RACHEL
Welcome to Idaho Skies for February 15th, 16th, and 17th. We’re your hosts, Rachel...
PAUL
...and Paul.
RACHEL
The moon passes a large star cluster this week and many people have never seen it.
PAUL
The cluster is the Beehive star cluster. It has an apparent diameter of ½ of a degree, or as large as the moon. The cluster resides in Cancer the Crab and can be glimpsed without binoculars, if you’re in dark skies. Since the star cluster is reasonably bright, it can be seen in town, but only through your binoculars.
RACHEL
The Beehive has been known since antiquity. However, its true nature was unknown at the time. Without optical aid, the star cluster only appears as a fuzzy cloud or nebula. Galileo discovered it was actually a collection of stars in 1609. But it took the invention of the telescope for him to make this discovery.
PAUL
On Sunday night, aim your binoculars at the nearly full moon. The moon is skirting the edge of the Beehive, so this is a great opportunity to compare the apparent size of the two. The moon’s light will create enough glare that it will make it difficult to see the faintest of the stars of the cluster. When the moon is not present, you can see around two dozen stars in this cluster.
RACHEL
A star cluster is created from a molecular hydrogen cloud, or a region of gas that’s denser than the gas that normally fills the galaxy. A shock wave or a passing star can create a slightly denser region in a molecular cloud. That lets gravity overcome gas pressure and shrink the clump of gas even more. And over time, the gas clump breaks up into hundreds or even thousands of tinier clumps that continue to collapse into individual stars.
PAUL
That’s Idaho Skies for the 15th, 16th, and 17th of February.
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.
Monday, February 11, 2019
Idaho Skies Transcript for February 13th and 14th
PAUL
Welcome to Idaho Skies for February 13th and 14th. We’re your hosts, Paul...
RACHEL
...and Rachel.
PAUL
The moon appears in Taurus the Bull and near its largest star cluster during the middle of the week.
RACHEL
The Hyades is a large star cluster. It’s not compact like the older globular clusters. Instead, it’s spread out and relatively young. Astronomers believe that the stars in this cluster are only 625 million years old. While that may seem old to us, to the sun and solar system, this is incredibly young.
PAUL
When the solar system was that young, Earth was near the end of the Hadean Eon. There are very few Earth rocks from this age for geologists to study. The available evidence however, suggests that Earth’s crust had just solidified by this time and that bodies of water existed on its surface. Earth’s atmosphere must have been much denser during this time in order to keep the oceans liquid on such a hot planet.
RACHEL
So if Earth is a typical example, any planets in the Hyades must be sterile of life. But if a planet’s atmosphere is clear, its sky would be loaded with bright stars. That’s because stars are packed about four times more densely in the Hyades than in the sun’s neighborhood. Just imagine what it would be like to stand on a planet with lots of volcanoes and geysers, while admiring its star-filled sky.
PAUL
To see the Hyades, just look to the right of the moon. The Hyades appears as a V-shape grouping of stars. The bright orange star closest to the moon is named Aldebaran, but it’s not really a member of the Hyades - it just happens to line directly between the Hyades and the solar system. Your best view of this star cluster is through a pair of binoculars. Don’t use a telescope, as it will magnify too much.
RACHEL
That’s Idaho Skies for the 13th and 14th of February.
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.
Welcome to Idaho Skies for February 13th and 14th. We’re your hosts, Paul...
RACHEL
...and Rachel.
PAUL
The moon appears in Taurus the Bull and near its largest star cluster during the middle of the week.
RACHEL
The Hyades is a large star cluster. It’s not compact like the older globular clusters. Instead, it’s spread out and relatively young. Astronomers believe that the stars in this cluster are only 625 million years old. While that may seem old to us, to the sun and solar system, this is incredibly young.
PAUL
When the solar system was that young, Earth was near the end of the Hadean Eon. There are very few Earth rocks from this age for geologists to study. The available evidence however, suggests that Earth’s crust had just solidified by this time and that bodies of water existed on its surface. Earth’s atmosphere must have been much denser during this time in order to keep the oceans liquid on such a hot planet.
RACHEL
So if Earth is a typical example, any planets in the Hyades must be sterile of life. But if a planet’s atmosphere is clear, its sky would be loaded with bright stars. That’s because stars are packed about four times more densely in the Hyades than in the sun’s neighborhood. Just imagine what it would be like to stand on a planet with lots of volcanoes and geysers, while admiring its star-filled sky.
