Terry's Astronomy Thread.

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Re: Terry's Astronomy Thread.

What's in the sky tonight?
December 19, 2012

-The first-quarter Moon shines at the dim Circlet of Pisces, below the much larger and brighter Great Square of Pegasus early in the evening.

-By week's end, use binoculars to try to spot Antares twinkling low in the dawn below Venus and to the right of Mercury.

Astro Picture of the Day:
December 19, 2012

Source:
Why is this nebula so complex? When a star like our Sun is dying, it will cast off its outer layers, usually into a simple overall shape. Sometimes this shape is a sphere, sometimes a double lobe, and sometimes a ring or a helix. In the case of planetary nebula NGC 5189, however, no such simple structure has emerged. To help find out why, the Earth-orbiting Hubble Space Telescope recently observed NGC 5189 in great detail. Previous findings indicated the existence of multiple epochs of material outflow, including a recent one that created a bright but distorted torus running horizontally across image center. Results appear consistent with a hypothesis that the dying star is part of a binary star system with a precessing symmetry axis. Given this new data, though, research is sure to continue. NGC 5189 spans about three light years and lies about 3,000 light years away toward the southern constellation of the Fly (Musca).

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
December 20, 2012

-Jupiter's moon Europa crosses Jupiter's face tonight from 9:45 p.m. to 12:07 a.m. EST, followed by its tiny black shadow (plainer to see in a telescope) from 10:40 p.m. to 1:04 a.m. EST.

-Look for Antares and Mercury low in the Southeast just before sunrise tomorrow morning. Antares is in the constellation Scorpius - the constellation that 'drags' the bulge of the milky way behind it.

Astro Picture of the Day:
December 20, 2012

Source:
The small, northern constellation Triangulum harbors this magnificent face-on spiral galaxy, M33. Its popular names include the Pinwheel Galaxy or just the Triangulum Galaxy. M33 is over 50,000 light-years in diameter, third largest in the Local Group of galaxies after the Andromeda Galaxy (M31), and our own Milky Way. About 3 million light-years from the Milky Way, M33 is itself thought to be a satellite of the Andromeda Galaxy and astronomers in these two galaxies would likely have spectacular views of each other's grand spiral star systems. As for the view from planet Earth, this sharp composite image, a 25 panel mosaic, nicely shows off M33's blue star clusters and pinkish star forming regions that trace the galaxy's loosely wound spiral arms. In fact, the cavernous NGC 604 is the brightest star forming region, seen here at about the 1 o'clock position from the galaxy center. Like M31, M33's population of well-measured variable stars have helped make this nearby spiral a cosmic yardstick for establishing the distance scale of the Universe.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
December 21, 2012

-By about 9 p.m. at this time of year (depending on how far east or west you live in your time zone), the dim Little Dipper hangs straight down from Polaris, as if from a nail on the cold north wall of the sky. If you have a light-polluted sky, all you may see are Polaris and the two stars forming the far end of the Little Dipper's bowl: Kochab and Pherkad, the "Guardians of the Pole."

-Winter begins in Earth's Northern Hemisphere at the solstice, 6:12 a.m. EST, when the Sun begins its six-month return northward. This is the shortest day of the year and the longest night. (But the Earth didn't flip over? No continents flying loose? Maybe next year.)

Astro Picture of the Day:
December 21, 2012

Source:
Welcome to the December solstice, a day the world does not end... even according to the Mayan Calendar. To celebrate, consider this dramatic picture of Orion rising over El Castillo, the central pyramid at Chichén Itzá, one of the great Mayan centers on the Yucatán peninsula. Also known as the Temple of Kukulkan it stands 30 meters tall and 55 meters wide at the base. Built up as a series of square terraces by the pre-Columbian civilization between the 9th and 12th century, the structure can be used as a calendar and is noted for astronomical alignments. In fact, the Mayans were accomplished astronomers and mathematicians, accurately using the cyclic motions of the stars, Sun, Moon, and planets to measure time and construct calendars. Peering through clouds in this night skyscape, stars in the modern constellation Orion the Hunter represented a turtle in the Mayan sky. Tak sáamal.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
December 22, 2012

-Every year during Christmas season, Sirius rises in the east-southeast, far below Orion, around 7 or 8 p.m. When Sirius is still low, binoculars often show it twinkling in vivid colors. All stars do this when low. But Sirius is the brightest, making the effect more pronounced.

