January's Star is Sirius

This month look for the star, Sirius. Sirius is the lucida of the constellation of Canis Major, the Big Dog. It’s half way up the sky when you face towards the southeast on January evenings. Sirius is the brightest star in the heavens and significantly brighter than any other star. In fact, the second brightest star, Canopus, is only half as bright as Sirius. Of the planets, only Venus, Mars, and Jupiter can surpass Sirius in brilliance. Sirius appears as a bright white spark of light. When it is low to the horizon, the star throws off shards of color because there’s thicker atmosphere to refract its starlight. If you were born in 2006, then Sirius is your birthday star this year because the light you see tonight left Sirius nine years ago. The name Sirius comes from the Greek word for scorching. During the Dog Days of summer (early August), the sun and Sirius reside close together in the sky. The Greeks believed that the additional heat of Sirius added to the sun’s heat to make these days especially hot.

A companion named Sirius B accompanies Sirius. Astronomer’s hypothesized the existence of Sirius B as early as 1844 due to the wobbling they observed in Sirius’s slow motion across the sky (a movement called the star’s proper motion). From the amount of measured wobble, astronomers deduced that the companion star had a mass equal to the sun. This created a problem, however. A star like the sun nine light years away would be easily visible. As the companion of Sirius was not visible in telescopes, the star had to be incredibly faint for its mass; and an astronomical mystery. It wasn’t until 1862 that astronomers finally observed the star through an 18.5 inch refractor telescope. Later measurements of the star’s spectrum indicated that it was incredibly hot. So hot in fact, that its surface brightness was greater than the sun’s surface brightness. The star’s high surface brightness but low total brightness was a sign that this star is a white dwarf star. Some 120 million years ago, Sirius B, or the Pup Star was a star like the sun. Today however, the star’s nuclear core has shut down, letting the star collapse into a smaller sphere. Since atoms consist of mostly empty space, there’s enough room for the atoms to squish down to one millionth their original volume. That compression is needed to convert a sun-like star into a white dwarf. White dwarf stars like Sirius B have a density in far excess of any material known on earth. Their typical densities are around 200,000 times greater than the density of Earth. Therefore, a sugar cube sized piece of white dwarf weighs roughly one ton on Earth.

Transcript for the fourth week of December

Idaho Skies

23 December – 29 December

 

PAUL

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

 

RACHEL

…and Rachel.

 

PAUL

Did you get a new telescope for Christmas?

 

RACHEL

If you did, you have an excellent opportunity to try it out. There’s a brilliant star above the gibbous moon on Christmas night.

 

PAUL

So after looking at the moon, point your new telescope towards the star.

 

RACHEL

Even at low power, you will discover that it is round in shape and accompanied by four tiny stars.

 

PAUL

What you are observing is the mighty planet Jupiter and three of its satellites, or moons.

 

RACHEL

The fourth star is really a distant star and not a satellite of Jupiter.

 

PAUL

In most telescopes, which invert images, you will observe from left to right, Io, Jupiter, Ganymede, Callisto, and the star HIP 20785.

 

RACHEL

The star is brighter than the satellites and gets its name from the Hipparcos star catalog.

 

PAUL

Astronomer and physicist Galileo discovered Jupiter’s four large satellites 403 years ago. Today we name the satellites in his honor.

 

RACHEL

The Galilean Satellites are roughly the size of our moon, give or take. In a telescope however, the satellites appear as stars.

 

PAUL

They are a diverse group of moons ranging from Io, the most volcanic body in our solar system to Europa, an ice-covered satellite which potentially houses a very deep ocean.

 

RACHEL

Watch them over several nights as they orbit around Jupiter. Every night they take on a new arrangement.

 

PAUL

The moon is full on the morning of the 28^th.

 

RACHEL

The full moon in December is called the Cold Moon.

 

PAUL

Through binoculars, or even your new telescope, shadows from changes in terrain are generally not visible on the full moon.

 

RACHEL

What we notice the most on the full moon is albedo features. Albedo refers to the reflectivity or darkness of the moon.

 

PAUL

The features most noticeable include dark lunar maria and bright crater aprons and rays.

 

RACHEL

Lunar maria are old seas of lava. How did these seas form on the moon?

 

PAUL

Well, after the moon’s formation, its core remained hot from gravitational collapse. Later it remained hot because of the decay of radioactive elements.