PAUL
To see the Hyades, just look to the right of the moon. The Hyades appears as a V-shape grouping of stars. The bright orange star closest to the moon is named Aldebaran, but it’s not really a member of the Hyades - it just happens to line directly between the Hyades and the solar system. Your best view of this star cluster is through a pair of binoculars. Don’t use a telescope, as it will magnify too much.
RACHEL
That’s Idaho Skies for the 13th and 14th of February.
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 February 11th and 12th
RACHEL
Welcome to Idaho Skies for February 11th and 12th. We’re your hosts, Rachel...
PAUL
...and Paul.
RACHEL
Hey, the moon reaches first quarter phase today.
PAUL
At first quarter, only the eastern half of the moon is visible. That’s because sunlight is also illuminating half of the moon’s farside. The boundary between day and night is called the moon’s terminator. It’s where sunrise is occurring on the moon. Since the sun is just rising along the terminator, shadows are especially long there. That makes it easier to see craters and mountains that reside along the terminator.
RACHEL
The moon has a near and far side because its day lasts 29 Earth days, the same time it takes for the moon to orbit Earth. Astronomers use the term tidally locked to describe this situation. Small moons are normally tidally locked to their host planet when the moons are close to the planet. Because it’s tidally locked, the lunar farside was luna incognita until the beginning of the Space Age.
PAUL
Once spacecraft began imaging the lunar farside, we discovered that it was very different from the near side. While the near side has lots of craters, maria, and mountain ranges, the farside is just battered with craters. The farside contains only 3% as much lunar maria as the near side. So why, astronomers have wondered, is the lunar farside so different than the near? One clue was the discovery that the crust on the farside is much thicker than the near side.
RACHEL
Perhaps a thicker crust makes it more difficult for subsurface magma to work its way to the surface and erupt as lava to create lunar maria. But why is the crust thicker here? One hypothesis is that left over material from the moon’s origin fell back on the lunar farside as a pancake of material. Another is that the still hot Earth prevented the moon’s near side from cooling down as quickly as the farside.
PAUL
That’s Idaho Skies for the 11th and 12th of February.
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.
Welcome to Idaho Skies for February 11th and 12th. We’re your hosts, Rachel...
PAUL
...and Paul.
RACHEL
Hey, the moon reaches first quarter phase today.
PAUL
At first quarter, only the eastern half of the moon is visible. That’s because sunlight is also illuminating half of the moon’s farside. The boundary between day and night is called the moon’s terminator. It’s where sunrise is occurring on the moon. Since the sun is just rising along the terminator, shadows are especially long there. That makes it easier to see craters and mountains that reside along the terminator.
RACHEL
The moon has a near and far side because its day lasts 29 Earth days, the same time it takes for the moon to orbit Earth. Astronomers use the term tidally locked to describe this situation. Small moons are normally tidally locked to their host planet when the moons are close to the planet. Because it’s tidally locked, the lunar farside was luna incognita until the beginning of the Space Age.
PAUL
Once spacecraft began imaging the lunar farside, we discovered that it was very different from the near side. While the near side has lots of craters, maria, and mountain ranges, the farside is just battered with craters. The farside contains only 3% as much lunar maria as the near side. So why, astronomers have wondered, is the lunar farside so different than the near? One clue was the discovery that the crust on the farside is much thicker than the near side.
RACHEL
Perhaps a thicker crust makes it more difficult for subsurface magma to work its way to the surface and erupt as lava to create lunar maria. But why is the crust thicker here? One hypothesis is that left over material from the moon’s origin fell back on the lunar farside as a pancake of material. Another is that the still hot Earth prevented the moon’s near side from cooling down as quickly as the farside.
PAUL
That’s Idaho Skies for the 11th and 12th of February.
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.
Monday, February 4, 2019
Idaho Skies Transcript for February 8th, 9th, and 10th
PAUL
Welcome to Idaho Skies for February 8th, 9th, and 10th. We’re your hosts, Paul…
RACHEL
…and Rachel.
PAUL
Mars and Uranus are very close together this week, but let’s start with an easier target, the moon.
RACHEL
By the evening of the 8th, the waxing crescent moon will appear in the low west-southwest after it gets dark. It’s four days old, or far enough away from the sun that stargazers will notice Earthshine illuminating its dark portion. This portion of the moon is experiencing night, so no direct sunlight is shining on it surface. The only light it receives is what was reflected from Earth.
