THE SOUTHWORTH PLANETARIUM
70 Falmouth Street Portland, Maine 04103
(207) 780-4249 usm.maine.edu/planet
43.6667° N 70.2667° W Founded January 1970
2022-2023: XC
Sunrise: 5:34 a.m.
Sunset: 7:43 p.m.
Civil twilight begins: 5:02 a.m.
Civil twilight ends: 8:15 p.m.
Sun's host constellation: Aries the Ram
Moon phase: Waxing gibbous (83% illuminated)
Moonrise: 3:29 p.m.
Moonset: 4:18 a.m. (5/2/2023
Julian date: 2460066.29
"A human who dares to waste an hour of time has not
discovered the value of life."
-Charles Darwin
THE DAILY ASTRONOMER
Monday, May 1, 2023
The Hobbit Sky
*Honestly, we love all the questions that we extract from Pandora's Jar.
Some of them, we admit however, are particularly delicious. The query
written on today's piece of parchment is just such a dainty confection. It
pertains to some of the Universe's most beautiful things: stars, hobbits,
and thoughts of verdant places. We needed to spend some time formulating
what we hope is a coherent answer, so we're limiting ourselves to just one
Pandora today.*
*"The other night I was looking at the stars and wondered. 'Can we see any
of the same stars that those little people in Hobbit village in New Zealand
can see?' I can't yet afford to visit the place myself -my birthday is
August 11th- but I thought it would be nice to know if there are any stars
I can see here that could also be seen in the night sky in Hobbit
Village. Please use the pseudonym I wrote down, but you might not want
to use just the first initials of each word. Thank you!"*
* -Wicked Tolkien Freak, Portland, Maine*
*Hello, Freak,*
*The short answer, which I know won't suffice, is, yes, we do see some of
the same stars that people can see in Hobbit Village in New Zealand. We
will actually try to work through the problem to determine which stars we
share with the hobbits. First, we need to know where on Earth Hobbit
Village is located. It is in Matamata, New Zealand. *
*The "Green Dragon Inn" in Matamata, New Zealand, the*
*location of the world renowned Hobbit Village. The coordinates*
*for this wonderland are about 38 degrees south, 175 degrees east.*
*The first value, the latitude, is necessary to answer today's question*
*Matamata, New Zealand, is located 38 degrees south of the Equator. We
know that Portland, Maine, is about 43 degrees above the equator. These
two pieces of information will help us determine which stars are visible
from Portland and Hobbit Village. We know that the night sky changes
dramatically with latitude because latitude determines which stars one can
see. Here we need to introduce the term "declination," which measures a
celestial body's angular distance from the celestial equator. (The
celestial equator is the projection of Earth's equator onto the sky.*
*Declination measures a celestial body's angular distance*
*north or south of the celestial equator. The celestial equator's*
*angle relative to an observer's horizon depends on the observer's*
*latitude. Portland, Maine's latitude is about 43 degrees. Therefore,*
*the celestial equator is 90 - 43 = 47 degrees above the southern horizon.*
*Thus, we can see any star whose declination is greater than -47 degrees.*
*Let's pretend we're on the equator. (I know Portland residents are
savouring the 7th straight day of drizzle and highs in the low 40s and are
therefore loath to venture to warmer regions, but we'll come right back.)
On the equator, the celestial equator would extend from due east to due
west and would pass through the zenith, the point directly overhead. The
celestial equator is 90 degrees above the southern horizon on the equator.
Now, pretend that you travel to 10 degrees N latitude. At this
location, the celestial equator is displaced from the zenith by 10
degrees. It would then be 80 degrees above the southern horizon.
Continue northward to 20 degrees N latitude. Now, the celestial equator is
20 degrees south of the zenith and 70 degrees above the southern
horizon. We have thus established a relation between the celestial
equator's angle above the southern horizon and the observer's latitude.
The angle will be 90 degrees minus your latitude. Here in Portland, our
latitude is 43 degrees and so the celestial equator passes 47 degrees above
the southern horizon. The stars that are aligned along our southern
horizon have a declination of -47 degrees. (They are 47 degrees south of
the celestial equator.) We know that every northern hemisphere observer
can see every star north of the celestial equator. So, any Portland
observer can see any star that is north of -47 degrees declination.*
*We go next to Matamata. New Zealand. Its latitude is 38 degrees south.
As it is in the southern hemisphere, the celestial equator draws closer to
the northern horizon as an observer travels south. In Matamata, the
celestial equator would be 90 - 38 = 52 degrees above the northern
horizon. An observer at this location would see all stars south of the
celestial equator and would also be able to see all stars that are less
than 52 degrees north of it. *
*By these two calculations we have determined that all we and the hobbits
share all stars that are within the region between 52 degrees north of the
celestial equator and 47 degrees south of it. This area is a wide swath
of the sky. *
*Orion the Hunter (called **Menelvagor in Middle Earth), Scorpius the
Scorpion, Hercules, Canis Major, Aquarius, Pisces, and the Summer Triangle
constellations Lyra the Harp, Aquila the Eagle and Cygnus the Swan are
examples of the *constellations we share with the Hobbits.
*This southern hemisphere planisphere shows some of the constellations that
we can see*
*here, such as Aquarius the Water Bearer and Pisces the Fish.*
*So, when you look up in the sky tonight, realize that our sky shares many
stars with the sky that the Hobbits admire.*
*Glow worms illuminating a cave in New Zealand, which resembles a*
*night sky. This has nothing whatsoever to do with the topic at hand, but*
*the photo was so gorgeous, we had to include it. (Courtesy: National
Geographic)*
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