Monday, June 8, 2015

Transcript for June 28th to July 4th

RACHEL
Welcome to Idaho Skies for the last week of June. We’re your hosts, Rachel...

PAUL
...and Paul.

RACHEL
Saturn appears to the moon’s lower right after dark on the 28th.

PAUL
Saturn is not a particularly bright planet, but it sure is attractive through a small telescope.

RACHEL
You can see the planet’s rings if you have a small telescope or even a good spotting scope.

PAUL
Use a magnification of at least 25 power.

RACHEL
Saturn is located close to the constellation of Scorpius the Scorpion this summer.

PAUL
The rest of the constellation is located to the left of Saturn.

RACHEL
Its brightest star is Antares and it’s the orangish star located to the lower left of the moon.

PAUL
Did you know that Antares is over 9,000 times larger than Saturn is?

RACHEL
Even though they both appear star-like to our eyes.

PAUL
Two bright stellar beacons, Jupiter and Venus, appear very close together after sunset on the 29th.

RACHEL
They’re only ½ of a degree apart.

PAUL
Which is also the apparent diameter of the moon.

RACHEL
Get a look at Jupiter and Venus soon because they’ll be too close to the sun in another two or three weeks.

PAUL
The moon has neighbors late on the night of the 30th and morning of July 1st.

RACHEL
Its neighbors are star clusters and nebulae and you can see them through binoculars.

PAUL
Scan the region to the moon’s left, both higher and lower, for fuzzy patches and small star clusters.

RACHEL
Hey, I see a teapot of stars when I star gaze this region without binoculars.

PAUL
That’s right. The teapot-shaped pattern of stars is a part of the constellation of Sagittarius the Archer.

RACHEL
Sagittarius represents the centaur Chiron

PAUL
Chiron was not a violent centaur like the others mentioned in Greek mythology.

RACHEL
He was also known as a good archer, which is how he is represented in the night sky

PAUL
So why is Chiron commemorated in the sky?

RACHEL
That’s because he took the place of Prometheus, who Zeus was punishing for giving fire to humanity.

PAUL
Chiron offered to take the place of suffering Prometheus because a poisoned arrow had injured him.

RACHEL
Since Chiron was immortal and couldn’t die, the wound caused him endless agony with no hope for an end to that suffering.

PAUL
So Zeus, the king of the Greek gods, placed him in to the heavens to honor his sacrifice.

RACHEL
That’s Idaho Skies for the last week of June. Join us next month for the space and astronomy events for Idaho.

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.

Transcript for June 21st to 27th

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

RACHEL
...and Rachel.

PAUL
Hey, summer begins this week.

RACHEL
To be exact, it begins on the 21st at 10:38 AM.

PAUL
The beginning of summer is called a solstice, which means, "to make the sun stand".

RACHEL
"to make the sun stand"?, what does this mean?

PAUL
Well, if you observe sunset, you’ll notice that its position on the horizon shifts every day.

RACHEL
Sure, that’s because Earth’s spin axis is tilted relative to its orbital plane around the sun.

PAUL
That’s right. However, what happens on the first day of summer?

RACHEL
The position of sunset has to stop moving north or else the position of sunset will go completely around the horizon in a full year.

PAUL
Yep. On the first day of summer, the position of sunset appears to stop moving for several days.

RACHEL
Hence, the term to make the sun stand, as in stand still.

PAUL
Here’s how you can find a large star cluster for your binoculars on the night of the 22nd.

RACHEL
After it gets dark, imagine a line up from the moon to Denebola, the bright star above the moon.

PAUL
Then extend that line the same distance above Denebola to a large, but sparse star cluster called Mel-111.

RACHEL
You can see the cluster without binoculars, but only if you observe from outside of town and city lights.

PAUL
You’ll notice that the star cluster becomes more apparent if you look slightly away from the cluster.

RACHEL
This technique of using sideways glances is called averted vision.

PAUL
And it works because the central core of our vision is best at detecting details...

RACHEL
...while the outer perimeter of our vision is more sensitive to faint light and motion.

PAUL
The moon is near the star Spica on the evening of the 25th.

RACHEL
While Spica is not a particularly interesting star for the casual observer, the moon will be in first quarter phase and an interesting target for binoculars and telescopes.

PAUL
So get your binoculars or telescope out and scan along the moon’s boundary between day and night.

RACHEL
You’ll find lots of craters in the southern half of the moon and mountains surrounding lunar seas in the north.

PAUL
One mountain range to look for is the Caucasus Mountains.

RACHEL
It’s the mountain range surrounding part of the Sea of Serenity

PAUL
Which is the lunar sea located in the moon’s upper right corner.

RACHEL
You’ll see the mountains on the left side of Serenity and near the lunar terminator.

PAUL
Some of its peaks are 19,000 feet tall.

RACHEL
That’s a mile taller than Mt. Borah.

