Salutations celestial sight seers!
I'm David Fuller, welcome to Eyes on the Sky; what's up this week?
Sometimes it's a worthwhile exercise to take a giant step back and get some perspective...
whoa, too far!
There, that's better.
The Milky Way is a barred spiral galaxy, and of course, we are inside it.
From a dark sky site at this time of year one can see the collective light of the stars
of our galaxy, shining across hundreds and thousands of light years of space, along with
large clouds of gas and dust that form dark rifts through it.
Towards the center of it is a “bulge” that is somewhat wider than the rest of the
galaxy's disk.
I know, I know... most of us CAN'T see, well, MOST of that, but it is still there, climbing
from Sagittarius in the south up to Altair, through the Summer Triangle, past Deneb, and
down towards Cassiopeia and Perseus in the north.
And this band of light – the galactic plane - is bisected by the ecliptic of our own solar
system, near the lid of the Teapot in Sagittarius, at about a 60 degree angle.
So not only does the Sun trace it's way across this region of our galaxy at times, the Moon
does too.
And this week, it passes near some great things to see – though perhaps best observed when
the Moon is NOT there.
Orbiting around our galaxy are some of the oldest gravitational objects in the Universe:
Globular clusters.
These compact groupings of hundreds of thousands of stars orbit around the center of our galaxy,
located at Sagittarius A, a supermassive black hole around which all the stars in our galaxy
revolve too.
It's located near the “spout” of the Teapot in Sagittarius, where the “steam” is escaping..
But globulars don't revolve along the plane with the other stars in the disk of the galaxy;
they often revolve above, below, and THROUGH the Milky Way.
And many globulars are near or around the “bulge” of our galaxy – that is, the
fatter central portion towards the middle “bar” region.
More in a moment.
Dark Sky Fact: Have you read Paul Bogard's book, 'The End of Night'?
Check it out; it's a wonderful way to get acquainted with light pollution issues and
reconnecting with the night sky.
The Moon cuts across that area this week, gliding past some of these globulars above
and below the galactic plane along the way.
On Monday, the Moon is in Scorpius, and the globulars M80 and M4 are near here.
In fact, they form a line that goes from the Moon to just south of Antares, the red giant
star in the scorpion.
An evening later, our natural satellite passes into Ophiuchus, the doctor, and there are
quite a few dimmer globular clusters here as we get close to the central part of our
home galaxy, but the brightest of these is Messier 9.
It is not far off from 2.5 magnitude Sabik, or Eta Ophiuchi.
On Wednesday, Luna sits above the lid of the Teapot, near where globular clusters M22 and
M28 are.
The Moon is also just about on the galactic plane then too.
M22 is the lovely, large, brilliant object here, but don't overlook it's smaller-appearing
cousin nearby.
It's not that M28 is actually smaller – okay, actually it is smaller – but it's also quite
a bit farther away.
On Thursday, the Moon has traveled along the ecliptic and will be below the galactic plane,
though mostly we just need to be patient for it to get out of Sagittarius, which it does
on Friday.
Inside the boundaries of Capricornus, we can now look to where the globular cluster M30
is.
As this graphic shows, this cluster is quite a ways below the galactic bulge compared to
M4, or the even further out M5, M10 and M12.
By the weekend, our bright gibbous phased satellite is nearly full, and it is also in
the dim, large Aquarius we discussed last week when looking for Neptune.
The globular cluster M2 is located here, though appearing somewhat closer to the galactic
plane than M30.
Take a few moments each evening this week to go outside and watch the Moon move through
the sky.
And then imagine how these far off islands of stars are orbiting around our own galactic
home.
Along the Ecliptic: Mars and Saturn still sit in the southwest during early evening.
And Jupiter continues it's climb above the eastern horizon in early morning.
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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.