Weird auroras / Mercury meets a dainty moon / See 5 evening planets!

An oval patch of glowing green aurora appeared in the northern sky in Cassiopeia last night (April 17). Credit: Bob King

An oval patch of glowing green aurora pulses in Cassiopeia last night (April 17). Credit: Bob King

It’s been a fantastic 4 nights of northern lights. For now, Earth’s magnetic environment has returned to quiet conditions. Similar to the run of auroras that began on St. Patrick’s Day, this one finished with the same peculiar, sausage-shaped patches.

Last night I noticed a single elongated glow about two fists across in the northern sky in late twilight that slowly pulsed in brightness, often disappearing for 10-15 seconds and then reappearing in the same spot. Like breath on a mirror.

Another view of the diffuse aurora seen last night across the northern sky. Credit: Bob King

Another view of the diffuse aurora seen last night across the northern sky. Credit: Bob King

During the night, the patch slinked slowly westward into Cassiopeia and then disappeared altogether around 11 o’clock. At midnight it reappeared in the northeastern sky below the Northern Cross.  The strange apparition added quiet intrigue to the evening’s boisterous calls from the frogs.

Use bright Venus to help point you in the right direction. This map shows the sky facing west-northwest around 40 minutes after sunset. Created with Stellarium

Use bright Venus to help point you in the right direction. This map shows the sky facing west-northwest around 40 minutes after sunset. Mercury is 7° to the lower right of the moon. Created with Stellarium

Tomorrow night (April 19), look to the northwest about 40 minutes after sunset for a rare alignment of a day-old moon and two planets. One of them, Mars, has been around since last spring. Back then it was much closer to Earth and brilliant. Since then the two planets have separated with Mars now far away and rather faint. You wouldn’t ordinary seek it out so low in a bright sky, but the youthful crescent moon will certainly lure you there.

Mercury's approximate path and altitude during its dusk appearance this spring. Notice how its phase changes from the current gibbous to half to crescent. Source: Stellarium, Bob King

Mercury’s approximate path and altitude during its dusk appearance this spring. Notice how its phase changes from the current gibbous to half to crescent. Source: Stellarium, Bob King

The moon will be just a bit more than one day old and appear as a razor-thin sliver about 5-7° high (three to four fingers held at arm’s length). It should be easily visible from anywhere with a wide open view to the west-northwest. Because of its relative faintness, Mars will probably require binoculars to see. Focus on the moon first and then slide to the right to find the star-like planet.

As an inner planet, Mercury goes through phases just like Venus and the Moon. We see it morph from crescent to “full moon” as its angle to the Sun changes during its revolution of the Sun. Credit: ESO

As an inner planet, Mercury goes through phases just like Venus and the Moon. We see it vary from crescent to “full moon” as its angle to the Sun changes during its revolution of the Sun. Credit: ESO

Mercury shines at magnitude -0.5, even brighter than Vega or Arcturus, but it’s only a few degrees high, so you might need binoculars to see it, too. Once again, the moon comes to the rescue. Look either with your eyes or binos 7° (four fingers) to its lower right.

Mercury quickly moves up from the horizon in the next two weeks for its best evening appearance of the year for northern hemisphere skywatchers. As it comes into better view, the planet will slowly fade and change phase just like the moon. You can see the phases through a small telescope magnifying about 75x. Be sure to look for Mercury early when it’s highest or the blurring effect of the atmosphere will turn it into a ball of quivering mush.

Saturn pops up in the head of the Scorpion in late April around 11-11:30 p.m. This photo was taken early this morning just after midnight. Credit: Bob King

Saturn pops up in the head of the Scorpion in late April around 11-11:30 p.m. This photo was taken early this morning just after midnight. Credit: Bob King

With Mercury joining the scene, we now have five — count ‘em — five planets visible in the evening sky. Throw in the Earth and that makes six out of a total of eight! Mercury and Mars hang low in the west; Venus can’t be missed, shining like a lighthouse high in the west at dusk; Jupiter dominates the southern sky in Cancer and if you stay up till 11:30, you’ll see Saturn rise in Scorpius low in the southeastern sky.

