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.

Totally awesome eclipse awes us all

An “around the clock” sequence starting with the uneclipsed moon (left), followed by the penumbral and then partial phases, flanks a photo at mid-totality when the moon was fully immersed in Earth’s shadow. The three frames at bottom are overexposed to better show how the moon looks in deep partial eclipse with a sunlit crescent cupping the red moon. Details: 4″ f/7 refractor, ISO 400, exposures from 1/250″ to 6 seconds. Credit: Bob King

What a fine eclipse! I hope you were as fortunate as we were to have clear skies. Here are a few photos taken during a very long night with my friend Will. After looking at and photographing the moon through the telescope in the countryside, we set off for the city to see how a big red ball paired with familiar scenes.

The moon just out of total eclipse, Spica (lower right of moon) and Mars (upper right) decorate the sky around the old Central High School clocktower in downtown Duluth, Minn. U.S. Tuesday morning. Credit: Bob King

I first noticed the penumbral or outer shadow of the Earth about a half hour before partial eclipse as a brownish shading along the moon’s left side. The edge of the inner, dark shadow – called the umbra – was fuzzy and smoky orange-brown in the telescope. What fun to watch it creep over the moon’s face covering one crater after another.

Pretty scene at the telescope taken during totality early this morning by Jim Schaff of Duluth

During total eclipse, the top of the moon, which was closest to the center of the umbra was very dark orange with the naked eye, while the bottom rind – the portion of the moon farthest from umbral center – glowed a dull yellow. Colors varied some depending on whether you viewed with the naked eye, binoculars or telescope.

The fully eclipsed moon is tucked inside the outline of a bird in the Wild Ricing Moon sculpture on the University of Minnesota-Duluth campus Tuesday morning. Credit: Bob King

One of our favorite sights was seeing the totally eclipsed moon alongside its starry companion Spica in binoculars. In the 8×40 glass, the moon looked pumpkin-colored. My older daughter said the eclipsed moon looked like a toasted marshmallow!

This wide field view showing the moon and Spica from Duluth is a composite of two photos – 0.6 seconds for eclipse, 5 seconds for stars, 200mm f/4 ISO400, Canon 50D.  Credit: Tom Nelson

As the moon progressed through the umbra, a yellow “smile” of a crescent slowly slid from one side to the other along the moon’s bottom edge. A minute after emerging from totality, the brilliant “cap” of light on the moon’s left side resembled a polar cap on the red planet Mars. What a fine coincidence the real Mars was just a fist away.

Most of us who saw the eclipse couldn’t help but also notice the bright star Spica in Virgo accompanying the moon. To the upper right Mars shone brilliantly. Credit:  Bob King

A favorite pastime during total lunar eclipses is watching the darkness return as the moon gets clipped by Earth’s shadow. The change is slow at first but soon you’re staring up marveling at how all those stars got there. During totality the sky’s was as dark as a moonless night and stayed that way for over an hour.

Soma Acharya sent several photos she and her husband Kaushik took of the eclipse. This one features the trio of the moon, Spica (right) and Mars. Credit: Soma Acharya

When moonlight returned, the stars fled and the Milky Way faded away in the lunar glare … until the next eclipse in October! Thank you everyone for sharing your images. I also encourage you to continue to share your impressions in the Comments section below.

The moon in partial eclipse along with Spica appear to remain still as a flag flaps in chilly winds in downtown Duluth, Minn. Credit: Bob King

I couldn’t resist. During total eclipse the sky became so dark the Milky Way sparkled across the eastern sky. After totality, it faded away. Credit: Bob King

Closeup of the moon near mid-eclipse. The top or northern half of the moon is darker than the bottom because it’s closer to the center of Earth’s umbral shadow. Also, the bottom of the moon is covered by more of the lighter-toned lunar highlands versus the “sea-heavy” northern half. Credit: Bob King

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.

Total lunar eclipse tonight! Updates – weather – live streaming

Beautiful sequence of the July 16, 2000 total lunar eclipse from Maui, Hawaii showing partial eclipse (upper left), totality (middle) and the return to partial eclipse at right. Credit: Fred Espenak

I’m excited. Beginning late tonight and continuing into the small hours tomorrow morning, skywatchers across the Americas will have ringside seats for one of nature’s most unique and colorful celestial events – a total eclipse of the moon.

