Salutations celestial sight seers!
I'm David Fuller, welcome to Eyes on the Sky; what's up this week?
Many constellations are obvious, because of both the well-formed shape, and the brightness
of the stars, as with Orion.
Others are more like, "Hey!
There's some leftover stars between these bright ones - what do they look like?"
"Ummm... a unicorn!?!"
That's seems to be the case with dim, large and not-well-shaped Monoceros - but!
Don't dismiss this area based on that; there's a LOT to see here.
Draw a line 10 degrees east from Orion's belt stars, stopping at 4-th magnitude Gamma Monocerotis.
In binoculars or a finderscope, centering that star or moving a bit more in that same
direction, there is another, similarly bright star, slightly above that line of directional
movement.
This is 4-th magnitude Beta Monocerotis, a fantastic TRIPLE star system, but - it is
a rather tight triplet to split.
The "B" and "C" stars are 590 times the "Earth-Sun" distance, and take 4200 years to orbit each
other, and just 2.8 arc seconds apart from our perspective.
The "A" star is more than 2.5 times as far away from the closer pair, and orbits both
of them over a period of 14,000 years.
That further distance makes it a bit easier to split at 7.4 arc seconds.
Now here's what's fascinating: These are all VERY young stars; less than 34 million years
old - they weren't even a gleam in the sky when dinosaurs ruled the Earth!
Dark Sky Fact: Last week, the International Dark Sky Association announced TWO new "dark
sky parks" - (BREH-cuhn) Brecon Beacons in South Wales, and Death Valley near Tuscon
Arizona in the United States.
Go visit these pristine skies if you get an opportunity!
Now let's start from Gemini, more towards overhead.
Hopping across the 2-nd thru 4-th magnitude "feet" of the twins, turn as if you're heading
back to Beta Monocerotis, after passing Xi Geminorum.
Just a half of a finderscope field of view away, but returning into Monoceros, is 4.7
magnitude 15 Monocerotis, easily seen with binoculars.
Look for this cluster of stars that William Herschel first noted back in 1784 that form
the Christmas Tree Cluster, with 15 as the "trunk" or base.
Using a telescope, there is more to see here - though it takes dark skies and a larger
optics to see not only the additional stars but the dark Cone Nebula that is part of this
young, O-B association of stars.
Now continue on that Xi Geminorum / 15 Monocerotis line.
Half a binocular field from 15, there is a unique 6-th magnitude star.
This is "Plaskett's Star" named for Canadian astronomer John Stanley Plaskett who discovered
its binary nature in 1922.
Very few stars have proper names like this.
It is impossible for us to split the two stars visually, because these hot O-class stars
make for one of the closest, and importantly, most massive binary star systems.
Unlike Beta Monocerotis A at 14,000 years for it's orbit, this pair orbits each other
in just over 14 DAYS, in an orbit smaller than that of Venus around the Sun!
And here's the really astounding thing: Between the two stars, they have a mass of over 100
Suns!
Check out this seemingly benign, quiet star system, which is also not far from the Rosette
Nebula and NGC2244.
Observing tip: Viewing double stars often requires good optics and a steady sky, like
planetary observing.
Make sure your telescope is cooled to outdoor ambient temperature, and view when the stars
are at or near the ecliptic for best viewing.
Along The Ecliptic: Jupiter increases the speed of it's prograde motion, passing above
two 6-th magnitude stars this week.
The Moon grazes past the 1-st magnitude Spica on the morning of the 2-nd, and then visits
the still-rising Saturn on the 3-rd, and achieving Last Quarter phase on the 4-th.
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.