Such riches for planetary enthusiasts. Go out and meet your solar system at the next opportunity.

Scars on Mars fade … sometimes / Comet-cluster mashup

Curiosity descent and heat shield impact. Best heat shield images are at the end.

It’s only been a couple years, but the blast marks left by the descent stage that delivered the Curiosity rover to Mars as well as it heat shield that protected it have changed markedly in appearance. But not exactly the way you’d think.

This sequence of images shows a blast zone where the sky crane from NASA's Curiosity rover mission hit the ground after setting the rover down in August 2012, and how that dark scar's appearance changed over the subsequent 30 months. Image Credit: NASA/JPL-Caltech/Univ. of Arizona

This sequence of images shows a blast zone where the sky crane from NASA’s Curiosity rover mission hit the ground after setting the rover down in August 2012, and how that dark scar’s appearance changed over the past 30 months. Credit: NASA/JPL-Caltech/Univ. of Arizona

Curiosity was carefully lowered to the Martian surface in August 2012 by a powered descent stage that blasted away bright Mars dust to expose darker material beneath. Shortly before it landed, the probe ejected its heat shield which slammed into the crust some distance away. Once Curiosity landed, the descent stage or sky crane shot away and crash landed as well. Since that time, the winds crisscrossing the Red Planet have gradually re-coated the darkened areas with bright dust.

sequence shows where the rover itself landed. Curiosity disappears after the first two of the seven frames because it drove away. Its wheel tracks heading generally east (toward the left) can be seen in subsequent frames, and they also fade over time. Credit: NASA/JPL

sequence shows where the rover itself landed. Curiosity disappears after the first two of the seven frames because it drove away. Its wheel tracks heading generally east (toward the left) can be seen in subsequent frames, and they also fade over time. Credit: NASA/JPL

You might assume that accumulating dust would erase the scars, and this was true at first. Lately however, the process appears to have reversed itself.

“We expected to see them fade as the wind moved the dust around during the months and years after landing, but we’ve been surprised to see that the rate of change doesn’t appear to be consistent,” said Ingrid Daubar, a HiRISE camera team scientist at NASA’s Jet Propulsion Laboratory who studied images of the blemishes taken by the Mars Reconnaissance Orbiter.

After fading for two years, the rate of change slowed with some areas re-darkening. Scientists are repeatedly checking the blast zones to compare their models against reality, revealing that we still don’ t fully understand how Martian dust is transported around the planet.

MarsBlast Heat shield

Five-frame sequence of the location where the spacecraft’s heat shield hit the ground. Credit: NASA/JPL-Caltech/Univ. of Arizona

Daubar’s work on this aids preparations for NASA’s next Mars lander, InSight, expected to launch in March 2016. The InSight mission will deploy a heat probe that will hammer itself a few yards, or meters, deep into the ground to monitor heat coming from the interior of the planet.

The brightness of the ground affects temperature below ground, because a dark surface warms in sunshine more than a bright one does.

Comet Siding Spring cruises past the bright globular star cluster M92 in Hercules on March 29, 2015. Credit: Rolando Ligustri

Comet Siding Spring cruises past the bright globular star cluster M92 in Hercules on March 29, 2015. Credit: Rolando Ligustri

Now that you’re brain’s completely flickered out after viewing three animations, let me share one additional photo from the weekend that has a Mars connection. It shows the comet C/2013 A1 Siding Spring passing very close in a beautiful way to the globular cluster M92 in the constellation Hercules. Siding Spring swept so close to Mars last fall it created a meteor shower in the planet’s atmosphere. Now it’s juxtaposed again, this time in the foreground of a star cluster that’s 26,700 light years from Earth.

Uranus preps for tomorrow’s hand off to Mars

Like a baton in a relay race, Uranus has been passed on from one bright planetary body to the next in a series of close conjunctions. Credit: Steve Kuchera

Like a baton in a relay race, Uranus has been passed on from one bright planetary body to the next in a series of close conjunctions. Credit: Steve Kuchera

In a relay race, a baton is passed from one teammate to another during each leg of the race. Uranus can relate. It was picked up by the moon on Feb. 21, handed off to Venus on March 4th and tomorrow night will be handed off again to Mars. Before the planet crosses the finish line at solar conjunction, here’s one last opportunity to see it in binoculars in the evening sky.

