Moon closes in on Saturn tonight, beckons us back to the sky

The moon, one day past full, rises over the ice on Lake Superior last night. Its squished shape is caused by atmospheric refraction. Near the horizon, light rays from the bottom half of the moon are bent more strongly upward than those from the top, causing the bottom half to “push up into” the top and creating an oval shape. Credit: Bob King

No way is the moon done serving up delights. Tireless as ever even after a long slog through Earth’s shadow Monday night, it lifts our gaze to the planet Saturn tonight.

Lovely shot of the moon reflecting off both ice and water in Lake Superior last night. Credit: Jan Karon

Look moon-ward after 11 o’clock tonight and bang – Saturn will be right in front of your nose. The two worlds are in conjunction this evening and paired up very close to one another in the southern sky.

Moonrise happens around 10 p.m. but I’d suggest you wait until after 11 to see them best. From most locations, the two will be only about a degree apart.

Glare made seeing Spica before last night’s eclipse challenging unless you covered the moon with your thumb. Saturn and the moon will be just as close tonight, but the moon’s slimmed and dimmed since full and Saturn’s brighter than Spica, so you should have no problem seeing them side by side.

Looking southeast around 11:30 p.m. this evening you’ll see the moon rise right alongside the planet Saturn. Stellarium

Use the opportunity to point your telescope at the planet famous for its hula hoop act. Saturn will be brightest and closest for the year on May 10 when it reaches opposition. Just as with Mars and the other outer planets, opposition is the time when a planet lines up with Earth on the same side of the sun. This cozy familiarity brings the planet into bright view. 10x binoculars will reveal the planet’s oval shape (thanks to the extra added width of the rings), and a small telescope magnifying 40x will bring at least one ring into clear view.

Saturn with its rings wide open to view on April 6, 2014. The three most prominent are visible: the innermost, translucent C Ring, the wide bright B Ring and the outer A ring. Cassini’s Division, a 3,000-mile-wide gap, separates the A and B rings. The rings shine brightly because they’re made of chunks of water ice. Credit: Anthony Wesley

Most skywatchers would agree that Saturn is most attractive when the rings are tilted near their maximum. During planet’s 29.5 year orbit around the sun, their inclination to Earth varies from 0 degrees (edge-on) to 27 degrees. This month we see the north face of the rings tilted near maximum at 21.7 degrees.

Open rings means you can spot Saturn’s biggest ring gap called Cassini’s Division more easily now than anytime in the past few years. Named after Giovanni Cassini, a Italian/French astronomer who discovered the division and four of Saturn’s moons back in 1675, this “clear zone” spans some 3,000 miles (4,800 km) and separates the bright, wide B Ring from the narrower A Ring.

Although it looks like a black, empty gap, spacecraft have discovered that Cassini’s Division is filled with material similar to that in the less massive and translucent C Ring. It shows up well in this photo taken by the Cassini spacecraft under the planet’s ring plane with the rings and division backlit by the sun. The moon Mimas is at top. Credit: NASA

Spacecraft like NASA’s Cassini probe, which has been orbiting and studying the planet since 2004, have revealed that the gap isn’t as vacant as it appears. As far back as 1980, the Voyager 1 probe showed that that Cassini’s Division contains material similar to that found in the less massive C Ring. It’s even organized into multiple concentric rings divided by yet finer gaps.

Wishing you a happy night.

Saturn makes a new moon named ‘Peggy’

The disturbance visible at the outer edge of Saturn’s A ring in this image from NASA’s Cassini spacecraft could be caused by an object replaying the birth process of icy moons. Credit: NASA/JPL

That bright swelling in Saturn’s A ring may very well be ice balls stirred up by a newborn moon nicknamed ‘Peggy’. Estimated at just a half-mile (1 km) across, the newcomer could be the first moon ever seen to form right before our eyes.

Images taken by the Cassini probe April 15, 2013, revealed several disturbances at the very edge of Saturn’s A ring, the outermost of the planet’s large, bright rings. One of them is the arc shown above that’s about 20 percent brighter than its surroundings and spans some 750 miles (1,200 km) long by 6 miles (10 km) wide. It even sports a little bump that interrupts the smooth profile of the ring’s edge.