The satellite view at 3:15 p.m. CDT this afternoon shows lots of clouds across the eastern half of the country. Clouds across the central and southwestern parts of the U.S. are expected to depart by eclipse time. Expect clear skies in those regions, partly cloudy conditions in the north central U.S. and overcast in the eastern third of the country. Credit: NOAA

Anyone hoping to see the eclipse will be paying attention to the local forecast. Weather really can mess with your head. While you can perform chemistry experiments clear or overcast, astronomy requires the fickle cooperation of Mother Nature. Remember last month’s widely-publicized occultation of Regulus by the asteroid Erigone? One of the rarest events to occur in years, clouds, snow and rain made sure that no one – not a single person to date – got to see it.

Tonight’s cloud cover forecast map. Dark green is clear, white is cloudy. Click to see the latest version. Credit: The Weather Channel

Today’s satellite weather map shows widespread clouds across the eastern third of the country but clear or clearing skies will be the rule across the western and central U.S. To get a local forecast, click HERE and enter your zip code or city name.

You can also consult Attila Danko’s Clear Sky Chart. Type in your city to get a detailed cloud/transparency forecast I’ve found to be surprisingly accurate.

During a total lunar eclipse, the moon moves into Earth’s shadow, becomes darkened and then exits out the other side and gradually returns to full brightness. Sunlight filtered and bent by Earth’s atmosphere spills into the shadow cone and colors the moon a coppery red. From the outer shadow – the penumbra – Earth only partially blocks the sun. That’s why the penumbral shadow isn’t nearly as dark as the umbral.  Credit: Starry Night

Just to refresh, a lunar eclipse occurs when the sun, Earth and moon are precisely lined up in a row at the time of full moon. Watching the moon slowly disappear will make even those who don’t pay much attention to the sky turn to look. The event begins with a brilliant full moon that disappears by degrees into the shadow until it hangs suspended among the stars like a dark cherry. Beautiful!

If you get skunked by bad weather, several organizations will be streaming the eclipse live. Here’a s few to check out:

* NASA TV live  – Commentary and coverage begin at midnight CDT Tuesday morning

* NASA Flickr for tagging, sharing images

* SLOOH – Coverage begins 1 a.m. CDT

* Virtual Telescope Project begins 1:30 a.m. CDT

Simulated binocular view of the moon only about a degree from the bright star Spica ten minutes before the start of total eclipse. Stellarium

Use a tripod-mounted camera to photograph the moon during the partial phases with exposures ranging from 1/250 (bright moon) to 1/8 second (closer to totality) with the lens opened to f/5.6 – f/8.

Increase your exposure to 4-5 seconds (or longer – depends on how dark this eclipse will be) and set your lens aperture to f/4 – f/5.6. These are general guidelines using ISO 400. As always, experiment.

I know there are lots of places to share images these days, but if you get one you like, I’d be happy to post it here on Tuesday. Just send an e-mail to rking@duluthnews.com with ‘Eclipse photo’ in the subject box. Thanks!

Below is a table with the times for all key eclipse events across the four major U.S. time zones beginning with the first hint of shading from Earth’s outer shadow, the penumbra. And here’s a link to more eclipse information.
Eclipse Events                     EDT             CDT                 MDT                PDT

Penumbra visible 1:20 a.m. 12:20 a.m. 11:20 p.m. 10:20 p.m.
Partial eclipse begins 1:58 a.m. 12:58 a.m. 11:58 p.m. 10:58 p.m.
Total eclipse begins 3:07 a.m. 2:07 a.m. 1:07 a.m. 12:07 a.m.
Mid-eclipse 3:46 a.m. 2:46 a.m. 1:46 a.m. 12:46 a.m.
Total eclipse ends 4:25 a.m. 3:25 a.m. 2:25 a.m. 1:25 a.m.
Partial eclipse ends 5:33 a.m. 4:33 a.m. 3:33 a.m. 2:33 a.m.
Penumbra visible  ——– 5:10 a.m. 4:10 a.m. 3:10 a.m.

Lunar eclipse will give NASA moon orbiters the shivers

Artist’s view of Earth eclipsing the sun next Tuesday morning April 15 as seen from the Lunar Reconnaissance’s Orbiter’s perspective. For several hours, it and NASA’s LADEE dust explorer will be cut off from sunlight. Back on Earth, we see the moon slide into our planet’s shadow. Credit: NASA

While we’re all bundled up for next Monday’s late night total eclipse of the moon, NASA will be taking special precautions to ensure its two moon probes survive the deep chill they’ll experience when the moon dives into Earth’s shadow.