Tonight the passed-along planet will lie just 1/2° or one full moon diameter to Mars’ upper left. Though just about any pair of binoculars, Uranus will look exactly like a star. Tomorrow night the two planets will be closest, separated by about 1/3° with Uranus directly below or south of the Red Planet. Thereafter they part, both hurrying in the Sun’s direction.

Uranus will be close to Mars tonight and even closer tomorrow evening March 11. Use binoculars to find it. Created with Stellarium

Uranus will be close to Mars tonight and even closer tomorrow evening March 11. Use binoculars to find it. Created with Stellarium

Venus, brilliant gem of dusk, stands high in the west as the sky darkens after sunset. Mars is considerably dimmer and shines not quite a fist to its lower right. Be sure you’re in a spot with nice open view to the west. To see Uranus, start at Venus and drop down to Mars. Point your binoculars at Mars and use the maps to help you spot it.

Because Mars sets early, I suggest you start looking about an hour after sunset. Take your time and stay out till nightfall, so you can also use those opera glasses to look at Comet Lovejoy, now passing very near the star Ruchbah in the familiar W of Cassiopeia high in the northwestern sky. Here’s a map to help you find it.

Full Worm Moon wriggles up, shows its head tonight

The nearly full moon rises within the framework of Duluth, Minnesota's iconic Aerial Lift Bridge yesterday evening March 4. Credit: Bob King

The nearly full moon rises within the framework of Duluth, Minnesota’s iconic Aerial Lift Bridge yesterday evening March 4. March’s Full Worm Moon is named for the time when the ground softens and earthworms show their heads again. Credit: Bob King

With 14 below on the thermometer this morning I don’t think Full Worm Moon quite fits as a description for tonight’s full moon. How about the Sap Moon, named for the time when sap begins to run again in maple trees? No, a little too early for that. These traditional Native American moon names obviously applied to other more clement regions of the country where March really does mean the start of spring.

More like the Full Stubborn Moon in my town. Yet the signs of spring are unmistakable. Longer days, shorter nights, a steeper slant to the sunlight. Spring stars are pushing up in the east as well – scintillatious Arcturus is up by 9:30 in the northeast, followed by Virgo’s Spica an hour or so later.

Last month's just-past-full moon rises below Jupiter over the ice-covered shore of Lake Superior in Duluth. Watch for the Full Worm Moon tonight. Click image to find the moonrise time for your location. Credit: Bob King

Last month’s just-past-full moon rises below Jupiter over the ice-covered shore of Lake Superior in Duluth. Watch for the Full Worm Moon tonight. Click image to find the moonrise time for your location. Credit: Bob King

We enjoy watching these seasonal changes. They help us get out of bed and renew that enjoyable sense of anticipation at what’s around the next corner. Constant motion. We’ve been told everything’s in continual movement. If you could shrink down to size of a bacterium you’d never be able to sit still. At that level, you’d feel the pinging of millions of molecules called Brownian motion. Getting up and walking to another room you’d be pelted by a hail of molecular snowballs.

Lucky then that humans are big enough to escape such atomic beatings. But the incredible variety of motions still can throw us off. The stars rise and set, reflecting the rotation of our planet, constellations shift westward with the seasons as Earth orbits the Sun, the moon and planets march east, contrary to the motion of the stars.

The Earth's rotation dominates the moon's apparent motion across the sky, causing it rise in the east and set in the west. Meanwhile, the moon itself is moving much more slowly toward the east or back down toward the horizon. Credit: Bob King

The Earth’s rotation dominates the moon’s apparent motion across the sky, causing it rise in the east and set in the west. The moon is simultaneously moving much more slowly toward the east or back down toward the horizon. Credit: Bob King

When you watch the moon rise tonight, be aware that as the Earth’s rotation brings it into view, the moon’s orbital movement wants to drag it back down to the horizon. Reminds me of trying to get a teenager out of bed. The Earth wins of course because the moon is far enough away that its apparent motion to the east amounts to only 1/2° or one moon diameter per hour. Meanwhile, Earth’s west-to-east rotation uproots our satellite and whips it to the west 30 times faster. Sorry moon, you lose.