“We have not seen anything like this before,” said Carl Murray of Queen Mary University of London, the report’s lead author. “We may be looking at the act of birth, where this object is just leaving the rings and heading off to be a moon in its own right.”

The object probably won’t grow any larger and in fact, may even be falling apart according to astronomers. Like the rings, many of Saturn’s moons are composed of ice. It’s believed that long ago, the rings were larger and more massive and gave rise to larger moons like Enceladus and Titan in a similar birthing process. Today these moons are relatively far from the planet but may have migrated there after self-assembling via gravity within the ring plane.

Similar to how planets formed and migrated in the early solar system, scientists think that ice in Saturn’s rings stuck glommed together to form some of its many moons. Credit: NASA/JPL/Caltech

As exciting as the birth of a new moon is, I find it equally fascinating that Saturn’s ring system may serve as a model of the early solar system when it was little more than rings of rocky and icy debris surrounding the infant sun. From these dribs and drabs, all the planets, comets and asteroids took form.

We’re almost certain that most if not all the planets migrated through this debris-strewn traffic jam similar to what appears to have happened  at Saturn. Earth and the inner planets were likely farther from the sun billions of years ago and migrated inward, while Jupiter and Saturn took off in the opposite direction.

“Witnessing the possible birth of a tiny moon is an exciting, unexpected event,” said Cassini Project Scientist Linda Spilker, of NASA’s Jet Propulsion Laboratory. According to Spilker, Cassini’s orbit will move closer to the outer edge of the A ring in late 2016 and provide an opportunity to study Peggy in more detail. Maybe even take a picture.

If theory is proven true then Saturn’s rings are much depleted after a life of making moons, leaving only enough material left to fashion a mini-moon or two.

I’m rooting for Peggy to step out of the shadows and lead a life of her own. How wonderful it would be to witness the birth of a new Saturnian moon in our lifetime.

Cassini ‘senses’ hidden ocean beneath Saturn’s moon Enceladus

Possible interior of Saturn’s moon Enceladus based on a gravity investigation by NASA’s Cassini spacecraft and NASA’s Deep Space Network in 2014. Gravity measurements suggest an ice outer shell and a low density, rocky core with a water ocean sandwiched in between at high southern latitudes. Jets of water vapor blast from cracks near the moon’s south pole. Credit: NASA/ JPL-Caltech

Long suspected as the source of the icy geysers on Saturn’s moon Enceladus, Cassini now has now uncovered evidence of an underground water ocean about 6 miles (10 km) deep, beneath the moon’s 19 to 25 miles (30 to 40 kilometers) thick crust of ice.

The ocean is likely restricted to the moon’s south polar region but given the moon’s 310 miles (500 km) diameter, that’s a potentially vast bathtub favorable for microbial life.

Enceladus is an inner, icy moon of Saturn 310 miles wide and shines as brightly as a fresh snowfall. The little moon reflects more light than any object in the solar system. Its surface has few craters and appears to have been reworked by heating. Credit: NASA

Earlier studies of the plumes or geysers blasting from the south polar region of Enceladus (en-SELL-uh-duss) by Cassini revealed most water ice particles with a small amounts amounts of methane, salts and even hydrocarbons such as propane, ethane and acetylene.

Geysers spray water ice, salts and organic compounds from fissures near the moon’s south pole nicknamed ‘tiger stripes’. Credit: NASA

To infer the presence of an ocean under miles of crust on a moon nearly 900 million miles from Earth, scientists made use of the Doppler Effect. Just to refresh, we experience the Doppler Effect every time an ambulance or fire truck goes by. As the vehicle approaches, the sound waves its horn gives off become more compressed and rise in pitch. When the truck passes and moves into the distance, the sound waves spread out and the pitch drops.

The same principal applies to light waves and radio waves. When Cassini flies past Enceladus, which it’s done now 19 times, it changes speed slightly and continuously depending upon the subtle variations in the moon’s gravity field caused by surface irregularities like a tall mountain or changes in density beneath the crust caused water in place of solid rock.

