Monday, February 8, 2016

Transcript for February 7 - 13

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

RACHEL
...and Rachel.

PAUL
The moon is new on the 8th.

RACHEL
So it reappears in the west two days later.

PAUL
Starting the 10th and for the next couple of nights, look for earthshine illuminating the dark portion of the moon.

RACHEL
And remember, earthshine is sunlight, but reflected by Earth.

PAUL
How is it possible for Earth to reflect so much towards the moon?

RACHEL
It’s because of Earth’s albedo and size.

PAUL
Explain albedo.

RACHEL
Sure, albedo is the astronomical term for reflectivity.

PAUL
And an albedo of zero is a perfect absorber of light and totally non-reflective.

RACHEL
While an albedo of 1 is perfectly reflective.

PAUL
So where does the moon’s albedo lie?

RACHEL
The moon’s albedo is 0.12

PAUL
Which is another way of saying the moon only reflects 12% of the sunlight incident on it.

RACHEL
That make the moon’s surface about as dark as an asphalt parking lot.

PAUL
And that’s on average.

RACHEL
Right, the lunar seas are darker and less reflective while the lunar highlands are just the opposite.

PAUL
So what about the Earth?

RACHEL
Earth’s albedo is 0.30.

PAUL
Most of that comes from its clouds and ice caps.

RACHEL
That’s correct; the oceans are darker.

PAUL
On average then, Earth is 2.5 times brighter than the moon.

RACHEL
So we can see that Earth is more reflective than the moon, what about their relative sizes?

PAUL
The moon’s diameter is 2,100 miles.

RACHEL
That small?

PAUL
Yep. The United States would wrap 50% of the way around the moon.

RACHEL
And I remember Earth is just about 7,900 miles in diameter.

PAUL
Which means Earth has a diameter nearly four times larger than the moon.

RACHEL
And that means about 14 times more surface area to reflect sunlight.

PAUL
Combining the 14 times larger surface area and 2.5 times more reflective surface...

RACHEL
...you get an Earth that appears about 35 times brighter in the lunar sky.

PAUL
That would be one big and bright blue and white orb.

RACHEL
And unlike the moon on Earth, to an astronaut standing on the moon, Earth would remain in the same position in the sky.

PAUL
However, the phase of Earth would change over a period of 30 days.

RACHEL
In fact, the phase of Earth would be opposite of the moon’s phase on Earth.

PAUL
So when the moon is new to us, Earth is in the full phase to the moon.

RACHEL
Best yet is during the New Earth phase.

PAUL
Some times at new, Earth will pass between the moon and the sun to create an amazing total solar eclipse.

RACHEL
Because of Earth’s atmosphere, lunar inhabitants would see all of the world’s sunsets as a ring of orangey-red fire surrounding Earth.

PAUL
And the lunar surface would be illuminated in that orangey-red glow.

RACHEL
That’s Idaho Skies for the second week of February. Next week we’ll tell you how to watch the occultation of Aldebaran.

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.

Tuesday, February 2, 2016

Transcript: January 31st to February 6th

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

PAUL
...and Paul.

RACHEL
You’ll find a planet and a double star next to the moon on the morning of the 1st.

PAUL
The planet is Mars and the double star is Zubenelgenubi.

RACHEL
Both are located to the lower right of the first quarter moon.

PAUL
Of the three, only the moon and Zubenelgenubi are objects fit for your binoculars.

RACHEL
Mars is approaching opposition this May, so it’s growing ever closer to Earth.

PAUL
Opposition?

RACHEL
Yes, opposition. It’s when a superior planet is opposite the sun from Earth’s perspective.

PAUL
Wait, go back. Superior planet?

RACHEL
A superior planet is one that is farther from the sun than Earth.

PAUL
Oh, so you mean Mars, Jupiter, Saturn, Uranus, and Neptune.

RACHEL
That’s right.

PAUL
What makes opposition so special?

RACHEL
At opposition, superior planets are their closest to Earth and therefore appear their brightest and largest.