It’s all illusion of course. The moon’s doing most of the moving. Its nightly rising in the east and setting in the west are nothing more than a reflection of our planet’s spin. Fake motion. By the way, those little 1/2 degrees add up – every 24 hours the moon moves more than a fist to the east.

Phobos, the larger of Mars' two moons, orbits just 3,700 miles above the planet's surface, so close it takes just 7 hours 39 minutes to complete its orbit. Phobos is only about 12 miles across. Credit: NASA/JPL-Caltech

Phobos, the larger of Mars’ two moons, orbits just 3,700 miles above the planet’s surface, so close it takes just 7 hours 39 minutes to complete its orbit. Phobos is only about 12 miles across. Credit: NASA/JPL-Caltech

While the moon may appear to lose to Earth, this isn’t true with Mars’ moon Phobos, which lies so close to the planet that it takes just 7 1/2 hours to orbit it. Moving eastward at 45° per hour (90 times faster than the moon), Phobos rises in the west and sets in the east after only 4 hours. Four hours later’ it’s back again at the western horizon ready for another trip across the night sky. Mars’ rotation rate of 24 hours 37 minutes just can’t keep up with this insanely fast moon.

While I’d be the first to purchase a cheap ticket to Mars just to see crazy Phobos, I rather like the unhurried and deliberate moon that rises over Earth. Time to watch moonlight transform the landscape and help us slow down a little after a busy day.

It’s double duo week: Moon-Jupiter and Venus-Uranus

The nearly full moon is in conjunction with Jupiter tonight. Their minimum separation of 5 happens around 10 p.m. (CST). Source: Stellarium

The nearly full moon is in conjunction with Jupiter tonight. Their minimum separation of 5° happens around 10 p.m. (CST). Source: Stellarium

I looked until around 11 p.m. last night but moonlight diluted any aurora that may have out. But the predicted storm did hit between about 2 a.m. and dawn this morning. While some readers might think I stay up all night, I really did sleep through this aurora. I know at least a few of you saw it. Tonight, there’s a chance for more minor storming.

There’s also an even better chance you’ll be struck by two very bright objects in the eastern sky at nightfall: a plump gibbous moon and the jolly giant planet Jupiter. They’ll be in conjunction tonight just ahead of Leo’s brightest star Regulus. Pairings like these make for great company and contemplation while walking the dog at night.

Venus and Uranus will be very close together on March 4th, an ideal time to find the fainter planet in binoculars. Source: Stellarium

Venus and Uranus will be very close together on March 4th, an ideal time to find the fainter planet in binoculars. Source: Stellarium

A planet-to-planet pairing occurs on Wednesday evening the 4th when Venus and Uranus will be just 1/3° apart. Like last month’s close graze with the crescent moon, this will provide yet another easy opportunity to see a planet that is too dim for most to see with the naked eye. Just point your binoculars at brilliant Venus in late twilight in the western sky and look for a tiny speck of light immediately below it.

I love how planets can appear so close and yet be so far from one another. Venus is a quick jaunt at 128 million miles from Earth compared to Uranus’ 1.9 billion miles, nearly 15 times farther away.

The stars in the constellation of Orion all look like they are at the same distance. Turn the constellation through 90 degrees and you can see the stars are actually at different distances. Two of the Belt stars plus the two bottom stars in the constellation are far from the sun but relatively near one another in space. Betelgeuse is much closer to us. Credit: ESA

The stars of Orion might be easily dismissed as all being at the same distance from us. That’s how they appear on the 2-D “surface” of the sky. Butturn the constellation through 90 degrees (look at it from the side) and you can see the true distances of each star. Notice that Betelgeuse is much closer to us than the Belt stars. Credit: ESA

When we see conjunctions and appreciate the real distances between objects in the sky, it’s helpful to remember the same applies to the constellations. We see familiar rectangular outline of Orion and the neat arrangement of his three belt stars by lucky chance. Looking back toward Orion’s stars from a different direction in space (a couple hundred light years beyond the solar system) Orion would be unrecognizable.