An animation illustrating how the Doppler effect causes a car engine or siren to sound higher in pitch when it is approaching than when it is receding. Sound waves bunch up on the left in the direction of the car’s motion to make a higher pitch and stretch apart on the right to make a lower pitch. Credit: Charly Whisky / Wikipedia

“As the spacecraft flies by Enceladus, its velocity is perturbed by an amount that depends on variations in the gravity field that we’re trying to measure,” said  Sami Asmar of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., a coauthor of the paper. “We see the change in velocity as a change in radio frequency, received at our ground stations here all the way across the solar system.”

Cassini and the Deep Space Network can detect changes in velocity as small as just under one foot an hour. With this precision, the flyby data yielded evidence of a zone inside the southern end of the moon with higher density than other portions of the interior.

Because Enceladus is made largely of ice, it’s surmised that the higher density comes from liquid water which is 7% denser than ice. While a large, subsurface ocean is implicated, there’s no certainty it’s behind the moon’s vaporous plumage. Let’s just say it’s a real possibility.

Closeup of Bagdad Sulcus, one of the ‘tiger stripes’ or fractures where the geysers originate on Enceladus. The picture shows a patch 5 miles (8 km) wide. Credit: NASA

Since the inside of Enceladus has the right stuff for life, astronomers believe the findings broaden our idea of places in which life might thrive.

“Their discovery expanded our view of the ‘habitable zone’ within our solar system and in planetary systems of other stars,” said Linda Spilker, Cassini’s project scientist at JPL. ”This new validation that an ocean of water underlies the jets furthers understanding about this intriguing environment.”

Saturn’s auroras dance the solar samba in cool new video


Dance of Saturn’s Auroras. The first set of images by Hubble shows an active aurora dancing around Saturn’s north pole on April 5. Next follows a quiet time from late April to mid-May. The aurora flares up again from May 20.

If I had my way there would always be a space probe orbiting every planet in the solar system. You just can’t beat the box seat views. NASA just released new photos and a movie of Saturn’s auroras taken in tandem by the Hubble Space Telescope and Cassini orbiter.

Ultraviolet and infrared images from NASA’s Cassini spacecraft and Hubble Space Telescope show active and quiet auroras at Saturn’s north and south poles. Image credit: NASA/JPL-Caltech/University of Colorado/Central Arizona College and NASA/ESA/University of Leicester and NASA/JPL-Caltech/University of Arizona/Lancaster University

The Hubble took in wide views from Earth orbit of the ringed world’s north polar auroras in ultraviolet light while the orbiter photographed the show up close in ultraviolet, infrared and visible light last April and May. During that time the sun was very active, sending gusts of solar wind in Saturn’s direction. As you watch the video you can see that Saturn’s auroras are as changeable as Earth’s as they respond to bursts in the solar wind.

This is how the aurora would look to the human eye on Saturn. The display was photographed by Cassini on Nov. 29, 2010. Saturn’s atmosphere is dominated by hydrogen which gives off red and purple light when excited by high speed particles arriving from the sun. The streaks are stars that trailed during the time exposure. This particular aurora was 870 miles (1,400 km) high.  Credit: NASA

The Cassini and Hubble photos are taken at wavelengths not visible with the human eye and are shown in false color. If you could see them for real, Saturn’s auroras would look like curtains with red at the bottom and purple at top. Earth’s are green and red due to the emission of light from oxygen and nitrogen molecules in the upper atmosphere. Hydrogen dominates the ringed planet’s atmosphere; when energized by gusty solar winds, the atoms release light of different colors.

Earlier photo by the Hubble Space Telescope of Saturn in ultraviolet light showing activity at both poles. Credit: NASA/ESA

“The movie also shows one persistent bright patch of the aurora rotating in lockstep with the orbital position of Saturn’s moon Mimas. While previous images had shown an intermittent auroral bright spot magnetically linked to the moon Enceladus, the new movie suggests another Saturn moon can influence the light show as well,” according to the NASA press release.

A question that remains to be answered is why the upper atmospheres of the gas giant planets Jupiter and Saturn are warmer than expected considering how far they are from the sun. The new images are helping scientists understand how and where auroras play a role in raising the heat.

