Transcript for April 8 to 14

RACHEL
Welcome to Idaho Skies for the second week of April. We’re your hosts, Rachel…

PAUL
…and Paul.

RACHEL
The moon is new on the 10th.

PAUL
If you’re searching for faint galaxies through your telescope, you’ll want to look for them before and after the night of the 10th.

RACHEL
That’s because the moonlight drowns out many of the fainter objects in the sky.

PAUL
What do astronomers call the brightness of an astronomical object?

RACHEL
They call the brightness of an object its magnitude. The Greek astronomer Hipparchus originally developed the stellar magnitude system in the second century BC.

PAUL
We best remember Hipparchus for his catalog of stars. It was the first major catalog of stars. His catalog contained entries for the brightness and position of 850 stars.

RACHEL
Hipparchus gave the brightest stars a magnitude of one. The magnitudes of fainter stars were given larger numbers.

PAUL
So does this mean that a star of magnitude two is fainter than a magnitude one star but brighter than a magnitude three star?

RACHEL
That’s right. Hipparchus’ faintest stars were given a magnitude of six.


PAUL
Because of the way our senses operate, a first magnitude star does not emit twice the amount of light of a second magnitude star.

RACHEL
A star appearing one magnitude brighter is actually two and a half times brighter.

PAUL
A first magnitude star is therefore one hundred times brighter than a sixth magnitude star.

RACHEL
If the brightest stars are given a magnitude of one, then what is the magnitude of the sun and moon?

PAUL
They are given negative magnitudes. So, the full moon is -12.5 magnitude and the sun is  -26.5 magnitude.

RACHEL
The perfect magnitude zero star is Vega and it passes over Boise at 5:30 AM in April.

PAUL
On April 12, 1961, Yuri Gagarin became the first person to orbit Earth.

RACHEL
In recognition of this historic event, April 12th is called Yuri's Night.

PAUL
Visitors to the Discovery Center of Idaho can make stomp rockets in celebration of Yuri’s orbit of Earth on April 12th.

RACHEL
The Teen Club will have a rocketry display.

PAUL
The moon is your guide to Jupiter on the evening of the 14th.

RACHEL
Jupiter will appear as a bright star just west of the four-day old moon.

PAUL
The crescent moon and Jupiter are close enough together to observe them at the same time in your binoculars.

RACHEL
Once you find Jupiter, steady your binoculars on a tree or car.

PAUL
You’ll find there are three faint stars forming a line with Jupiter.

RACHEL
These are three of Jupiter’s four large satellites. In a small telescope, all four satellites are visible.

PAUL
The satellite appearing most distant from Jupiter and therefore easiest to see is Callisto.

RACHEL
Next in line and closer to Jupiter is Ganymede, the largest satellite in the solar system.

PAUL
Closer still to Jupiter is Europa, a satellite with a deep liquid ocean covered in a crust of ice.

RACHEL
Check the Idaho Skies blog for a map of Jupiter and its satellites on the night of the 14th.

PAUL
That’s Idaho Skies for the second week of April. Next week is our first meteor shower in three months. It’s also Astronomy Day and there are a lot of activities for the public to enjoy.  

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

PAUL
and Paul.

RACHEL
Dark skies and bright stars.