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.

Curiosity rover revels in ravishing rocks at ‘the Kimberley’

A view of Curiosity’s new digs called ‘the Kimberley’, named for a wilderness region in Western Australia. Taken on April 11 it shows tilted sandstones separated by windblown sands. The hilly rim of Gale Crater is seen in the distance. Click to enlarge. Credit: NASA/JPL-Caltech

NASA’s one-ton Curiosity rover has beamed back thousands of photos of amazing landscapes within Gale Crater since landing in August 2012. And that’s after driving only 3.8 miles, probably the distance to the nearest grocery store for many of us.

The Kimberley seen from orbit with the rover’s path highlighted. Curiosity rolled into the new location around the 589th Martian day or “sol”. Scientists selected the area based on pictures and studies made from orbit showing it to be rich in different rock types all exposed in the same location. Credit: NASA/JPL-Caltech

Earlier this month, the rover entered the Kimberley, a rise within the crater dotted with three buttes – Mounts Remarkable, Joseph and Christine – that exposes several varieties of rock scientists are eager to study. The area will be the focus of exploration for weeks to come before Curiosity resumes its journey to the slopes of Mount Sharp, a broad peak that rises 3 miles (5 km) from the crater’s floor.

Sandstones on Mars near the Kimberley photographed on March 29, 2014. Click to enlarge. Credit: NASA/JPL-Caltech

The Kimberley is strewn with some of the most beautiful sandstones yet seen on Mars. Sandstones form when water or wind carries along grains of sand until depositing them in a layer at the bottom of a stream or on the ground as in a desert. Minerals within the pore spaces between the sand grains cement the grains together to create sandstone. Sometimes layers of deposited sand can build up one atop another helping to further compact the material into stone.

Differing degrees of resistance to erosion result in a stair-stepped pattern visible in this photo taken 1/4 mile northwest of the Kimberley on Feb. 25, 2014. Steeper steps result from more resistant rock, so the flat, tan surface (foreground) is a weakly resistant sandstone. The small steps to the right center are a bit more resistant, and the steeper steps near the top of the scene are even more resistant. Click to enlarge. Credit: NASA/JPL-Caltech/MSSS

Cement materials vary greatly. Clay minerals build sandstones that crumble with a rap of a hammer and more quickly erode in the Martian winds. Quartz cement creates a tougher rock more resistant to erosion. If you’ve ever marveled at the sight of a western, canyon-filled landscape, you’re seeing the varying resistance of sandstone to erosion at work. The same thing happens on Mars:

Another spectacular view of tipped and tilted sandstones with Mt. Remarkable in the distance photographed on April 11, 2014. Click to enlarge. Credit: NASA/JPL-Caltech

“A major issue for us now is to understand why some rocks resist erosion more than other rocks, especially when they are so close to each other and are both likely to be sandstones,” said Michael Malin of Malin Space Science Systems, San Diego. Malin added that variations in cement material of sandstones could provide clues to different types of wet environmental conditions in the area’s history.

Curious furrows are seen in the foreground in this photo taken at the Kimberley on April 3, 2014. Click to enlarge. Credit: NASA/JPL-Caltech/MSSS

At Yellowknife Bay, Curiosity’s last major waypoint, erosion had exposed both sandstones and a lower layer of mudstone that was once part of an ancient lake bottom. The rover will be tooling around the Kimberley for a while – why not join the exploration by periodically checking out the Mars raw image archive?

A conglomerate rock formation at the Kimberley formed of boulders and rocks that were transported from elsewhere – by river or glacier for instance – and cemented together. Click to enlarge. Credit: NASA/JPL-Caltech/ MSSS

Forbidding Planet: Scientists find remains of monster asteroid impacts on early Earth

Artist’s view of Earth several billion years ago during the Late Heavy Bombardment, when the planet is thought to have been battered by impacts of comets and asteroids. Credit: Chris Butler/SPL

Earth 3.5 billion years ago was a terrifying place. Picture a rocky landscape pounded by meteorites and asteroids with a surface resembling that of the moon. Volcanoes spewed water vapor but also a toxic mix of carbon dioxide, sulfur dioxide and methane. If you could whisk yourself back to this world by time machine, you’d need to be fully protected by a spacesuit and lucky enough to not get picked off by a falling space rock. Oh, and bring a boat too. Hot-water oceans likely covered a fair portion of the planet back then.


This time-lapse illustration of the Nice (pronounced ‘neece’) model of solar system evolution shows how outer planet migrations kick asteroids into the inner solar system

Scientists call the period from about 3.8 billion to 1.8 billion years ago the Late Heavy Bombardment (LHB), a time when the number of asteroids and their fragments pelting the inner planets and their moons spiked. Why then? No one’s absolutely certain, but the leading theory posits that the migration of the giant outer planets to their present positions “stirred the gravitational pot”, slinging boatloads of asteroids into the inner solar system, where they rained down on Earth and its neighbors in hellish monotony for millions of years.