PAUL
In the case of Mars, opposition is very important since it’s significantly closer to Earth than any other planet.

RACHEL
Yes, and opposition lets telescopes see the greatest details possible.

PAUL
So what can we expect to see on Mars this spring?

RACHEL
Not much for binoculars, unfortunately. However, if you have a large amateur telescope, you’ll be able to see Martian features like Syrtis Major.

PAUL
What about the canals?

RACHEL
Sorry, no canals.

PAUL
Zubenelgenubi is the second binocular object you’ll see near the moon on the 1st.

RACHEL
It’s a double star that some people can split into two separate stars using just their eyes.

PAUL
To find the trio of Mars, the moon, and Zubenelgenubi, go outside at 5:30 AM on the 1st and look in the southeast.

RACHEL
The moon, Mars and Zubenelgenubi will all fit within the view of binoculars.

PAUL
Now that you know the superior planets, you know that the inferior planets are Venus and Mercury.

RACHEL
And the moon passes each in turn on the 5th and 6th.
PAUL
On the 5th, you’ll find Venus below the moon in the east.

RACHEL
In fact, it’s so bright you can’t miss it.

PAUL
Because Venus isn’t very far from the sun, you’ll need to go out between 6:30 and 6:45 AM if you want to see this pair.

RACHEL
Mercury reaches its greatest distance from the sun on the 6th.

PAUL
So on the morning of the 6th look for Mercury and Venus paired up together in the low eastern sky.

RACHEL
But there’s also some bad news.

PAUL
The tilt of Mercury’s orbit is shallow relative to the horizon.

RACHEL
That means Mercury won’t be very far above the horizon, even though it’s quite some distance from the sun.

PAUL
To find Mercury, go outside by 7:00 AM on the 6th and put Venus it in the upper right edge of your binoculars.

RACHEL
Mercury will be the star located at the lower left edge of your binoculars.

PAUL
Dawn causes the sky to brighten by 7:00 AM, so you don’t have too much time to find Mercury.

RACHEL
That’s Idaho Skies for the first week of February. Next week we’ll talk about something called albedo.

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.
This month, look for the star, Procyon, the lucida of the constellation of Canis Minor (the Little Dog) and the seventh brightest star in the sky. If you were born in 2005, then Procyon is your birthday star this year because the light of Procyon you see tonight left the star 11 years ago. The name Procyon comes from Greek and means Before the Dog. This refers to the fact that in mid-latitudes, Procyon rises shortly before Sirius, the Dog Star.

Procyon has twice the diameter of our sun due to its 70% greater mass. Its greater temperature and diameter combine to make Procyon over seven times more luminous than the Sun. Procyon has consumed enough of its hydrogen that it can now fuse helium. In several tens of millions of years, just a blip of time for our sun, Procyon will expand into a red giant star.  

White dwarf companion stars orbit both Procyon and Sirius. White dwarfs are stars that have consumed their supply of nuclear fuel. Without fusion to support them, gravity has compressed them into spheres the size of planets, or about 100 times smaller that they use to be. This means a cubic centimeter of white dwarf weighs about a ton. So imagine your car fitting on a teaspoon.

You’ll find Procyon half way up in the south-southeast early February nights.

Monday, January 25, 2016

Transcript for January 24th to 30th

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

RACHEL
...and Rachel.

PAUL
Late on the 25th, you’ll find the star Regulus above the moon.

RACHEL
Regulus is the alpha star of Leo the Lion and it has a faintly yellow-orange tint to it.

PAUL
However, it’s actually two pairs of stars orbiting each other.

RACHEL
Two pairs?

PAUL
That’s right, four stars in total.

RACHEL
Hey, Regulus is also 79 light years away.

PAUL
So if you know someone who is 79 years old, then Regulus is his or her birthday star this year.

RACHEL
The primary star of the Regulus star system is 3.5 times more massive than the sun.

