Salutations celestial sight seers!
I'm David Fuller, welcome to Eyes on the Sky; what's up this week?
Crossing the meridian in mid-July after it gets dark for most of us is Ophiuchus.
How did this "physician in the sky" come to be?
That's the subject of this episode's "Astronomy Theater".
In Roman lore, Asclepius was the son of the god Apollo and the mortal Coronas and trained
to be a physician.
while thinking on how to heal a patient, a snake climbed up his wooden staff.
Frightened, Asclepius killed the snake "I hate snakes!" but then another one came along
with an herb that restored the dead snake back to life.
Using the same herb he learned to bring humans back to life, but Pluto complained to Zeus,
who struck Ascelpius dead with a thunderbolt arrow.
But at the intervention of his father Apollo, Asclepius was placed in the sky by Zeus.
Hi name means "serpent bearer" as that was how he learned his healing art.
Even today, the "Rod of Asclepius" is found as a symbol of medicine, though it is sometimes
confused with the caduceus.
Ophiuchus is a large constellation -- the eleventh largest in the entire night sky.
In the northern reaches of the good doctor there is a section that protrudes towards
the east.
It is here that we will set our sights this week.
The 2.8 magnitude Beta Ophiuchi makes a convenient guidepost to several objects to see near here.
The brightest and easiest to find is IC4665, sometimes known as the "HI" cluster for it's
resemblance to the capital letters "H" and "I" when seen through a reflector telescope.
It is somewhat "young-ish" as open clusters go, having formed some 40 million years ago
at a distance of 1,400 light years.
Best seen at very low power, the cluster is also visible in binoculars from most areas
as most of the bright stars are 7-th and 8-th magnitude.
Dark Sky Fact: Blue light at night harm's sleep by suppressing melatonin.
The best outdoor streetlights are low pressure sodium, but other lights that do not emit
light in wavelengths shorter than 540 nanometers are okay too such as high pressure sodium
-- provided they ar well-shielded to block glare and light trespass, of course.
For best sleep conditions, in indoor situations use incandescent, halogen, or warm white LED's
to limit blue wavelengths exposure after dark.
From there, things get interesting.
70 Ophiuchi, a double star, is located less than six degrees from Cebalrai, and is easy
to find too.
Just hop 2 degrees to Gamma, 3 degrees to 67 Ophiuchi, and then one additional degree
to 70.
This double star is a mere 16.6 light years from Earth, with two K-spectral class stars
orbiting around a barycenter.
These two stars have an average distance of a bit more than the furthest out Sun/Uranus
distance.
However, their orbit is highly elliptical, so we get this mesmerizing dance between the
two stars like this.
One orbit takes just over 83 years, so many of us can at least observe and plot half an
orbit - or more - over our lifetimes, depending one when we start our observations.
Keep good notes!
The angular separation varies from 6.7 arc seconds to as close as 1.7 arc seconds and
is currently a bit less than 4 arc seconds.
Their colors have been variously described as yellow and red, or gold and violet.
What colors do YOU see?
And lastly we can find one of the closest stars to Earth.
Barnard's star is just 5.9 light years away and also has a very fast proper motion, moving
over 10 arc seconds per year.
It is just north and west of the triangle of stars formed by 66, 67 and 70 Ophiuchi.
Follow an arcing line from 70 through 67, fourth and fifth magnitude stars respectively,
and look for this lambda shaped set of stars.
These are largely 7-th through 9-th magnitude stars, and Barnard's star is 10.5 magnitude.
Draw a line from the apex of the lambda, and in a one degree field of view, you can spot
the fast-moving star here.
If you liked this video, there are more videos like it and others with basic telescope information.
Visit eyesonthesky.com and click on the "Videos" tab or choose from the drop down menus.
And be sure to subscribe, follow and like on social media sites -- Eyes on the Sky is
more than just weekly videos.
Thanks for watching...
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.