For the Northern Hemisphere
December 21, 2010 - January 20, 2011
All times are local unless otherwise specified.
Look Up!
Planetary Treats
"On Sabbatical"
Celestial Delights
Three Seasons of Stars Twinkle
Is the Winter Sky Brighter? Twinkles ~ How Many, Why?
Find the New Year's Star!
Earth and Sun Are at Their Closest
Plus ...
Sky Lights "On Sabbatical"
Sky Calendars
Moon Dances 12/5/10-1/4/11
Moon Dances 1/4/11-2/2/11
Capricorn Navigation Page
The Night Sky ~ Home Page
Planetary Treats
This Section Is "On Sabbatical"
The
Planets
Is it
a planet? ... What planet? When you look up at the night sky, how do you
know you are looking at a planet? Learn
what a plutoid is. Click
here.
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Celestial
Delights
Three Seasons of Stars Twinkle!
The Northern Cross Stands Upright in the Christmas
Season!
Image: Star Gazer graphic made with TheSky Astronomy Software
Shown
around 9:30pm on December 15 for mid-northern
latitudes.
Look for these constellations at 7pm any night during
Capricorn.
... the constellations of any season are always those which are most prominent, that is the highest, before midnight ... Face north and above the North Star and the Little Dipper you'll see autumn's famous constellation which looks like a squashed out letter M, Cassiopeia. In the northwest the three stars which make up the Summer Triangle [Image] with its constellations Aquila the Eagle, Lyra the Harp, and Cygnus the Swan are also visible ... Cygnus got its other name, the Northern Cross because every December in early evening this cross can be seen standing upright on the northwest horizon which early Christians saw as a fitting symbol in the month of Christmas ... And if you look east you'll see that Orion the Hunter has just risen announcing that winter's just around the corner and that he will soon take center stage. So if you miss summer and autumn you can still see them in the heavens ... Star Gazer
The Northern Cross
Here's another view ... looking west
Deneb, Vega, Altair create the Summer Triangle
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Twinkle, Twinkle Little Star Why
do the stars appear brighter in winter than in any other season? How many stars
can you see with the unaided eye? Why do stars twinkle and planets don't? These
are all great questions and you may find that the answers surprise you. Here
goes ...
Is the winter sky brighter?
Yes, for two reasons. The first is because there are actually more bright stars in our winter sky than in other seasons. About half of the 25 brightest stars in our sky are visible in the winter, a higher proportion of these bright stars than in any other season. The Winter Triangle and The Great Winter Hexagon are made up of some of the brightest stars in the heavens.
The second reason has to do with cold air.
During winter, especially in the northern parts of the U.S., cold air masses do a good job of sweeping our atmosphere clean of water vapor. And without all that moisture in the air the sky has that extra crisp look. Westchester Astronomers posted 2/8/04
As autumn fades into winter and temperatures plummet, temperate latitudes receive frequent rushes of cold air that sweep our atmosphere clean. In place of the haze and smog we have become accustomed to gazing through, dark skies set ablaze by bright stars. Astronomy.com subscriber article
APOD:
November 6, 2002 - The Winter Hexagon
Where is it? Roll your cursor over the image
;-)
Image: Jerry
Lodriguss
Note: This image was created in 2002. Saturn is not within the Winter Hexagon now, nor is any other planet.
Some of the brightest stars form a large and easily found pattern in the winter sky of Earth's Northern Hemisphere. Dubbed the Winter Hexagon, the stars involved can usually be identified even in the bright night skies of a big city.
Sirius is the brightest star in the heavens, Capella is the sixth brightest, Rigel and Procyon are the seventh and eighth brightest stars. Aldebaran is the fourteenth, Pollux is the seventeenth and Castor is the twenty-third. And right in the middle of this geometric gem is the red-giant Betelgeuse (the shoulder of Orion), the ninth brightest star.
Imagine the Winter Triangle: See a line drawn from Betelgeuse to Sirius to Procyon and back to Betelgeuse and you have an equilateral triangle! Note: Look closely below Betelgeuse and above Rigel to see Orion's three-starred belt and the sword, which hangs from it. To the right of Aldebaran you'll find the blue-white Pleiades star cluster.
How many stars can we see with the naked eye?
