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: 2459062.16
2019-2020:  CLXXXVII

THE DAILY ASTRONOMER
Friday, July 31, 2020
Remote Planetarium 74: Week 16 Quiz and Weekly Skywatch

Heavens, this week was truncated, wasn't it? The bright side to having a
shortened week is a shorter quiz!  Only ten questions, five from each
class.    Next week, barring any unforeseen event, we should have an entire
week of classes to "enjoy!"  Thank you for staying with us!  Just a
reminder that we'll be taking our summer vacation starting August 10th.
When we return, we'll continue the "Remote Planetarium" series.      Oh,
and, no, I did not make up the God of Stupidity.


*1.  Approximately how quickly is our solar system traveling through the
galaxy?*
a.  55 miles per hour
b. 1,000 miles per minute
c. 143 miles per second
d. the speed of light

*2. Proper stellar motion is affected by all but which one of the following
factors?*
a.  distance
b. transverse velocity
c.  radial velocity
d. absolute magnitude

*3.  How noticeably will the constellation Orion change over your lifetime,
assuming you live to be 100?*
a.  not at all
b. the stars will have shifted about two degrees from their original
positions (on my birth year)
c.  the stars will have shifted between 5 - 7 degrees from their original
positions
d. the constellation will be barely recognizable.

*4.  If a star exhibited a high negative radial velocity (moving away from
us) and zero transverse velocity, it would___________*
a.  appear to diminish in brightness over a long period of time, while
maintaining the same position
b. appear to move toward the south
c. appear to move toward the northeast
d. appear to intensify in brightness over a long period of time, while
maintaining the same position

*5.  The Sun completes one orbit around the galaxy every __________ years,
approximately.*
a.  3000
b. 19 million
c.  104 million
d.  225 million

*6.  How far away is the closest visible star to us?*
a.  6 light years
b. 22 light years
c. 37 light years
d. 60 light  years

*7.  If you traveled on a spaceship moving away from the Sun, at what
distance would the Sun first become invisible to the unaided eye?*
a.   20 light years
b.   40 light years
c.   60 light years
d.  110 light years

*8.  Which astronomer discovered the relationship between a Cepheid's
variability period and its luminosity?*
a.  Edwin Hubble
b.  Henrietta Swan Leavitt
c.  Harlow Shapley
d.  Vesto Slipher

*9. Are there as many stars "below our feet" as "above our head?"*
a.  No.   The vast majority of the stars are in our sky and not below us
b. Yes, there are.
c.  Actually, there are many more stars below our feet than above our heads.
d.  No.  The sky contains about 54% more stars than the regions below our
feet.

*10. _________________ of the 30 closest stars to the Sun are visible to
the unaided eye.*
a.  less than 10
b. 15
c. 21
d. 29

ANSWERS
*1.  Approximately how quickly is our solar system traveling through the
galaxy?*
c. 143 miles per second
That rate is certainly rapid by terrestrial standards.    The solar system
could travel from Portland (ME) to Boston in less than one second.  (Of
course, that sentence doesn't make much sense!)   Yet, by galactic
standards, the solar system is moving at a somewhat lethargic pace.

*2. Proper stellar motion is affected by all but which one of the following
factors?*
d. absolute magnitude
The closer the star, the greater the proper motion.   The proper motion is
a combination of the radial velocity and transverse velocity.

*3.  How noticeably will the constellation Orion change over your lifetime,
assuming you live to be 100?*
a.  not at all
It is sobering to realize that a constellation will appear exactly the same
on your 100th birthday as it did when you were a newborn.  The stars are
moving quite quickly.  However, they are so far away, the proper stellar
motions are negligible over a human lifetime.

*4.  If a star exhibited a high negative radial velocity (moving away from
us) and zero transverse velocity, it would___________*
a.  appear to diminish in brightness over a long period of time, while
maintaining the same position
Radial velocity refers to velocity toward and away from the observer.  If a
star's motion is only radial, its position relative to the vernal equinox
will remain the same, but its brightness will change.  It will become
dimmer if it recedes from us, and brighter if it approaches.

*5.  The Sun completes one orbit around the galaxy every __________ years,
approximately.*
d.  225 million
The period of time the Sun requires to complete one orbit is called a
"galactic year."    During its lifetime, the Sun has completed more than
twenty circuits around the Milky Way.  Incidentally,  the entire Mesozoic
Era, the time period when the non-avian dinosaurs existed, was about 50
million years shorter than a galactic year.

6. *6.  How far away is the closest visible star to us?*
a.  6 light years
Barnard's star is the closest star not visible to the unaided eye.   With
an apparent magnitude of 11.2, this star is 120 times dimmer than the
faintest naked eye stars.      Barnard's star is also famous for exhibiting
the greatest proper motion of any star.

*7.  If you traveled on a spaceship moving away from the Sun, at what
distance would the Sun first become invisible to the unaided eye?*
c.   60 light years
Compared to many stars in our night sky, the Sun is intrinsically faint.
If the Sun were only 60 light years away, it would no longer be visible to
the unaided eye.    The Orion Belt stars -Mintaka, Alnilam, and Alnitak-
appear quite bright even though they are all more than 1,200 light years
from the solar system.