PAUL
What’s really weird about it is that it spins once on its axis in just 16 hours.

RACHEL
When you compare that to the sun, which rotates on its axis once per month, you’ll realize just how much faster this massive star spins on its axis.

PAUL
In fact, if it rotated 2.5 hours faster, the star would fling itself apart.

RACHEL
Because of its rapid spin, Regulus is significantly flattened at its poles and bulges at its equator.

PAUL
This makes the poles of the star five times brighter than its equator.

RACHEL
You’ll find two nice binocular objects paired up late on the night of the 27th.

PAUL
They’re the moon and Jupiter.

RACHEL
The pair is only 3.5 degrees apart, or close enough together to seen at the same time in a pair of binoculars.

PAUL
Jupiter, which appears as the bright star just above the moon, will have a slightly creamy color.

RACHEL
And it won’t twinkle like the other stars.

PAUL
Point your binoculars at Jupiter and you’ll see two or three of its largest satellites forming a line with Jupiter.

RACHEL
The satellite at the bottom of the line is Callisto, a world larger than our moon.

PAUL
The next one up and very close to Jupiter is Io.

RACHEL
It’s a world of frequent volcanic eruptions.

PAUL
In fact, there are more ongoing eruptions on Io than on Earth.

RACHEL
The last satellite, which is located above Jupiter, is named Ganymede.

PAUL
Ganymede, like Callisto, is a large satellite and also very icy.

RACHEL
What about that star appearing to the lower right of the moon on the morning of the 30th?

PAUL
Why that’s Spica, the brightest star of Virgo the Maiden.

RACHEL
Spica and the moon will be very close together on the morning of the 30th.

PAUL
The pair is so close that you can see both together at the same time in binoculars.

RACHEL
It’s sad that the rest of Virgo isn’t as eye catching as its brightest star.

PAUL
But hey, this is still a good time to learn how to identify this star.

RACHEL
That’s Idaho Skies for the fourth week of January. The moon passes very close to Mars and a double star next week.

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.

Tuesday, January 19, 2016

Transcript for January 17 - 23

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

PAUL
...and Paul.

RACHEL
The moon forms a triangle of astronomical objects with the Pleiades and the Hyades star clusters on the night of the 18th.

PAUL
All three of these astronomical objects are great targets for your binoculars.

RACHEL
The moon will be a bit on the bright side and will show mostly lunar seas in your binoculars.

PAUL
But the Pleiades and Hyades will show a multitude of stars that are invisible to the naked eye.

RACHEL
Whoa, the moon covers up the brightest star in Taurus the Bull on the 19th.

PAUL
Astronomers call this event an occultation and it’s with the star Aldebaran.

RACHEL
The occultation begins at 6:17 PM when the moon covers up Aldebaran.

PAUL
Unfortunately, it will still be light outside, so this part of the occultation is not observable.

RACHEL
However, at 7:28 PM when the moon uncovers Aldebaran, it will be quite dark outside.

PAUL
To watch the reappearance of Aldebaran, look along the right edge of the moon with your binoculars at 7:25.

RACHEL
Aldebaran will suddenly pop into view a few minutes later and it will just a bit above, half way up the moon’s limb.

PAUL
The rapidity of Aldebaran’s reappearance is evidence that the moon has no atmosphere.

RACHEL
That’s because even a modest lunar atmosphere would make Aldebaran’s reappearance more gradual.

PAUL
By observing an occultation from multiple locations, astronomers can determine information regarding the size, shape, and atmosphere of asteroids, moons, and planets in our solar system.

RACHEL
Orion the Hunter is an easy constellation to find, but it’s even easier on the evening of the 20th.

PAUL
That’s because the moon appears just above Orion that night.

RACHEL
Orion will be the tall rectangle of stars below the moon.

PAUL
Once you locate Orion, look for his belt.

RACHEL
Which is a row of three stars across Orion’s waist.

PAUL
Once you have located his belt, look below the middle star of the belt.