NASA’s LRO has been orbiting, mapping and studying the moon since 2009. Credit: NASA

The Lunar Reconnaissance Orbiter (LRO), launched in 2009, has spent the past four-plus years photographing and mapping the moon in great detail from an orbit dipping as low as 31 miles (50 km). One of its goals is to determine future lunar landing sites. The craft also examines the moon’s radiation environment and maps the concentration of hydrogen – the main ingredient of water – across the globe. Hydrogen “hot spots” imply potential locations of water ice beneath the surfade or bound to moon rocks.

LRO will orbit the moon twice in Earth’s shadow. All instruments will be shut down since they would otherwise drain the batteries which can’t recharge without sunlight. Credit: NASA

LRO depends on sunlight to keep its batteries charged and instruments running. During the upcoming lunar eclipse, the moon will be either partially or fully within Earth’s shadow for several hours. With no sunlight reaching the probe’s solar panels, recharging the batteries isn’t possible.

To prevent damage to the either instruments or batteries, NASA plans to shut down all of LRO’s science instruments next Monday night for the duration of the eclipse. As soon as the event is over, the sun will slowly recharge the batteries and mission control will bring everything back online.

While LRO’s no stranger to eclipses,this time the spacecraft will have to pass through the complete shadow twice before the eclipse ends – longer than in any previous event.

“We’re taking precautions to make sure everything is fine,” said Noah Petro, Lunar Reconnaissance Orbiter deputy project scientist. “We’re turning off the instruments and will monitor the spacecraft every few hours when it’s visible from Earth.”


Understanding lunar eclipses

During other briefer eclipses, scientists have used the opportunity to study how the moon’s surface cools during these events, shedding light on the composition of the lunar crust. During the June 15, 2011 eclipse, temperatures on some areas of the moon dropped 180 degrees F compared to sunny, pre-eclipse conditions.

While LRO is expected to emerge from the shadow with flying colors, the forecast for NASA’s Lunar Atmosphere and Dust Explorer (LADEE) spacecraft is sketchy. The probe was never designed to withstand hours in the deep freeze of a shadowed moon.

“The eclipse will really put the spacecraft design through an extreme test, especially the propulsion system,” said Butler Hine, LADEE project manager.

Prior to impact on or before April 21, ground controllers at NASA’s Ames Research Center in Moffett Field, Calif., are maneuvering the spacecraft to fly approximately 1 to 2 miles (2-3 km) above the lunar surface to gather science measurements at the lowest altitude possible. Credit: NASA

LADEE (pronounced ‘laddie’) has been circling the moon studying dust in its extremely rarefied atmosphere since last fall. Much of the dust sputters off the surface during small meteorite impacts. If it survives the eclipse, LADEE will perform additional week of science before the mission is terminated. Rather than just shutting the probe off, mission control will direct it to crash into the moon near on or around April 21. LRO will locate study the impact site when it makes its next flyover a few months later.

Meanwhile, NASA invites you to  “Take the Plunge Challenge” and guess  what date LADEE will slam into the surface. Winners will be announced after impact and e-mailed a commemorative, personalized certificate from the LADEE program. The submissions deadline is 5 p.m. CDT tomorrow April 11.

For more information on the April 14-15 total eclipse of the moon including viewing times for your time zone, please see my earlier blog.

Brilliant Mars opening act for upcoming total lunar eclipse

Brilliant Mars shines atop dimmer Spica in the constellation Virgo in this photo taken Sunday night April 6. The planet now rises at sunset and is easy to spot around 9:30 p.m. in the southeastern sky. Yes, we still have almost 4 feet of snow here in Duluth, Minn. Credit: Bob King

Mars reaches opposition today, its closest approach to Earth since Dec. 2007 and the brightest we’ve seen it since 2012. What a sight it’s become. Last night, while walking our respective dogs, my daughter took one look at the gleaming pink-orange “star” in the southeastern sky and knew immediately it was Mars.

