THE SOUTHWORTH PLANETARIUM
207-780-4249   www.usm.maine.edu/planet
<http://www.google.com/url?q=http%3A%2F%2Fwww.usm.maine.edu%2Fplanet&sa=D&sntz=1&usg=AFQjCNHulkHuLP13bOG2PkNrPazsGWFs2A>
70 Falmouth Street   Portland, Maine 04103
43.6667° N                   70.2667° W
Altitude:  10 feet below sea level
Founded January 1970
Julian Date: 2459041.16
2019-2020:  CLXXV

THE DAILY ASTRONOMER
Friday, July 10, 2020
Remote Planetarium 63:  Week 13 Quiz  and Skywatch!

Greetings!
We're adding a new feature to the weekly quiz: a transcript of the Sky
Watch Hotline.    If you call 207-780-4719, you can hear this recording.
It provides listeners with information about the Sun, moon, planets, and
other notable celestial events.  I will be writing and recording this
message each Friday morning.   As a few subscribers have asked about the
sky calendars, I thought it would be worthwhile to include the Skywatch
Hotline transcript.    (My apologies for those subscribers outside the
Portland area.  The times listed are specific to southern Maine.)
Because of the extra space the Sky Watch occupies, the quiz will include
sixteen questions instead of twenty.

*1.  "Mira," a star in the constellation Cetus, literally means ___________*
a. "variable"
b. "wonderful"
c.  "enigmatic"
d.  "reflection."

*2.  Mira variables are an example of what type of variable star?*
a. Algol
b. Cepheid
c.  Long period
d. none of the above

*3.  How massive is a Mira variable?*
a. up to two times as massive as the Sun
b. 10 - 20 times more massive than the Sun
c. 25 - 40 times more massive than the Sun
d. 45 - 100 times more massive than the Sun

*4.  Astronomers divide semi-regular long period variables into how many
categories?*
a. 2
b. 3
c. 4
d. 5

*5.  A Type Ia Supernova occurs in a binary star system in which one of the
components is a ____________.*
a.  black hole
b. neutron star
c. white dwarf
d. brown dwarf

*6. Why are Type Ia Supernovae useful to determine the distances to remote
celestial objects?*
a.  they are always close
b.  Type Ia supernovae are of equal brightness, in theory
c.  they only appear in nearby galaxies
d. none of the above. Type Ia Supernovae are not actually useful for
distance determination.

*7.  Type II supernovae occur when a highly massive star explodes from the
inside out.   This explosion happens after the star accumulates _________
in its core.*
a. iron
b. silicon
c. gold
d. silver

*8. What is the main difference distinguishing periodic and cataclysmic
variables?*
a. periodic variables are brighter
b. cataclysmic variables don't reach maxima at regular intervals
c. periodic variables are only found in our galaxy
d.  none of the above

*9. If a star's parallax angle is 0.1", how far away is it?*
a.  1 parsec
b. 10 parsecs
c. 100 parsecs
d. 1000 parsecs

*10.  The declination of Porrima, a star in Virgo the Maiden, is -01
degrees 26'.  Where does Porrima pass directly overhead?*
a. just south of the equator
b. just north of the equator
c. along the Tropic of Capricorn
d. along the Arctic Circle

*11. The declination of Bellatrix is about +6 degrees.  Where in the world
would one NOT be able to ever see Bellatrix?*
a. anywhere north of 84 degrees north latitude
b. anywhere south of 84 degrees south latitude
c. at the north pole
d. at the equator

*12. Which is hotter: a type A star or a type B star?*
a. A
b. B
c. their temperatures are equal
d. the question doesn't make sense.  The designations A and B do not
pertain to temperature.

*13.  What is meant by "interstellar extinction?"*
a. the process by which stars explode
b.  the obscuration of stars by interstellar dust
c. the reddening of stars by dust grains
d. none of the above

*14.  Interstellar dust grains will also make celestial objects appear
_________*.
a. redder
b. bluer
c. greener
d. more yellowish

*15.  Along the galactic plane, a star's brightness is reduced by _______
magnitudes per kiloparsec.*
a. 1
b. 1.4
c. 1.8
d. 2.6

*16. Interstellar extinction affects a star's ______________.*
a. absolute magnitude
b. apparent magnitude
c. intrinsic brightness
d. all of the above
e.  none of the above


ANSWERS
*1.  "Mira," a star in the constellation Cetus, literally means ___________*
b. "wonderful"
Johannes Hevelius (1611-1687) named the star "Mira," meaning "wonderful"
because it seemed to appear and then disappear.

