Archive for November, 2015

The Sky This Week, November 24 – December 1, 2015 !

The Sky This Week, 2015 November 24 – December 1

The Thanksgiving Star.
Lunar Terminator, 2015 November 20, 22:30 – 22:45 UT
Imaged with USNO’s 30.5-cm (12-inch) f/15 Clark/Saegmüller refractor
1.6X Antares Barlow Lens, and Canon EOS Rebel T2i DSLR

The week begins with a bright Full Moon lighting up the evening sky. November’s Full Moon is popularly known as the Frosty Moon or Beaver Moon. The latter name derives from the frenzied activity of beavers as the frozen nights of winter fast approach. Full Moon occurs on the 25th at 5:44 pm Eastern Standard Time. Look for the bright star Aldebaran just over three degrees to the east of the Moon’s fully illuminated disc on the evening of the 25th. Over the course of the next few nights Luna will pass north of the rising stars of the Great Winter Circle.

Besides Aldebaran, one of the other early-rising stars of winter is the golden-hued star Capella, sixth-brightest stars in the sky. You’ll find this star nearly overhead at midnight around the time of Thanksgiving. It’s very appropriate that Capella occupies such a prominent place at this time of the year. In Roman mythology Capella represented a she-goat which nursed the infant Jupiter. During some rather rambunctious play by the super-human toddler one of the goat’s horns was accidentally broken. From the severed horn a virtually limitless supply of food and drink emerged, and the horn became known as the “cornucopia”, or “horn of plenty”. When Jupiter matured he placed the goat in a prominent place in the sky. Indeed, of all the first-magnitude stars, Capella is the closest to the north celestial pole, and so is visible in northern skies for a longer period of time than any other of the bright stars. On a clear night you may be able to spot a small triangle of stars adjacent to Capella; these are her three kids, which a grateful Jupiter also placed in the sky according to legend. These stars have been seen as harbingers of bad weather for over two millennia. Their visibility is highly dependent on the presence of high clouds, so if they are easily seen the weather tended to be favorable, but if they weren’t so easily seen it was time for mariners to batten down the hatches.

Capella and Aldebaran lead the bright stars of the Great Winter Circle into the sky, and by midnight all of them are well above the horizon. They will gradually work their way into the earlier evening, and by the time of the winter solstice they will straddle the meridian at midnight, providing bright companionship for skywatchers throughout the year’s longest nights. Nine of the 25 brightest stars in the sky fall within the Circle’s boundary, and a full spectrum of stellar colors add variety to the black of night.

The pre-dawn sky is where you’ll find most of the action for the next several weeks. Three bright planets appear like beads on a string above the eastern horizon. The brightest of these is Venus, whose brilliant glow will immediately grab your attention. During the course of the week Venus will catch up to and pass the bright star Spica. The pair will be closest on the mornings of the 29th and 30th. Jupiter is also easily seen, 50 degrees up among the stars of Leo, the Lion. In between them is the more subdued glimmer of Mars, but he lies in a very sparse star field and his ruddy tint should easily identify him.

Before the Moon moves into the morning sky you might want to take a look for a rare visitor from the distant solar system. Comet C/2013 US10 (Catalina) is visible in binoculars about an hour before sunrise. If you extend an imaginary line from Mars through the star Spica to the same distance on the other side of the star you might be able to pick it up about 15 degrees above the horizon. It’s been seen by many amateurs over the past week or so, and appears to be quite condensed with two tenuous tails.


The Sky This Week, November 17 – 24, 2015 !

The Sky This Week, 2015 November 17 – 24

The Navy on the Moon, and USNO’s best-known comet.
Lunar Terminator, 2015 November 16, 22:50 – 23:10 UT
Imaged with USNO’s 30.5-cm (12-inch) f/15 Clark/Saegmüller refractor
1.6X Antares Barlow Lens, and Canon EOS Rebel T2i DSLR

The Moon brightens the evening sky this week, waxing from a crescent low in the southwest to a robust gibbous by the week’s end. With First Quarter occurring on the 19th at 1:27 am Eastern Standard Time, this is a great week to watch the terminator gradually creep across Luna’s face, revealing a different moonscape each night. This week marks the 46th anniversary of the landing of Apollo 12 on the Moon’s so-called Ocean of Storms for humanity’s second lunar surface exploration. The all-Navy crew of Charles “Pete” Conrad and Alan Bean achieved a pinpoint landing in the Lunar Module “Intrepid” at the site of the robotic Surveyor 3 probe’s touchdown in 1967 while Richard Gordon orbited the Moon 45 times in the Command Module “Yankee Clipper”. Conrad and Bean deployed the first nuclear-powered suite of science instruments and walked to the derelict Surveyor, bringing its camera and other pieces back for study along with about 35 kilograms (75 pounds) of rocks and lunar soil. Their landing site, now known as Statio Cognito, will be near the terminator on the evening of the 20th, the anniversary of the departure of “Intrepid” from the surface.