About every two years, Mars and Earth line up on the same side of the sun at opposition. Because Mars’ orbit is eccentric (less circular than Earth’s) the two planets are closer at some oppositions than others. This year’s opposition is a relatively distant one. Illustration: Bob King

While it sounds like an act of defiance, opposition refers to Mars being on exactly opposite side of the sky as the sun. The planet rises at sunset this evening and sets when the sun pops up tomorrow morning. Not only is Mars out all night long, but being opposite the sun, it’s paired up closely with Earth on the same side of the sun as shown above.


One full rotation of Mars on April 8 created by Tom Ruen. North polar cap at top.

That’s why Mars is so doggone bright – it’s close! Of course we know that’s a relative term in astronomy. Today the Red Planet is 57.7 million miles away, which sounds rather terribly far. But keep in mind that it can be up to 249 million miles away. So yes, Earth and Mars are practically neighbors … for a little while. The same orbital motions that brought them together will also move them farther apart in the coming months.

Now here’s the kicker. Because the orbits of Earth and Mars aren’t perfect circles, the two planets are actually closest on April 14, six days past opposition. That’s the same night as the total eclipse of the moon. Even better, the moon will only be a “fist” away from the planet. What a sight they’ll make – two red orbs aglow in the southern sky.

Mars outshines its neighbors Spica and Arcturus in the east and is ever so slightly brighter than magnitude -1.46 Sirius off to the southwest. The map shows the sky around 9:30 p.m. local time tonight. Stellarium

The Red Planet far outshines the nearby stars Spica and Arcturus and at magnitude -1.5 glows a hair brighter than Sirius, the brightest star in the entire sky. While similar in brightness, their colors are dramatically different. Compare the two and tell us what you think.

One side of Mars, the side turned toward the Americas during the best observing times this week, shows relatively few features. Use the map below to help you identify other dark markings as they rotate into view in the coming days and weeks. North at bottom. Credit: Mark Justice

Mars won’t appear bigger or brighter until its next opposition in May 2016 so take a look at this miniature “eye of Sauron” beaming in the south the next clear night.

If you have a telescope, use a magnification of 150x or higher to look for the planet’s very tiny north polar cap (it’s summer there and the cap has shrunk!) and other dark markings on its surface. This week, the planet’s “blank” hemisphere is presented for observers in the Americas. Be patient. The more obvious features like Mare Erythraeum, Syrtis Major and Mare Acidalium will soon rotate into view (see map below).

Complete Mars map showing many more features. Click to learn more about Mars’ upcoming opposition. Credit: Association of Lunar and Planetary Observers (A.L.P.O).

 

Seven ways to savor the upcoming total eclipse of the moon

Next Monday night April 14-15, skywatchers across much of North and South America will get to see a total eclipse of the moon. Lunar eclipses last for hours and can be safely viewed with the naked eye. This photo was taken of the June 2011 eclipse. Credit: Muhammed Mahdi Karim

It’s been too long. The moon last slipped into Earth’s shadow for North America in Dec. 2011. Next Monday night’s eclipse will end the current dry spell and make for a thrilling night out.

Map showing where next Monday night’s (April 14-15) eclipse will be visible. The western hemisphere has prime viewing seats. Credit: Fred Espenak

This eclipse is the first of four total lunar eclipses spaced about six months apart that will be visible across most of the Americas. The others occur on Oct. 8 this year, April 4, 2015 and Sept. 27, 2015. This particular sequence of four total lunar eclipses with no partials in between is called a ‘tetrad’. While we all hope for clear skies, if the weather’s uncooperative next week, you won’t have to wait long for another eclipse.


Eclipse tetrads explained

Lunar eclipses unfold slowly, lasting up to five hours. Unlike a total solar eclipse, where the sun disappears at most a few minutes, totality during a lunar eclipse can easily last more than an hour, giving you lots of time to enjoy the spectacle.

The only downside will be the late hour. Try to get some shuteye early as most of the eclipse happens after midnight in the wee hours Tuesday morning.

Because the moon’s orbit is tilted 5 degrees, the full moon normally misses the cone of shadow cast by the Earth and we see no eclipse. But several times a year, the moon’s orbit intersects Earth’s at the time of full moon and we see an eclipse. The Credit: Wikipedia

Lunar eclipses occur during full moon when the sun, Earth and moon line up in a neat row, and the moon passes into the shadow cast by our planet. You’d think eclipses would happen every full moon, but they don’t because the moon’s orbit around the Earth is tipped 5 degrees to Earth’s orbit around the sun.