PAUL
However, unlike Mt. Borah, lunar quakes didn’t create the Caucasus mountain range over millions of years.

RACHEL
Instead the mountain range was created in a geological flash of time by an impact.

PAUL
The impact was by the asteroid that created the Sea of Serenity.

RACHEL
Along with blasting and vaporizing rock, the impact threw back the lunar crust to form a mountain range.

PAUL
That’s Idaho Skies for the fourth week of June. Did you know there’s a centaur in the sky? Hear about that and three planets next week.

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

PAUL
...and Paul.

RACHEL
Dark skies and bright stars.

Transcript June 14th to 20th

RACHEL
Welcome to Idaho Skies for the third week of June. We’re your hosts, Rachel...

PAUL
...and Paul.

RACHEL
It’s amazing what you can do in astronomy using just a stick and a shadow.

PAUL
Yep and here’s one example.

RACHEL
On June 19th, 240 BC, Greek scientist Eratosthenes made the first successful measurement of Earth’s circumference.

PAUL
You’ve probably heard of Eratosthenes, he was the chief librarian in Alexandria, Egypt.

RACHEL
At the library, he learned that at noon on the first day of summer, objects cast no shadow in the town of Syene.

PAUL
Syene is an ancient name for the modern town of Aswan.

RACHEL
...and it’s located south of Alexandria where Eratosthenes lived.

PAUL
Eratosthenes observed that sticks did cast shadows in Alexandria on the same day.

RACHEL
Because sticks cast shadows in Alexandria but not in Syene, Eratosthenes reasoned that Earth must be spherical.

PAUL
So he compared the amount of shadow cast in Alexandria to the distance between Alexandria and Syene.

RACHEL
The amount of shadow indicated the proportion of Earth’s circumference covered by the distance between these two towns.

PAUL
Then he compared the circumference of a complete circle to the portion of Earth’s circumference between Alexandria and Syene.

RACHEL
Based on the ratios, Eratosthenes determined Earth’s circumference to within 16%.

PAUL
So much for the claim that ancients thought the world was flat.

RACHEL
Because the sun casts no shadow at noon on the solstice, Syene must lie on a Tropic.

PAUL
The Tropics are two circles of latitude that are 23.5 degrees north and south of the equator.

RACHEL
Why 23.5 degrees?

PAUL
That’s because Earth’s spin axis is tilted 23.5 degrees with respect to its orbit around the sun.

RACHEL
It means that anyone standing on either circles of latitude must see the sun pass straight overhead on the day of the solstice.

PAUL
The name for the northern circle of latitude is the Tropic of Cancer.

RACHEL
And the southern one is called the Tropic of Capricorn.

PAUL
The names Cancer and Capricorn were chosen because the sun appears in those constellations on the solstices.

RACHEL
These names were given to the tropics about 2,000 years ago

PAUL
And because the Earth’s spin axis slowly wobbles, the sun’s position today on the solstices has shifted by one constellation.

RACHEL
You can’t miss the line formed by Jupiter and Venus on the evening of the 20th.

PAUL
These two bright beacons are just calling for your attention.

RACHEL
Even better, the thin crescent moon appears to their left.

PAUL
Get binoculars out and look for look for Earthshine on the moon and Jupiter’s largest satellites.

RACHEL
That’s Idaho Skies for the third week of June. Next week is the start of Northern summer and we’ll tell you more.

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.

Transcript June 7th to 13th

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

RACHEL
...and Rachel.

PAUL
What’s the bright star in the west after dark?

RACHEL
It’s Venus, the Evening Star.

PAUL
This week Venus approaches closer and closer to the Beehive star cluster.

RACHEL
They’re at their closest on the evening of the 12th.

PAUL
Find the Beehive by looking left of Venus with your binoculars.

RACHEL
Each night you’ll see the Beehive closer to Venus.

PAUL
Through binoculars, you’ll see over a dozen stars in the cluster.

RACHEL
And once you see it, you’ll know why people call it the Beehive star cluster.

PAUL
The Space Age has allowed astronomers to determined that Venus is one hellish planet

RACHEL
It’s even worse than Mercury, which has a surface temperature of 800 degrees Fahrenheit.

PAUL
Venus is hotter with a surface temperature of 860 degrees because of its dense atmospheric cloak of carbon dioxide.

RACHEL
Both Earth and Venus developed atmospheres of carbon dioxide after their birth.

PAUL
However, Earth’s carbon dioxide was safely trapped inside of the ocean and rocks like limestone.

RACHEL
Venus on the other hand formed 26 million miles closer to the sun than Earth.

PAUL
And that extra solar heating eventually evaporated its oceans away.

RACHEL
Without oceans, heat from the sun eventually released Venus’ trapped carbon dioxide.

PAUL
Which has created an atmosphere 90 times denser than the Earth’s.

