Terry's Astronomy Thread.

[Bluearrowll]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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.

[Bluearrowll]

What's in the sky tonight?
January 3, 2013

-In this coldest time of the year, the dim Little Dipper hangs straight down from Polaris after dinnertime as if from a nail on the cold north wall of the sky.

-Algol should be at minimum light for a couple hours centered on 7:52 p.m. EST.

Astro Picture of the Day:
January 3, 2013

Source:
Open clusters of stars can be near or far, young or old, and diffuse or compact. Found near the plane of our Milky Way galaxy, they contain from 100 to 10,000 stars, all of which formed at nearly the same time. Bright blue stars frequently distinguish younger open clusters. M35, on the upper left, is relatively nearby at 2800 light years distant, relatively young at 150 million years old, and relatively diffuse, with about 2500 stars spread out over a volume 30 light years across. An older and more compact open cluster, NGC 2158, is at the lower right. NGC 2158 is four times more distant than M35, over 10 times older, and much more compact with many more stars in roughly the same volume of space. NGC 2158's bright blue stars have self-destructed, leaving cluster light to be dominated by older and yellower stars. Both clusters are seen toward the constellation of Gemini.

[Bluearrowll]

What's in the sky tonight?
January 4, 2013

-The latest sunrise of the year happens this morning (at 40° north latitude).

-Last-quarter Moon tonight (exact at 10:58 p.m. EST). The Moon, between Corvus and the head of Virgo, rises around 11 or midnight. By dawn Saturday morning, the Moon is high in the south with Spica and Saturn to its left, as shown here.

Astro Picture of the Day:
January 4, 2013

Source:
Tycho crater's central peak complex casts a long, dark shadow near local sunrise in this spectacular lunarscape. The dramatic oblique view was recorded on June 10, 2011 by the Lunar Reconnaissance Orbiter. Shown in amazing detail, boulder strewn slopes and jagged shadows appear in the highest resolution version at 1.5 meters per pixel. The rugged complex is about 15 kilometers wide, formed in uplift by the giant impact that created the well-known ray crater 100 million years ago. The summit of its central peak reaches 2 kilometers above the Tycho crater floor. The highest resolution image can be found by clicking this link.

[Bluearrowll]

What's in the sky tonight?
January 5, 2013

-Before dawn Sunday morning, Spica shines to the upper right of the waning Moon, and Saturn shines to the Moon's upper left, as shown here.

-Mercury is hidden in the glare of the Sun.

-Venus (magnitude –3.9) appears lower in the dawn each morning. Look for it above the southeast horizon about 45 minutes before your local sunrise.



Astro Picture of the Day:
January 5, 2013

Source:
Get out your red/blue glasses and float next to Helene, small, icy moon of Saturn. Appropriately named, Helene is one of four known Trojan moons, so called because it orbits at a Lagrange point. A Lagrange point is a gravitationally stable position near two massive bodies, in this case Saturn and larger moon Dione. In fact, irregularly shaped ( about 36 by 32 by 30 kilometers) Helene orbits at Dione's leading Lagrange point while brotherly ice moon Polydeuces follows at Dione's trailing Lagrange point. The sharp stereo anaglyph was constructed from two Cassini images (N00172886, N00172892) captured during a close flyby in 2011. It shows part of the Saturn-facing hemisphere of Helene mottled with craters and gully-like features.

[Bluearrowll]

What's in the sky tonight?
January 6, 2013

-At this coldest time of the year, Sirius rises around 7 p.m. (depending on how far east or west you live in your time zone). Orion's three-star Belt points down almost to Sirius's rising place; watch for it there. Once Sirius is up, it twinkles slowly and deeply through the thick layers of low atmosphere, then faster and more shallowly as it gains altitude. Its flashes of color also speed up and blend into shimmering white as the star climbs to shine through thinner air.