*2.  Mira variables are an example of what type of variable star?*
c.  Long period
Mira variables are one of the main type of long period variables, those
stars whose variability periods vary between 80 - 1000 days, on average.

*3.  How massive is a Mira variable?*
a. up to two times as massive as the Sun
Mira variables are solar mass stars that are toward the end of their lives.

*4.  Astronomers divide semi-regular long period variables into how many
categories?*
c. 4
They designate the categories a, b, c and d.

*5.  A Type Ia Supernova occurs in a binary star system in which one of the
components is a ____________.*
c. white dwarf
A Type Ia Supernova occurs when gases from an active star collects onto a
white dwarf.  When the white dwarf's mass exceeds 1.44 solar masses, it
will explode as a Type Ia Supernova.

*6. Why are Type Ia supernovae useful to determine the distances to remote
celestial objects?*
b.  Type Ia supernovae are of equal brightness, in theory
Because Type Ia supernovae occur when the white dwarf's mass exceeds 1.44
solar masses, each one should release the same amount of energy and be of
equal brightness.

*7.  Type II supernovae occur when a highly massive star explodes from the
inside out.   This explosion happens after the star accumulates _________
in its core.*
a. iron
Stars can fuse any element up to iron.  Iron fusion is an endothermic
process, meaning that the amount of energy required to fuse the iron is
greater than the energy the fusion reaction imparts onto the star.

*8. What is the main difference distinguishing periodic and cataclysmic
variables?*
b. cataclysmic variables don't reach maxima at regular intervals
Cataclysmic variables flare up often only once or at different times
depending on the mechanisms responsible for their variability.

*9. If a star's parallax angle is 0.1", how far away is it?*
b. 10 parsecs
To determine a star's distance, one must divide the number 1 by the
parallax angle expressed in arc-seconds.  1/0.1  = 10 parsecs.

*10.  The declination of Porrima, a star in Virgo the Maiden, is -01
degrees 26'.  Where does Porrima pass directly overhead?*
a. just south of the equator
Porrima is located about one and a half degrees south of the celestial
equator.  Observers one a half degrees south of the Equator will see it
pass directly overhead.

*11. The declination of Bellatrix is about +6 degrees.  Where in the world
would one NOT be able to ever see Bellatrix?*
b. anywhere south of 84 degrees south latitude
The closer a star appears to the celestial equator, the wider its
visibility region.   Bellatrix is visible in all regions north of 84
degrees south latitude.

*12. Which is hotter: a type A star or a type B star?*
b. B
The sequence is as follows
O B A F G K M.
O's are the hottest stars; M the "coolest."

*13.  What is meant by "interstellar extinction?"*
b.  the obscuration of stars by interstellar dust
Incoming starlight will be partially obscured by dust grains located within
interstellar space.   The obscuration relates directly to distance.  The
more distant the star, the greater the extinction.

*14.  Interstellar dust grains will also make celestial objects appear
_________*.
a. redder
The interstellar dust grains are generally equal in size to the wavelength
of blue light.   So, the blue light within a stream of starlight will often
be absorbed or scattered away.  Consequently, the incoming light from a
celestial object will appear redder than it would were it to pass through a
vacuum.

*15.  Along the galactic plane, a star's brightness is reduced by _______
magnitudes per kiloparsec.*
c. 1.8
The interstellar extinction is greatest along the galactic plane where the
dust is concentrated.

*16. Interstellar extinction affects a star's ______________.*
b. apparent magnitude
Apparent magnitude measures a star's apparent brightness.   Absolute
magnitude refers to a star's intrinsic brightness.   Interstellar
extinction affects how bright a star appears, but cannot alter a star's
actual brightness.

___________________________________________________
*SKYWATCH HOTLINE *  July 10 - 16, 2020

Greeting, Stargazers!

On July 10 the Sun will rise at 5:10 a.m. and set at 8:23 p.m, giving us 15
hours and 13 minutes of daylight, a 13 minute decrease since the Summer
Solstice.   On July 16, the Sun will rise at 5:15 a.m. and set at 8:19 p.m,
providing us with 15 hours and 4 minutes of daylight.  The Sun appears to
be moving through the constellation Gemini the Twins.