Planetary traffic jam lookback / Speedy comet update

To capture the planet Uranus (at lower right) I had to overexpose the bright, sunlight lunar crescent. Naturally, this made the earth-lit portion stand out very clearly. Credit: Bob King

To capture the planet Uranus (at lower right) I had to overexpose the bright, sunlight lunar crescent. Naturally, this made the earth-lit portion stand out very clearly. Credit: Bob King

Wow, we had quite a weekend. The moon visited every evening sky planet while Venus and Mars squeezed together for their closest approach of the year. We’ve already looked at the “triple play” conjunction that occurred Friday. I thought it would be fun to look at the other alignments that have made the past few nights so memorable.

The moon (top) along with Venus and Mars Saturday evening Feb. 21, 2015. Credit: Guy Sander

The moon (top) along with Venus and Mars Saturday evening Feb. 21, 2015 from near Duluth, Minn. Credit: Guy Sander

Here, Guy has enlarged portions of the image to better see all three planets involved. Credit: Guy Sander

Here, Guy has enlarged portions of the image to better see all three planets involved. Credit: Guy Sander

Venus and Mars were still close Sunday night Feb. 22, but they will part in the coming days as Venus moves up and Mars slides closer to the Sun. Credit: Bob King

Venus and Mars were still close Sunday night Feb. 22, but they will part in the coming days as Venus moves up and away from the Sun while Mars slides closer. Credit: Bob King

As for that fast-moving comet discovered last week and en route to the evening sky, Karl Battams, an astrophysicist and computational scientist based at the Naval Research Laboratory (NRL) in Washington DC, is right now at his computer measuring positions of the comet from photos made with the orbiting Solar and Heliospheric Observatory (SOHO).

Comet SOHO-2875 survived its close passage of the Sun and may make an appearance in the evening sky soon. This photo montage was made using the coronagraph (Sun-blocking device) on SOHO. Click to watch a movie of the comet. Credit: NASA/ESA

Comet SOHO-2875 survived its close passage of the Sun and may make an appearance in the evening sky soon. This photo montage was made using the coronagraph (Sun-blocking device) on SOHO. Click to watch a movie of the comet. Credit: NASA/ESA

Once enough positions are known, he’ll send the data off to the Minor Planet Center where a preliminary orbit will be determined. With that information I can make a nice map showing us where to look for it. Stay tuned.

Mars mystery plumes might be auroras

Mystery plume in Mars' southern hemisphere photographed by amateur astronomer Wayne Jaeschke on March 20, 2012

Mystery plume in Mars’ southern hemisphere photographed by amateur astronomer Wayne Jaeschke on March 20, 2012. The feature extended between 310-620 miles and lasted for about 10 days.

Strange plumes in Mars’ atmosphere first recorded by amateur astronomers two years ago have planetary scientists still scratching their heads.

On two occasions in 2012 amateurs photographed cloud-like features rising to altitudes of over 155 miles (250 km) above the same region of Mars. By comparison, similar features seen in the past haven’t exceeded 62 miles (100 km). Back then, no one was certain of the cloud’s nature; it was thought ice crystals or even dust whirled high into the Martian atmosphere by seasonal winds could be the cause.

Mars High-altitude_plume_on_Mars

The top image shows the location of the mysterious plume on Mars (yellow circle)  along with different views of the plume’s changing shape taken by Wayne Jaeschke and Don Parker on March 21, 2012

But a recent paper by scientist Agustin Sanchez-Lavega of the Universidad del País Vasco in Spain explores other possibilities. One problem with dust or ice is altitude – 155 miles is way, way up there where Mars’ atmosphere grazes outer space. Just how clouds could form so high is unknown.

“One idea we’ve discussed is that the features are caused by a reflective cloud of water-ice, carbon dioxide-ice or dust particles, but this would require exceptional deviations from standard atmospheric circulation models to explain cloud formations at such high altitudes,” said Agustin.