PAUL
Use your binoculars. Earthshine can be seen with the unaided eye, but binoculars gather so much more light that you’ll be able to see surface features on the moon. Since Earthshine is not like morning sunlight, your binoculars won’t let you see details like craters and mountains. Instead, you’ll see maria or lunar seas. Look especially for a large round patch in the moon’s upper left. That will be Mare Imbrium, or the Sea of Rains.
RACHEL
This next object will definitely require your binoculars. Uranus the solar system’s sixth planet and it shines at a magnitude of 5.8. Now, good eyes and dark skies will let you see down to a slightly fainter 6th magnitude. But dark skies are not what we have in the Treasure Valley. However, if you get out from under your local street light, binoculars will let you see objects fainter than Uranus – if you know where to look.
PAUL
This is why the moon and Mars will come in handy on Sunday the 10th. At around 8:00 PM, aim your binoculars at the moon. Then place the moon on the left side of your binoculars. Mars will appear as the orangish star on the right, so you can’t miss it. Notice that Mars is the top star in an equilateral triangle of stars that spans about 1/4th of your binocular’s field of view. The fainter of the three stars in this triangle is Uranus. You’ll find a star map on our twitter account.
RACHEL
That’s Idaho Skies for the 8th, 9th, and 10th of February.
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.
Welcome to Idaho Skies for February 8th, 9th, and 10th. We’re your hosts, Paul…
RACHEL
…and Rachel.
PAUL
Mars and Uranus are very close together this week, but let’s start with an easier target, the moon.
RACHEL
By the evening of the 8th, the waxing crescent moon will appear in the low west-southwest after it gets dark. It’s four days old, or far enough away from the sun that stargazers will notice Earthshine illuminating its dark portion. This portion of the moon is experiencing night, so no direct sunlight is shining on it surface. The only light it receives is what was reflected from Earth.
PAUL
Use your binoculars. Earthshine can be seen with the unaided eye, but binoculars gather so much more light that you’ll be able to see surface features on the moon. Since Earthshine is not like morning sunlight, your binoculars won’t let you see details like craters and mountains. Instead, you’ll see maria or lunar seas. Look especially for a large round patch in the moon’s upper left. That will be Mare Imbrium, or the Sea of Rains.
RACHEL
This next object will definitely require your binoculars. Uranus the solar system’s sixth planet and it shines at a magnitude of 5.8. Now, good eyes and dark skies will let you see down to a slightly fainter 6th magnitude. But dark skies are not what we have in the Treasure Valley. However, if you get out from under your local street light, binoculars will let you see objects fainter than Uranus – if you know where to look.
PAUL
This is why the moon and Mars will come in handy on Sunday the 10th. At around 8:00 PM, aim your binoculars at the moon. Then place the moon on the left side of your binoculars. Mars will appear as the orangish star on the right, so you can’t miss it. Notice that Mars is the top star in an equilateral triangle of stars that spans about 1/4th of your binocular’s field of view. The fainter of the three stars in this triangle is Uranus. You’ll find a star map on our twitter account.
RACHEL
That’s Idaho Skies for the 8th, 9th, and 10th of February.
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 February 6th and 7th
RACHEL
Welcome to Idaho Skies for February 6th and 7th. We’re your hosts, Rachel…
PAUL
…and Paul.
RACHEL
The moon finally reappears in the evening sky this week.
PAUL
The moon was new on the 4th. That day, it passed above the sun from Idaho’s perspective. That meant there was no solar eclipse, since the moon didn’t pass in front of the sun. That also meant that sunlight fully illuminated the moon’s far side, while the near side that we see was left in complete darkness. People are being careless when they call the far side of the moon its dark side. It’s not dark; it gets two weeks of sunlight per month just like the near side.
RACHEL
Sometimes, stargazers can see the moon when it’s less than 24 hours after new. There are three astronomical conditions that improve your chances of seeing a moon this young. First, the moon must be closer to Earth than average, that way it travels swiftly away from the sun from our perspective. Second, new moon must occur between December and March. That way the moon’s orbit, relative to the horizon, tilts at its highest angle.
PAUL
The last condition takes advantage of the moon’s tilted orbit, which is tilted 5 degrees relative to Earth’s equator. This means it’s easier to see a young crescent moon when it’s at the highest point of its tilted orbit. So what is the youngest moon that stargazers have observed? Well, if we only count times that it was observed without optical aid, that would be 15.5 hours old.
RACHEL
Unfortunately, this month the moon is poorly placed for an early observation. However, stargazers will be able to observe the two-day old moon on the 6th. Look in the low west-southwest at about 7:00 PM. The thin crescent will probably be easier to find if you scan the area with your binoculars first. But please, wait until after sunset before you use binoculars anywhere close to the sun.