-Watch Jupiter gradually creeping toward a better lineup between Aldebaran and the Pleiades. It won't quite get there, however. Instead it will gradually stop and reverse direction at the end of January, just short of forming a straight line. (The 10° scale is about the width of your fist held at arm's length.)

Astro Picture of the Day:
January 6, 2013

Source:
In silhouette against a crowded star field toward the constellation Scorpius, this dusty cosmic cloud evokes for some the image of an ominous dark tower. In fact, clumps of dust and molecular gas collapsing to form stars may well lurk within the dark nebula, a structure that spans almost 40 light-years across this gorgeous telescopic portrait. Known as a cometary globule, the swept-back cloud, extending from the lower right to the head (top of the tower) left and above center, is shaped by intense ultraviolet radiation from the OB association of very hot stars in NGC 6231, off the upper edge of the scene. That energetic ultraviolet light also powers the globule's bordering reddish glow of hydrogen gas. Hot stars embedded in the dust can be seen as bluish reflection nebulae. This dark tower, NGC 6231, and associated nebulae are about 5,000 light-years away.

[Bluearrowll]

What's in the sky tonight?
January 7, 2013

-As dawn begins to brighten on Tuesday morning, spot the waning crescent Moon in the southeast. Below it is Antares, a summer-evening star just beginning its months-long trek backward through the night. Much farther lower left of the Moon, Venus rises. Higher in the south are Saturn and, two fists to Saturn's right, Spica.

The waning crescent Moon appears lower each morning until dawn on Thursday, when it forms a spectacular pair with Venus very low in the southeast.

Astro Picture of the Day:
January 7, 2013

Source:
AE Aurigae is called the flaming star. The surrounding nebula IC 405 is named the Flaming Star Nebula and the region seems to harbor smoke, but there is no fire. Fire, typically defined as the rapid molecular acquisition of oxygen, happens only when sufficient oxygen is present and is not important in such high-energy, low-oxygen environments. The material that appears as smoke is mostly interstellar hydrogen, but does contain smoke-like dark filaments of carbon-rich dust grains. The bright star AE Aurigae, visible near the nebula center, is so hot it is blue, emitting light so energetic it knocks electrons away from atoms in the surrounding gas. When an atom recaptures an electron, light is emitted creating the surrounding emission nebula. In this cosmic portrait, the Flaming Star nebula lies about 1,500 light years distant, spans about 5 light years, and is visible with a small telescope toward the constellation of the Charioteer (Auriga).

[Bluearrowll]

What's in the sky tonight?
January 8, 2013

-Jupiter's moon Io crosses Jupiter's face from 8:03 to 10:13 p.m. EST, followed by Io's tiny black shadow from 8:55 to 11:06 p.m. EST. Jupiter's Great Red Spot transits the planet's central meridian around 2:02 a.m. Wednesday morning EST.

-Mars (magnitude +1.2, in Sagittarius) still glimmers low in the southwest in the fading glow of sunset. Don't confuse it with Fomalhaut far to its left.

Astro Picture of the Day:
January 8, 2013

Source:
How was the unusual Red Rectangle nebula created? At the nebula's center is an aging binary star system that surely powers the nebula but does not, as yet, explain its colors. The unusual shape of the Red Rectangle is likely due to a thick dust torus which pinches the otherwise spherical outflow into tip-touching cone shapes. Because we view the torus edge-on, the boundary edges of the cone shapes seem to form an X. The distinct rungs suggest the outflow occurs in fits and starts. The unusual colors of the nebula are less well understood, however, and current speculation holds that they are partly provided by hydrocarbon molecules that may actually be building blocks for organic life. The Red Rectangle nebula lies about 2,300 light years away towards the constellation of the Unicorn (Monoceros). The nebula is shown above in unprecedented detail as captured recently by the Hubble Space Telescope. In a few million years, as one of the central stars becomes further depleted of nuclear fuel, the Red Rectangle nebula will likely bloom into a planetary nebula. A diagram that may help show how the current nebulae can look like this is below:

[Bluearrowll]

What's in the sky tonight?
January 9, 2013

-The waning crescent Moon appears lower each morning until dawn on Thursday, when it forms a spectacular pair with Venus very low in the southeast.