Another idea is even more intriguing. The wisps could be Martian auroras linked to regions on the surface with stronger-than-usual magnetic fields.

 

The small protrusion extending into the night sky of Mars in this 1997 Hubble photo is probably a high cloud catching sunlight. Credit: NASA/ESA

The small protrusion extending into the night sky of Mars in this 1997 Hubble photo resembles the March 2012 plumes in appearance and altitude. Credit: NASA/ESA

Once upon a very long time ago, Mars may have had a global magnetic field generated by electrical currents in a liquid iron-nickel core much like the Earth’s does today. In the current era, the Red Planet has only residual fields centered over regions of magnetic rocks in its crust.

Instead of a single, planet-wide field that funnels particles from the Sun into the atmosphere to generate auroras, Mars is peppered with pockets of magnetism, each potentially capable of connecting with the wind of particles from the Sun to spark auroras.

Mars has magnetized rocks in its crust that create localized, patchy magnetic fields (left). In the illustration at right, we see how those fields extend into space above the rocks. At their tops, auroras can sometimes form. Credit: NASA

Mars has magnetized rocks in its crust that create localized, patchy magnetic fields (left). In the illustration at right, we see how those fields extend into space above the rocks. At their tops, auroras can form. Credit: NASA

Auroras were first discovered on Mars in 2004 by the European Space Agency’s Mars Express orbiter. NASA’s MAVEN spacecraft, which has been orbiting Mars since last September, is well-equipped to study the planet’s upper atmosphere and auroras, so perhaps we’ll have a more definitive answer soon on the makeup of the mysterious plumes.

Spectacular fireball over Pittsburgh / Juvenile moon alert


Pittsburgh fireball February 17

A fireball meteor at least as bright as the full moon flared over the Pittsburgh region around 4:50 a.m. Eastern time Tuesday morning. The object, detected by three NASA meteor cameras, was moving at a speed of 45,000 miles per hour. Based on its brightness, NASA’s Meteoroid Environment Office estimated the object at 2 feet across with a weight of 500 pounds. Something like a very heavy TV falling out of the sky.

“I’ve seen many meteor showers and this wasn’t anything like that. Instead of crossing the upper atmosphere, this feel almost directly down and brighter than any thing I’ve ever seen of this nature,” reported John D. of Elyria, Ohio. “It looked so big that my son and I expected to hear or see an impact.”

Based on data from pictures taken by multiple cameras, an orbit for the Pittsburgh fireball could be made. Originating in the asteroid belt between Mars and Jupiter, it came a long way to get to PA.Copyright David L. Clark, prepared by NASA MEO

Based on pictures taken by multiple cameras, NASA scientists determined an orbit for the Pittsburgh fireball. Originating in the asteroid belt between Mars and Jupiter, it came a long way to get to PA. Copyright David L. Clark, prepared by NASA MEO

“The entire landscape was lit up like daytime. Startling experience. I was very fortunate to be looking out window at the time.” So wrote Robert M. of Clarion, Penn. in his report to the American Meteor Society’s fireball reporting website.

Map showing reported sightings of the fireball. To date, 125 reports have been received. Credit: AMS

Map showing reported sightings of the fireball. To date, 125 reports have been received. Credit: AMS

NASA’s cameras first spotted the meteor at an altitude of 60 miles northwest of Pittsburgh and last saw it 13 miles above Kittanning, northeast of Pittsburgh. Around 13 miles altitude, the meteoroid entered its “dark flight” phase, when the air slowed it down enough to drop in free fall.

When we see a meteor, we don’t actually see the object itself but rather a brilliant “tube” of ionized air caused by the rock’s incredibly speedy passage through the atmosphere. Once a meteoroid loses sufficient speed, it no longer has the energy to ionize or make the air glow around it and falls in dark flight.