*8.  Which astronomer discovered the relationship between a Cepheid's
variability period and its luminosity?*
b.  Henrietta Swan Leavitt
 By studying the Cepheid variables in the Small Magellanic Cloud, Leavitt
observed that the variability periods of the brightest Cepheids were longer
than those of the dimmer ones.      These observations lead to the
development of the Period-Luminosity Relation.

*9. Are there as many stars "below our feet" as "above our head?"*
b. Yes, there are.
Although it might seem strange, the amount of stars below our feet is the
same as above our head.    Earth is moving through the galaxy which is more
than 1000 light years "thick" in this location.

*10. _________________ of the 30 closest stars to the Sun are visible to
the unaided eye.*
a.  less than 10
Most stars in the galaxy are red dwarfs, those stars that were just massive
enough to become active stars.
Of the 30 closest stars, the following are visible to the unaided eye:

   - Alpha Centauri
   - Sirius
   - Epsilon Eridani
   - 61 Cygni
   - Procyon
   - Tau Ceti
   - Epsilon Indi

___________________________________________________________________________________________________



*SKYWATCH:  July 31 - August 6, 2020*



On July 31 the Sun will rise at 5:22 a.m. and set at 8:06 p.m, giving us 14
hours and 34 minutes of daylight, a 52 minute decrease since the summer
solstice.  On August 6, the Sun will rise at 5:36 a.m. and set at 7:57 p.m,
providing us with 14 hours and 19 minutes of daylight.  The Sun is passing
through the constellation Cancer the Crab this week.


At week's beginning the moon will move through the waxing gibbous phase.
The moon will be full on August 3rd.  The full moon rises around sunset and
sets at sunrise. Common names for the August full moon include the “Green
Corn Moon,” the “Barley Moon,” “Fruit Moon” and “Grain Moon.”   These names
all relate to the later summer season and our preparations for the
harvest.    The moon will then pass through the waning gibbous phase toward
the end of the week.  The moon reaches the last quarter phase on August 11th
.  This year, the Harvest Moon falls on October 1st.



On August 2nd, be certain to find the waxing gibbous moon close to Jupiter
and Saturn in the early evening eastern sky.  They will remain together
throughout most of the night and will set together in the pre-dawn western
sky.



*Mercury* rises around 4:03 a.m at week’s beginning and will be visible
briefly in the eastern pre-dawn sky before being obscured by the
intensifying twilight, Mercury reached greatest western elongation on July
20th and will now appear to move closer to the Sun. *Venus,* as always the
brightest planet, currently occupies the Taurus constellation and will rise
at 2:18 a.m. on July 31st.  The optimal time to view Venus is between 3 - 5
a.m, when the brilliant planet remains visible against the pre-dawn glow.
It was at its maximum brightness of the year on July 10th. Though slightly
dimmer now at magnitude -4.3, Venus will still be 15 times brighter than
Sirius.    *Mars* rises by 11:02 p.m.  As it is currently located almost
precisely on the celestial equator within the constellation Pisces, Mars
rises nearly due east and will remain an eastern evening sky object through
the rest of the night. At magnitude -0.9, Mars is now brighter than any
night sky star except Sirius, which is not currently visible.    Mars will
continue to rise earlier and grow brighter as it approaches its next
opposition on October 13, 2020.      *Jupiter *reached opposition on July 14
th and will now slowly move away from Earth and grow gradually dimmer.
However, at magnitude -2.6, Jupiter outshines all the stars and planets,
save Venus. It will rise in the eastern sky at 7:30 p.m. at the beginning
of the week and will set just before 4:30 a.m.  Jupiter reaches opposition
again on August 19, 2021. *Saturn *reached opposition on July 20th and
attained its maximum brightness at that time.   Saturn is also now moving
away from Earth and will become dimmer as a consequence.   However, at
magnitude 0.1, Saturn remains brighter than Vega and will rise at 7:54 p.m.
at week’s beginning. Both Jupiter and Saturn are currently passing through
the constellation Sagittarius the Archer.



Comet NEOWISE is about to fade to black.   Currently dimmer than magnitude
5.0, NEOWISE appears as a faint smudge within the constellation Coma
Berenices.    Now, it has begun its long, arduous trek toward the outer
solar system.  The comet is due to reappear in our skies in approximately
67 centuries.



A flow of solar wind is expected to strike Earth on August 2- 3rd.   Its
arrival could precipitate an aurora event in mid to high latitudes.     We
advise you to consult the web-site  www.spaceweather.com for updates on
this possible aurora event.



The brightest fly over of the International Space Station occurs this week
on August 1st. The ISS will rise at 8:35:18 p.m. and attain its maximum
altitude of 79 degrees at 8:40:47 p.m.  At that time the ISS will shine at
magnitude -3.7, more than three and a half times brighter than Jupiter!
The International Space Station then will vanish into the shadow at 8:44:13
p.m.    During this passage, the ISS will appear to slice through the Big
Dipper’s bowl, graze Draco the Dragon’s head and pass almost directly in
front of Vega, the brightest star in the Summer Triangle.


[image: PassSkyChart2.png]


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