Anyone with a small telescope can see resulting devastation to this day. Just take a long look at the moon’s battered and cratered surface and thank your lucky stars you’re around during a more peaceful time. Finding Earth’s craters is trickier because water and wind erosion, along with the continual recycling of much of our planet’s crust through plate tectonics, has erased much of our violent past.

The Vredefort Dome – these concentric hills, which rebounded after the impact that created Vredefort Crater – are what remains after an asteroid about 3-6 miles wide struck Earth 2 billion years ago. Credit: NASA

About 180 craters are known on Earth today, but we’re aware of only three resulting from the Late Heavy Bombardment. The oldest, estimated at 3 billion years old and 62 miles (100 km) wide, is also the most recently discovered. Found in western Greenland in 2012, all that remains of the impact are rocks rattled by the massive shock wave that penetrated 15 miles (25 km) deep within Earth’s crust.

You can still see the remains of the impacts that formed the 112-mile-wide (180 km) Vredefort Crater in South Africa, which is 2 billion years old, and the youngest LHB member, the 155-mile (250-km) Sudbury crater in Canada dated at 1.85 billion years.

Map of South Africa with the Barberton greenstone belt shown in red. Shock waves from the impact of an asteroid 3.26 billion years ago created telltale formations within the belt. No one knows yet where the impact happened.

Now, a group of scientists have announced they’ve found evidence for an even older impact, one that occurred 3.26 billion years ago and left its signature in a South African region known as the Barberton greenstone belt.

A recent press release describes the huge impactor as between 23 and 36 miles wide (37- 58 km). Colliding with the planet at 12 miles per second, the jolt delivered was bigger than a 10.8 magnitude earthquake and propelled seismic waves hundreds of miles through the Earth, breaking rocks and setting off other large earthquakes. Tsunamis thousands of feet deep swept across the oceans that covered most of the planet at that time.

A graphical representation of the size of the asteroid thought to have killed the dinosaurs (left), and the crater it created, compared to an asteroid thought to have hit the Earth 3.26 billion years ago and the size of the crater it may have generated. A new study reveals the power and scale of the event some 3.26 billion years ago which scientists think created geological features found in a South African region known as the Barberton greenstone belt. Credit: American Geophysical Union

“We knew it was big, but we didn’t know how big,” Donald Lowe, a geologist at Stanford University and a co-author of the study, said of the asteroid.

The collision would have blasted out a crater some 300 miles (500 km) wide, filled the atmosphere with fiery rock vapor and set the surface of the ocean a-boil. We’re talking serious cataclysm. Somehow life found a way through the heat and crater-punching to gift us with the rolling green hills, coral reefs and forests that characterize Earth today.

Table from the book “Near Earth Objects – Finding Them Before They Find Us” by Donald Yeomans showing average asteroid impact results and probabilities by size. Credit: Donald Yeomans

I try to imagine the dark days of the LHB to help me appreciate these calmer times. Yet we know in our gut – and in fact, thanks to probability – that we’ll never truly be out of the woods. Asteroids lurk in the deep that could one day cause a similar scenario. Don’t let it worry you too much – the chance of a 10-mile-wide space rock striking Earth is once every 89 million years. You’ve still got time to take a nap, catch a show and enjoy a few nights out on the town. Probably.

Auroras possible for northern U.S. overnight April 11-12

Aurora borealis shot on March 21, 2014 from Mt. Cleary outside of Fairbanks, Alaska with an 8mm fisheye lens. The Big Dipper is at top. Details: ISO 1600, 15-second exposure. Credit: John Chumack

While it’s mostly cloudy at my domicile, the sky above yours may be clear. If you live in the northern U.S. and southern Canada, take a look at the northern sky this early morning April 12. There’s a decent chance you might see the aurora borealis.

The Kp index shot up to “5″ or moderate storm Friday evening when the interplanetary magnetic field bundled up in the sun’s wind took a sharp dip southward. This usually allows the sun’s charged particles to enter Earth’s magnetic domain and spiral down into the upper atmosphere to spark auroras.

The auroral oval sags southward around midnight April 12 in this view based on satellite photos indicating some aurora could be visible in the northern U.S. in the early morning hours Saturday April 12. Credit: NOAA

Both the Ovation Auroral oval map and the POES satellite map of the auroral oval – that band of aurora around either pole – show it spreading southward with the visibility line crossing into northern Minn. and North Dakota.


Time lapse aurora near Fairbanks, AK. on March 26, 2014

There’s no guarantee activity will continue through the early morning hours but as of 1 a.m today (April 12) things look promising. We do have a moon tonight which could hamper viewing of faint auroras, but it’s no match for moderate to strong displays.

