Monday, November 26, 2018

Idaho Skies Transcript for November 30th and December 1st and 2nd

RACHEL
Welcome to Idaho Skies for November 30th and December 1st and 2nd. We’re your hosts, Rachel…

PAUL
…and Paul.

RACHEL
The moon is rapidly approaching new, so stargazers only have a few more days to see it.

PAUL
The waning crescent moon will be visible in the low east before sunrise, so stargazers will need to rise early enough to see it. Not only will the moon appear as a thin crescent, its dark portion will be covered with an ashen light. That illumination is called earthshine and it’s the result of sunlight reflecting off of Earth’s bright clouds. An astronaut standing on the dark portion of the moon would see a large and mostly full Earth shining light upon the lunar surface.

RACHEL
Use your binoculars when looking for earthshine. They’re useful not only because of their magnification, but because of their light gathering ability. The human pupil can reach about ¼ of an inch in diameter. So that’s the greatest amount of light they can admit to our retina. Binoculars on the other hand have lens two inches across. All that light gets concentrated into a region less than ¼ inch across.

PAUL
Since binocular lenses are eight times wider than our pupil, they gather eight-squared or 64 times more light than our eyes can unaided. It’s their ability to gather more light than our eye that makes them so useful for astronomy. In fact, many astronomical objects are plenty large enough. It’s that they’re so faint to makes them difficult to see. So just imagine what the 200-inch mirror on Mt. Palomar could do for your vision.

RACHEL
Just by coincidence, the glass for the 200-inch mirror was poured into a ceramic mold 84 years ago on the 2nd. The glass is actually Pyrex, a glass recipe designed to minimize expansion due to temperature changes. It took over 11 months to cool the glass down enough that it could be ground into a telescope mirror. But World War II intervened and prevented the completion of the telescope until 1947.

PAUL
That’s Idaho Skies for the 30th of November and the 1st and 2nd of December.

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.

Idaho Skies Transcript for November 28th and 29th

PAUL
Welcome to Idaho Skies for November 28th and 29th. We’re your hosts, Paul…

RACHEL
…and Rachel.

PAUL
On Monday and Tuesday, we mentioned that the Mars InSight lander was arriving at Mars on the 26th. But that’s not all.

RACHEL
Along with the InSight lander are two CubeSats called Mars Cube One A and B, or MarCo A and MarCo B. CubeSats are nanospacecraft cubes measuring ten centimeters or four inches on a side. MarCo is a six-unit CubeSat that measures eight inches wide, twelve inches tall, and four inches thick. Until now, CubeSats have only been used in Earth orbit. This makes MarCo the first to leave Earth orbit, let alone reach Mars. 

PAUL
The CubeSat design was developed by California Polytechnic University and Stanford. They use off-the-shelf components to keep their cost very affordable. They are also very light meaning several can be launched at a time. They are typically launched as a secondary payload of the rocket launching its paying customer’s payload into orbit. The cubes are stacked one on top of the other and ejected from a tube called a P-Pod. Springs push the CubeSats out of the P-POD and away from the rocket only after the primary payload has left.

RACHEL
MarCo A and B are a test of how well CubeSat technology can function during a deep-space mission. If they are successful, they will relay data from the InSight lander back to Earth during InSight’s entry, descent, and landing. This will allow JPL to receive up to date information on InSight’s landing without having to wait hours later for a Mars-orbiting satellite to find time to relay the data after the landing. So far, MarCo A and B have successfully relayed images of a very distant Mars.

PAUL
Finally, stargazers looking for something interesting to see will want to look for the moon every early on the 28th. At around 1:00 AM, the moon will appear seven degrees from the Beehive star cluster. So aim your binoculars at the moon and then shift them to place the moon outside the view in the 7 o’clock position. The Beehive will appear at the 1 o’clock edge of your view. The cluster will appear about the size of the moon and contain over a dozen stars. 

RACHEL
That’s Idaho Skies for the 28th and 29th of November.

PAUL
Be sure to follow us on Twitter @IdahoSkies for this week’s event reminders and sky maps.

For Idaho Skies this is Paul…

RACHEL
…and Rachel.

PAUL
Dark skies and bright stars.

Idaho Skies Transcript for November 26th and 27th

RACHEL
Welcome to Idaho Skies for November 26th and 27th. We’re your hosts, Rachel…

PAUL
…and Paul.

RACHEL
The next mission to Mars is scheduled to arrive on the 26th.