-Venus (magnitude –3.9) is still the bright "Morning Star," but it's moving lower in the dawn every week. Look southeast.

Astro Picture of the Day:
December 22, 2012

Source:
Splendors seldom seen are revealed in this glorious picture from Saturn's shadow. Imaged by Cassini on October 17, 2012 during its 174th orbit, the ringed planet's night side is viewed from a perspective 19 degrees below the ring plane at a distance of about 800,000 kilometers with the Sun almost directly behind the planet. A 60 frame mosaic, images made with infrared, red, and violet filters were combined to create an enhanced, false-color view. Strongly backlit, the rings look bright away from the planet but dark in silhouette against the gas giant. Above center, they reflect a faint, eerie light on the cloud tops while Saturn casts its own dark shadow on the rings. A similar Cassini image from 2006 also featured planet Earth as a pale blue dot in the distance. Instead, this scene includes icy moons Enceladus (closer to the rings) and Tethys below the rings on the left.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
December 23, 2012

-With the coming of winter, the Great Square of Pegasus is once again balancing on one of its corners as it descends the western evening sky.

-It's a busy evening at Jupiter. Ganymede, Jupiter's largest satellite, emerges from behind Jupiter's eastern limb at 7:26 p.m. EST — then just 6 minutes later it disappears into eclipse by the planet's shadow. Ganymede emerges from Jupiter's shadow farther out from the planet at 9:42 p.m. EST. Twenty-two minutes after that, Io starts crossing the planet's face, followed by Io's tiny black shadow at 10:36 p.m. EST. At 10:45 p.m. EST, Jupiter's Great Red Spot should cross the planet's central meridian.

News:

December 12, 2012
Big River on Titan

December 20, 2012
Planets Around Tau Ceti?

Astro Picture of the Day:
December 23, 2012

Source:
Comet Hale-Bopp, the Great Comet of 1997, became much brighter than any surrounding stars. It was seen even over bright city lights. Away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail, consisting of ions from the comet's nucleus, is pushed out by the solar wind. The white dust tail is composed of larger particles of dust from the nucleus driven by the pressure of sunlight, that orbit behind the comet. Observations showed that Comet Hale-Bopp's nucleus spins about once every 12 hours. A comet that may well exceed Hale-Bopp's peak brightness is expected to fall into the inner Solar System next year.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
December 24, 2012

-The Moon, nearly full, shines upper right of Jupiter and Aldebaran early this evening, as shown above. Look too for the Pleiades closer left of the Moon. By around 9 p.m. Jupiter and the Moon are level with each other, when they're both very high overhead.

Astro Picture of the Day:
December 24, 2012

Source:
Recognized since antiquity and depicted on the shield of Achilles according to Homer, stars of the Hyades cluster form the head of the constellation Taurus the Bull. Their general V-shape is anchored by Aldebaran, the eye of the Bull and by far the constellation's brightest star. Yellowish in appearance, red giant Aldebaran is not a Hyades cluster member, though. Modern astronomy puts the Hyades cluster 151 light-years away making it the nearest established open star cluster, while Aldebaran lies at less than half that distance, along the same line-of-sight. Along with colorful Hyades stars, this stellar holiday portrait locates Aldebaran just below center, as well as another open star cluster in Taurus, NGC 1647 at the left, some 2,000 light-years or more in the background. The central Hyades stars are spread out over about 15 light-years. Formed some 800 million years ago, the Hyades star cluster may share a common origin with M44 (Praesepe), a naked-eye open star cluster in Cancer, based on M44's motion through space and remarkably similar age.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
December 25, 2012

-Christmas conjunction of the Moon and Jupiter, with Aldebaran right nearby! Jupiter and the Moon are only a degree or two apart, depending on your location (in the Americas) and the time of evening. Watch them change separation and orientation as the night progresses. Binoculars show stars of the big, loose Hyades cluster in their background.

