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Salutations celestial sight seers! I'm David Fuller, welcome to Eyes on the Sky; what's
up this week?
Aquila the Eagle is similar to Lyra that was highlighted last week: One bright star, with
mostly 3-rd and 4-th magnitude ones making up the remainder of the constellation - although
this one is significantly larger in area. There are also various mythological tales
associated with Aquila.
The eagle is said to have been the one to carry out the killing of the physician Ophiuchus
by using one of Zeus's arrows due to the doctor learning the art of healing. The bird also
carried the beautiful Ganymede up from Earth to Mount Olympus to serve wine to the gods,
which was pleasing to Zeus. The eagle was also called to inflict the punishment of eating
the liver of chained Prometheus every day, until Hercules killed the eagle with a poisoned
arrow. Due to such devoted service, Zeus placed Aquila in the stars.
Brightest and easiest to find in Aquila is Altair, the closest of the three prominent
stars near the eagle's beak, and its name is the abbreviation meaning "The flying eagle."
It is brilliant at magnitude one, and this is largely because it is close, at 16.7 light
years distance. Strangely, it spins very quickly, rotating once in just nine hours, making it
20 percent wider at the equator than at the poles. Compare that to our Sun which rotates
in just over 25 days.
Dark Sky Fact: The U.S.-based home improvement store Lowes carries dark sky friendly lighting
in its stores. Find their display or look for these fixtures on the shelves.
To the north and slightly west of Altair is Tarazed, a very young, 100 million years old
star. At 2,500 times the brightness of our Sun, we can get a sense of that difference
by recognizing that Tarazed, while only 6 times dimmer than Altair visually from Earth,
is 24 times farther away! At 95 times the size of our Sun and 6 times the mass, it is
quite the "Live hot, die young" star, already fusing helium and carbon and in the later
stages of it's life.
To the south and slightly east of Altair is Alshain. All three of these stars were collectively
known as the Beam, or a balance scale, and were given the Persian name, šhīn tarazū
(or possibly tara zed), meaning, "the beam of the scale," and the three stars can easily
be seen as such. "Al shain" (meaning "beam" or royal falcon) was later assigned just to
the star Beta, and with Tarazed going to Gamma. At 45 light years distance, it is also relatively
close, and is similar in spectral class to our Sun, but farther along in stellar evolution,
no longer fusing hydrogen.
Because Aquila itself does not hold any Messier or prominent deep sky objects, we can look
not far from the eagle's beak to Sagitta, the arrow -- which makes sense given the mythology.
About 10 degrees from Altair towards the heart of Cygnus, is the brightest star in Sagitta,
Gamma Sagittae. This entire constellation can be observed in most binoculars, so use
them to find it, and note the four most prominent stars. Alpha and Beta make up the arrow's
feathers, while Delta and Gamma (along with the dimmer Eta) form the arrow's shaft. Halfway
between Gamma and Delta lies Messier 71, a globular cluster that is smaller and less
concentrated than Messiers 5 or 13. The lower star concentration is perhaps explained by
this cluster orbiting the galaxy's center within the galactic plane, and interacting
with other nearby objects along the way.
Along The Ecliptic: Venus will be in the midst of the Beehive Cluster on July 3, though seeing
it will require a very low horizon as the brilliant planet sinks towards it near dark.
Meanwhile, watch as Saturn slows down this week near Kappa Virginis; later in the month
it will speed off towards the east.
That's all for this week. Keep your eyes on the sky and your outdoor lights aimed down,
so we can all see, what's up. I'm David Fuller, wishing you clear and dark skies.