The moon’s tipped orbit (red) is the reason we only get occasional eclipses at full moon. Most of the time the moon is either a little above or below the ideal alignment. Credit: Bob King

The moon spends most of the time above or below the plane of Earth’s orbit. And since Earth casts a shadow across its orbital plane, a lunar eclipse can only happen if the moon happens to be crossing that plane at the same time it’s full. That’s why eclipses are such a now and again thing.

While total solar eclipses are only visible along a narrow strip of land or ocean, a total lunar can be seen across half the globe wherever the sky is dark and the moon is up.

The moon’s past from west to east (right to left) across the dual shadow cast by Earth. The diagram shows key times (CDT) during the eclipse listed in the table below. Credit: Fred Espenak with additions by the author

Earth’s shadow is composed of two nested components – the inner umbra, where the Earth completely blocks the sun from view, and an outer penumbra, where the planet only partially blocks the sun. Because the penumbra is a mix of shadow and sunlight, it’s nowhere near as dark as the umbra.

An eclipse is divided into stages beginning with the moon’s entry into Earth’s lighter penumbral shadow. Most of us won’t notice any shading at all until about a half hour in, when the moon is deep enough inside to reveal a subtle darkening along its eastern edge. The table below lists the times for each stage of the eclipse across the four time zones:

Eclipse Events                     EDT             CDT                 MDT                PDT

Penumbra visible 1:20 a.m. 12:20 a.m. 11:20 p.m. 10:20 p.m.
Partial eclipse begins 1:58 a.m. 12:58 a.m. 11:58 p.m. 10:58 p.m.
Total eclipse begins 3:07 a.m. 2:07 a.m. 1:07 a.m. 12:07 a.m.
Mid-eclipse 3:46 a.m. 2:46 a.m. 1:46 a.m. 12:46 a.m.
Total eclipse ends 4:25 a.m. 3:25 a.m. 2:25 a.m. 1:25 a.m.
Partial eclipse ends 5:33 a.m. 4:33 a.m. 3:33 a.m. 2:33 a.m.
Penumbra visible  ——– 5:10 a.m. 4:10 a.m. 3:10 a.m.

During a total lunar eclipse (seen on Earth) an astronaut on the moon would instead see the Earth cover the sun, its atmosphere aglow with the combined light of all the sunrises and sunrises “leaking” around the rim of the planet. The light would bathe the moonscape in deep orange light. Stellarium

Partial eclipse begins when the moon treads within the dark umbra. Nibble by nibble the shadow eats away at the lunar disk. When only a sliver of the moon remains in sunlight, you’ll notice the shadowed portion glowing an eerie red or deep copper. To understand why, imagine an astronaut on the moon looking back at Earth during the eclipse.

During the next Tuesday morning’s eclipse, the moon will be just 1.5 degrees from Spica and not far from the planet Mars in the southern sky. Don’t forget to give Saturn a nod, located about two “fists” to the left of the moon. Stellarium

From her perspective, as the Earth passes in front of the sun, it’s surrounded by a glowing red-orange ring of light. Our atmosphere bends the light from all the sunrises and sunsets around the planet’s circumference into the umbra, coloring the moon red. Earth’s shadow isn’t really black after all but more a deep rusty red. Back on Earth, the moon will hang like a ghostly amber globe near the bright star Spica.

After mid-eclipse, the moon slowly exits the Earth’s shadow and performs the whole show in reverse, transitioning back to partial eclipse and finally exiting the penumbra.

Different aspects of a total lunar eclipse from start to near finish photographed in Hefei, China on Dec. 10, 2011. Credit: Reuters

You can take in the eclipse as casually as you like, but are seven cool things you might like to watch for:

#1 – When will you detect the first hint of penumbral shading? Keep an eye on the eastern (left) side of the moon for a “dented” appearance.

#2 – What color and how bright is the totally eclipsed moon? Depending upon the aerosol content of the atmosphere (greatly affected by volcanic eruptions), eclipses range from bright copper to dark brown and even black. Try rating this one on the traditional Danjon scale where “4″ is bright and “0″ is nearly invisible.

#3 – Watch for “the night within the night” phenomenon. If you thought it was dark out at the start of the eclipse, you’ll be amazed at how inky the landscape becomes during totality. As the eclipse progresses, the stars and Milky Way return to view.

