but it contains some of the solar
system's largest structures.   Olympus Mons' summit is 72,000 feet above
the Martian surface and its base is as large as Missouri.       Its immense
canyon system, the Valles Marineris, extends more than 2500 miles!

*5.  _____________ was the most distant planet known to antiquity.  *
b. Saturn

See below:

[image: ptolemaic.gif]
Andrew Borde's *"The First Book of the Introduction of Knowledge (1542)*"
includes this detailed diagram depicting the Ptolemaic Universe.   Earth
occupies the center and Saturn the seventh circle.  No other planets are
listed as none were known at the time.

William Herschel discovered *Uranus in 1781.*

John Couch Adams and Urbain Leverrier independently discovered *Neptune in
1846.*
[Credit is sometimes extended to Johann Galle who used Leverrier's
predictions to find Neptune in his telescope.  He and his assistant,
Heinrich d'Arrest, were the first to observe Neptune telescopically.  Adams
and Leverrier determined its approximate location mathematically.]

Clyde Tombaugh discovered* Pluto in 1930.*

*6. If an inferior planet is at its greatest western elongation, where will
it be visible? *
  a.  the eastern pre-dawn sky

   - when a planet is at greatest western elongation, it will be visible in
   the eastern predawn sky.
   - when a planet is at greatest eastern elongation, it will be visible in
   the western evening sky.


*  7.  After Venus passes through inferior conjunction, where would you
expect to find it in our sky?  *
  b.  the eastern predawn sky

   1. After inferior conjunction, the planet will move into the predawn
   eastern sky until reaching greatest western elongation.
   2. The planet will appear to move back toward the Sun in our sky as it
   moves toward superior conjunction when it will no longer be visible again.
   3. After superior conjunction, the planet will then move into the
   western evening sky until it reaches greatest eastern elongation.   It then
   appears to move back toward the Sun and then vanishes before reaching
   inferior conjunction again.

[image: download.png]
*8.  Jupiter was last at opposition on June 10, 2019.    When should it be
at opposition again?  *
a. July 14, 2020
Jupiter's average synodic period is 399 days, meaning that Jupiter requires
about 399 days to reappear at the same point relative to Earth.   A period
of approximately 399 days separates successive oppositions.    As a rule of
thumb, one can say that Jupiter will be at opposition about every 13 months
and a few days.
Jupiter's future opposition dates

   - August 19, 2021
   - September 26, 2022


*9.  One can find Venus in the western evening sky.    Based on this one
piece of information, what conclusions can we draw?*
 a.  the next time Venus is in conjunction with the Sun, it will be between
the Sun and Earth


   - After superior conjunction, the planet will then move into the western
   evening sky until it reaches greatest eastern elongation.   It then appears
   to move back toward the Sun and then vanishes before reaching inferior
   conjunction again.


 *10. How many times a year will Mercury generally be in inferior
conjunction?  *
  c.  three times
Mercury's synodic period is about 116 days, equal to the time period
separating successive inferior conjunctions.  We can expect Mercury to pass
between the Sun and Earth about three times a year.

*11. Force equals mass times ____________*
  c.  acceleration
Newton's second law:  F = ma  (F = force; m = mass; a = acceleration)
The amount of force one applies to a massive object determines its
acceleration.   Accelerating a light object to a given speed is easier than
accelerating a more massive object.  (Example: easier to push a grocery
cart than a stretch Hummer.)

*  12.  How can the Voyager 1 spacecraft continue to travel at a speed of
more than 35,000 miles per hour?  *
  c.  it is moving at this speed because it is traveling on its own
volition through the vacuum of outer space
Newton's first law states that "an object remains in a constant state of
motion unless acted upon by an external force."     The Voyager 1 craft is
moving on its own volition through the vacuum of outer space.   Because
nothing is impeding the Voyager 1 spacecraft it can maintain its motion
indefinitely.

