Monday, September 26, 2016

Idaho skies Transcript for September 30th to October 2nd

PAUL
Welcome to Idaho Skies for September 30th and October 1st and 2nd. We’re your hosts, Paul…

RACHEL
…and Rachel.

PAUL
Don’t forget to look for Mercury in the morning this weekend.

RACHEL
It’s already reached its highest distance above the horizon…

PAUL
…and is rapidly approaching the horizon again.

RACHEL
To see Mercury, go outside at about 6:30 AM.

PAUL
And look for a star very low in the east.

RACHEL
The star is bright enough that you’ll have no trouble finding it.

PAUL
The only problem might be is having a horizon too high for Mercury to clear before sunrise.

RACHEL
Did you know that a year on Mercury only lasts for 88 Earth days?

PAUL
And a day last 58 Earth days?

RACHEL
Mercury also has a much more elliptically shape orbit than Earth.

PAUL
Its elliptical orbit means the orbital speed of the planet changes more dramatically than it does for Earth.

RACHEL
By traveling faster as it approaches the sun…

PAUL
…and slower as it travels away from the sun.

RACHEL
Combining its changing orbital speed and rotational rate means the sun doesn’t travel neatly from one horizon to the other as it does on Earth.

PAUL
In fact, the sun actually moves backwards across the sky for part of a Mercurian day.

RACHEL
Before 1974, astronomers thought that Mercury’s day lasted as long as its year.

PAUL
This is called being tidally locked and it happens to astronomical bodies orbiting close to their parent.

RACHEL
In the case of Mercury, its year lasts 1.5 days and perhaps in the future, the day and year will come into sync.

PAUL
That’s Idaho Skies for the 30th, 31st of September and the 1st of October.

RACHEL
Be sure to follow us on Twitter at Idaho Skies for this week’s event reminders and sky maps.

For Idaho Skies this is Rachel…

PAUL
…and Paul.

RACHEL

Dark skies and bright stars.

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