Archive for December, 2014

The Sky This Week , December 23, 2014 thru January 6, 2015 !

The Sky This Week, 2014 December 23 – 2015 January 6

Our annual tribute to a holiday classic…
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 Full Moon rising over USNO, 2012 November 26

‘Tis the Night Before Christmas and up in the dome
We eagerly wait for the nightfall to come.
The slit has been opened, the lens cap’s been stowed
The night sky awaits like a wide-open road.

The Moon is now waxing through autumn’s dim stars
Christmas Eve finds her quite close to red Mars.
First Quarter Moon on the 28th appears
Then fills out to Full on the 4th of next year.

Bright Venus now shines in the soft twilight glow
In the southwestern sky as the Sun sinks below.
By New Year’s she starts her fast climb to the sky
And early next year she’s a treat for the eye.

Red Mars keeps apace of the Sun’s creeping light
And sets at the same time on each passing night.
He’s passing through stars of the Goat Capricorn
Passing close to its tail as the New Year is born.

That’s Jupiter rising by the nine o’clock time
In the east between Cancer and Leo the Lion.
Old Jove will delight you the overnight long
He’ll keep up the dazzle once Venus has gone.

Orion is rising high in the southeast,
Shield raised in defiance of Taurus the beast.
The Great Winter Circle surrounds his bold shape,
While faithful dog Canis leaps up in his wake.

Late night brings Sirius, the Dog Star on high,
By New Year’s he transits as midnight draws nigh.
The brightest of stars warm the long winter’s night,
His cohorts all add to the breathtaking sight.

Nine of the brightest of stars in the sky,
Light these dark nights of winter as Old Sol plays shy.
But the solstice is past us and now we are glad,
For the days getting longer than the ones we’ve just had.

By morning comes Saturn, a golden-hued glow
Who rises with bright summer stars in his tow.
You’ll see him in twilight in the southeast at dawn
With the “head” of the Scorpion tagging along.

With Peace to your families, neighbors, and friends
We wish you the best that the holiday sends.
The stars mark the comings and goings of time,
So stop to enjoy them, and so ends my rhyme.

 

Happy Holidays from all of us at the U.S. Naval Observatory!

 

And my most sincere apologies to Clement Clark Moore.

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The Sky This Week, December 16 – 23, 2014 !

The Sky This Week, 2014 December 16 – 23

Bright lights on the longest nights
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Orion and Friends
Imaged near Morattico, Virginia, New Year’s Eve, 2011-12

The Moon dives toward the southern stretches of the ecliptic in the pre-dawn hours this week.  New Moon falls on the 21st at 8:36 pm Eastern Standard Time.  Luna’s waning crescent may be found about five degrees to the east of the bright star Virgo on the morning of the 17th.  On the morning of the 19th, look for the yellow glimmer of Saturn about five degrees to the east of the Moon. Look for Luna’s slender crescent to return to the evening sky by the week’s end.

The Winter Solstice occurs on the 21st at 6:03 pm EDT, marking the beginning of the astronomical season of winter.  At this time the Sun will reach its most southerly point along the ecliptic at a point above the Tropic of Capricorn some 5000 kilometers (3000 miles) south of the Hawai’ian Islands.  For those of us in the Northern Hemisphere this will also correspond to the shortest length of daylight we’ll experience for the year.  Here in Washington we’ll have just 9 hours 26 minutes between sunrise and sunset.  Of course, for our friends in the Southern Hemisphere, this marks the beginning of summer, and they see their shortest nights.

The December solstice has been an important yearly event that has been observed and commemorated by people since very ancient times.  In particular it was widely observed by the Neolithic people of Europe, and many of the ancient monuments that dot the landscapes of the British Isles and northern France were used to observe the passing of this special day.  Our modern holidays have been adapted from many of these ancient observances, many with a common theme of light to chase away the long winter darkness.  For ancient people this was a welcome turning point in the year since it portended the gradual return of the warming Sun and the (eventual) end of winter.

