Idaho Skies Transcript for February 21st to 27th

PAUL
Welcome to Idaho Skies for the fourth week of February. We’re your hosts, Paul...

RACHEL
...and Rachel.

PAUL
After it gets dark on the 21st, look for a yellowish-orange star to the left of the moon.

RACHEL
This is Regulus, the brightest star of Leo the Lion.

PAUL
Because of the yellowish-orange tint in the star and it location in the constellation, Regulus represents the heart of the lion.

RACHEL
You’ll find the head and mane of Leo easy to identify.

PAUL
The back of his head and mane are outlined by the backwards question mark of stars above Regulus.

RACHEL
It takes the moon two days to traverse Leo.

PAUL
And by then, the moon will have reached its next destination, Jupiter.

RACHEL
Jupiter appears as a bright creamy-white star 2.5 degrees above the moon on the evening of the 23rd.

PAUL
Since the moon is ½ degrees across, Jupiter is five lunar diameters above the moon.

RACHEL
However, it may appear even closer than that to the moon.

PAUL
The reason why is that our eyes and brain makes the moon appear even larger when it’s near the horizon.

RACHEL
This is called the Moon Illusion.

PAUL
You can test this illusion by comparing the size of your thumb nail to the apparent size of the moon when it first rises and then several hours later.

RACHEL
So pretend to be hitch-hiking and extend your arm and thumb.

PAUL
Then compare the size of your thumb to the recently risen moon.

RACHEL
The moon will seem larger to your mind because it has just risen.

PAUL
However, your thumbnail measurement will show the moon’s about equal to half the width of your thumbnail.

RACHEL
Now repeat this experiment an hour or two later.

PAUL
Because the moon is no where near the horizon, it should appear smaller than it did an hour or two ago.

RACHEL
But surprise, you’ll find it’s still half as wide as your thumb nail when your arm is fully extended.

PAUL
So both times the moon was the same size.

RACHEL
However, to your mind, the newly risen moon appeared significantly larger.

PAUL
There’s no consensus on why the moon near the horizon appears larger than the moon when it’s overhead.

RACHEL
However, it may be due to the way our brain interprets how far away the sky is.

PAUL
After performing this experiment, get your binoculars out and take a peek at Jupiter.

RACHEL
Through binoculars, you’ll at least one of Jupiter’s satellites, Callisto.

PAUL
It will appear as the star located below Jupiter.

RACHEL
If you steady your binoculars, like on a fence post, you might also see another satellite, Europa.

PAUL
Europa will be another faint star, but located above Jupiter.

RACHEL
Europa will be more difficult to see because it’s closer to the Jupiter than Callisto.

PAUL
Jupiter’s other two satellites are Io and Ganymede.

RACHEL
...which are located below Jupiter, like Callisto.

PAUL
But they’re too close to the glare of Jupiter to see through binoculars.

RACHEL
A small telescope or spotting scope however, has enough magnification to see all four satellites.

PAUL
But watch out, through a telescope, the view will be upside down compared to what you will see in binoculars.

RACHEL
That’s Idaho Skies for the fourth week of February. Most stars have companion stars and we can see some of them with modest optical aid. Learn more next week.

PAUL
Be sure to read our blog for additional information. It’s at idahoskies.blogspot.com.
For Idaho Skies this is Paul...

RACHEL
...and Rachel.

PAUL
Dark skies and bright stars.