RACHEL
In binoculars, you’ll see what appears to be a fuzzy star below his belt.

PAUL
This is the Orion Nebula.

RACHEL
The nebula is easy to see with binoculars.

PAUL
But it’s even more spectacular through a telescope.

RACHEL
Through a telescope, it takes on a swirled pattern of pale greenish light.

PAUL
The very attractive Beehive star cluster appears just 8 degrees away from the moon on the night of the 23rd.

RACHEL
To find it, point your binoculars at the moon and then shift your view to the left.

PAUL
Shortly after the moon exits the right side of your binocular’s field of view, the star cluster enters the left side.

RACHEL
Since the average pair of binoculars has a field of view of 5 degrees, you don’t have to shift the binoculars very far before the Beehive appears.

PAUL
In binoculars, the Beehive appears as a small grouping of tightly bound stars.

RACHEL
And it will have a strong resemblance to a swarm of bees around their hive

PAUL
That’s Idaho Skies for the third week of January. The moon will help you locate the planet Jupiter next week.

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.

See Five Planets at One Time

Here's a link to Sky and Telescope and their article on seeing the five visible planets at one time.

http://www.skyandtelescope.com/astronomy-news/observing-news/get-up-early-see-five-planets-at-once-01182015/

Monday, January 11, 2016

Transcript for January 10 - 16

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

RACHEL
...and Rachel.

PAUL
The moon was new on the 9th.

RACHEL
A new moon means the moon is passing between Earth and the sun.

PAUL
That happens every 29 or 30 days, or once every lunar orbit.

RACHEL
The moon is dark at new moon, but not because the "dark side" of the moon is turned toward us.

PAUL
In fact, we always see the same face of the moon.

RACHEL
The reason the moon is dark at new is that the portion of the moon in night also happens to be the half facing Earth.

PAUL
We only see one half of the moon because its period of rotation, which is also the length of its day, is the same as its orbit around Earth.

RACHEL
The same thing would happen between Earth and the sun if our day were 365 days long rather than 24 hours long.

PAUL
After its birth, the moon probably rotated much faster on its axis.

RACHEL
However, because of it closeness to us, Earth’s gravity slowed down the moon’s rotation until now it rotates once every revolution around Earth.

PAUL
Astronomers call the moon tidally locked with Earth.

RACHEL
This is the current situation between Pluto and its largest moon, Chiron.

PAUL
And probably with some of the hot Jupiter exoplanets that astronomers have discovered outside our solar system.

RACHEL
In time, the moon may be able to slow down Earth’s spin until both are tidally locked together.

PAUL
Then only one half of Earth will be able to see half of the moon.

RACHEL
Sadly, because of the tilt of the moon’s orbit around Earth, the new moon passed above the sun from Earth’s perspective.

PAUL
Robbing Idaho of its chance to see a solar eclipse this month.

RACHEL
The moon reappears low in the south-southwest on the evening of the 11th.

PAUL
The moon will be two days old then, so it will be very thin.

RACHEL
In another day or two, you should be able to see earthshine on the dark portion of the moon.

PAUL
Binoculars give a better view of earthshine than the eye alone.

RACHEL
Keep observing the moon through binoculars, as it will look pretty neat for the next four or five days.

PAUL
That’s because you’ll see lots of craters and mountains along the lunar terminator.

RACHEL
The terminator is the moon’s boundary between day and night.

PAUL
At the terminator, shadows bring out the greatest lunar detail.

RACHEL
The view is even better when the moon’s seven days old and the terminator faces directly towards Earth

PAUL
That makes the lunar shadows appear especially long.

RACHEL
And that extended length readily emphasizes small changes in the lunar terrain.

PAUL
Because of the moon’s small size and slow rotation, the terminator travels around the moon at just under 10 miles per hour.

RACHEL
Therefore, it would be easy for a runner to keep up with the movement of the terminator.

PAUL
That’s Idaho Skies for the second week of January. Next week, Idahoan’s get to observe a lunar occultation.

 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.