*13.  Let's say you had two asteroids separated by one million miles.    If
you reduce their separation distance to half a million miles, their mutual
gravitational attraction *______________
  b.  becomes four times greater
The Universal Law of Gravitation states that the gravitational attraction
between two massive objects is proportional to both and inversely
proportional to the square of their separation distance.    If you double
the separation distance between two massive objects, the gravitational
force between them is reduced to one quarter of its original value. If you
halve the distance, the force increases to four times its original value.


*14.  The range of gravity is _________________  *
  a. infinite
Gravity has an infinite range.   The Andromeda Galaxy and even all the
stars in the Capricornus Supercluster are all exerting their gravitational
influence on us.   Of course, as gravity falls off with the square of the
distance, this influence is negligible.

*15.  The "Fundamental Theorem of Astrophysics" states that*
 b.  the laws of physics governing Earth are applicable throughout the
Universe
Astrophysics is only possible because remote physical objects are governed
by the same physical principles that govern objects in our local
neighborhood.

*16.  What is the Sun's right ascension on the first day of spring
(northern hemisphere)?  *
  a. 0 hours
Right ascension is the celestial equivalent of longitude.    It measures a
celestial object's angular distance from the vernal equinox, the
intersection point between the ecliptic and celestial equator on the first
day of spring.      The scale extends from 0 hours to 24 hours, both of
which specify the vernal equinox.

   - On the first day of spring, the Sun's right ascension is 0 hours
   - On the first day of summer, the Sun's right ascension is 6 hours
   - On the first day of autumn, the Sun's right ascension is 12 hours
   - On the first day of winter, the Sun's right ascension is 18 hours

* 17. The declination of Regulus, the brightest star in Leo the Lion, is
almost +12 degrees.  Which of the following statements about Regulus is/are
true*
They are all true:
a. it is visible everywhere in the northern hemisphere
[Any celestial object north of the celestial equator is visible everywhere
in the northern hemisphere.]
b. it is directly overhead for observers at latitude 12 degrees N
[A star's declination is equal to the latitude at which that star can pass
through the zenith, the point directly overhead.    Regulus' declination is
12 degrees and so will occupy the zenith at 12 degrees N latitude]
c. it isn't visible to observers south of 78 degrees S latitude
[To determine a star's visibility region, subtract its declination from 90
degrees.
90 - 12 = 78.    As Regulus is located north of the celestial equator, it
will be visible anywhere north of 78 degrees S latitude.]
d. it is circumpolar above latitude 78 degrees N
[If  you know a star's visibility region, you can also know the star's
circumpolarity region.  Regulus isn't visible south of 78 degrees S, so it
will be circumpolar anywhere north of 78 degrees N.]

*18.  What will the Celestial Equator's maximum height be for an observer
at 60 degrees N?  *
  c. 30 degrees
From the perspective of a northern hemisphere observer, the Celestial
Equator attains its maximum height due south.  That height equals 90 -
observer's latitude.    For an observer at 60 degrees N, the Celestial
Equator's angle is 30 degrees.

*19.  Alpha Centauri's declination is approximately -60 degrees.   Can we
see it here in Portland (ME)?  *
a. no
Alpha Centauri cannot be seen north of 30 degrees N.
We can calculate its visibility region by subtracting 60 from 90.
90 - 60 = 30
As Alpha Centauri is south of the celestial equator, it is visible
everywhere in the southern hemisphere.  It will also be visible south of 30
degrees N latitude.

   - Note: Alpha Centauri will be very difficult to observe at 30 degrees N
   as it will be so low along the horizon.
   - Note:  The atmospheric refraction causes objects on the horizon to be
   elevated by about half a degree.  So, Alpha Centauri would be visible
   slightly north of 30 degrees N. However, for the sake of simplicity, we're
   ignoring the atmosphere

*20.  Sirius' declination is - 17.  Which of the following statements about
Sirius is/are true?  *
b. it passes directly overhead at latitude 17 degrees S
[The star's declination is equal to the latitude at which it passes through
the zenith.
-17 declination  =  passes through the zenith at 17 degrees S latitude]
d. it is circumpolar at the South Pole
[Every celestial object south of the celestial equator is visible
everywhere in the southern hemisphere.  Every celestial object visible in
the southern hemisphere is circumpolar at the South Pole.]

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