PAUL
The uncrewed Mars InSight lander is designed to study the subsurface of Mars. It was launch last May and has spent the last six months traveling the distance to Mars. When it gets there, it will spend several minutes using the atmosphere to slow down. After dropping its heat shield, the lander will deploy a parachute to slow down even further. But unlike the Mars rovers, InSight will land using rocket motors rather than a big inflatable bag. So no bouncing across the Martian surface during this landing.

RACHEL
InSight will deploy its seismograph after landing and measure the strength and frequency of Martian quakes. Mars quakes will tell geologists about the internal structure of the planet. So we could learn about the thickness of the Martian crust, mantle, and its iron core. To prevent the wind and the mechanical motions inside the InSight lander from reducing the quality of the seismology data, the lander’s robotic arm will deploy the seismograph directly to the Martian surface.   

PAUL
A second experiment will drive a heat flow probe as deep as 16 feet below the surface. The heat flow probe is like a self-driving nail connected to the lander through a long cable. The cable carries a series of temperature sensors that will generate a temperature profile of the Martian subsurface. How the temperature changes with depth will indicate how much heat the core of Mars is still producing.

RACHEL
The third experiment is a retro-reflector. Retro-reflectors are special prisms that reflect light, or laser light in this case, back to their source. Orbiting spacecraft use the time between sending a laser pulse and its return as way to determine the exact distance between the satellite and the lander. Changes in the distance will give scientists an indication of how much the planet wobbles on its axis.

PAUL
That’s Idaho Skies for the 26th and 27th of November.

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.

Friday, November 16, 2018

Idaho Skies Transcript for November 23rd, 24th, and 25th

RACHEL
Welcome to Idaho Skies for November 23rd, 24th, and 25th. We’re your hosts, Rachel…

PAUL
…and Paul.

RACHEL
The moon is passing through the outskirts of the Hyades star cluster on the 23rd.

PAUL
The Hyades is a much larger star cluster than its neighbor the Pleiades. To the unaided eye, between half a dozen and a dozen stars are visible within the Hyades. With binoculars, several dozen and perhaps close to one hundred stars are visible. However, you’ll need to look in dark skies clear of haze to see that many stars.   

RACHEL
Like the Pleiades, in mythology the Hyades are also sisters. Their father was Atlas, the same father of the Pleiades. This makes the Hyades and Pleiades at least half-sisters, depending on which myth you choose to follow. Their brother was Hyas who was killed in a hunting accident. The Greeks therefore claimed that the Hyades were weeping for their lost brother. The time of the year that the Hyades rose with the sun was the rainy season for the Greeks. And this is may be why they associated the Hyades with weepiness. 

PAUL
The Hyades is not the only star cluster the moon appears close to. A smaller one, M-35 is close to the moon on the 24th. Their distance apart is only four degrees, which is just over half a binocular’s field of view. So to see this star cluster, aim your binoculars at the moon at around 11:00 PM on the 24th. Then shift the moon to the right side of your binoculars.

RACHEL
M-35 will appear near the middle of binoculars. The stars will be spread across an area about the size of the moon. At least a dozen stars should be visible in your binoculars if you view it from dark skies. Try to use your averted vision when viewing this cluster. That means not looking straight at the cluster, but looking at them with the edge of your vision. That way you’ll see signs of more stars as a brighter background haziness. 

PAUL
That’s Idaho Skies for the 23rd, 24th, and 25th of November.

RACHEL
Be sure to follow us on Twitter @IdahoSkies for this week’s event reminders and sky maps.

For Idaho Skies this is Paul…

PAUL
…and Paul.

RACHEL
Dark skies and bright stars.

Idaho Skies Transcript for November 21st and 22nd

PAUL
Welcome to Idaho Skies for November 21st and 22nd. We’re your hosts, Paul…

RACHEL
…and Rachel.

PAUL
The full moon appears near two large star clusters on the 22nd.

RACHEL
The star clusters are the Pleiades and the Hyades. The smaller of the two is the Pleiades or the Seven Sisters because of the mythology surrounding it. The usual claim is that a sharp-eyed stargazer can see seven members of this star cluster. However, most of us can only see six. So there’s a story explaining the missing Pleiad, which according to the Greek Eratosthenes, is named Merope. 

PAUL
Merope’s other sisters are named Alcyone, Asterope, Calaeno, Electra, Maia, and Taygete. They were the daughters of the titan Atlas and the Oceanid Pleione. The brightest of the sisters is Alcyone. Stargazers will see her at the middle left of the star cluster during November evenings. 