No matter what, it’s worth a look if you happen to be up late. Beleaguered by clouds like me? You can still enjoy this sweet video of northern lights made by Ohio astrophotographer John Chumack.

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.

Love at first sight – smitten by a cosmic diamond ring

Astronomers using the European Space Agency’s Very Large Telescope (VLT) in Chile captured this remarkable image of planetary nebula Abell 33. Created when an aging star blew off its outer layers, this beautiful blue bubble happens to be aligned with a foreground star, and bears an uncanny resemblance to a diamond engagement ring. Click to enlarge. Credit: ESO

Such a beautiful sight. You’ve got to love how nature works, creating masterpieces by happenstance. There’s no denying our pleasure in patterns and symmetry. I think it makes us feel connected to the cosmos when we perceive order and organization in what seems at times a chaotic universe. And what’s more iconic than a diamond ring?

Abell 33 and the star HD 83535 are located inside the red circle in the sprawling constellation of Hydra. Although the star is easily seen in binoculars, the nebula itself is a dim object only visible in larger amateur telescopes. Credit: ESO, IAU Sky & Telescope

The pretty blue bubble is the planetary nebula Abell 33 in the constellation Hydra the Sea Snake, which coils across the evening sky this month beneath Leo and Virgo. It’s located 1,500 light years away, while the diamond, a 7th magnitude star named HD 83535, gleams in the foreground only half as far.

The sun spends most of its lifetime slowly burning hydrogen in its core into helium. As it ages, the sun will expand into a red giant with a surface reaching nearly to Mars. Internal changes will later cause it throw off its atmosphere into space in an expanding cloud of gas and dust called a planetary nebula. Click to learn more about the sun’s evolution. Credit: ESO/S. Steinhofel

Planetary nebulae are gassy shells blown off by sun-like stars as they age. Several billion years from now, the sun will bloat up into a red giant star big enough to gulp down the Earth. Powerful winds resulting from pulses of helium burning deep within the sun will blast most of its atmosphere into space, leaving behind an extremely a planet-sized core called a white dwarf.

One of the closest and most familiar white dwarfs is the star Sirius B, the tiny companion to the brilliant wintertime star Sirius. It’s twice as massive as the sun yet 500 miles smaller than Earth. Credit: NASA/ESA

White dwarf stars are exceedingly dense – one teaspoon weighs 5 tons – and are made of carbon and oxygen, the radiant ash left over from the fusion of hydrogen and helium during the sun’s lifetime as a typical star. Our sun fuses these elements in its core to generate the heat and light spring-starved humans need on Earth.

The sun’s surface temperature is around 10,000 degrees F, too hot and bright to stare at without damaging your eyes. But that’s arctic compared to a white dwarf’s temperature of 180,000 degrees! Hot enough that the dwarf emits copious amounts of ultraviolet light causing its former atmosphere, now expanding into space as a shapely nebula, to fluoresce blue, green and pink.

A selection of planetary nebulae photographed by the Hubble Space Telescope. Some show multiple shells from several episodes of strong winds blasting from the core through the outer layers of the stars. Credit: NASA / ESA

Abell 33 is just one of the 86 objects included in astronomer George Abell’s 1966 Abell Catalogue of Planetary Nebulae. Planetaries, as they’re called, are often spherical but not always. Some are shaped like hourglasses, barrels and giant rings. Near the center of Abell 33 you’ll see what appears to be a double star. One of these is the white dwarf, the other might be its companion or it could be another chance alignment.

While planetary nebulae are beautiful in their own right, this particular chance meeting of Abell 33 and HD 83535 is clearly a match made in heaven. Ba-dum-bump!

Norwegian skydiver update: It’s a rock, not a meteorite


Video of the rock falling past Anders Helstrup. The rock falls at the 2:51 mark.

I never imagined the mystery of the falling meteoroid and Norwegian skydiver would be solved so quickly. But it appears we have an answer. While some may still doubt the conclusion, many will agree it’s the most likely scenario: skydiver Anders Helstrup accidentally packed a pebble into his parachute after an earlier dive. Somehow it escaped his attention.

That’s the conclusion of Steinar Midtskogen, one of the people who helped make the video. In his blog post published today April 8 he writes:

“We think we can reconstruct what happened: A pebble, a few cm in size at most, was accidentally caught inside the parachute at the landing site after the previous jump. Then the parachute was packed on a clean floor and the pebble was not noticed.”

Midtskogen and those involved may be disappointed it didn’t turn out to be a meteorite, but they’re happy a reasonable explanation was found thanks to their crowd sourcing efforts. Please check out Steinar’s blog for complete details.

I have to admit I hoped it was a meteorite, but I’ll take the truth over a wish anytime.

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.