Since we can only view one half of the sky at a time, the maximum number of stars we can actually see with the unaided eye under ideal conditions is only between 2,500 and 3,000 (6,000 for the entire sky). In fact, it is said that one could count them all in a matter of a few hours! Taking into consideration the light pollution of our cities the number drastically drops. When we casually Look Up on any night, we do not see "thousands and thousands" or even "billions and billions" of stars in the sky. We are lucky, if we can see hundreds at any given time. Using geometry and a toilet paper tube it's possible to estimate the total number of stars visible to the unaided eye at any one time!
Why do stars twinkle?
One of the ways you can tell a bright star from a planet is that planets generally don't twinkle, yet stars seem to twinkle, or change their brightness, all the time. In fact, most of the stars and all the planets are shining with a steady light. So why the twinkle and no twinkle? It has to do with turbulence and apparent surface size.
Turbulence, the movement of air in the Earth's atmosphere, causes the point-like image of starlight to shift around and fluctuate in brightness and color. This means that some of the light reaches us directly and some gets bent slightly away as it travels from the distant star through the atmosphere down to us on the ground. To our eyes, this makes the star seem to twinkle. Because planets appear as small disks, not points, the shift amount is only a small percentage of their size. As a result, "twinkleness" is absent.
You will notice that stars closer to the horizon will appear to twinkle more than other stars. This is because there is a lot more atmosphere between you and a star near the horizon than between you and a star higher in the sky. Mercury, which stays close to the eastern and western horizons and is point-like, is the only planet that twinkles, flashing a bright yellow color. Go out some night soon and check it out! Look Up!
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The New Year's Star ~ Sirius
Image: NASA, ESA, H.
Bond (STScI),
and M. Barstow (University
of Leicester)
The above image is a photograph of Sirius A, the brightest star in our nighttime sky, along with its faint, tiny stellar companion, Sirius B. Sirius A is twice as massive as the Sun with a surface temperature of 18,000 degrees Fahrenheit (10,000 degrees C)
Sirius B is 98% as massive as the Sun with a surface temperature of 45,000 degrees Fahrenheit (25,000 degrees C)! This measurement, announced 12/13/05, was done by an international team of astronomers using the Hubble Space Telescope. The white dwarf’s mass was calculated by noting how its intense gravitational field alters the wavelengths of light emitted by the main star. Read More ~ Hubble News Release
Image: Sirius Compared to Our Sun
Our Sun is a million-mile-wide cool yellow star.
Sirius is almost twice as wide and a very hot white star.
The New Year's Star is Sirius, the brightest star in the night sky. Every New Year’s Eve at midnight, Sirius reaches its highest point in the sky directly on the meridian, known as its zenith point. It's as close as it gets to your crown chakra (the top of your head). No matter where you live, just look due south and up to see this dazzling star heralding in the New Year. Star maps If you miss it at New Year’s, you can still see Sirius in this location through the first week of January. Find Sirius anytime of the evening by Navigating with Orion.
BTW: When we look at Sirius we see the light that left it 8 1/2 years ago!
The Ageless Wisdom teaches us that the energies and powers of this star are instrumental in our creation and in the establishment of the guiding forces of our planet and the mysteries of initiation. It has been referred to as the Christ Star. It is also said that a sacred planet is responsive to the life of Sirius. What the Soul is to our personality is what Sirius is to our Solar System. For this reason Sirius is known as the God Star. It is also known as the Dog Star, for it is the brightest star in Canis Major.
The Sirius system is directly "upstream" of our solar system within the galactic arm of our Milky Way Galaxy. Because of this, we now know that the polarized energies of Sirius do indeed wash over us. Modern science is yet to discover if this vast current of highly charged particles affects solar activity or life on Earth.
By coming directly towards us, Sirius creates an axis of rotation with Earth relative to the stellar background. Because of this, of all the stars in the sky, only the annual heliacal rising of Sirius exactly matches the length of our solar year, 365.25 days.
Even today, unbeknownst to most of the people of the world, our New Years Eve celebration is a continuation of a most ancient ritual honoring the return of Sirius to the midheaven position at midnight. Occurring down through the ages around January 1, this midnight alignment marks the moment when the energies of Sirius, directly overhead, most closely touch our lives with her most singular purity. For countless thousands of years and all around the world, without knowing the hidden reason, we have marked this midnight moment by jumping for joy as the rush of this vital connection surges through us. Freya Owlsdottir
These Sirian forces can aid in the service of those who are spiritually attuned. If you are one of these people, just open your crown chakra and allow the evolutionary energies to flow in and take hold. May only the Greatest Good come forth for all of us this New Year!