-Venus (magnitude –3.9) appears lower in the dawn each morning. Look for it above the southeast horizon about 45 minutes before your local sunrise.

Astro Picture of the Day:
January 9, 2013

Source:
Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic view. Drifting near bright star Eta Geminorum, at the foot of a celestial twin, the Jellyfish Nebula is seen dangling tentacles from the bright arcing ridge of emission left of center. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, IC 443 is known to harbor a neutron star, the remnant of the collapsed stellar core. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be about 100 light-years across.

[Bluearrowll]

What's in the sky tonight?
January 10, 2013

-Saturn (magnitude +0.6, in Libra) rises in the east-southeast around 2 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 10, 2013

Source:
Cosmic bullets pierce the outskirts of the Orion Nebula some 1500 light-years distant in this sharp infrared close-up. Blasted out by energetic massive star formation the bullets, relatively dense, hot gas clouds about ten times the size of Pluto's orbit, are blue in the false color image. Glowing with the light of ionized iron atoms they travel at speeds of hundreds of kilometers per second, their passage traced by yellowish trails of the nebula's shock-heated hydrogen gas. The cone-shaped wakes are up to a fifth of a light-year long. The detailed image was created using the 8.1 meter Gemini South telescope in Chile with a newly commisioned adaptive optics system (GeMS). Achieving a larger field of view than previous generation adaptive optics, GeMS uses five laser generated guide stars to help compensate for the blurring effects of planet Earth's atmosphere.

[Bluearrowll]

What's in the sky tonight?
January 11, 2013

-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) to low in the west (Pegasus's nose).

-New Moon (exact at 2:44 p.m. EST).

Astro Picture of the Day:
January 11, 2013

Source:
How do clusters of galaxies form and evolve? To help find out, astronomers continue to study the second closest cluster of galaxies to Earth: the Fornax cluster, named for the southern constellation toward which most of its galaxies can be found. Although almost 20 times more distant than our neighboring Andromeda galaxy, Fornax is only about 10 percent further that the better known and more populated Virgo cluster of galaxies. Fornax has a well-defined central region that contains many galaxies, but is still evolving. It has other galaxy groupings that appear distinct and have yet to merge. Seen here, almost every yellowish splotch on the image is an elliptical galaxy in the Fornax cluster. The picturesque barred spiral galaxy NGC 1365 visible on the lower right is also a prominent Fornax cluster member.

[Bluearrowll]

What's in the sky tonight?
January 12, 2013

-As twilight turns to night, look low in the northwest for Vega. To its upper left, by two or three fists at arm's length, shines Deneb. Deneb is the head of the big Northern Cross, which is now swinging down and soon will stand nearly upright on the northwest horizon (as seen from mid-northern latitudes).

-The crescent Moon marches higher each evening as it waxes thicker farther away from the Sun. Use the Moon to locate faint little Mars.

News Posted Today:
January 12, 2013
NGC 6872: Largest Spiral Galaxy Known


Astro Picture of the Day:
January 12, 2013

Source:
How common are Earth-sized planets? Quite common, according to extrapolations from new data taken by NASA's orbiting Kepler spacecraft. Current computer models are indicating that at least one in ten stars are orbited by an Earth-sized planet, making our Milky Way Galaxy the home to over ten billion Earths. Unfortunately, this estimate applies only to planets effectively inside the orbit of Mercury, making these hot-Earths poor vacation opportunities for humans. This histogram depicts the estimated fraction of stars that have close orbiting planets of various sizes. The number of Sun-like stars with Earth-like planets in Earth-like orbits is surely much less, but even so, Kepler has also just announced the discovery of four more of those.