Astro Picture of the Day:
December 25, 2012

Source:
Merry Christmas! In this evocative night skyscape a starry band of the Milky Way climbs over Yosemite Valley, Sierra Nevada Range, planet Earth. Jupiter is the brightest celestial beacon on the wintry scene, though. Standing nearly opposite the Sun in the constellation Taurus, the wandering planet joins yellowish Aldebaran and the Hyades star cluster. Below, Orion always comes up sideways over a fence of mountains. And from there the twin stars of Gemini rise just across the Milky Way. As this peaceful winter night began, they followed Auriga the charioteer, its alpha star Capella near the top of the frame.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
December 26, 2012

-Now the Moon is lower left of Jupiter in the evening, as shown above. The Moon is in the area of Beta and especially Zeta Tauri, the horn tips of Taurus.

-Jupiter (magnitude –2.8, in Taurus) is up and glaring in the east as twilight fades. It climbs to dominate the high eastern and southeastern sky in the evening, with orange Aldebaran 5° below it and the Pleiades twice as far to its upper right. Jupiter is highest in the south around 10 p.m. local time. In a telescope it's still a big 47 arcseconds wide.

Astro Picture of the Day:
December 26, 2012

Source:
Makemake is one of the largest objects known in the outer Solar System. Pronounced MAH-kay MAH-kay, this Kuiper belt object is about two-thirds the size of Pluto, orbits the Sun only slightly further out than Pluto, and appears only slightly dimmer than Pluto. Makemake, however, has an orbit much more tilted to the ecliptic plane of the planets than Pluto. Discovered by a team led by Mike Brown (Caltech) in 2005, the outer Solar System orb was officially named Makemake for the creator of humanity in the Rapa Nui mythology of Easter Island. In 2008, Makemake was classified as a dwarf planet under the subcategory plutoid, making Makemake the third cataloged plutoid after Pluto and Eris. Makemake is known to be a world somewhat red in appearance, with colors indicating it is likely covered with patchy areas of frozen methane. No images of Makemake's surface yet exist, but an artist's illustration of the distant world is shown above. Careful monitoring of the brightness drop of a distant star recently eclipsed by Makemake indicates that the dwarf planet has little atmosphere.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
December 27, 2012

-Full Moon tonight (exact at 5:21 a.m. Friday morning Eastern Standard Time). The Moon is in the top of Orion's dim club, just under the feet of the Castor figure in Gemini.

-Mercury (magnitude –0.5) can be spotted during dawn, well to the lower left of brilliant Venus low in the southeast. They're 8° or 9° apart.

-For a neat way to see how fast planets move in just one week relative to stars, I've included both today's picture of Mercury and Venus's location with last week as well.

Astro Picture of the Day:
December 27, 2012

Source:
What's in this smooth soil on Mars? In late October, NASA's robotic Curiosity rover stopped near a place dubbed Rocknest as it continues to explore Gale Crater on Mars. Rocknest is the group of stones seen near the top left of the above image - just to the left of Curiosity's mast. Of particular interest was the unusually smooth patch of soil named Wind Drift seen to the left of Curiosity, which was likely created by the Martian wind blowing fine particles into Rocknest's wake. The above image shows part of Mt. Sharp in the background to upper right, and, oddly, almost the entire rover itself, digitally reconstructed from 55 frames while digitally removing an extended arm. Curiosity scooped several sand samples from Wind Drift into its Chemistry and Mineralogy Experiment (CheMin) and the Sample Analysis at Mars (SAM) laboratory for a detailed analysis. Preliminary data from the soil indicates a small amount of one-carbon organic material the origin of which it presently unknown. Although the organic signal might be just contaminants from Earth, the exciting possibility that it could be from Mars itself will remain a focus of future exploration and research.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
December 28, 2012

-Look left of the just-past-full Moon this evening for Castor and Pollux, one above the other. Castor is the one on top. Farther right of the Moon is Orion.

