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

Rendezvous with Rosetta’s comet – new 3-D simulator lets you be the pilot

A new interactive visualization of the Rosetta mission to Comet Churyumov-Gerasimenko. Go ahead and hit play – it’s live.

Up for an interplanetary ride along? Now you can with this fantastic new interactive model that tracks Rosetta’s 4.3 billion mile journey to comet 67P Churyumov-Gerasimenko.

While the embedded simulation above gives you a taste, be sure to visit the full-screen version for the full experience. You can simply play the movie from start to end or select from a list of mission highlights.

Simulator view of Rosetta in August when in orbit around the comet. Credit: INOVE

To interact with the model, simply click the screen. The action stops, allowing you to zoom in and out by scrolling. If you’d like to change your point of view and see Rosetta’s travels from above or below or the plane of the planets, hold down the mouse button and drag. Nothing to it. A live timeline at the bottom of the screen shows the date of each new maneuver.

The team at INOVE Space Models, the same folks that brought you the 3-D interactive solar system model and Comet ISON visualization, created the new model to help armchair astronauts enjoy and better understand Rosetta’s complex series of planetary flybys and the mission ahead.

Simulator view of Rosetta’s first Earth flyby- gravity assist in March 2005. The probe flew by Earth three times and Mars once to conserve fuel and send it beyond the asteroid belt to rendezvous with Comet Churyumov-Gerasimenko. Credit: INOVE

No single rocket was capable of sending the probe directly to the comet. Instead scientists sent it bouncing around the inner solar system on a series of close encounters with Earth and Mars. Rosetta buzzed Earth three times and Mars once. At each flyby, the spacecraft got a gravitational ‘kick’ that boosted its speed and shaped its orbit for the coming comet encounter. I’m reminded of a bee gathering nectar flower by flower to feed the next generation of bees.

To pocket all the gravitational nectar Rosetta needed, it ended up circling the sun four times, the reason its odometer will ping 4.3 billion miles by the time it reaches the comet. Consider that Pluto’s ‘only’ 3.6 billion miles away.

Scientists employed similar gravity assists to send the Voyager I and II probes from Jupiter to more distant Saturn, Uranus and Neptune back in the late 1970s-early ’80s.

This artist’s impression shows the Rosetta spacecraft and the comet’s nucleus and hazy coma at the time the Philae lander is dispatched this November. Credit: ESA

Launched in 2004, Rosetta will begin braking maneuvers near Churyumov-Gerasimenko in May and orbit it by August. On Nov. 11, the probe will dispatch a smaller craft named Philae that will land on the surface of the comet and study it close up. Plans call for Rosetta to scrutinize Comet C-G for a year centered on its closest approach to the sun.

I think you’ll really enjoy the new simulator, and I guarantee you’ll come away with a better understanding and appreciation of one of the boldest missions ever attempted.

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.”

Norwegian skydiver has close shave with falling meteorite – and gets video!

Complete video/story of the possible meteorite that flew by Norwegian skydiver Anders Helstrup. You’ll see the meteor in real time at 1:54 and in slo-mo at 4:25.

Thought you’d like to see this remarkable video of what may be the first-ever recording of a meteorite tumbling through the sky right in front of a human being! Norwegian skydiver Anders Helstrup didn’t even know he’d recorded it with the two cameras fixed to the back and front of his helmet during the dive made back in 2012, but upon later review, he discovered a fast-moving, apple-sized rock flying through the footage.

While you’ve no doubt seen pictures and videos of meteors streaking through the atmosphere, no one has ever recorded the next-to-impossible “dark flight” phase of a meteorite. Somewhere between 9 and 12 miles (15-20 km) high, most incoming meteoroids slow down, cool and cease to make the air glow. From here, they continue to drop until reaching speeds of 200-400 mph before striking the Earth. While that sounds fast,consider that a typical meteoroid first enters the atmosphere between 25,000 and 160,000 mph!

A frame from the video showing the possible meteorite tumbling rapidly by within feet of Anders Helstrup. Had he jumped a second or two earlier he would most likely have been killed by the speeding stone. Credit: NRK

While it’s certainly not beyond the realm of possibility to capture a falling, non-luminous meteor on camera, the odds are extremely remote. That’s why many think the story and video are either a monumental April Fools’ joke or a deliberate hoax. Hard to blame them with all the goofy stuff spun as truth on the Web.

However, the staff at Universe Today got in touch with Norwegian physicist Pal Brekke. He confirmed that the story was true and kept secret for two years so Helstrup and a small band of scientists and meteorite hunters could track the meteorite down. Using the videos, they calculated a trajectory and possible landing locations. Unfortunately, the fall area is wooded and braided by streams. Lots of places for a meteorite to hide from curious eyes.