PAUL
That’s Idaho Skies for the 6th and 7th of February.
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.
Welcome to Idaho Skies for February 6th and 7th. We’re your hosts, Rachel…
PAUL
…and Paul.
RACHEL
The moon finally reappears in the evening sky this week.
PAUL
The moon was new on the 4th. That day, it passed above the sun from Idaho’s perspective. That meant there was no solar eclipse, since the moon didn’t pass in front of the sun. That also meant that sunlight fully illuminated the moon’s far side, while the near side that we see was left in complete darkness. People are being careless when they call the far side of the moon its dark side. It’s not dark; it gets two weeks of sunlight per month just like the near side.
RACHEL
Sometimes, stargazers can see the moon when it’s less than 24 hours after new. There are three astronomical conditions that improve your chances of seeing a moon this young. First, the moon must be closer to Earth than average, that way it travels swiftly away from the sun from our perspective. Second, new moon must occur between December and March. That way the moon’s orbit, relative to the horizon, tilts at its highest angle.
PAUL
The last condition takes advantage of the moon’s tilted orbit, which is tilted 5 degrees relative to Earth’s equator. This means it’s easier to see a young crescent moon when it’s at the highest point of its tilted orbit. So what is the youngest moon that stargazers have observed? Well, if we only count times that it was observed without optical aid, that would be 15.5 hours old.
RACHEL
Unfortunately, this month the moon is poorly placed for an early observation. However, stargazers will be able to observe the two-day old moon on the 6th. Look in the low west-southwest at about 7:00 PM. The thin crescent will probably be easier to find if you scan the area with your binoculars first. But please, wait until after sunset before you use binoculars anywhere close to the sun.
PAUL
That’s Idaho Skies for the 6th and 7th of February.
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 February 4th and 5th
PAUL
Welcome to Idaho Skies for February 4th and 5th. We’re your hosts, Paul…
RACHEL
…and Rachel.
PAUL
Forty-five years ago this Tuesday, Mariner 10 became the first spacecraft to use gravity assist to reach a second planet.
RACHEL
The Mariner 10 spacecraft was built by the Jet Propulsion Laboratory and designed to explore the inner solar system. Specifically, its mission was to visit the planets Venus and Mercury. It was the last of the Mariner spacecraft, a series of spacecraft famous for being the first ones to visit the inner planets.
PAUL
The Mariner series began in 1962 and ended with the launch of Mariner 10 in 1973. Not all the Mariners completed their missions. Three of them failed because of problems with their booster rockets. The first successful Mariner was number 2, which flew past Venus to become the first interplanetary space mission. Another one, Mariner 9, was the first spacecraft to enter orbit around another planet – Mars in this case.
RACHEL
Mariner 10 is famous because it was the first spacecraft to visit two planets, Venus and Mercury. Since Mariner 10 was launched from Earth, it had to lose a lot of potential energy to reach Mercury. Earth orbits the sun at a speed of 19 miles per second while Mercury orbits the sun at 29 miles per second. So losing enough potential energy to fall to Mercury’s distance from the sun meant Mariner 10 also increased speed by 50%.
PAUL
To reach Mercury, Mariner 10 had to slow down in order to fall closer to the sun. However, its rocket couldn’t provide enough thrust to both reach Earth orbit and then slow the spacecraft down to reach Mercury. Mariner 10 instead used the gravity of Venus to rob enough of its potential energy to fall even closer to the sun. And this was the first time that a spacecraft had used a gravity assist to change its orbit like this.
RACHEL
That’s Idaho Skies for the 4th and 5th of February.
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.
Welcome to Idaho Skies for February 4th and 5th. We’re your hosts, Paul…
RACHEL
…and Rachel.
PAUL
Forty-five years ago this Tuesday, Mariner 10 became the first spacecraft to use gravity assist to reach a second planet.
RACHEL
The Mariner 10 spacecraft was built by the Jet Propulsion Laboratory and designed to explore the inner solar system. Specifically, its mission was to visit the planets Venus and Mercury. It was the last of the Mariner spacecraft, a series of spacecraft famous for being the first ones to visit the inner planets.
PAUL
The Mariner series began in 1962 and ended with the launch of Mariner 10 in 1973. Not all the Mariners completed their missions. Three of them failed because of problems with their booster rockets. The first successful Mariner was number 2, which flew past Venus to become the first interplanetary space mission. Another one, Mariner 9, was the first spacecraft to enter orbit around another planet – Mars in this case.