RACHEL
Carbon dioxide is a greenhouse gas that prevents the escape of surface heat into space

PAUL
So even though the clouds of Venus reflect most of the sun’s light, very little heat can actually escape the planet’s atmosphere once it reaches the surface.

RACHEL
In fact, its surface temperature is high enough to melt lead.

PAUL
So it was surprising when 40 years ago on the 8th, the Soviet Union launched the first successful Venus landers.

RACHEL
Venera 9 and 10 spend just short of an hour returning data from the surface of Venus.

PAUL
Including images of its rocky surface.

RACHEL
The amount of sunlight reaching the surface of Venus was surprisingly high.

PAUL
And onboard instruments indicated that the surface was basaltic, like Craters of the Moon.

RACHEL
After an hour on the surface, high heat and pressure fried the Venera landers and their electronics.

PAUL
So today, they lie on the surface slowly eroding away due to exposure to caustic gas and high heat.

RACHEL
That’s Idaho Skies for the second week of June. Some people say that Christopher Columbus proved the world wasn’t flat, but the Greeks knew that almost 2,000 years earlier.

 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.

Monday, June 1, 2015

This month's star is Alkaid

This month look for the star Alkaid in Ursa Major. Alkaid is known to astronomers as Eta Ursae Majoris and it’s located at the end of the Big Dipper’s handle. In Arabic, Alkaid means “the leader”. Its name is a reference to the stare being the lead daughter (the three stars of the handle are sisters) at a funeral bier. If you know someone who is 100 years old this year, then Alkaid is his or her birthday star because the light of Alkaid you see tonight left in 1915.

Alkaid is a big star that’s four times hotter then the sun and 700 times brighter. It’s hotter and brighter because it has a mass six times greater than our sun’s. Alkaid’s greater mass creates intense pressure that’s crushing its core. The extra compression heats up the core and increases its rate of fusion. On the down side, that extra mass will burn out the star far sooner than our sun.

The Big Dipper is not a constellation. Rather, it’s an asterism, or popular pattern of stars. This means the pattern is not officially recognized by professional astronomers. The Big Dipper is part of a much larger constellation called Ursa Major or the Big Bear. The dipper portion of Ursa Major just represents the bear’s body and a very long tail. The rest of Ursa Major is fainter and not as well known. However, in dark skies you can make out three legs, head, and snout of the bear.   

Look for Alkaid tonight almost overhead in the north during June.  

Transcript for May 31 to June 6

RACHEL
Welcome to Idaho Skies for the first week of June. We’re your hosts, Rachel...

PAUL
...and Paul.

RACHEL
Just after dark on the 1st, you’ll observe Venus in a line with the brightest two stars of Gemini the Twins

PAUL
The stars are named Castor and Pollux.

RACHEL
You’ve probably heard of them before, Castor and Pollux are the twins of Greek mythology.

PAUL
Let Venus show you how to identify Castor and Pollux.

RACHEL
Start by looking in the low west for brilliant Venus.

PAUL
You’ll find the twin stars forming a line on the moon’s right.

RACHEL
Pollux is the brightest of the pair.

PAUL
Later on the 1st, you’ll see the moon and Saturn meet up near Scorpius the Scorpion.

RACHEL
Saturn will be a slightly yellow star located to the moon’s right.

PAUL
The bright star below the moon is orangish Antares, the heart of Scorpius the Scorpion.

RACHEL
After midnight of the 2nd...

PAUL
...actually that’s early morning of the 3rd...

RACHEL
...you can use the moon to find a nice star cluster for your binoculars.

PAUL
Greek astronomer Claudius Ptolemy of Alexandria described this star cluster in the second century AD.

RACHEL
However, it would another 1,500 years before the telescope was invented.

PAUL
Therefore, Ptolemy only identified the star cluster as a little cloud or nebula.

RACHEL
You can find Ptolemy’s little cloud by locating a horizontal pair of stars directly below the moon.

PAUL
The pair represents the stinger of Scorpius and they’re close together.

RACHEL
Place the stinger at the bottom center of your binoculars and then scan to the left.

PAUL
Soon after the stinger leaves your binoculars on the right, the star cluster enters your binoculars on the upper left.

RACHEL
The star cluster will fill about 1/3rd of your binocular’s view.

PAUL
Hey, Venus reaches its greatest distance from the sun on June 6th.

RACHEL
That places the planet at nearly its highest above the horizon after it gets dark.

PAUL
And it’s so high that it won’t set until after midnight.

RACHEL
If you look at Venus through a small telescope before the sky gets dark, you’ll notice that Venus is only half full.

PAUL
And as the weeks pass, the planet will grow larger and thinner.

RACHEL
That’s Idaho Skies for the first week of June. Next week we’ll discuss Venus even further.

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

For Idaho Skies this is Paul...

RACHEL
...and Rachel.

PAUL
Dark skies and bright stars.