RACHEL
To the unaided eye, the Pleiades look like a frosty patch of night sky, just perfect for chilly autumn nights. This frosty appearance is due to a multitude of stars too faint to be seen without optical aid. It’s not due to the dusty cloud that the star cluster is moving through. The Merope nebula, as this glowing cloud is known as, is the result of the Pleiades’ starlight reflecting off of dust. Astronomers call this a reflection nebula and you need a telescope to see it. 

PAUL
The Pleiades appear as a tiny dipper, but please don’t confuse it for the Little Dipper. The Little Dipper or Ursa Minor is much larger and located in the northern sky tonight. The Pleiades are a true star cluster, meaning all of its stars formed together about 100 million years ago. However, due to the gravitational interactions between the stars, the cluster will dissolve into the galaxy in another 250 million years. So be sure to observe this star cluster before it’s too late.   

RACHEL
That’s Idaho Skies for the 21st and 22nd of November.

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.

RACHEL
Dark skies and bright stars.

Idaho Skies Transcript for November 19th and 20th

RACHEL
Welcome to Idaho Skies for November 19th and 20th. We’re your hosts, Rachel…

PAUL
…and Paul.

RACHEL
On the 20th we celebrate the birthday of American astronomy Edwin Powell Hubble

PAUL
Most listeners will be familiar with the Hubble Space Telescope. The telescope was launched into Earth orbit by the Space Shuttle in 1990 and named after astronomer Edwin Hubble. Early last century, astronomers thought the entire night sky of stars as being the entire universe. Astronomers did not believe that the stars were grouped into units that were larger than star clusters and smaller than the entire universe.

RACHEL
A raging debate between astronomers in 1920 was whether or not the fuzzy oval clouds that they could see through telescopes were large groupings of stars. Those believing that this was the case called them island universes. These island universes, they claimed, were as large as the Milky Way galaxy and millions of lights years away. That there could be millions of island universes in a universe at least hundreds of millions of light years across was too much for some astronomers to accept.   

PAUL
In 1912, astronomer Henrietta Leavitt discovered that some types of variable stars can be used to estimate distances. The stars were called Cepheid variables and Leavitt noticed that the brighter these stars were, the longer it took for them to oscillate in brightness. Hubble used his observations of the great nebula in Andromeda and the relationship Leavitt discovered to determine that the nebula was 1.5 million light years away, or far outside the Milky Way galaxy.

RACHEL
Hubble then used a spectroscope to discover an important fact about these island universes or galaxies. When the light of an external galaxy is split with a spectroscope, the colors emitted by each element are shifted. The amount of shift depends on how fast the galaxy was moving towards or away from the observer. Hubble discovered that the more distant the galaxy, the faster it was receding from us. In other words, the universe of millions of galaxies was expanding. And not only that they were expanding, but that they had originated from a point several billion years ago. 

PAUL
That’s Idaho Skies for the 19th and 20th of November.

RACHEL
Be sure to follow us on Twitter @IdahoSkies for this week’s event reminders and sky maps.

For Idaho Skies this is Rachel…

PAUL
…and Paul.

RACHEL
Dark skies and bright stars.

Monday, November 5, 2018

Idaho Skies Transcript for November 9th, 10th, and 11th

PAUL
Welcome to Idaho Skies for November 9th, 10th, and 11th. We’re your hosts, Paul…

RACHEL
…and Rachel.

PAUL
The moon was new on the 7th and will reappear as a thin crescent on the 11th.

RACHEL
The waxing moon has company that evening. Look in the low southwest at around 8:00 PM and you’ll find a pale star to the moon’s lower right. The star is Saturn, the fifth planet of the solar system. You’ll need a telescope to see its rings and largest moon, Titan. However, a spotting scope capable of magnifying 25 times is sufficient for seeing the planet’s rings. But you won’t have long to see them.

PAUL
That’s because Saturn is located in the constellation of Sagittarius the Archer. Both Sagittarius and Saturn are quickly approaching the sun and will be too close in a few more weeks. Now actually, Sagittarius is not approaching the sun. Earth instead is traveling to the other side of the sun from where Sagittarius appears to be located. That movement changes the perspective between Earth’s horizon and Sagittarius and that makes the constellation approach closer and closer to the sun. 

RACHEL
Since the moon is only a few days old, be sure to look for Earthshine. Binoculars will make it easier to see this faint light on the dark portion of the moon. Over the next few days, see if earthshine makes the lunar markings visible in your binoculars. In dark and clear skies, you should be able to see lunar maria, or lunar seas of frozen lava faintly in Earthshine. 