After two years of hunting and coming up short, the video was released in hopes of recruiting more people to the effort. Skeptics would argue instead that scientists fell for a good story and are wasting their time looking.

Frame grab from the video showing geology professor describing the possible meteorite. The fractured side faces to the left. The pale gray color could be a clean break to the lighter interior of the stone or covered with a thin coating of secondary fusion crust. Credit: NRK

In the video (above) by Norwegian broadcaster NRK, geologist Hans Amundsen had no doubt it was a meteorite based on appearance alone. The stone has one flat side, likely due to fracturing seconds earlier in its flight, and the other half is rounded from heating and melting due to air friction. A fracture also implies there might be more than one fragment out there.

Morton Bilet, Norwegian meteorite expert, organized a search near Rena in eastern Norway where the object fell. Bilet is “100% certain” the video is not a fake, but whether it’s a space rock or something else, neither he nor anyone else knows for sure. Hopefully more searches are planned for this spring. For more information, photos and graphics check out the Norwegian Meteorite Society and NRK

Frame grab from a security camera video of the largest piece (circled) of last year’s Russian fireball falling into Chebarkul Lake. Click for a video, and be sure to also see the video below.

UPDATE April 4: While not photographed by a human being, I’d almost forgotten about the security camera video of the final moments of dark flight of the largest hunk of the Chelyabinsk meteorite crashing into the ice on Chebarkul Lake recorded last Feb. 15.
Video of clips of the Russian meteorite fall Feb. 15, 2013. Go to 10:30 to see a quick view of the meteorite falling into the lake.

Stardust captures 7 precious pieces of cosmic dust

Weighing in at 3.1 trillionths of a gram, the “Orion” interstellar dust particle (upper right) was captured by the Stardust spacecraft. The particle contains aluminum (red), iron (green) and magnesium (blue). Credit: NASA and Anna Butterworth at the Advanced Light Source Lawrence Berkeley National Laboratory (inset)

Definition of finding a needle in a haystack? 100 million searches by over 30,000 people to find seven “probable” interstellar dust particles in debris collected by NASA’s Stardust spacecraft. These minute motes are not of this solar system but alien dust from intergalactic space.

The discoveries top a 7-plus year search by the Stardust team and thousands of volunteers to track down samples of the primordial dust wafting through interstellar space – the same stuff that long ago congealed to form the sun and planets.

I should be careful of my terms. These bits of cosmic debri, a thousandth the mass of comet dust, tear across space at nearly 10,000 mph (15,000 km/hr). They’re also incredibly sparse. Catching even one requires VERY delicate handling and a bit of luck.

Aerogel is a unique substance with a spongy, airy structure excellent for capturing high speed particles like comet  and interstellar dust without damaging them. Credit: NASA

Scientists used one of the most bizarre substances ever invented to grab the speedy dust particles without damaging them: aerogel. Sometimes called “frozen smoke”, aerogel is a pale blue, airy substance made of 99.8% empty space webbed with silica. Particles traveling thousands of miles an hour can safely speed through aerogel until they slow down and bury themselves within its porous, sponge-like texture. A high tech butterfly net as it were.

The collector tray mounted on Stardust featured many small trays filled with aerogel for collecting comet and dust between the stars. Credit: NASA

The Stardust spacecraft, launched in 1999, accomplished its main objective of collecting dust particles from the misty atmosphere or coma of comet Wild 2 and returning them in a reentry capsule when the probe passed by Earth in 2006.

That’s not all. For a total of 200 days in 2000 and 2002, Stardust stuck out its tennis racket-sized collector tray to snatch bits of interstellar dust that sifts across the solar system as the sun and planets orbit the galaxy at 4.3 miles per second.


A Stardust researcher examines a centimeter (about 1/2 inch) thick block of aerogel for interstellar dust particles. Credit: NASA

Problem was, there were so many pieces of aerogel to examine for tracks and possible particles, the Stardust team knew it would take ages unless they got help. So they went public and set up the Stardust@home website.

Regular folks like you and I were offered (and still have) the opportunity to examine microscopic images of aerogel slices on our computers and look for tracks left by debris from alien stars and Milky Way gas clouds. 30,714 people signed up, and after years of work doing one of the things humans do best – recognize patterns – seven possible candidates were found.

Track and possible interstellar particle captured in aerogel. Credit: NASA

Two particles weighed in at just three trillionths of a gram; another came in so fast it left only a bit of residue. Four missed the aerogel but blasted microscopic craters in the surrounding aluminum foil, leaving traces of vaporized debris within the craters.

Track and closeup of a small particle captured from Comet Wild 2 by Stardust. Credit: NASA

To confirm that the specks are truly from beyond the planets, researchers must now transfer them from the aerogel to instruments for close examination. They’re so incredibly small, great care must be taken not to lose the precious pieces.