 

RACHEL

This occurred around 3.8 billion years ago, when the moon and planets collided with the last of the planetesimals, or building blocks of the solar system.

 

PAUL

The collision between the moon and planetesimals created large impact basins on the moon’s surface.

 

RACHEL

Heat in the moon’s core eventually led to the creation of pockets of magma, or molten rock deep beneath the moon’s surface.

 

PAUL

The magma was able to rise to the moon’s surface where the planetesimals had created the deep impact basins.

 

RACHEL

Over millions of years, the basins filled with sheet after sheet of thin lava.

 

PAUL

In some basins, there is evidence for layers of lava over a mile thick.

 

RACHEL

That’s Idaho Skies for the fourth week of December. The Quadrantid meteor shower reaches its peak next week.

 

PAUL

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.

 

Idaho Skies is a production of NearSys and Radio Boise 89.9 FM Caldwell/Boise and 93.5 FM downtown, K228EK Garden City.

 

PAUL

Dark skies and bright stars.

During December, look for the star Aldebaran, the lucida of Taurus, the Bull.  It’s half way up in the sky when you face towards the east.  The star is orange in color and forms the apex of the “V” of Taurus (where it represents the eye of the bull).  If you were born in 1947 then Aldebaran is your birthday star this year because the light you see tonight left Aldebaran 65 years ago.

While Aldebaran is consisted to be the eye of a bull, its name is however Arabic and means the follower. Arab astronomers probably gave it this name because it follows the Pleiades star cluster. The star appears as the brightest member of the Hyades star cluster, a widely spaced cluster of stars that forms the “V” of Taurus. However, this is just a chance alignment. Taurus is only half as far away as the Hyades.

Aldebaran is a giant orange star with a spectral classification is K5. The star, being more massive than the sun, has consumed most of the hydrogen in its core. The star’s core is contracting as a result and growing hotter as it does so. Eventually the core of Aldebaran will grow hot enough begin fusing its helium ash into hydrogen. This release of fusion energy will stave off the further collapse of its core. Currently the temperature of its core has expanded the star to a size 44 times greater than the sun’s diameter.     

 

Idaho Skies for December 9th to December 15th

Idaho Skies

9 December – 15 December

PAUL

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

RACHEL

… and Rachel.

PAUL

Hey early birds, the moon passes very close to Spica on the morning of the 9^th.

RACHEL

Spica rises around 3:30 AM and will be just over one degree above the moon. That’s a distance of about twice the moon’s diameter.

PAUL

This should be nice in binoculars, especially since the moon is a waning crescent.

RACHEL

The star Spica is the 16th brightest star in the sky and the brightest star of the constellation of Virgo.

PAUL

Spica is 262 light years away from Earth. That means the light you see tonight left the star in the year 1750.

RACHEL

Spica means sheaf of wheat. Virgo is the goddess of harvest, and fittingly, Spica represents the sheaf of wheat she holds in her hand.

PAUL

On the morning of the 10th, the moon is close to Saturn.

RACHEL

Saturn is too distant and too small to be visible in binoculars, except as a star. So your best views of Saturn are through a telescope, even a small one.

PAUL

Saturn will be the brightest star above the moon.

　

RACHEL

On the morning of the 11th, the moon appears near brilliant Venus.

　

PAUL

Venus will be bright and easy to see. The thin crescent moon will be difficult.

RACHEL

A pair of binoculars is helpful in finding the very thin crescent moon.

PAUL

First, locate Venus in your binoculars. Venus appears just below the moon and both will fit within the field of view of standard 7 by 50 binoculars.

RACHEL

Look closely and you may be able to locate Mercury much closer to the horizon.

PAUL

The moon is new on the 13th at 2:42 AM.

RACHEL

You need a day or two before the moon appears as a large enough thin crescent to be visible.

PAUL

A nice challenge is to search for the youngest moon. How soon after the new moon can you see it again after sunset?

RACHEL

The youngest new moon seen without optical aid was just under 24 hours old.

PAUL

Since the moon is new, we have a good opportunity to see the Geminid meteor shower.

RACHEL

Dress for the cold if the sky is clear on the night of the 14th. Also, be prepared to spend at least 20 minutes letting your eyes become adapted to the dark.