Don’t miss this Saturday’s Saturn-moon conjunction

The big picture in the southern sky this Saturday morning at dawn shows the moon just a degree below Saturn with Mars at upper right in the south and Venus very low in the southeastern sky. Stellarium

A very nice, close pairing of Saturn and the waning 3rd quarter moon will happen Saturday morning at dawn. With late sunrises still the rule, this should be a very easy event to catch even through a parted window shade.

At closest, the two will be just two moon widths or 1 degree apart. Saturn’s in Libra the Scales, a dim constellation that precedes the brighter, more picturesque Scorpius the Scorpion. You can see part of the scorpion to the lower left of the duo. In particular, look for the bright red supergiant star Antares.

Both Libra and Scorpius are late spring-early summer constellations, visible at nightfall in May when the butterflies fly. It’s thoughts like these that lift our spirits on cold winter nights. I had the same feeling two nights ago when I happened to be out observing around 11:30 p.m. and caught sight of a “new” star flashing in the northeastern sky – Arcturus. If there were ever a vanguard of spring, this star is it. Arcturus creeps higher every frigid night until the snow is gone, the leaves turn out and jackets are shed.

Mobile phone shot of Venus in twilight Monday morning. Credit: Sean Cassidy

While you’re out enjoying Saturday’s conjunction (by the way, Saturday’s named for the Roman god Saturn) stay out a little longer to enjoy the reappearance of Venus low in the southeastern sky about 40 minutes before sunrise. Sean’s photo will help you know what to expect.

Guide to the Best Astronomical Sights of 2014

Orion climbs over snow-clad spruce trees to welcome in the new year. Credit: Bob King

As the 2013 comes to an end, we look back for a moment at the year’s biggest stories then telescope into the new year to check out all the astronomical sights that await us.

Here are my picks for 2013′s Top Ten stories in order of importance:

1. Chelyabinsk meteorite fall over Russia Feb. 15
2. Comet ISON’s dusty endComets Lovejoy and PANSTARRS pick up the slack
3. Curiosity discovers water-tumbled pebbles on Mars
4. China’s Chang’e 3 mission lands on the moon
5. Voyager I probe enters interstellar space
6. Juno’s extremely flyby of Earth en route to Jupiter
7. Cassini’s photo of Earth, Mars and Venus taken from Saturn
8. Kepler spacecraft’s demise and legacy of 3, 603 potential extrasolar planets
9. One of the brightest novae in years flares in Delphinus
10. U.S. government shutdown in October and its effects on NASA

Now on to 2014 and a brand new host of celestial offerings. For the record, the majority of events listed are western hemisphere-centric and visible with the naked eye or binoculars. Times and dates are Central Standard or Central Daylight as noted. Clear skies!

January 

1 – The very first day of the year offers the opportunity for North American observers to break their personal “youngest crescent moon” record. The moon will be just 12 hours old from the Midwest and 14 hour from the West Coast.

Watch for meteors from the Quadrantid shower before dawn on Jan. 3. Credit: John Chumack

3 – The peak of the annual Quadrantid meteor shower with a sharp maximum occurring at 1:30 p.m. (CST) on 1/3. Best time for viewing from North America will be 5-6:30 a.m. Jan. 3. The evening crescent moon will not interfere; eastern hemisphere skywatchers will have a dark sky at peak.

5 – Jupiter at opposition to the sun in Gemini and closest and brightest for the year. The planet rises at sunset and stays up all night. Great time for telescope viewing!

11 – Venus passes between the Earth and sun at inferior conjunction. For a week on either side of this date, you can see the planet as an exceedingly thin crescent in the daytime sky.

14 – Venus reappears very low in the eastern dawn sky 30 minutes before sunrise about this time

31 – Mercury at greatest elongation east of the sun and well-placed for viewing during evening twilight. Joined by a very thin crescent moon this day.

February 

14 – Give that special someone a big kiss under tonight’s Valentine’s Day full moon

26 – Spectacular close conjunction of the crescent moon and Venus at dawn as seen from Europe and Africa. The two will be separated by only 0.3 degrees.

March

10 – The waxing gibbous moon occults the 3.6 magnitude star Lambda Geminorum for North America this evening.


Demonstration and path of the Erigone occultation of Regulus 

20 – Asteroid 167 Erigone occults the bright star Regulus for observers living in a 45-mile-wide (72 km) band from New York City into Ontario, Canada. For those in the center of the path, Regulus will blank out for 12 seconds. The whole event will be easily visible with the naked eye. More information HERE.

