THE SOUTHWORTH PLANETARIUM
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Altitude: 10 feet below sea level
Founded January 1970
Julian date: 2458739.5
2019-2020: IX
"Truth is the daughter of time and I feel no shame in being her mid-wife."
-Johannes Kepler (1571-1630)
THE DAILY ASTRONOMER
Friday, September 13, 2019
Quiz II: Inferior Worlds
The first quiz pertained to the moon and other moons in our solar system. This week's quiz brings us a bit farther out into the solar system, or, at least, closer to the Sun. The inferior worlds are merely those that are closer to the Sun than Earth. The term "inferior" is planet specific. A Venusian observer would consider Mercury to be the inferior world. A Plutonian observer would consider all the other planets to be inferior.
We're ploughing through the cosmos inch by inch. Today, our trek takes us to the inner two worlds around the Sun.
1. Why is Venus hotter than Mercury?
a. Venus is covered with a much thicker atmosphere that traps heat so efficiently, the surface temperature exceeds 900 degrees F
b. Venus is much larger than Mercury. Larger planets tend to be hotter
c. Venus' orbit is more elongated, so it actually veers closer to the Sun than Mercury. Its average distance from the Sun just happens to be greater than Mercury's
d. Actually, Mercury is hotter than Venus
2. Mercury will next transit the Sun on November 11, 2019. When will Venus next transit the Sun?
a. December 10-11, 2117
b. December 8, 2125
c. June 11, 2247
d. June 9, 2255
3. As of now, Mercury can only transit the Sun in May or November, while Venus can only transit the Sun in June and December. When will Mercury and Venus next transit the Sun simultaneously?
a. 69,163 AD
b. 224,504 AD
c. 458,151 AD
d. they will never transit the Sun simultaneously
4. Is Mercury EVER brighter than Venus in our sky? (apart from the times when Mercury is visible and Venus isn't, of course)
a. never
b. only once every 243 years
c. yes, if Mercury happens to be at greatest elongation when it is at aphelion at the time when Venus is at theoretical dichotomy when it is near perihelion at the time when Earth is at perihelion, which can happen about once every 1,367 years
d. yes, during a total solar eclipse.
5. Which planet has more moons, Mercury or Venus?
a. neither planet has a moon
b. Mercury has 1; Venus has 1
c. Mercury has 0; Venus has 2
d. they both have 3 moons
6. As Mercury and Venus are closer to the Sun than Earth, the Sun will appear larger in the Mercurian and Venusian skies. Which one of the following statements about the Sun's size from these inner worlds is true? Note: On Earth, the Sun is about 0.5 degrees in angular diameter.
a. On average, the Sun is about 1.4 degrees in angular diameter from Mercury; 0.7 degrees in angular diameter from Venus
b. On average, the Sun is about 10.5 degrees in angular diameter from Mercury; 7.3 degrees in angular diameter from Venus
c. On average, the Sun is about 13.4 degrees in angular diameter from Mercury; 8.9 degrees in angular diameter from Venus
d. On average, the Sun is about 14 degrees in angular diameter from Mercury; 7 degrees in angular diameter from Venus
7. Venus completes one orbit around the Sun every 225 days. How long does Mercury require to complete one orbit?
a. 67 days
b. 88 days
c. 113 days
d. 179 days
8. Which statements about Venus is/are true?
a. Venus has the longest day of any planet
b. Venus rotates in a different direction than the other planets
c. Venus is the hottest planet
d. Venus is only visible in our morning sky.
9. Venus was the Roman goddess of _________; Mercury was the _____________.
a. music; winged messenger
b. love; god of craftsmen
c. love; fate who cut the cloth of each person's life
d. love; winged messenger
10. If we were to list the planets (Mercury to Pluto) by size, how would Mercury and Venus rank?
a. Mercury 8th; Venus 6th
b. Mercury 9th; Venus 6th
c. Mercury 8th; Venus 7th
d. Mercury 7th; Venus 5th
BONUS QUESTION: Since transits of Mercury and Venus were first observed in the 17th, have Mercury and Venus ever transited the Sun in the same year?
a. no
b. yes, once
c. yes, twice
d. yes, thrice (I've always wanted to use that word.)