Those of us who love to watch the stars truly find this to be “The Most Wonderful Time of the Year” with darkness settling over the land in the early evening giving us plenty of time to enjoy celestial sights and still get to bed at a decent hour.  As a reward for us Nature has given us the best and brightest stars to enjoy through the long nights.  Just as evening twilight ends we see Orion climbing up over the eastern horizon, and by 8:30 pm he is in full view, attended by his bright retinue of bright stellar companions.  Orion sits in the middle of a large arc of stars that are known as the Great Winter Circle.  Just below and to the left of Orion’s “belt” you’ll see Sirius, the brightest star in the sky, twinkling furiously in the turbulence above the horizon.  Moving northward you’ll pass Procyon, then come to the Gemini twins, Pollux and Castor.  From there swing northwestward toward the golden glimmer of Capella, then look southward toward the reddish “eye” of Taurus, the Bull and the bright star Aldebaran.  Now continue on toward Rigel, the bright blue star that marks one of Orion’s “knees”, and you’ll complete the circle.  Within the confines of this figure you’ll find nine of the 25 brightest and most colorful stars in the sky, and they will remain visible for the night’s duration.  While many of us decorate our homes with glittering multi-colored light at this time of the year, it’s pretty hard to beat the show that plays out overhead!

The longest nights now also give us the opportunity to see the “wandering” bright lights of the planets, starting with Venus in the evening twilight sky.  The dazzling planet can be glimpsed low in the southwestern sky shortly after sunset, and by the week’s end she herself sets an hour after Old Sol.  She will steadily climb higher into the sky as the new year dawns, and she will put on a dazzling show for us for the first half of 2015.

Mars remains visible in the southwestern sky for a couple of hours after sunset, glowing like a dull cinder in a very sparsely populated part of the sky.  From now until the end of the year he sets at the same time each night, 8:13 pm, so if you go out to observe him at around 6:30 he will appear in the same relative part of the sky each night during that time.

Jupiter continues his rapid progress into the evening sky.  This week the giant planet rises at around 9:00 pm, and I have had him as a companion while driving home from the Observatory after late evening events for the past week.  By midnight he’s well up in the east and provides a great target for the telescope, but if your penchant is to get a look at him in the morning before sunrise he’s still well-placed at that time, too.

As mentioned earlier, the Moon is within a few degrees of Saturn before dawn on the 19th.  He’s still a bit too low for good telescopic viewing, but he promises to also put on a good show in 2015.  Welcome him back if you happen to see him that morning.

The Sky This Week, December 9 – 16, 2014 !

The Sky This Week, 2014 December 9 – 16

How many stars can you see in Perseus?
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NGC 7789, “Caroline’s Rose” star cluster in Cassiopeia
This is one of the many galactic star clusters that may be found in the
Milky Way between Cassiopeia, Perseus, and Auriga.
It was discovered by Caroline Herschel, sister of astronomer William Herschel, in 1783.

The Moon glides into the morning sky this week, wending her way through the rising stars of the springtime sky.  Last Quarter occurs on the 14th at 7:51 am Eastern Standard Time.  Luna rises near bright Jupiter late on the evenings of the 10th and 11th.  You’ll find her waning crescent near the bright star Spica before sunrise on the morning of the 16th.

Those of us who keep track of these things will be heartened to know that by the end of the week we will start to see evening sunset times gradually edging later.  This is an aspect of several phenomena that occur around the time of the winter solstice.  Most of us probably won’t notice the change until around Christmas, and by the end of the year Old Sol will be setting a full 10 minutes later than he does right now.

The final monthly observing campaign for the citizen-science program “Globe at Night” begins on the 11th and runs through the 20th.  So far this year over 18,000 observers have contributed star visibility reports to help chart the degradation of the night sky due to the effects of light pollution.   The premise is incredibly simple: find a familiar constellation on a moonless night and compare the number of stars you see with the naked eye to a visibility chart on the program’s Web site.  Astronomers will use these data to chart out the locations of major sources of artificial lighting that is obscuring more and more of the night sky.  The intention is to make people more aware of the disappearance of the night sky as a natural resource and to engage the public in reducing this wasteful use of energy resources.  It is now a well-established fact that artificial nighttime lighting disrupts the migratory senses of many animal species as well as our own circadian rhythms, and there is growing evidence that it may pose many other long-term health effects in humans.  Fortunately this is an energy problem which is quite easily solved with a bit of public awareness.  You can do your part by simply going out on a moonless night and looking up.  This month the constellation of Perseus, the Hero is our star-counting focus.  You can find Perseus high in the northeast at 7:00 pm, between the “W”-shaped asterism of Cassiopeia and the bright golden star Capella.  If you’re away from the lights of the city, explore this part of the sky with binoculars.  You’ll be rewarded with a view of many star clusters interspersed among the star-clouds of the Milky Way.

By now you should be able to easily locate dazzling Venus in the southwestern sky as evening twilight deepens.  By the end of the week she sets 50 minutes after the Sun, and as we approach the year’s end she will set 2 minutes later on each successive night.