20 – Spring (vernal equinox) begins in the northern hemisphere at 11:57 a.m. (CST)

Ganymede and Io will cast their shadows on Jupiter’s cloud tops for North and South American skywatchers on March 23. Credit: Created with Claude Duplessis Meridian software

21 – Saturn and the waning gibbous moon in close conjunction only 0.3 degrees apart as seen from Europe and Africa. Western hemisphere observers will see them about 3 degrees apart.

22 – Venus reaches greatest elongation of 47 degrees west of the sun in the morning sky. Despite its great separation from the sun, the planet will stand only about 15 degrees high at sunrise from mid-northern latitudes.

23 – Double shadow transit of Jupiter’s moons Io and Ganymede occurs from about 9:10-35 p.m. CDT. Easy to see in a small telescope.

April

8 – Mars at opposition and closest to the Earth since 2008. March-April will be the best time to observe the planet, when it’s up all night in the constellation Virgo near the bright star Spica and shining at magnitude -1.5, nearly as bright as Sirius.

The first of two total lunar eclipse in 2014 happens overnight April 15-16. Credit: NASA

15 – Total eclipse of the moon! The moon slips into Earth’s inner shadow starting at 12:58 a.m. CDT with maximum eclipse at 2:46 a.m. More information HERE.

15 – Asteroid Vesta at opposition and brightest for the year at magnitude 5.5. It should be easily visible with the naked eye from a dark sky site.

22 – Peak of the annual Lyrid meteor shower this morning with rates of 10-20 meteors per hour. Look to the south in wee hours before dawn. Some interference from the last quarter moon.

29 – Annular solar eclipse visible from Australia, the Southern Indian Ocean and Antarctica. More information HERE.

May

6 – Early morning peak of the annual Eta Aquarid meteor shower with rates of around 30 per hour. Each flash represents the burn-up of a small crumb left by Halley’s Comet.

10 – Saturn at opposition and brightest and closest for the year shining at magnitude 0. The rings will be inclined some 22 degrees to our line of sight, almost wide open. The planet will appear noticeably “out of round” in binoculars and present a beautiful sight in any size telescope.

24 - Possible big-time meteor shower from comet 209P/LINEAR when Earth passes through dust trails it deposited a century ago. Expect a peak between 2-3 a.m. (CST) with rates of 100+ per hour possible. No interference from the morning crescent moon.

25 – Mercury at greatest elongation east of the sun and easily visible low in the northwestern sky during evening twilight for observers in mid-northern latitudes.

June

3 – Triple shadow transit of Jupiter’s moons Callisto, Europa and Ganymede from 18:05 – 19:44 Greenwich time. Eastern Europe is favored. Not visible from the U.S.

21 – Start of summer (summer solstice) in the northern hemisphere at 12:51 a.m. CDT

Venus and the thin crescent at dawn on June 24. Stellarium

21 and for several days around this time – The International Space Station remains in sunlight throughout its orbit for northern hemisphere observers allowing us to see it on multiple passes throughout the night.

24 – Close conjunction of the crescent moon and Venus at dawn. With the moon so close you can use it to spot the planet even after sunrise.

July 

5 – First quarter moon and Mars in conjunction less than a degree apart at dusk.

5 – Asteroids Ceres and Vesta – targets of NASA’s Dawn Mission – are less than 1/5 degree apart in Virgo during early evening hours. A rare event!

12 – The first of three “Super Moons” of 2014. The moon reaches perigee, closest to Earth, only 21 hours before it’s full and will appear slightly larger than a typical full moon.

29 – Peak of the annual Delta Aquarid meteor shower with a maximum of 20 per hour after midnight.

August 

10 – Biggest Full Moon of the year! The moon turns full at 1:09 p.m. CDT. Nine minutes earlier it will have arrived at its closest point to Earth in 2014 of 221,765 miles (356,896 km).

12-13 – Peak of the annual Perseid meteor shower with rates of around 60-80 per hour. Spoiled this year by a bright moon just two days past full.