PAUL
For listeners interested in the mythology of the constellations, Sagittarius is a Centaur, or half man and half horse. The centaur’s name is Chiron, but he wasn’t wild and misbehaved like the other centaurs. Chiron was instead wise and gentle because his parents were a Greek titan and nymph. He’s most famous for teaching the arts to the Greek hero Achilles.   

RACHEL
That’s Idaho Skies for the 9th, 10th, and 11th of November.

PAUL
Be sure to follow us on Twitter @IdahoSkies for this week’s event reminders and sky maps.

For Idaho Skies this is Paul…

RACHEL
…and Rachel.

PAUL
Dark skies and bright stars.

Idaho Skies Transcript for November 7th and 8th

RACHEL
Welcome to Idaho Skies for November 7th and 8th. We’re your hosts, Rachel…

PAUL
…and Paul.

RACHEL
Edmond Halley was born on November 8th, 1656.

PAUL
Halley was an English astronomer and physicist. His earliest astronomical work of importance involved creating an accurate star chart for the Southern hemisphere. Until 1676, the best stellar maps only included the Northern skies. So Halley sailed to the island of Saint Helena to begin his observations and correct this problem. 

RACHEL
His catalog was written in Latin and it listed the name, position, and brightness of 341 stars visible from the Southern hemisphere. The stellar data was followed by notes on his observations on the transit of Mercury. He realized that observations like these could be used to find the size of the solar system. But only if the observations were made using Venus and from several locations across the world. 

PAUL
When Halley arrived back to England, he continued his observations, but mainly of the moon and its motions. Halley knew that years earlier, astronomer Johannes Kepler discovered that the planets orbited the sun in ellipses. Kepler couldn’t however explain why this was the case. Halley wondered if the nature of gravity held the explanation. So he asked Isaac Newton if he could show that a gravitational forced that varied as the distance squared could explain elliptical orbits.

RACHEL
Newton’s theory of gravity and his mathematical proof was the evidence that Halley was looking for. So impressed was Halley with Newton’s work, that Halley paid for the publication of his book on gravity, which we call the Principia for short. Using the work of Newton, Halley predicted that the comet observed in 1682 would return in 1758. This was the first prediction for the return of a comet and now we name the comet after him, or Comet Halley. 
 
PAUL
That’s Idaho Skies for the 7th and 8th of November.

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.

Idaho Skies Transcript for November 5th and 6th

PAUL
Welcome to Idaho Skies for November 5th and 6th. We’re your hosts, Paul…

RACHEL
…and Rachel.

PAUL
Last week was the anniversary of the launch of Sputnik 2.

RACHEL
Sputnik 2 is best known as the second spacecraft to reach Earth orbit and for its passenger, the dog Laika. But did you known that it was almost famous for discovering a dangerous belt of radiation? We call this donut of radiation encircling Earth the Van Allen Radiation Belts. It gets its name from Dr. James Van Allen of the University of Iowa and they were the first major discovery of the Space Age.

PAUL
Physicists hypothesized years earlier that Earth’s dipole magnetic field might trap charged particles emitted by the sun. If so, then the concentration of the trapped radiation could grow high enough to become dangerous to organisms. It wasn’t until 1958 and the launch of the American Explorer 1 that the radiation was first detected. The designer of the geiger counters used to detection this radiation was Dr. James Van Allen.

RACHEL
Early satellites determined that there were actually two belts of trapped radiation circling Earth. The belts were tipped relative to the North and South Poles because our magnetic north and south poles don’t align with Earth’s spin axis. The belts begin 300 miles above Earth and end at around 36,000 miles higher. In the middle, between the two belts, is a safe region where radiation levels are much lower. Now you might be asking just what does this have to do with Sputnik 2?

PAUL
Well, Sputnik 2 carried geiger counters and passed through the radiation belts during its very elliptical orbit around Earth. Specifically, Sputnik 2 passed through the far northern portion of the belt, but only when it was out of range of Soviet telemetry stations. Since the Soviets didn’t explain how to decode the satellite’s telemetry, tracking stations in other parts of the world did not know how to interpret the data. Had the Soviets shared their telemetry format with the rest of the world, we could be calling this region of radiation the Vernov Belt today. 

RACHEL
That’s Idaho Skies for the 5th and 6th of November.

PAUL
Be sure to follow us on Twitter @IdahoSkies for this week’s event reminders and sky maps.

For Idaho Skies this is Paul…

RACHEL
…and Rachel.

PAUL
Dark skies and bright stars.