Ruddy Mars continues to keep ahead of the Sun, setting at the same time, 8:13 pm each night through the end of the year.  The red planet is now transiting the dim autumnal constellation of Capricornus, the Sea-Goat, and will be the brightest object in this part of the sky after Venus sets.  His reddish tint should help distinguish him from the more southerly beacon of the bright star Fomalhaut.

Bright Jupiter now rises at around 9:30 pm and is progressing steadily toward being the dominant object in the evening sky.  Old Jove rises with the waning gibbous Moon in the late evening of the 11th.  Early risers can get a great view of him just west of the meridian at 5:00 am, and pre-sunrise times are still the best for catching a good glimpse of his roiling cloud belts and scuttling moons.  We won’t have to wait much longer for him to put on a similar show in the evening sky, though; he’ll reach opposition in early February of the new year.

The Sky This Week, December 2 – 9, 2014 !

The Sky This Week, 2014 December 2 – 9

The Moon lights the sky for The Hunter.
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Orion Rising, Blue Ridge Regional Park, Bluemont, VA

The Moon passes through the bright stars of the Great Winter Circle this week, a fitting backdrop for the most northerly Full Moon of the year, which occurs on 6th at 7:27 am Eastern Standard Time.  December’s Full Moon is popularly known as the Moon Before Yule, Cold Moon, or Long Night Moon.  The latter is particularly appropriate as we approach the year’s longest nights around the time of the Winter Solstice.  Watch Luna glide just a degree north of the bright star Aldebaran on the night of December 5th.  On the following night her bright crisp disc hovers above the figure of Orion, the Hunter.

For most folks living in the mainland United States this week begins the series of phenomena associated with the winter solstice.  For the next 10 days we will experience the earliest sunsets of the year.  Here in Washington they occur at 4:46 pm EST.  By the 12th the sunset time slowly begins to creep a bit later; however, the time of latest sunrise is still advancing.  That event falls on the several days before and after January 4th.  Thus, when we measure the total length of daylight/night, we find that the year’s shortest day indeed does fall on the solstice on December 21st.  This “lag” in the times of sunrise and sunset is a result of our method of keeping time by using a standard second and by the slightly elliptical orbit of the Earth around the Sun.  If we still used sundials for keeping time the effect wouldn’t exist.

This is probably the one time of the year when the Full Moon gets some competition from the surrounding sky.  I’ve always liked the coincidence of having nine of the 25 brightest stars in the sky surrounding the most recognized and brightest constellation, Orion.  In addition to their brightness, the stars of the Great Winter Circle also offer a wide range of colors which are easily perceived with the naked eye.  From the reddish glimmers of Betelgeuse in Orion and Aldebaran in Taurus we find a nice blue-tinted contrast in the stars Rigel and Sirius.  The most northerly of the circle’s stars is Capella, which glows with a subtle golden yellow hue.  To my eyes the three “belt stars” of Orion have the most striking icy colors, probably because they serve to remind me that I forgot some piece of cold-weather observing gear when I trek away from the city lights.  Although they appear “cold” in hue, these are among the hottest and brightest stars in the galaxy.  They are the epitome of what we astronomers call “hot, young stars”, and like many of their Hollywood counterparts, they live their lives quickly and “burn out” at a relatively young age.  Compared to our Sun they are true powerhouses, shining with luminosities over 100,000 times that of our little star and surface temperatures five to six times hotter.  At this intensity they will exhaust their hydrogen fuel very quickly and have life spans measured in tens of millions of years.  Our much more modest Sun, leading a much more sedate life, should be around for a few billion years.  Fortunately for us, these stars are very far away, on the order of 700 to 800 light years.  If we could somehow move one of them to the same distance of Sirius, just over 8 light-years distant, it would be as bright as the Full Moon in our sky and we would all perish from the intense ultraviolet radiation pouring off its surface!

On a cheerier note, bright Venus is gradually working her way back into the evening sky.  You can catch her just after sunset, low in the southwest in bright evening twilight.  She sets about 40 minutes after the Sun on the 2nd, but gains 10 minutes by the week’s end.

Mars spends the week drifting eastward into the stars of the dim constellation of Capricornus, the Sea-Goat, located in the southwestern sky.  By the week’s end he drifts about five degrees south of Dabih, the constellation’s second-brightest star. From now through the year’s end the red planet sets at the same time each night, 8:13 pm here in the Washington area.

Jupiter now rises at around 10:00 pm EST, and late-night skywatchers will see his unmistakable glow dominating the eastern sky.  The giant planet reaches the first stationary point in this year’s apparition on the 9th.  For the next few months he’ll trace a westward track against the stars near the bright star Regulus in Leo.