Comet Oukaimeden may glow around 8th magnitude in late August 2014 when it rises with the winter stars before dawn. Stellarium

18 – Spectacular close conjunction of Jupiter and Venus in the morning sky. They’ll be just 1/4 degree apart as seen from Europe and slightly wider by the time the pair rises for North and South American observers.

23 – Beautiful grouping of the thin crescent moon, Jupiter and Venus in the morning sky

25 – Mars and Saturn just 3.4 degrees apart in conjunction in the evening sky

27 – Comet C/2013 Oukaimeden should be within reach of binoculars in the morning sky near Orion.

29 – Neptune at opposition and brightest for the year at magnitude 7.8 in Aquarius

September

5 – Venus passes just 0.7 degrees north of Leo’s brightest star Regulus this morning in the east before sunrise.

8 – The final Super Moon of 2014 occurs 22 hours after perigee

22 – First day of fall (autumnal equinox) begins at 9:29 p.m. CDT in the northern hemisphere

October

Diagram show the moon’s path through Earth inner umbral shadow during the Oct. 8 total lunar eclipse. Credit: NASA

7 – Uranus at opposition and brightest for the year at magnitude 5.7 in Pisces

8 – Total eclipse of the moon, the second visible from the U.S. this year. Partial eclipse begins at 4:15 a.m. CDT with totality occurring from 5:25 – 6:24 a.m. Only the East Coast will miss a small portion of this eclipse. More information HERE.

19 – Comet C/2013 A1 Siding Spring encounters Mars. It will pass close enough that the coma may envelop the planet with a potential meteor storm to boot. Mars will be 151 million miles from Earth at the time and located in the constellation Ophiuchus and visible low in the southwestern sky at dusk.

18 – Comet C/2012 K1 PANSTARRS should be nearing peak brightness of magnitude 5.5. Mid-northern latitude observers can watch for it low in the southern sky in Puppis before dawn.

22 – The annual Orionid meteor shower peaks this morning with up to 25 meteors per hour visible. With the moon a day before new, dark skies will rule.

Diagram showing the visibility of the Oct. 23 partial solar eclipse. Credit: NASA

23 – Partial solar eclipse visible across the U.S. and Canada during late afternoon hours. At maximum for the central U.S. about half the sun will be covered by the moon. Click HERE for more information.

 

November 

1 – Mercury reaches greatest elongation west of the sun and shines brightly at magnitude -0.5 in the morning sky for skywatchers in mid-northern latitudes. Best morning appearance of the year.

17 – Peak of the annual Leonid meteor shower. This year is an off-year for the Leonids with only 10-15 meteors visible per hour. Glare from the thick waning crescent moon will interfere somewhat.

December

7 – Double shadow transit of Jupiter’s moons Europa and Io occurs from 10:18 – 10:27 p.m. CST. They shadows will be on exactly opposite sides of the planet.

14 – Peak of the annual Geminid meteor shower, one of the richest and most reliable meteor showers with rates topping 100 per hour. Expect maximum activity overnight Dec. 13-14. Some interference from the last quarter moon after midnight.

21 – Start of winter (winter solstice) at 5:03 p.m. CST

If you know of an important event that I may have missed, please drop me a line at rking@duluthnews.com

Thanks everyone and enjoy a Happy New Year!

 

Mars doubles up with Virgo’s loveliest double tomorrow morning

Tomorrow morning Dec. 29, 2013, Mars will be in conjunction less than a degree south of the double star Gamma in Virgo. You can enjoy the naked eye view or use your telescope to split the star into two equally bright components. The map shows the sky around 6 a.m. CST or 1.5 – 2 hours before sunrise. Stellarium

Mars will slide only 3/4 of a degree south of the striking double star Gamma Virginis tomorrow morning. Also known as Porrima, the close proximity of star and planet will certainly get your attention if you’re willing to risk the winter chill. They’re ideally placed too – high in the southern sky before the start of dawn.

If you have any trouble finding this temporary “double”, just follow the celestial steppingstones of crescent moon, Saturn and Spica to lead you there.

