Transcript for June 9 - 15

PAUL
Welcome to Idaho Skies for the second week of June. We’re your hosts, Paul…

RACHEL
…and Rachel.

PAUL
On the evening of the 10th, the young crescent moon passes very close to Mercury and Venus.

RACHEL
You’ll need to look for this trio of astronomical objects after 10:00 PM, but before 10:30. You’ll need a clear west-northwestern horizon to see them, as they will be low.

PAUL
The 10th also marks the tenth anniversary of the launch of the Spirit Mars Rover.

RACHEL
Spirit was one of two solar-powered rovers launched to the red planet in 2003.

PAUL
For six years, Spirit traversed the Martian surface looking for evidence of water in Mars’ past.

RACHEL
The rover traveled nearly five miles during its search and made multiple measurements of the Martian rocks near the Columbia Hills.

PAUL
Spirit’s instruments detected slight chemical alterations in the composition of the outer layers of rocks.

RACHEL
It also found a type of chemical called sulfates in the Martian soil.

PAUL
These results indicated that water was present in the Martian past.

RACHEL
However, the amount was small compared to the amount of water found on Earth.

PAUL
Spirit’s mission ended after it became stuck in soft Martian sand.

RACHEL
Unable to extract itself from the loose sand, Spirit couldn’t properly orient its solar array for the approaching winter.

PAUL
The limited amount of sunlight available during the winter prevented Spirit’s solar array from acquiring enough power to survive the brutal cold.

RACHEL
On June 12th, Mercury is at its greatest eastern elongation.

PAUL
Elongation is a property of the orbits of inner planets and not outer planets.

RACHEL
Inner planets, which astronomers call inferior planets are those that orbit closer to the sun than Earth.

PAUL
Like Mercury and Venus.

RACHEL
And superior planets are those that orbit the sun farther than Earth.

PAUL
Since inferior planets reside closer to the sun than Earth, we will never see them in the sky opposite of the sun.

RACHEL
The greatest distance away from the sun that we see an inferior planet is called its greatest elongation.

PAUL
Because of its small orbit, Mercury can only travel 24 degrees away from the sun.

RACHEL
That sounds impressive. After all, 24 degrees is nearly 1/3rd of the distance from the horizon to overhead.

PAUL
That would be correct if Boise was located on the equator. However, at a latitude of 43 degrees north, Mercury’s orbit around the sun is very slanted with respect to our local horizon.

RACHEL
So how far above the horizon will Mercury appear when its 24 degrees from the sun?

PAUL
Our solar system’s smallest planet will only appear ten degrees above horizon at 10:00 PM. That means by 10:45, the planet will be all but impossible to see.

RACHEL
Hey, the earliest sunrise this year occurs on the 13th!

PAUL
That means from now until mid December, the sun will set earlier each night.

RACHEL
That’s Idaho Skies for the second week of June. Next week the moon passes close to Saturn, so you will have more than just Mercury and Venus to observe.

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

RACHEL
and Rachel.

PAUL
Dark skies and bright stars.