If you’d like to learn more and become a “duster” yourself, the name given to those teasing tracks from photos, click over to Stardust@home.  Bruce Hudson of Ontario, Canada discovered the first particle and was given the privilege of naming it. He chose “Orion”, and it’s featured in the photo at the top of this article.

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!

April Fools’ Night aurora? / Wee crescent ‘smiles’ again in the west

If the aurora does show tomorrow night, it usually begins as a quiet, pale green arc like this one low in the northern sky. Often the arc will double and sprout rays if the display becomes more active. Credit: Bob King

This will probably turn out to be an April Fools’ joke, but space weather forecasters are predicting a 25% chance of minor aurora storms overnight April 1-2 when several particle blasts from the sun are expected to pound on Earth’s magnetic door.

That’s the forecast for skywatchers in mid-latitudes; polar folks will see a 60% chance of a major, sky-filling aurora. Be sure to check the skies starting tomorrow evening. The crescent moon sets early and won’t interfere with even the faintest auroras.

A very thin crescent moon appears low in the western sky this evening about a half hour after sunset. Stellarium

Speaking of the moon, you can watch a one-day-old crescent put on a smile starting about a half hour after sunset tonight March 31. Find a place with a wide-open view to the west northwest and look a short distance above the horizon a most delicate crust of moon.

We see the moon tipped on its back in spring because of the much steeper angle its path makes to the western horizon at dusk compared to fall. The planets, sun and moon all track on or near the same path called the ecliptic, which defines the plane of the solar system. Created with Stellarium

During northern hemisphere spring, the moon’s path across the sky makes a steep angle to the western horizon at dusk. That’s why it’s tipped over on its back and resembles a smile. In early fall, the crescent moon’s path intersects the evening horizon at a very shallow angle, tipping the moon upright on its southern cusp.

February’s crescent moon hovers over a snow-covered road. Credit: Bob King

Later this week, a thicker crescent moon will cross the Hyades star cluster, temporarily blocking up to three of its bright stars. Stay tuned – I’ll post a guide on how to watch it tomorrow.

Strong solar flare creates rare magnetic ripples in Earth’s atmosphere

Energy stored in twisted magnetic fields above sunspot group 2017 was released a as a strong X1-class flare at 12:52 p.m. CDT March 29. Powerful X-rays from the flare sent magnetic currents through Earth’s upper atmosphere minutes later. Credit: NASA

An fast, intense X1-class solar flare yesterday afternoon not only blasted a cloud of solar electrons and protons into space but also sent magnetic ripples across Earth’s upper atmosphere creating what astronomers call a magnetic crochet.

X1 solar flare on March 29, 2014

Normally it takes an average of 4 days for a cloud of fast moving solar particles called a coronal mass ejection or CME to reach the Earth. Fast ones moving at 620 miles per second (1,000 km/sec) arrive in about 42 hours. But energy levels rose so rapidly in yesterday’s flare that Earth’s atmosphere was affected only minutes after the onset of the storm.

How could something from the sun get here so fast? Well, it does everyday. Sunlight traverses the 93 million miles between Earth and sun in just 8.3 minutes. There are many forms of light from radio waves to visible light to X-rays. Flares are so powerful they kick out waves of light energy across the entire spectrum from radio to deadly gamma rays.

The Earth’s ionosphere, divided into layers D, E and F, begins about 37 miles high and extends nearly to space. Solar and cosmic radiation strips electrons from atoms turning them into ions, which respond to electrical and magnetic fields. Credit: Rutherford Appleton Laboratory

A burst of X-rays from sunspot region 2017 arrived 8.3 minutes after the blast and increased the electrical conductivity in the D and E layers of Earth’s ionosphere by stripping electrons from the atoms there, making electric currents flow more easily. Because moving electrical currents create magnetic fields, the flare caused a sudden jump or ripple of magnetic energy to pulse through the ionosphere. As the flare subsided, those layers returned to normal.

You can see for yourself how an electric current creates a magnetic field by holding a compass near an operating electric shaver or hairdryer. As you move the shaver back and forth, the compass needle will swing wildly as it responds to the local magnetic field created by the flow of electrons in the current.

Even though we can’t see them, magnetic fields have very real effects.

Magnetic crochets are rare because they only occur during large flares that peak quickly. They’re also typically recorded at locations where the sun is overhead at the time of the flare.

Just one more way the sun touches our lives. As for the particles propelled by the flare, most of them took off northward of Earth but a glancing blow is expected around April 1 when Arctic observers may see a nice show of northern lights during their rapidly diminishing nighttime hours.