-Mercury (magnitude –0.6) is disappearing low in bright dawn, well to the lower left of Venus low in the southeast. They're 11° to 13° apart. Look early in the week, and bring binoculars.

-Venus (magnitude –3.9) is still the bright "Morning Star," but it's moving lower in the dawn every week. Look southeast.

News Posted today:
December 27, 2012
Radio Astronomy in the Aussie Outback


Astro Picture of the Day:
December 28, 2012

Source:
Fantastic shapes lurk in clouds of glowing hydrogen gas in NGC 6188, about 4,000 light-years away. The emission nebula is found near the edge of a large molecular cloud unseen at visible wavelengths, in the southern constellation Ara. Massive, young stars of the embedded Ara OB1 association were formed in that region only a few million years ago, sculpting the dark shapes and powering the nebular glow with stellar winds and intense ultraviolet radiation. The recent star formation itself was likely triggered by winds and supernova explosions, from previous generations of massive stars, that swept up and compressed the molecular gas. Joining NGC 6188 on this cosmic canvas is rare emission nebula NGC 6164, also created by one of the region's massive O-type stars. Similar in appearance to many planetary nebulae, NGC 6164's striking, symmetric gaseous shroud and faint halo surround its bright central star at the lower right. The field of view spans about two full Moons, corresponding to 70 light years at the estimated distance of NGC 6188.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
December 29, 2012

-In early evening at this time of year, the Great Square of Pegasus balances on one corner high in the west. The vast Andromeda-Pegasus constellation complex runs all the way from near the zenith (Andromeda's foot) down through the Great Square (Pegasus's body) almost to the western horizon (Pegasus's nose).

-Mars (magnitude +1.2, in Sagittarius) still remains low in the southwest in evening twilight. Don't confuse it with Fomalhaut far to its left or upper left. In a telescope Mars is just a tiny blob 4.3 arcseconds in diameter.

News Posted today:
December 28, 2012
Triple Stars in Far-Flung Relationships


Astro Picture of the Day:
December 29, 2012

Source:
Like a ship plowing through cosmic seas, runaway star Zeta Ophiuchi produces the arcing interstellar bow wave or bow shock seen in this stunning infrared portrait. In the false-color view, bluish Zeta Oph, a star about 20 times more massive than the Sun, lies near the center of the frame, moving toward the left at 24 kilometers per second. Its strong stellar wind precedes it, compressing and heating the dusty interstellar material and shaping the curved shock front. Around it are clouds of relatively undisturbed material. What set this star in motion? Zeta Oph was likely once a member of a binary star system, its companion star was more massive and hence shorter lived. When the companion exploded as a supernova catastrophically losing mass, Zeta Oph was flung out of the system. About 460 light-years away, Zeta Oph is 65,000 times more luminous than the Sun and would be one of the brighter stars in the sky if it weren't surrounded by obscuring dust. The image spans about 1.5 degrees or 12 light-years at the estimated distance of Zeta Ophiuchi.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
December 30, 2012

-Sirius and Procyon in the balance: Sirius, the Dog Star, sparkles low in the east-southeast after dinnertime. Procyon, the Little Dog Star, shines in the east about two fist-widths at arm's length to Sirius's left. If you live around latitude 30° north (Tijuana, New Orleans, Jacksonville), the two canine stars will be at the same height above your horizon soon after they rise. If you're north of that latitude, Procyon will be higher. If you're south of there, Sirius will be the higher one.

-Jupiter forms a straight line with Aldebaran and, between them, 3.5-magnitude Epsilon Tauri, the other tip of the Hyades V pattern.