Think of it ... the brightest star visible from our planet reaches its highest point above the horizon at midnight every year on New Year's Eve. How wonderful, how poetic, almost like a cosmic reminder that this most brilliant of stellar lights is welcoming in and shining on the new year, giving us all hope for a bright new beginning. Star Gazer
World
Healing Day and Meditation
New Year's Eve
4:00am PST; 12:00 UT
World
Spirituality Day
New Year's Eve
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Image: Anthony Ayiomamitis ~ Image Details
The
Sun ~ Far and Near
Earth at Aphelion and Perihelion
The Earth's orbit is not a perfect, sun-centered circle therefore our distance from the Sun varies throughout the year. In early July when the Earth is at aphelion the Sun is at apogee, far away from our planet, at its most distant point in Earth's orbit; in early January when the Earth is at perihelion the Sun is at perigee, near our planet, at its closest point. The above image by Anthony Ayiomamitis of Athens, Greece shows how the apparent size of the Sun varies at these two times of the year.
Earth and Sun are at their closest on January 3, 2011 at 11:00am PST (19:00 UT). In fact, every January the Earth is at perihelion, the closest to the Sun for the year, and in July it is at apehelion, the farthest away from the Sun for the year. On January 3 we will be only 91.4 million miles away from the Sun, which is 3 million miles closer than when our Earth is at aphelion on July 4, 2011 at 8:00am PDT (15:00 UT). We are so close to the Sun in January that it can appear 7% brighter than it does in July!
Sunlight falling on Earth at perihelion is 3.5% stronger than the year-long average. spaceweather.com 1/4/04
So why is it colder in January and hotter in July for the Northern Hemisphere? What's the weather like in the Southern Hemisphere right now? The tilt of the Earth plays a big role in answering these questions. Here's a fun and simple explanation ... with the following disclaimer!!
Does
one hemisphere have a hotter summer
and colder winter than the other?
You might expect northern summer to be cooler because it occurs when Earth is farther from the Sun. Not so, explains Roy Spencer of the Global Hydrology and Climate Center. "The oceans and land on Earth are not evenly distributed around the globe. The Northern Hemisphere has more land; the Southern Hemisphere has more water. This tends to moderate the impact of differences in sunlight between perihelion and aphelion."
At aphelion the land-crowded northern half of our planet is tilted toward the Sun. For a given amount of sunlight, land warms up more than water (in other words, land has a lower heat capacity). Sunlight is therefore more effective at raising the temperature of the Northern Hemisphere. This results in the surprising fact that northern summer is a little warmer than southern summer even though Earth is farther from the Sun in July. NASA's Apehelion Day 2000
Solar Distance Affects the Length of Seasons
... the shape of our orbit does affect the length of the seasons. Right now, when we're closest to the Sun, Earth is moving faster than at other times of the year. Six months from now, when we're farthest from the Sun, Earth will be moving slower than average. As a result, winter in the northern hemisphere passes quickly, while summer lingers a bit longer — about five-and-a-half days longer. Southern-hemisphere seasons are reversed, so summer is the shortest season, winter the longest. StarDate Online: Earth at Perihelion 1/4/04
... according to Kepler's second law of planetary motion whenever an object is closest to the Sun it travels at its fastest. And when it's at its farthest from the Sun it travels at its slowest with constantly varying speeds between closest and farthest. ... January ... our Earth is highballing at a speed of 68,000 miles per hour but by July ... it will have slowed down by about half a mile a second and will be moving only 65,499 miles per hour. ... Fasten your seat belts and keep looking up! Star Gazer 2006 Script 1/2–1/8
Here are a few more Earth/Sun facts as well as a review of perihelion and aphelion. Here's a year to year chart of Equinoxes, Solstices, Perihelion, and Aphelion.
BTW: If you have trouble remembering the difference between perihelion and aphelion, an old astronomer's trick is to recall that the words "away" and "aphelion" both begin with the letter "A".
Have
a heavenly
Christmas!
May the birth of the Christ consciousness
within us be our greatest
gift to each other.
Peace on Earth and Goodwill
to All.
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Sky Lights
This Section Is "On Sabbatical"
I'd like to know your thoughts about The Night Sky ...
send me an email.
May your Night Sky traveling always be filled
with Celestial Delights and Treats!
Susan Sun
Getting
Started in Astronomy
Includes a downloadable Moon map and bimonthly star charts.
At Skymaps.com download a current monthly guide, evening sky map & calendar.
Link to Sky and Telescope's This Week's Sky at a Glance.
Spaceweather.com keeps you looking up!
Online
Schools
A space and science study guide for kids
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