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:  2459362.18
2020-2021: CXXXIX


THE DAILY ASTRONOMER
Tuesday, June 1, 2021
June 2021 Night Sky Calendar


_____________________________
*Error!*
Yes, time to acknowledge a mistake (not the first time)
The base 10 system consists of numbers between 0 - 9, not 1-9,
as  I wrote in an earlier DA.
My beloved Kindergarten teacher Mrs. Estes would scold me
quite harshly for that error were she not presently weaving
ornate tapestries for Athena in some corner of the Elysian fields.
Thanks to the DA subscriber Max who brought this
mistake to my attention!
______________________________

Summer begins...at least meteorologically.  Astronomically, summer is still
about three weeks in the future. All the same, the summer stars are rising
and many of the winter stars are hiding around or behind the Sun.    In
other words, the celestial cycles are abiding precisely by their
itineraries, which is a true comfort for us bewildered mortals.    As is
our wont, we are dividing these calendar into parts because tomorrow we
shall focus on a partial solar eclipse that WE WILL SEE here in southern
Maine.



*TUESDAY, JUNE 1:  JUPITER CLOSE TO THE MOON*
A perfect opportunity to find our solar system's largest planet.      Find
Jupiter close to the waning gibbous moon.   Both will rise by 1:30 a.m.
Honestly, though, Jupiter will not be difficult to find.  However, seeking
it will prove all the easier with the gibbous moon nearby.

*[image: skychart.ashx.png]*

*WEDNESDAY, JUNE 2: LAST QUARTER MOON*

*WEDNESDAY, JUNE 2:  INTERNATIONAL SPACE STATION FLY OVER*
Sometimes, one will see the International Space Station many times each
week.  Other times, the ISS vanishes from view for a while.   This month,
we'll experience three visible fly overs (1st, 2nd and 4th) before the ISS
goes away for a couple of weeks.    (It returns on June 26th.)    The June
2nd apparition is the brightest of the three, so we're including it in this
calendar.  The time table and the star chart showing its path is below.
(Thanks to heavens-above.com for these graphics.)

Chart size (500 - 1600)

Date: 02 June 2021
Orbit: 417 x 422 km, 51.6° (Epoch: 01 June)

Event Time Altitude Azimuth Distance (km) Brightness Sun altitude
Rises 20:57:27 0° 296° (WNW) 2,365 2.0 -6.7°
Reaches altitude 10° 20:59:41 10° 285° (WNW) 1,498 0.3 -7.1°
Maximum altitude 21:02:42 31° 222° (SW) 763 -2.4 -7.5°
Drops below altitude 10° 21:05:42 10° 158° (SSE) 1,492 -1.5 -7.9°
Enters shadow 21:05:58 9° 156° (SSE) 1,591 -1.4 -7.9°

*SATURDAY, JUNE 5:  FIND THE HERCULES KEYSTONE*

[image: herculescentered-5b2b08c304d1cf00362a834b.jpg]

The Hercules' Keystone:  a four star quadrilateral marking the Hercules'
mid-section.   The "Keystone" is an asterism, or a star pattern within a
larger constellation.   One can locate the Keystone by drawing an imaginary
line connecting Deneb and Vega in the Summer Triangle. Extend the line
slightly westward and it will intersect the Keystone.

Today's focus is the "Keystone," a quadrilateral centered on Hercules.
The image seen above  shows Hercules "upside down," as he is portrayed as
kneeling on Draco the Dragon's head.     Draco is often identified
mythologically as the dragon who guarded the golden apples within the
Garden of the Hesperides.     The eleventh of Hercules' twelve labours
required him to steal these apples, a task rendered all the easier once he
slew the dragon.


Though it consists of no bright stars, this keystone is somewhat easy to
find provided one first locates the Summer Triangle.    Vega, the brightest
Summer Triangle star, is just east of the Keystone.    Extend a western
line connecting Deneb, the Summer Triangle's eastern star, and Vega.   This
line slices neatly through the Hercules asterism.      The Keystone stands
out because,though not brilliant, is still brighter than the
constellation's other features.    Often, observers are only able to find
the asterism, as the legs and arms are lost amongst the surrounding stars.