#4 – With the entire moon darkened during totality, it will be relatively easy to watch it block or occult any star within its path. Many stars ranging from magnitude +8 and 12 will be occulted when viewed through small to medium telescopes. Click HERE for stars and times.

#5 – Binocular and telescope users should also look for a blue tinge to the encroaching umbral shadow as it slowly envelops the moon caused by light refracted by the upper atmosphere’s ozone layer.

#6 – Variation in the moon’s brightness. The top half will be closer to the center of the umbra and appear darker than the bottom. How obvious will this be?

#7 – Bring home a souvenir with your camera. If you have a telescope, you can hold a cellphone over the eyepiece to get great shots of the bright phases. During total eclipse, longer exposures of 1 to 10 seconds are necessary. For that you’ll need a tripod and a camera that can shoot time exposures. Telephoto lenses will pump up the moon’s size, but even a standard lens can do a great job of recording the sunset-colored moon in a landscape setting. Set your lens to its widest-open setting (f/2.8, 3.5) and expose 10-30 seconds to include the scene.

 

See the space station this week / Jupiter and moon a sparkling sight tonight

One of the Expedition 39 crew members aboard the International Space Station photographed a curtain of aurora hovering over blue twilight over northeastern Kazakhstan recently. Click to enlarge. Credit: NASA

The International Space Station (ISS) returns this week to highlight the evening sky. Outside of Venus and the moon, the ISS is the brightest, star-like object in the nighttime sky. It orbits from west to east, the same direction the Earth rotates, and crosses the sky in about five minutes. At an altitude of about 250 miles, the station orbits above most of the auroras we see which is why astronauts get such cool photos of the northern and southern lights from orbit.

Expedition 38 photo of the Kavir Desert in Iran taken with a 200mm lens looks more like swirly water than rock formations. The lack of soil and vegetation allows the geological structure of the rocks to stand out. According to geologists, the patterns result from the gentle folding of numerous, thin, light and dark layers of rock. Later erosion by wind and water cut a flat surface across the folds exposing their internal structure. Click to enlarge. Credit: NASA

The new evening observing season begins for many locations across the northern hemisphere with passes happening once or twice a night. To watch the space station, go out a couple minutes before it’s expected to appear and look for a pale yellow “star” brighter than any other moving from west to east across the sky.

You might be able to also see the Progress 54 cargo craft in the coming week after it undocks with the ISS tomorrow morning and before its destructive re-entry over the Pacific Ocean on April 18. I’ll have viewing tips and times when they’re available. The departure makes way for the arrival of Progress 55 on April 9, which will deliver almost 3 tons of food, fuel and supplies.

Flight Engineer Oleg Artemyev looks at the Earth through the windows of the International Space Station’s cupola this past week. The Expedition 39 crew has been busy with biomedical research this past week focusing on how the immune system responds to living in space. Click to learn more. Credit: NASA-TV

Click HERE or HERE to find times and directions to look for your town. I’ve included a list of times when the ISS will be visible for skywatchers in the Duluth, Minn. U.S. region at the end of this article.

The half moon will be in conjunction with the brilliant planet Jupiter this evening. The map shows the sky facing southwest around 9 p.m. local time. Stellarium

While you’re waiting for the six-man crew of the station to fly over your house or apartment, don’t forget to look up at the first quarter moon in the constellation Gemini tonight. Just “three fingers” or 5 degrees above it shines Jupiter. They’ll make an eye-catching pair for sure.

The moon tonight as seen from North America. How many dark seas or lunar maria (MAH-ree-uh) can you see? Credit: Christian Legrande, Patrick Chevalley / Virtual Moon Atlas

For another easy observing project, try spotting all five of the lunar “seas” visible tonight. These largish, dark spots that form the face of the man in the moon are plains of now-solidified basaltic lavas that erupted 3-3.5 billion years ago in the basins of what were then enormous impact craters. They’re rich in iron and slightly younger than the lighter, older lunar highlands (white regions) which makes them appear darker.

Funny, isn’t it, that all that lunar tranquillity and sweetness should be marred by “crisis”, but I guess this half of the moon serves as a metaphor for life.