Dwarf planet ‘Biden’ hints at Planet X at solar system’s edge

Artist’s view of a remote icy asteroid with the sun in the distance. Astronomers recently announced the discovery of 2012 VP113, the most distant asteroid ever seen. Credit: NASA/JPL

Asteroids have been hot this week. Just days after discovering the first asteroid with rings, astronomers reported the discovery of a new dwarf planet that orbits farther from the sun than anything else ever seen. It’s called 2012 VP113, but the discovery team prefers the more playful ‘VP’ or ‘Biden’ for short.

Photographs of 2012 VP113 as it slowly moves across the sky. It was discovered with the new Dark Energy Camera at the National Optical Astronomy Observatory’s 4-meter (157-inch) telescope in Chile. Click to learn more about the instrument. Credit: Scott Sheppard / Carnegie Institution for Science

2012 VP113 gets no closer than 7.4 billion miles or 80 times Earth’s distance from the sun. That’s more than twice Pluto’s distance. But the mind reels when you realize that 2012 VP113 loops out to 44 billion miles (70 billion km) distance when at it most distant point from the sun plying an orbit that takes 4,000 years to complete!

Assuming average reflectivity, 2012 VP113 is 280 miles (450 kilometers) in diameter, potentially placing it in the dwarf planet category like Pluto and several other largish solar system objects too small to be planets but large enough for gravity to have crunched them into spherical shapes.

2012 VP113 moved between each image as seen by the red, green and blue dots. The background stars and galaxies did not move and thus their red, green and blue images combine to show up as white sources. Credit: Scott S. Sheppard/Carnegie Institution for Science

‘Biden’ joins the previous distance record holder, Sedna, as one of only two bodies found in the inner Oort Cloud, a reservoir comets, some of which eventually find their way into the inner solar system to the delight of skywatchers.

“The detection of 2012 VP113 confirms that Sedna is not an isolated object; instead, both bodies may be members of the inner Oort Cloud, whose objects could outnumber all other dynamically stable populations in the Solar System,” authors Scott Sheppard and Chadwick Trujillo wrote in their discovery paper, published this week in Nature.

Cross section of the solar system the familiar inner and outer planets plus the more distant Kuiper Belt and the remote Oort Cloud. Credit: NASA

The known solar system is divided into half a dozen zones: the inner, rocky planets which includes the Earth; the inner asteroid belt where the traditional rocky asteroids reside; the giant outer planets; the Kuiper Belt, reaching from 2.8-4.6 billion miles from the sun, that includes Pluto and countless other icy asteroids; the inner Oort Cloud that Sedna and ‘Biden’ call home and finally the remote outer Oort Cloud located between 5,000 and 100,000 times Earth’s distance from the sun.

Orbits of Sedna and 2012 VP113 are shown along with the Kuiper Belt and out planets (purple circles). The sun is at center. It’s empty out there! Dwarf planets Sedna and 2012 VP113 are the only known objects in the inner Oort Cloud. Credit: Scott S. Sheppard/Carnegie Institution for Science

Billions of icy, inert comets are believed to exist in this last, more remote region of the solar system. Disturbed by the gravity of passing stars, Oort Cloud comets can “drop in” to the inner solar system. Their orbital periods can easily be a million years or longer.

But back to 2012 VP113 and Sedna. Because only a tiny amount of sky has been examined for faint objects like these two planetary dwarfs,Trujillo and Sheppard estimate that some 900 objects with similar orbits and up to 620 miles (1000 km) across are still waiting to be found.

The total population of the inner Oort Cloud may be even larger than the inner asteroid belt and Kuiper Belt combined. Most intriguingly, some of these objects could be as big as Earth or Mars. Only their extreme faintness makes their discovery a painstaking process, says Sheppard.

View from the surface of the remote Oort Cloud planetoid Sedna, looking back towards the Sun and the inner Solar System. The view would be similar from 2012 VP113. Credit: NASA/ESA/ A. Schaller

The similarity in the orbits of Sedna, 2012 VP113 and several other objects in the Kuiper Belt suggests that an unknown massive body perhaps even larger than Earth exerts a gravitational influence on the bunch. But before Planet X aficionados jump out of their seats, don’t forget the results of NASA’s WISE satellite survey. Seeing the sky in infrared light, which can reveal even cold, dark objects at great distances across the solar system, nothing even close to a planet-sized object was discovered.

WISE’s two complete infrared sweeps of the sky found that no object the size of Saturn or larger exists out to a distance of 930 billion miles from the sun and no object larger than Jupiter exists out to 2.4 trillion miles. That doesn’t negate the possibility that something Earth-sized remains hidden in that profound darkness.

Who knows?? What’s perhaps most fascinating in all of this is how our view of the solar system has matured from nine planets to a much more complex place with room for many more possibilities than we might have imagined a generation ago.