At week's beginning the moon will be progressing through the latter stages
of the waning gibbous phase.    The moon will be at the last quarter phase
on July 12th, and will rise at 12:10 a.m on that date.   On July 11, see
Mars close to the moon.  On July 16th, the waning crescent moon appears to
pass close to the Pleiades Star Cluster in Taurus the Bull.  One shall see
both the moon and cluster in the eastern sky after 2:30 a.m. on the 16th.

The main planetary event this week is the opposition of Jupiter on July
14th.  The fifth world will rise at sunset on this date and will remain
visible all night.    When at opposition, a superior planet -defined as one
that is farther from the Sun than Earth- moves to the far side of Earth
relative to the Sun.  A planet attains its maximum brightness at or around
this time.   Jupiter's opposition magnitude measures -2.8, making it 3.6
times brighter than Sirius, the night's sky brightest star.  (Sirius,
incidentally, is not currently visible)  Jupiter will continue to progress
slowly toward the setting Sun throughout the remainder of 2020 and will
vanish into the dusk by year's end.

*Mercury* rises after 4:35 a.m. and owing to its apparent closeness to the
Sun will not be visible this week.   *V**enus,* as always the brightest
planet, currently occupies the Taurus constellation and will rise just
before 3:00 a.m.   The optimal time to view Venus is between 4 - 5 a.m,
when the brilliant planet remains visible against the intensifying morning
twilight. It will be at its maximum brightness of the year on July 10th. At
magnitude -4.7, Venus will be thirty times brighter than Sirius.
*Mars* rises
almost at midnight.  As it is currently located almost precisely on the
celestial equator within the constellation Cetus, Mars rises nearly due
east and will remain an eastern evening sky object through the rest of the
night. At magnitude -0.7, Mars outshines all the stars except Sirius and
Canopus, a star not visible at this latitude.     Mars will continue to
rise earlier and grow brighter as it approaches its next opposition on
October 13, 2020.       *Saturn* rises just before 9:00 p.m. in the eastern
sky.     Even though quite bright by its own standards at magnitude 0.2,
Saturn is the dimmest of the naked eye planets this week.     Saturn will
be at opposition on July 20, 2020.      Both Jupiter and Saturn are
currently passing through the constellation Sagittarius the Archer.

The main highlight this week is the Comet NEOWISE, named for the Near-Earth
Object Wide-Field Infrared Survey Explorer that astronomers used to
discover this icy interloper on March 27th.     Comet NEOWISE is currently
shining at magnitude 1.7 and can be observed low in the eastern pre-dawn
sky this week.  NEOWISE passed perihelion-its closest point to the Sun- on
July 3rd and should brighten.  Also, by the end this coming week, NEOWISE
will also be visible for approximately one hour after sunset.   It is
moving currently from the constellation Auriga through Lynx en route to
Ursa Major.    To see a star chart showing its mid-week location, consult
the planetarium's sky watch image web-page at
www.usm.maine.edu/planet/sky-watch-hotline
<https://usm.maine.edu/planet/sky-watch-hotline>   On July 22, NEOWISE will
attain its minimum distance from Earth, approximately 103 million
kilometers.  Astronomers do not know how the comet will appear in the
coming weeks.   Its outgassing could deplete its ice reserves and render it
effectively invisible or it could disintegrate in a spectacular outburst.
  They do know that NEOWISE is an Oort Cloud object moving along an orbit
so wide that the comet requires many millennia to complete one circuit
around it.  After this apparition, NEOWISE is slated to return to Earth's
skies in approximately 6,800 years.

Of all the International Space Station flyovers visible to us this week,
the brightest will occur in the early morning of July 16th.      The ISS
will rise at 3:43:01 a.m. in the northwestern sky.    It will attain its
maximum altitude of 56 degrees and its maximum brightness of magnitude -3.8
at 3:48:26 a.m. and then will set in the southeast at 3:53:49 a.m.      Its
passage will bring it across Hercules, through the Summer Triangle, along
the southern reaches of Pegasus and along Cetus the Whale.  Consult the
web-page  www.usm.maine.edu/planet/sky-watch-hotline  to see its path
against the stars.

The next transmission of the Sky Watch Hotline is scheduled for July 17,
2020, Julian date 2459048.16. If you would like to contact the Skywatch
Hotline, just send an e-mail to [log in to unmask]    Until then,
the Southworth Planetarium wishes you beautiful nights, joyous days and
clear skies.
_______________________________________________________________


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