Welcome to Idaho Skies for the fourth week of December. We’re your hosts, Paul...
RACHEL
...and Rachel.
BRING DOWN MUSIC
PAUL
The sun reaches its southernmost declination at 5:00 PM on the 21st.
RACHEL
That means it appears overhead to anyone residing at 23 degrees south latitude.
PAUL
That makes it the first day of summer in Australia and the first day of winter for us in the Northern hemisphere.
RACHEL
Ahh, just imagine, spending Christmas on an Australian beach.
PAUL
The distance between the sun and Earth has nothing to do with the seasons.
RACHEL
That’s right; the seasons are solely the result of Earth’s tilt with respect to its orbital plane around the sun.
PAUL
As a result of this tilt, the sun crosses the sky at its lowest path on the first day of winter.
RACHEL
And the hours of daylight are at their shortest length.
PAUL
The result is that the sun’s light is less intense and provides warmth for least number of hours.
RACHEL
Adding insult to injury, the night lasts it longest.
PAUL
Therefore, the ground has even more time to radiate its warmth back into the sky.
RACHEL
The combination of these three effects creates the coldest days of the year.
PAUL
However, its takes the ground and atmosphere another month to catch up to all that cold.
RACHEL
A minor meteor shower peaks on the night of December 22nd and morning of the 23rd.
PAUL
It’s the Ursid meteor shower and you can see it radiating out of the high north, near the Little Dipper or Ursa Minor.
RACHEL
Usually we don’t see more than 10 meteors per hour from this shower.
PAUL
However, it once produced an outburst of 100 meteors per hour.
RACHEL
The moon is only a day old tonight, so its light won’t interfere if you choose to watch the Ursid meteor shower.
PAUL
The 23rd presents us with the opportunity to observe a two-day old moon.
RACHEL
This is such a thin crescent moon that most people won’t chance upon it unless they know to look for it.
PAUL
So begin your search low in the southwest at around 6:15 PM.
RACHEL
You might find a pair of binoculars helpful.
PAUL
But please, please only use them after the sun has set.
RACHEL
After all these months, Mars is still visible in our night sky.
PAUL
Yep. And you can find the red planet on the 24th.
RACHEL
You first need to find the moon in the low southwest.
PAUL
Mars will be the slightly yellowish star located to the moon’s left.
RACHEL
Mars is not really red; its surface is more orange in color.
PAUL
That color comes from the oxidized iron in its soil.
RACHEL
So the surface of Mars is actually rusty.
PAUL
Because its soil doesn’t contain organic material, we actually call the soil of Mars its regolith.
RACHEL
That’s Idaho Skies for the fourth week of December. You can use your Christmas binoculars to observe a star cluster 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.
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