ANSWERS
1. a. Venus is covered with a much thicker atmosphere that traps heat so efficiently, the surface temperature exceeds 900 degrees F
Consider it the "greenhouse effect" drawn out to its logical extreme. Venus's atmosphere is 96.5% carbon dioxide and 3.5% nitrogen by volume. Carbon dioxide is a powerful greenhouse gas that traps heat on a planet's surface. Note: Earth's atmosphere is 0.4% carbon dioxide.
2. a. December 10-11, 2117
We only have to wait about 98 more years for the next transit of Venus to occur. Granted, the December 10-11, 2117 transit won't be visible in the eastern US. People in the eastern US will be able to observe the December 8, 2125 event, provided the overlords of the new world order haven't come to their senses and criminalized astronomy. Note: the four dates listed as choices in question 2 are the dates of the next four transits of Venus. One can tell that Venusian transits are few and far between.
3. a. 69,163 AD
Between 0 - 300,000 AD, Mercury and Venus will transit the Sun simultaneously only twice. In 69,163 AD, Mercury will just graze the Sun while Venus moves along a longer chord across the Sun. In 224,504 AD, both planets will move along arcs that veer closer to the center. The year 458,151 is just an arbitrary number I wrote down because it looked fantastic and, if you wrote down one million digits of pi, 458151 would be the last six digits.
4. a. never
Venus will always be the brightest planet. Even when at maximum brightness, Mercury will only shine at magnitude -1.9, making it slightly brighter than Sirius, but still seven times dimmer than Venus is at its minimum possible brightness of -3.7
5. a. neither planet has a moon
Neither Mercury nor Venus has a moon. They are the only two planets in our solar system that are not orbited by another world. In fact, moons are generally a giant world possession. Earth has only moon, but perhaps only because a Mars-sized body crashed into it early in its history. Mars has two moons that are likely captured asteroids.
6. a. On average, the Sun is about 1.4 degrees in angular diameter from Mercury; 0.7 degrees in angular diameter from Venus
The orbits of both Mercury and Venys are more elongated than that of Earth. Consequently, the Sun's appearance changes noticeably from Mercury and Venus as the planet approaches and then moves away from the Sun. See graphic below: Image: Astronomy Magazine
7. b. 88 days
A year on Mercury is about equal to three Earth months. The planets closer to the Sun move faster than planets farther away. They also have shorter orbital paths to follow. Consequently, Mercury completes an entire orbit in just about 88 Earth days. Pluto requires 248 Earth years to complete a single orbit.
8.
a. Venus has the longest day of any planet
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b. Venus rotates in a different direction than the other planets
c. Venus is the hottest planet
-Venus' day is about 243 Earth days long, so its day is longer than its year! It's day is longer than that of any other planet.
-If we viewed the planets from above Earth's north pole, all the planets save Venus would appear to spin counter-clockwise. Venus spins clockwise, perhaps due to a collision during its early history that was so powerful it altered the planet's spin direction
-Venus bakes at 900 degrees F pole to pole. Even Mercury's surface temperature doesn't approach that value
-Venus is visible in both the eastern morning and western evening sky.
9. d. love; winged messenger
Venus was the Roman counterpart of the Greek goddess Aphrodite;
Mercury was the Roman counterpart of the Greek Hermes
10. a. Mercury 8th; Venus 6th
The list of planets by size
1. Jupiter
2. Saturn
3. Uranus
4. Neptune
5. Earth
6. Venus
7. Mars
8. Mercury
9. Pluto
BONUS QUESTION ANSWER
c. yes, twice
1631 and 1769
We'll have to wait until 2611 until Mercury and Venus transit the Sun in the same year again.