Salutations celestial sight seers!
I'm David Fuller, welcome to Eyes on the Sky; what's up this week?
With autumn constellations ascendant, let's look at one of the prominent ones... but first!
Some Astronomy Theater.
The princess Andromeda was the daughter of Cepheus and Cassiopeia.
Unfortunately for Andromeda, her mom boasted about her beauty, and the only way to stave
off the sea monster sent by Poseidon was for Cepheus to sacrifice his daughter on the shore.
But Perseus the hero was passing through and killed the sea creature before it could harm
Andromeda.
The hero and the princess then were married.
Rising in the east after sunset are the three brightest stars of Andromeda; Alpheratz, Mirach
and Almaak.
These second magnitude suns may all appear similar in brightness to us, but there's quite
a bit of difference among the three.
Alpheratz is a B-class blue-white star that is almost 100 light years away.
This star is hot at about 13,800 Kelvin, but what's more interesting is the specifics of
the spectral class, at B9.
That means it is a mercury magnanese star, containing not only high concentrations of
those elements but also xenon and gallium.
And Alpheratz is the brightest star of this type that is known.
Mirach, by contrast, is much different.
An M-class red star, it is less than 1/3 as hot as Alpheratz, radiating at just 3700 Kelvin.
But while Alpheratz was about 3 times the size of the Sun, Mirach has bloated up to
100 times the Suns size, which is why it looks nearly as bright as Alpheratz despite being
located twice as far away at 197 light years.
Look for the yellowish-orange color through a small telescope.
And at the foot of Andromeda is Almaak.
This is like the autumn Albireo, as this double star sports a yellow and blue pair, though
they are closer together than the actual Albireo over in Cygnus.
Almaak is quite an interesting system, as the dimmer, blue companion isn't just a single
star, it is actually part of a three star system.
Though we can't see the two dimmer components, the blue and yellow pair is a superb sight
in any small telescope.
Dark Sky Fact: This week, give a hand to Globe at Night!
If you can locate the Great Square of Pegasus, you can submit what your sky looks like to
help measure and track light pollution.
It only takes a few minutes – visit globe at night dot org, click on the “Observe”
tab, and then scroll down to the current month's constellation.
For October, it's Pegasus – easy to find and see, and easy to measure and submit observations!
Do it this week.
Backing up to Mirach, we can find the next closest spiral galaxy to our own Milky Way.
Look from Mirach up towards Cepheus, about an a right angle from Almaak.
Just a short four degrees away is Mu Andromedea.
Mu is an A-class star, so it really does look very white in color.
Travel on a line from Mirach through Mu, and hop a similar distance past Mu.
Even in many small finderscopes, the glow from the heart of the Andromeda Galaxy is
visible.
While this immense spiral of billions of stars spans about 3 degrees of sky, in most telescopes
from light polluted areas only the bright, central core is visible.
This galaxy is 2.2 million light years away.
Think about that for a moment: Light from the stars of this galaxy left there on it's
way towards the Milky Way around the time the first members of the Homo genus were evolving
as life forms here on Earth.
And the light from that galaxy is finally reaching your Home Sapiens eye, tonight.
Pretty amazing, eh?
Something fun to think about as you observe this next-closest spiral over the course of
this week.
Mars is the lone naked eye planet left in the evening sky though at 6 arc seconds of
diameter, it won't be much to look at without a larger telescope at 300x magnification or
higher.
Over in the morning sky, the king of the planets sits just west of Leo the Lion, and the Moon
joins Jove on the morning of October 17-th and 18-th.
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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.