[image: 34672316993_727379e78f_b.jpg]
M13: The Hercules Star Cluster    A globular star cluster "located" in the
Hercules Keystone.   Approximately 25,000 light years distant, this cluster
contains more than 100,000 stars within a "globe-shaped" arrangement.
 Image:  Sara Wager

Apart from being Hercules' sole prominent section, the Keystone also marks
the location of M13,** a globular star cluster.   The Hercules Cluster is a
gorgeous globular cluster consisting of more than 100,000 stars located in
the galactic halo.     So named due to their resemblance to globes,
globular clusters are significantly older and larger than the open
(galactic) clusters that swarm about the galaxy's spiral arms.       Of
course, we can easily see a couple such open clusters (Praesepe and the
Pleiades), while the much more distant Hercules cluster is only visible
through a telescope.

TUESDAY, JUNE 8:  CIRCUMPOLAR GALLERY

Some have described the night sky as a comforting constant in an ever
changing world.  In some respects the night sky seems immutable.
Throughout the year, the same constellations appear each season.  For
instance, Orion the Hunter will be due south in the early evening in
February as the Summer Triangle looms high overhead in the early evening
now.   We even have a retinue of constellations that one can see throughout
the year at any time of night.   We refer to this subset of constellations
as "circumpolar."   They appear to describe circles around the North
Celestial Pole and, at our latitude, never set.

We recognize six circumpolar constellations:
Camelopardalis the Giraffe
Cassiopeia the Queen
Cepheus the King
Draco the Dragon
Ursa Major the Great Bear
and
Ursa Minor the Little Bear

Three of these patterns - Ursa Major, Ursa Minor and Cassiopeia- are quite
easy to observe provided one's night sky is reasonably dark.

Two of these constellations - Cepheus the King and Draco the Dragon- are
not so easy to locate.   Their stars are generally fainter and Draco
meanders through the sky, making it difficult for any star gazer to discern
the pattern.

One of the circumpolar constellations (Camelopardalis the Giraffe) is
almost impossible to observe.

We'll quickly examine each circumpolar constellation in turn:




*CAMELOPARDALIS:  The Giraffe*
The circumpolar constellation that hardly anyone has ever seen.
 Invented by Petrus Plancius in the early 17th century, this constellation
was a "filler star pattern" meant to occupy a patch of dark sky.   Of all
the circumpolars, Camelopardalis is the only "modern constellation,"
meaning that it doesn't date from antiquity.  The constellation name
derives from "Camel Leopard" a term once applied to the animal we now call
the giraffe.

*CASSIOPEIA: the Queen*
A queen of ancient Ethiopia, Cassiopeia resembles an elongated "w." This
constellation is identified mythologically with Cassiopeia, the mother of
Andromeda.    Cassiopeia's boast that her daughter was more beautiful than
Poseidon's Nereids incited the god's ire.  Poseidon summoned Cetus the
Seamonster from the depths to ravage Cassiopeia's village.  A Delphic
oracle instructed Cassiopeia to sacrifice her daughter to Cetus in order to
mollify Poseidon.  The miserable queen followed these orders.  Fortunately,
however, Perseus the warrior intervened by slaying Cetus before he could
devour Andromeda

*CEPHEUS: the King*
When you refer to Cepheus was Cassiopeia's husband, you've said just about
everything about him. His role in the Cassiopeia-Andromeda debacle was one
of a quiet spouse who dutifully helped his wife tie Andromeda to the rocks
as an offering to Cetus.    Mythologically, he does little else but look on.

*DRACO: the  DRAGON*
Dragons do almost everything.   One cannot cite just one adventure or one
task.  Dragons have guarded sacred apples, reclined on stolen treasure,
eaten hapless maidens, inadvertently sent castles into orbit ("Dragons is
so stupid!"), what have you.  Of all chimerical creatures, dragons are so
common throughout world mythologies as to be almost ubiquitous.    Draco's
curvaceous body weaves through the northern sky.  To find it, either look
first to Hercules's keystone asterism as Draco's head is just to the north
of it.  Or, look between the dippers to trace the serpentine star line
representing the monster's body.

*URSA MAJOR: The Great Bear*
The "Big Dipper" is only part of this constellation.    The Big Dipper's
bowl represents the bear's body and the handle forms the tail.    The rest
of the bear consists of stars surrounding the dipper.

*URSA MINOR: The Little Bear*
The "Little Dipper" is the main part of this constellation.  Polaris, the
north star, is the end-handle star in the Little Dipper.

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