Astro Picture of the Day:
December 30, 2012

Source:
Eta Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now. Eta Carinae's mass - about 100 times greater than our Sun - makes it an excellent candidate for a full blown supernova. Historical records do show that about 150 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky. Eta Carinae, in the Keyhole Nebula, is the only star currently thought to emit natural LASER light. This image, taken in 1996, brought out new details in the unusual nebula that surrounds this rogue star. Now clearly visible are two distinct lobes, a hot central region, and strange radial streaks. The lobes are filled with lanes of gas and dust which absorb the blue and ultraviolet light emitted near the center. The streaks remain unexplained. The bottom image is an artist's impression by J. Gitlin (STScI), NASA. In this model, Eta Carinae emits many LASER beams from its surrounding cloud of energized gas. Infrared LASERS and microwave MASERS are extremely rare astrophysical phenomena, but this natural ultraviolet LASER is the first of its kind to be discovered.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
December 31, 2012

-After the New Year's cheering at midnight is over, step outside into the cold, silent dark. The bright Moon will be shining in the southeast, with Regulus to its left. Due south is Sirius at its greatest height, with Orion to its upper right and the Jupiter-Aldebaran-Pleiades arrangement farther on — tipped differently than we're used to seeing it in the evening. Upper left of Sirius is Procyon.

-Algol should be at its minimum light, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 11:02 p.m. EST. Algol takes several additional hours to fade and to rebrighten.

Astro Picture of the Day:
December 31, 2012

Source:
What do Saturn's rings look like from the dark side? From Earth, we usually see Saturn's rings from the same side of the ring plane that the Sun illuminates them - one might call this the bright side. Geometrically, in the above picture taken in August by the robot Cassini spacecraft now orbiting Saturn, the Sun is behind the camera but on the other side of the ring plane. Such a vantage point gives a breathtaking views of the most splendid ring system in the Solar System. Strangely, the rings have similarities to a photographic negative of a front view. For example, the dark band in the middle is actually the normally bright B-ring. The ring brightness as recorded from different angles indicates ring thickness and particle density of ring particles. At the top left of the frame is Saturn's moon Tethys, which although harder to find, contains much more mass than the entire ring system.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
January 1, 2012

-The two leading asteroids, Ceres and Vesta, are still in good binocular range at magnitudes 7.1 and 6.9, respectively. Vesta is near Jupiter and Aldebaran, and Ceres is between the horns of Taurus not far away. A finder chart exists here: http://media.skyandtelescope.com/doc...CeresVesta.pdf

Astro Picture of the Day:
January 1, 2012

Source:
Few star clusters are seen to be so close to each other. Some 7,000 light-years away, though, this pair of open or galactic star clusters is an easy binocular target, a lovely starfield in the northern constellation Perseus. Also visible to the unaided eye from dark sky areas, it was cataloged in 130 BC by Greek astronomer Hipparchus. Now known as h and chi Persei, or NGC 869 (above right) and NGC 884, the clusters themselves are separated by only a few hundred light-years and contain stars much younger and hotter than the Sun. In addition to being physically close together, the clusters' ages based on their individual stars are similar - evidence that both clusters were likely a product of the same star-forming region.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
January 2, 2012

-By about 8 or 9 p.m., the Big Dipper is swinging upward in the north-northeast. It drags the end of its handle along the horizon, depending on your latitude, as its bowl rises upward.

-Earth is at perihelion, its closest to the Sun for the year (just 3% closer than at aphelion in July).

-Saturn (magnitude +0.7, in Libra) rises in the east-southeast around 2 or 3 a.m. local time. By the beginning of dawn it's fairly high in the southeast. That's the best time to get your telescope on it. Saturn's rings are tilted 19° to our line of sight, the widest open they've been in seven years.

Astro Picture of the Day:
January 2, 2012

Source:
Most galaxies have a single nucleus - does this galaxy have four? The strange answer leads astronomers to conclude that the nucleus of the surrounding galaxy is not even visible in this image. The central cloverleaf is rather light emitted from a background quasar. The gravitational field of the visible foreground galaxy breaks light from this distant quasar into four distinct images. The quasar must be properly aligned behind the center of a massive galaxy for a mirage like this to be evident. The general effect is known as gravitational lensing, and this specific case is known as the Einstein Cross. Stranger still, the images of the Einstein Cross vary in relative brightness, enhanced occasionally by the additional gravitational microlensing effect of specific stars in the foreground galaxy.