Porrima is a true double star where each component revolves around the pair’s common center of gravity. They complete an orbit in 169 years.   Credit: Damian Peach

Right now, Porrima’s two equally bright stars (both are magnitude 3.6) are separated by 2 arc seconds. To split them apart you’ll need a 3-inch (80mm) or larger scope magnifying around 150x. They’re a beautiful sight – two tiny, close set pearls glimmering in black velvet.

While you’re at it, don’t miss looking at nearby Mars as well as Saturn and the lunar crescent. Heck, they’re all laid out for us like a four-course meal.

Diagram showing the orbit of the secondary companion around the primary star in the Gamma Virginis double. The two were too close together to split in any but the largest telescopes in 2005. Since then they’ve been opening up. Look for the pair to be approximately north-south of one another in your telescope. Credit: www.dibonsmith.com

Porrima’s stellar twins are similar to the sun but hotter and nearly identical in size. They go around each other every 169 years in an elliptical orbit that cyclically brings them closer together and farther apart as seen from Earth. Closest approach happened in 2005 when the duo was separated by the same distance Jupiter is from the sun or about 500 million miles. When farthest apart, around the year 2080, they’ll be twice Pluto’s distance from each other.

Right now the duo is “opening up” and easier to see in small scopes, but you’ll need to use higher magnifications. Let us know how you fare.

Merry Christmas to all, and to all a clear night!

Ornament hanging from a Christmas tree? Cassini peers up at Saturn’s south polar region from 44 degrees beneath the ring plane last July. The black, curved stripes are the shadows of the rings on the planet’s atmosphere. Credit: NASA/JPL

Merry Christmas everyone! It’s been a joy to share the sky with you the past year. Thank you for sharing your comments, observations and photos. I hope this day finds you with family, friends and maybe even the stars.

We’ll soon step into a brand new year filled with eclipses – two lunars and a partial solar – an extremely close conjunction of Jupiter and Venus, a Mars opposition and much more. In a couple days I’ll have a complete month-by-month list of upcoming astronomical highlights.

Seen from STEREO-B, Earth, Jupiter and Venus line up inside a 2-degree-wide circle in conjunction on Dec. 24. Jupiter and the Earth were especially close – just 0.4 degrees or slightly less than one full width apart. Credit: NASA

Did you know that today the Earth is in conjunction with Venus and Jupiter today? Too bad you have to floating in outer space to see it. NASA’s STEREO-B probe, which looks back toward Earth from the opposite side of the sun, photographed a very compact grouping of the three worlds on Christmas Eve.

The three planets early this Christmas morning as seen by STEREO-B. Credit: NASA

Today they’re still very close with Jupiter practically on top of Venus. Coincidentally, a similar near-overlap of the two planets (as seen from Earth) on June 17, 2 B.C. was one possibility for the famed Star of Bethlehem we explored in yesterday’s blog.

Titan, a place to stretch your wings and fly

Saturn’s largest moon Titan slowly covers smaller Tethys with its prominent Odysseus Crater in Nov. 2009. Credit: NASA/JPL-Caltech/Space Science Institute

Feeling hemmed in by winter? Held back by cold? Time to consider a Web vacation to Saturn’s largest moon Titan. One thing’s for sure, the place has a lot of atmosphere. Thickly cloaked in a blanket of air composed of 98% nitrogen, Titan’s atmosphere is so dense (1.45 times that of Earth) and gravity so weak, that humans could fly by donning a pair of homemade wings and flapping like a bird. Since many of us have dreamed of flying on our own power, who would have guessed Titan would be the closest outpost to offer that opportunity.

In this photo taken in near-infrared light, we see Saturn’s ring plane cutting across the foreground. Dark land features are visible on Titan’s surface beneath this haze. Credit: NASA/JPL-Caltech/Space Science Institute

Titan spans 3,200 miles (5,150 km) across or almost exactly 1 1/2 times the size of the moon. Besides nitrogen, the atmosphere also contains 1.4% methane and a smattering of hydrocarbons like ethane and propane. Ultraviolet light from the sun cooks these into an orange, smoggy moon-wide haze; to image the surface requires infrared cameras and telescopes that can “see” in haze-busting infrared light.