Early risers on the morning of the 18th may see a few fast-moving meteors as Earth encounters the scattered debris of Comet 55P Tempel-Tuttle. The annual Leonid Meteor Shower has been known to produce some of the most spectacular sky shows ever seen, with huge outbursts of activity occurring in 1833, 1866, and 1966. During these “storms” thousands of meteors streaked across the sky each hour. More recent displays between 1999 and 2002 also saw increased activity. I watched the 2001 display from a field in Alexandria, Virginia and gave up counting after seeing well over 400 in a half-hour period. The parent comet of this meteoroid stream orbits the Sun with a 33-year period, so we can expect increased performance each time the comet nears the inner solar system. Comet 55P was co-discovered by Wilhelm Tempel in Germany and Horace P. Tuttle here at the U.S. Naval Observatory, the latter spotting it on January 5, 1866. We now know that the Leonid shower has been seen since at least 902 AD. This year’s display will probably not reach “storm” levels, but an observer at a dark sky site can expect to see around 20 or more fast-moving meteors per hour before the onset of morning twilight. The shower is active from the 15th to the 20th.

The bright stars of the Great Winter Circle are gradually finding their way into the late evening sky. As moonlight washes out the fainter stars of autumn it’s nice to find these bright, colorful beacons illuminating the eastern sky. By 9:00 pm you should see the familiar figure of Orion in the east, seemingly jumping up from the horizon. Orion is a wonderful constellation to study with binoculars, offering bright stars with striking colors that are enjoyable even from urban locations.

The bright planets are grouped in the morning sky right now. If you’re up before the Sun you can see them strung out like pearls in the east as the first wisps of twilight begin to light the horizon. Jupiter is now well up in the sky, nearly 45 degrees high at 5:00 am. Dazzling Venus is hard to miss. Even though she was close to Jupiter a mere three weeks ago, she’s left the giant planet in her wake and is now over 20 degrees from Old Jove. In between you’ll see the more diminutive ruddy glimmer of Mars. The red planet will seem to stay equidistant from his brighter rivals through the end of the year.

The Sky This Week, November 10 – 17, 2015 !

The Sky This Week, 2015 November 10 – 17

The Moon returns with some early winter stars.
Capella (left center) and the Pleiades (right) bathed in the Northern Lights
Imaged 2015 October 11 with a Canon EOS Rebel T2i DSLR in Karasjok, Norway

The Moon returns to the evening sky this week, waxing from a slender crescent low in the southwest to First Quarter, which occurs on the 19th at 1:27 am Eastern Standard Time. Luna spends this time passing through the barren star fields of the autumn sky with no bright planets or stars to share the limelight with. This is a great week to watch Luna progress through the sky as her phase becomes more generous. The nights before First Quarter offer views of some of the Moon’s most ancient terrain. The jumbled, closely-packed craters and escarpments in Luna’s southern highlands stand in mute testament to the violence that forged the early solar system.

As the Moon settles toward the western horizon the bright stars of the Great Winter Circle begin to pop into view in the east. One of the first of these is Capella, which you’ll find high in the northeast at around 9:00 pm. Capella is the sixth-brightest star in the sky and boasts a distinctive yellowish tint. It is actually a pair of yellow giant stars some 42 light-years away, each with a luminosity some 75 times that of the Sun. They orbit each other at a distance comparable to earth’s distance from the Sun with a period of 104 days. Capella was the first binary star to be measured spectroscopically, and its components can only be resolved using telescopes arranged as an interferometer. Capella is the brightest star in the constellation of Auriga, the Charioteer. The constellation resembles a large pentagon that shares a bright star with the constellation of Taurus, the Bull. The Milky Way passes through Auriga, and sweeping the area with binoculars or a small telescope will reveal several bright star clusters.