RACHEL
Mariner 10 is famous because it was the first spacecraft to visit two planets, Venus and Mercury. Since Mariner 10 was launched from Earth, it had to lose a lot of potential energy to reach Mercury. Earth orbits the sun at a speed of 19 miles per second while Mercury orbits the sun at 29 miles per second. So losing enough potential energy to fall to Mercury’s distance from the sun meant Mariner 10 also increased speed by 50%.
PAUL
To reach Mercury, Mariner 10 had to slow down in order to fall closer to the sun. However, its rocket couldn’t provide enough thrust to both reach Earth orbit and then slow the spacecraft down to reach Mercury. Mariner 10 instead used the gravity of Venus to rob enough of its potential energy to fall even closer to the sun. And this was the first time that a spacecraft had used a gravity assist to change its orbit like this.
RACHEL
That’s Idaho Skies for the 4th and 5th of February.
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.
Tuesday, January 22, 2019
Idaho Skies Transcript for January 25th, 26th, and 27th
PAUL
Welcome to Idaho Skies for January 25th, 26th, and 27th. We’re your hosts, Paul…
RACHEL
…and Rachel.
PAUL
The moon reaches the third quarter phase on the night of the 26th and morning of the 27th.
RACHEL
The third quarter moon will rise over Boise at 11:38 PM. That’s often too late for most people, but it is a weekend. If you aim your binoculars at the moon, you will notice a large round sea in the upper right of the moon. This is the Sea of Rains or Mare Imbrium. Along its lower right edge is the Apennine Mountains. You should also notice two large craters in this lunar sea.
PAUL
The large crater inside of the Sea of Rains is named Archimedes and the other one at the top is called Plato. Archimedes and Plato are very old craters that formed after a giant impact created the Sea of Rains. Astronomers know this because these craters have flat and dark interiors. In other words, they’re not bowl-shaped.
RACHEL
The decay of unstable elements led to the creation of magma, or liquid rock beneath the lunar surface. In time, the less dense magma oozed out of cracks or fissures in the Sea of Rains. That magma became sheets of lava that filled in the giant impact scar. It took many layers of lava to fill in the Sea of Rains. That’s why this lunar sea looks dark and is free of many large craters.
PAUL
Astronomers know that Archimedes and Plato formed after the impact that created the Sea of Rains and before lava filled in the impact site. If they had formed first, then the impact responsible for the Sea of Rains would have obliterated the craters. If they formed after the moon’s magma cooled, they would have never filled with lava. So when do astronomers think these craters were created? About 3.8 billion years ago.
RACHEL
That’s Idaho Skies for the 25th, 26th, and 27th of January.
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.
RACHEL
Dark skies and bright stars.
Welcome to Idaho Skies for January 25th, 26th, and 27th. We’re your hosts, Paul…
RACHEL
…and Rachel.
PAUL
The moon reaches the third quarter phase on the night of the 26th and morning of the 27th.
RACHEL
The third quarter moon will rise over Boise at 11:38 PM. That’s often too late for most people, but it is a weekend. If you aim your binoculars at the moon, you will notice a large round sea in the upper right of the moon. This is the Sea of Rains or Mare Imbrium. Along its lower right edge is the Apennine Mountains. You should also notice two large craters in this lunar sea.
PAUL
The large crater inside of the Sea of Rains is named Archimedes and the other one at the top is called Plato. Archimedes and Plato are very old craters that formed after a giant impact created the Sea of Rains. Astronomers know this because these craters have flat and dark interiors. In other words, they’re not bowl-shaped.
RACHEL
The decay of unstable elements led to the creation of magma, or liquid rock beneath the lunar surface. In time, the less dense magma oozed out of cracks or fissures in the Sea of Rains. That magma became sheets of lava that filled in the giant impact scar. It took many layers of lava to fill in the Sea of Rains. That’s why this lunar sea looks dark and is free of many large craters.
PAUL
Astronomers know that Archimedes and Plato formed after the impact that created the Sea of Rains and before lava filled in the impact site. If they had formed first, then the impact responsible for the Sea of Rains would have obliterated the craters. If they formed after the moon’s magma cooled, they would have never filled with lava. So when do astronomers think these craters were created? About 3.8 billion years ago.
RACHEL
That’s Idaho Skies for the 25th, 26th, and 27th of January.
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.
RACHEL
Dark skies and bright stars.
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