Low winter sunlight catches the edge of Titan’s south polar vortex in this photo taken by the Cassini space probe in July and recently released by NASA. Click for a closeup color photo. Credit: NASA/JPL-Caltech/Space Science Institute

Today it’s summer in the orange moon’s northern hemisphere and winter in the south. During Cassini’s long stay at Saturn (since 2004), it’s seen seasonal changes on Titan. When it first arrived, a hood of high clouds named the north polar vortex, swirled above the north pole. A similar hood – the south polar vortex – recently formed over the south polar region. Scientists believe it’s related to the beginning of southern winter.

Watch the south polar vortex spin in this animation compiled of Cassini photos. Credit: NASA/JPL-Caltech/Space Science Institute

The vortex spins around once every 9 hours hours, some 42 times faster than Titan’s 16-day rotation period, floats above the regular cloud deck, high enough for its curving edge to catch the last of the sun’s rays. A beautiful sight!

According to NASA, scientists think these new images show open cell convection – air sinks in the center of the cell and rises at the edge, forming clouds at cell edges. No one knows exactly what creates the vortex,but it does appear to be a seasonal feature.

Besides a thick atmosphere, methane clouds and hydrocarbon haze, Titan dazzles with thousands of lakes filled with liquid natural gas – ethane and methane – that range in size from pond-size to larger than Lake Superior. Only Titan’s extremely cold surface temperature of -290 F (-179 C) and substantial atmospheric pressure can turn what are normally gases on Earth into liquids and keep them that way.

Clouds cross the sky above lakes filled with ethane and methane near Titan’s north pole in this image/diagram made by Cassini. The Kraken Sea is as large as Europe’s Caspian Sea. Credit: NASA

A most fascinating world where humans might one day fly of their accord and even ply boats across hydrocarbon lakes beneath a peach-colored sky.

 

Mercury, Saturn meet a meager moon / Space station back at dusk


A very nice conjunction/pairing of the moon, Mercury and Saturn happens tomorrow morning Dec. 1. This map shows the sky facing southeast 45 minutes before sunrise. Stellarium

Feeling well rested? If your answer is yes, I invite you to spend some of your sleep surplus watching a wonderful celestial gathering tomorrow morning. Mercury, Saturn and a very thin crescent moon will bunch up low in the southeastern sky at mid-dawn.

The crescent, just a day and half before new, passes almost directly between the two planets some 2 degrees below Saturn and 3 degrees to the right of Mercury. To see the trio, find a place with a wide-open vista to the east-southeast and start looking about an hour before sunrise.

As always, bring binoculars to help out in case Mercury’s too low to see at first. A little bit of optical aid will also show the full outline of the moon more clearly. This dim part of the lunar globe is illuminated by sunlight reflected off Earth or earthshine.

ISS astronauts, including guitar-playing Chris Hadfield, in festive spirits last Christmas. Credit: NASA

The International Space Station (ISS) got a visit this week from the Russian cargo craft Progress 53 Friday. The unmanned delivery vehicle ferried 2.9 tons of food, fuel and supplies for the station crew, including 1,763 pounds of propellant, 48 pounds of oxygen, 57 pounds of air, 925 pounds of water and 3,119 pounds of spare parts, experiment hardware and holiday gifts.

Last month, the ISS cruised the morning skies. Now it’s back in the evening for many locations and easier to see at dusk. But only for a few brief nights. I’ve listed all evening pass times for the Duluth, Minn. region below, but you can always find out when and where it flies over your house simply by dropping by Heavens-Above or typing in your zip code on Spaceweather’s Satellite Flybys page.

The station travels from west to east and can take anywhere from a couple minutes to 5 minutes to cross the sky depending on its angle to the horizon. A small telescope magnifying around 40x will easily show the shape of the ISS if you’re quick enough to track it.

* Tonight Nov. 30 starting at 7:35 p.m. Low, brief pass above the planet Venus in the southwestern sky. Maximum altitude: 33 degrees. One fist held at arm’s length equals 10 degrees.

* Sunday Dec. 1 at 6:46 p.m. Bright pass from southwest to southeast. Max. altitude: 42 degrees

* Monday Dec. 2 at 7:35 p.m. Very low pass across the western sky. Max. altitude: 14 degrees

* Tuesday Dec. 3 at 6:45 p.m. Travels from southwest to north-northeast. Low. Max. altitude: 32 degrees