High in the east at this time you’ll see the small knot of stars known as the Pleiades. Of all the star patterns in the sky, this group has the most prominent place in cultural sky lore. Virtually every civilization for which we have a record has a name and a story about this group, and even the Hobbits of J.R.R. Tolkien’s Middle Earth stories knew them as “Remmirath”, the Netted Stars. In Mesoamerica the midnight culmination of the Pleiades marked the ends of cycles in the Maya and Aztec calendar counts, and the ancient city of Teotihuacan in Mexico was built in alignment with the setting point of the Pleiades as seen from the largest New World pyramid. The sighting of the Pleiades rising in the late autumn was a sign to ancient mariners of the coming of winter storms and rough sailing; to me they have been a harbinger of crisp, cold winter nights. The view of this cluster on such a night from a dark sky sight is a real treat with steadily held binoculars or a small telescope. My favorite views are through my little 3.1-inch refractor with a magnification of about 25 power. The icy blue color of the cluster’s principal stars seems accentuated in the frosty air, and dozens of fainter stars fill the field between their brightest sisters. In the middle of the cluster is a small triangle asterism that has a lonely reddish star at one of its apexes. On exceptionally clear nights it’s possible to see a faint haze around many of the bright stars. This is leftover dust and gas from the stars’ formation reflecting their blue light.

The early morning sky is still the place to look for the bright planets. If you get up at around 5:00 am you’ll see dazzling Venus, fainter ruddy Mars, and bright Jupiter stretching up from the horizon. The planets are beginning to string out from each other after their series of close conjunctions over the past few weeks. We’ll need to wait another month before Jupiter rises before midnight, but by next spring we’ll have some great views to look forward to.

The Sky This Week, November 3 – 10, 2015 !

The Sky This Week, 2015 November 3 – 10

Some basic geometry in the night sky.
Messier 31, the Great Andromeda Galaxy
Imaged 2015 August 8 with a Canon EOS Rebel T2i DSLR, 80mm f/6 Antares Sentinel refractor,
20 90-second subframes @ ISO 3200 at Fishers Island, New York

The Moon wanes in the morning sky this week, passing through the gathering of planets in the pre-dawn hours. New Moon occurs on the 11th at 12:47 pm Eastern Standard Time. Look for Luna just over two degrees from bright Jupiter before sunrise on the 6th. The next morning the Moon provides an excellent photo opportunity with brilliant Venus and the more subdued ruddy Mars. The three objects will form a tight triangle spanning just over two degrees. In the middle of this triangle you’ll find the third-magnitude star Zavijah.

Late autumn nights are characterized by large geometric asterisms that dominate different times of the nighttime hours. The early evening is marked by the lingering stars of the Summer Triangle, Vega, Deneb, and Altair, hanging high in the western sky. From dark-sky locations this group of bright blue-white stars is pierced by the wafting glow of some of the brighter star-clouds of the Milky Way. There are a number of interesting objects to look at here if you have a small telescope. The star Albireo lies in the center of the triangle and resolves into a fine pair of blue and golden-hued stars in almost any telescope. Near the bright star Vega a pair of binoculars will reveal a close pair of white stars. Looking at this wide pair of stars with a three-inch or larger aperture telescope shows that each component is itself a close double star.

By 9:00 pm another geometric figure may be found crossing the meridian high in the south. This is the so-called “Great Square” of Pegasus. Even though none of the square’s stars are brighter than second-magnitude, they are the brightest stars in this part of the sky. You can get a good idea of the quality of your sky by counting the faint stars inside the square. Urban skywatchers will be lucky to see one or two, but those well away from city lights may be able to see up to a dozen! If you look at the upper left star in the square, Alpheratz, you’ll see two diverging “chains” of stars; follow the lower, brighter chain to the second star, then hop up past the second star in the fainter chain. From a dark site you’ll see a fuzzy patch of light with your unaided eye, and even from the city binoculars will show a glowing luminous patch. This is the Great Andromeda Galaxy, the closest large external galaxy too the Milky Way. It represents the combined light of some 200 million stars and lies at a distance of 2.5 million light years!

By midnight our last geometric figure is climbing in the east. The Great Winter Circle surrounds the familiar outline of Orion, the Hunter, and here you’ll find nine of the 25 brightest and most colorful stars in the sky. This is another area that’s a treat to look at in binoculars.

Early risers will find the Great Winter Circle sliding past the meridian as the stars of the springtime sky move into the east. This is where you can see the season’s bright planets. Jupiter is the highest of the three worlds in this part of the sky. Venus is the brightest of the three, and you’ll find the dazzling planet pulling away from the much fainter glow of Mars. For added drama, the Moon glides through these assembled worlds for what will be one of the best astro-photo opportunities of the year.