Idaho Skies Transcript for August 27th and 28th

RACHEL
Welcome to Idaho Skies for August 27th and 28th. We’re your hosts, Rachel...

PAUL
...and Paul.

RACHEL
The innermost planet makes a brief appearance this week.

PAUL
In fact, on the morning of the 27th, little Mercury appears at its highest above the horizon.

RACHEL
Mercury orbits the sun at a distance of 36 million miles, with a variation of seven million miles.

PAUL
Whoa, Mercury has a very eccentric orbit.

RACHEL
That’s right; in fact, its orbit is the most eccentric of all the planets.

PAUL
For a comparison, Earth’s orbit varies by less than two million miles from its average.

RACHEL
But remember, Earth’s orbit is three times larger than Mercury’s to begin with.

PAUL
Therefore, the 1.5 million mile variation in Earth’s orbit is like a half million mile variation to Mercury.

RACHEL
The farthest Mercury can appear away from the sun is 28 degrees.

PAUL
And since Idaho is far from the equator, Mercury travels in a tilted line that can never appear that high above the horizon.

RACHEL
So to see Mercury this week, look in the low east-northeast at around 6:15 AM.

PAUL
You’re looking for the brightest white star close to the horizon.

RACHEL
You can be certain it’s Mercury you’re looking at if the star doesn’t twinkle like the other stars.

PAUL
And that its position relative to the horizon changes significantly over several days.

RACHEL
Mercury’s small orbit means the Sun’s gravitational attraction to Mercury is much stronger than it is to Earth.

PAUL
Since the orbit is three times smaller than Earth’s, the sun’s gravitational force is nine times greater.

RACHEL
A stronger gravitational pull means Mercury must orbit faster or else plunge into the sun.

PAUL
Which is one reason why it only takes Mercury 88 days to orbit the sun once.

RACHEL
And that’s another reason why Mercury doesn’t appear above the horizon for more than about two weeks at a time.

PAUL
That’s Idaho Skies for the 27th and 28th of August.

RACHEL
Be sure to follow us on Twitter @IdahoSkies for this week’s event reminders and sky maps.

For Idaho Skies this is Rachel...

PAUL
...and Paul.

RACHEL
Dark skies and bright stars.