PAUL

We can expect around 50 meteors per hour from this shower.

RACHEL

Since the constellation Gemini is high above the horizon on December nights, you can begin seeing meteors just after dark. However, if you can wait until 2:00 AM when Gemini is overhead, you might be able to glimpse up to 100 meteors per hour.

PAUL

That’s Idaho Skies for the second week of December. Listen next week and we’ll tell you about the winter solstice.

　

RACHEL

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.

Idaho Skies is a production of NearSys and Radio Boise 89.9 FM Caldwell/Boise and 93.5 FM downtown, K228EK Garden City.

RACHEL

Dark skies and bright stars.

Idaho Skies Transcript for December 2 to December 8

RACHEL

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

PAUL

… and Paul.

RACHEL

This week, you won’t want to miss an attractive alignment of three planets.

PAUL

Look in the east-southeast in the morning at about 6:30 AM. Starting from the horizon and going up, you will see the planets Mercury, Venus and Saturn.

RACHEL

Mercury will be the most difficult to see because it sits close to the horizon. You will need a clear view of the horizon in order to spot this elusive planet.

PAUL

You can be certain that you are seeing Mercury because it will be the brightest star forming a line with Saturn and Venus.

RACHEL

This month, Saturn is climbing higher above the horizon. Meanwhile, Venus is approaching closer to the horizon and will soon be located on the opposite side of the solar system.

PAUL

Jupiter is at opposition on the 3^rd.

RACHEL

That means the planet is at its closest to Earth. In Jupiter’s case, that’s 370 million miles.

PAUL

At 70 miles per hour, it would take your car over 600 years to reach Jupiter on the night of December 3rd.

RACHEL

Whenever a planet is at opposition, it appears the largest and brightest in our sky.

PAUL

That makes opposition the best time to view the solar system’s outer planets and their satellites, or moons.

RACHEL

Mercury reaches its highest elevation above the horizon on the morning of the 4th.

PAUL

Although Mercury can be seen all week, along with Saturn and Venus, the best time to view it is on the morning of the 4th.

RACHEL

Up close, Mercury looks like a larger version of our moon.

PAUL

With its close proximity to the sun, the surface temperature of Mercury at noon is about 800 degrees Fahrenheit.

RACHEL

That’s hot enough to melt metals like zinc and tin.

PAUL

At night, Mercury cools down to about minus 300 degrees Fahrenheit. That gives Mercury the largest change in temperature over the course of one day.

RACHEL

In Mercury’s case, one day lasts 58 Earth days.

PAUL

During the course of one day on Mercury, a person could experience three sunrise/sunset cycles.

RACHEL

If you stood on the surface of Mercury, the sun would first rise and then set in the same direction in the sky. Then it would rise again, move across to the opposite end of the sky, and set.

PAUL

Then it would rise a third time and set in the same direction at the opposite end of the sky.

RACHEL

That’s Idaho Skies for the first week of December. Next week, you can see a great meteor shower.

PAUL

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.

Idaho Skies is a production of NearSys and Radio Boise 89.9 FM Caldwell/Boise and 93.5 FM downtown, K228EK Garden City.

PAUL

Dark skies and bright stars.

Jupiter Recorded with a Digital Camera

Sunday night I attached my digital camera to a camera tripod and aimed it at Jupiter. Sunday was our first clear night in roughly a week and it was impossible to miss Jupiter during my walk.

The following image is a five second exposure taken through a FinePix S7000. The camera lens was zoomed to its maximum six-power optical zoom and the digital zoom was not used. The tripod was required to hold the camera motionless long enough for the exposure. I used a cable release to reduce the amount of shaking that comes from pressing down on the camera’s shutter.

As you can see, the camera recorded two of the Galilean satellites. The other two, Io and Europa were too close to Jupiter’s glare for the camera to separate them from the planet.

Jupiter is close to the Hyades star cluster this autumn and winter. Over a dozen of its members are visible in this five second long picture. The Hyades is the closest star cluster to Earth, at only 153 light years away. That means the light we see from the cluster tonight left in 1859. That’s the year Charles Darwin published his book on the origin of species.

Our Twitter Account

Idaho Skies has a Twitter account. We post reminders and star charts there. The twitter account is @IdahoSkies. http://www.twitter.com/idahoskies