Space station viewing times for Duluth, Minn. region:

* Tonight Sun. April 6 starting at 8:29 p.m. Low pass across the south-southeastern sky. Max. elevation: 18 degrees (10 degrees equal one fist held at arm’s length against the sky)
* Mon. April 7 at 9:15 p.m. high across the southern sky. Brilliant pass with max. elevation of 66 degrees
* Tues. April 8 at 8:26 p.m. (high in the south at 42 degrees) and again at 10:03 p.m. across the northwestern sky. Max. elevation: 48 degrees.
* Weds. April 9 at 9:14 p.m. high in the northern sky. Max. elevation: 63 degrees

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.”

Watch the moon gobble up some Hyades Thursday night

The moon is shown about 15 minutes before passing in front of Delta 1 in the Hyades star cluster for Duluth, Minn. this Thursday night April 3, 2014. The green arrow shows the moon’s direction of motion. Star magnitudes are: Delta 1= 3.8, Delta 2 = 4.8 and Delta 3 = 4.3. Created with Chris Marriott’s SkyMap software

Here’s something very fun and enjoyable to see with a small telescope or even a pair of 50mm binoculars. This Thursday night across North America the crescent moon’s dark, earth-lit edge will cover up to three stars in the familiar V-shaped Hyades star cluster.

Never heard of the Hyades? Its next door neighbor is the Pleiades cluster, the one shaped like a little dipper and better known as the Seven Sisters. At just 153 light years away, the Hyades is the closest star cluster to Earth, one of the reasons it covers a nice-sized chunk of sky and is plainly visible to the naked eye. The bright orange giant Aldebaran helps to complete the cluster’s nifty V-shape, but isn’t a true member; the star simply happens to lie along the same line of sight.

Time exposure of the Hyades star cluster shows bright Aldebaran (left) and many, many stars. Although the “three Deltas” are the highlights, the moon will cover up other fainter cluster members as well. Credit: Bob King

The moon passes near the Hyades every month but only passes through the cluster for a six-year period every 18.6 years, the time it takes the moon’s orbit to precess or cycle once around the ecliptic. This last happened from 1995 to 2001. We begin a new cycle this year.

The sun’s gravity causes the moon’s orbit to slowly rotate westward once every 18.6 years. The nodes in the diagram are the two places where the moon’s tipped orbit intersects the plane of Earth’s orbit called the ecliptic. The line connecting the nodes makes a complete circle every 18.6 years. Credit: Prof. Marcia Rieke

The sun’s gravitational pull on the moon forces its orbit to slowly rotate westward. Combined with the 5-degree tilt of the lunar orbit, the moon’s track across the zodiac constellations varies continuously to the attentive observer over an 18.6 year cycle. During part of that cycle, it crosses the Hyades; during another part it swings north and misses them.

Thursday night the dark edge of the moon will cover one, two or even three bright Hyades depending where you live. Eastern and central U.S. and Canadian observers will see the moon blot out Delta 1 followed by Delta 2 for observers in the northern U.S. and Canada. The final bright star, Delta 3, slides behind the moon for much of the central and western U.S. and Canada.

Because the moon is close to the Earth compared to the planets and stars, observers in different locations see it against a slightly different background of stars. Travel north in North America, the moon slides south. Travel south and the moon’s path shifts north.

By 10 p.m. CDT, the southern edge of the moon has covered Delta 2 and will soon cover Delta 3 as seen from Duluth, Minn. Occulted stars will reappear along the moon’s bright limb, where they’re much harder to see. For Duluth, Minn. U.S. the stars will disappear within a few minutes of 9:03 p.m., 9:56 pm. and 10:35 p.m. Created with Chris Marriott’s SkyMap software

To find out which stars and when they’ll be covered for your city or region, click the links for each below:

* Delta 1
* Delta 2
* Delta 3 

When you visit these sites, select the disappearance times of the star. Note that the times are given in Greenwich or Universal Time for April 4. Subtract 4 hours for Eastern, 5 for Central, 6 for Mountain and 7 for Pacific. For example, 2 hours UT April 4 = 9 p.m. CDT April 3.

The fun in watching occultations is to see how suddenly the star disappears when it touches the edge of the moon. Were there a substantial lunar atmosphere, it would gradually fade away instead. It’s also just plain cool to see the moon move in real time as it approaches and then blinks out the star.

Some of you will be able to see one or more of the Deltas graze the edge of the moon, popping in an out of view as they’re hidden by crater walls and mountains along the lunar profile.

Good luck!