Earth seen from the perspective of the meteoroid moments before it entered our atmosphere to become a fireball. Click to see the movie. Credit:

Earth seen from the perspective of the meteoroid moments before it entered our atmosphere to become a fireball. Click to see the movie. Credit: Copyright David L. Clark, prepared by NASA MEO

Some people heard sonic booms during the fall, a good sign that the meteoroid (what you call a meteorite before it hits the ground) fragmented and dropped pieces on the ground east of Kittanning. According to Bill Cooke of the Meteoroid Office, seismographs in the region recorded the pressure wave created by the meteoroid’s flight.

Like most meteors and meteorites, this one’s a visitor from the main asteroid belt located between Mars and Jupiter. If pieces did survive the atmosphere’s ferocity, may I be the first to welcome them to their new home.

Watch for a 1-day-old super-thin crescent moon below the duo of Venus and Mars tonight. This map shows the sky about 35 minutes after sundown. Source: Stellarium

Watch for a 1-day-old super-thin crescent moon below the duo of Venus and Mars tonight. This map shows the sky about 35 minutes after sundown. Source: Stellarium

On another note, I wanted to remind moon lovers that a very young, very thin 1-day-old moon will be visible during early twilight in the western sky this evening starting about 25 minutes after sundown.

The moon’s about about one fist held at arm’s length below the pair of Mars and Venus. Tonight’s act is a warm-up for tomorrow night’s very close gathering of the moon with the two planets. For more information on that event, click HERE.

Tracking down February’s mystery supermoon – where is it?

This week’s new moon will be unusually close to Earth. Think of it as a ghostly supermoon. As is true for any new moon, it will be too close to the Sun in the daytime sky to see. This illustration shows the moon’s appearance and location if our eyes could somehow make it out through all the daylight. Source: Stellarium

Here comes the supermoon! But wait, doesn’t that only happen around full moon? Well, not always. Every month the moon swings around Earth in its elliptical (oval) orbit. On one side of the ellipse, it’s closest to Earth and on the opposite side, farthest. When it’s at its closest point, called perigee, at the time of full moon, we call it a supermoon.

During the closest supermoons, our satellite can appear up to 30% brighter and 14% larger. Whether anyone can actually see the difference is open to debate simply because there’s no normal-distance moon nearby with which to make a comparison.

No one pays attention to first quarter or crescent supermoons even though the moon can be closest to us at those phases, too. Thanks to incessant media coverage, only full supermoons get coverage. We like full moons for all sorts of reasons. When an extra close one’s in the offing, as happens on Sept. 27 this year, that’s just one more reason to like them.

The moon’s orbit around Earth is an ellipse with the Earth off-center at one the ellipse’s foci. During its 27-day-long orbit, the moon passes through perigee (closest) and apogee (farthest) points. This week’s new moon will be the second closest perigee of the year after the Sept. 27 full moon. Illustration not to scale. Credit: Bob King

Lest crescents and quarters get short shrift I’m here to hawk this month’s supermoon. Full disclosure. Since it occurs during new moon phase on Feb. 18 you won’t see it. No one sees a new moon except when it happens to be eclipsing the Sun. But northern hemisphere skywatchers can spot the moon two days before new and just one day after new this month, and it’ll be nearly as super as on the18th.

Tomorrow morning Feb. 16 the planet Mercury will lie about 9.5° (about one fist held at arm’s length) to the lower left of the thin crescent two days before new moon phase. This map shows the sky facing southeast about 40 minutes before sunrise. Source: Stellarium

What’s more, if you have a good view of the southeast horizon, tomorrow morning’s skinny crescent will lie near the planet Mercury low in the southeastern sky 40 minutes before sunrise. Be sure to carry along a pair of binoculars as Mercury is near “last quarter” phase and not nearly as bright as it can be.

The moon’s average distance is 240,000 miles, but tomorrow morning at 6 a.m. (CST) it will lie just 226,549 miles from Earth. At 1 a.m. Feb. 18 – the time of the invisible supermoon –  it will be 4,723 miles closer. The following day the moon slides out a bit to 222,092 miles en route to a striking double conjunction with Mars and Venus on Friday the 20th.

Even though we won’t see February’s supermoon, our planet will sense the difference. The additional gravitational force exerted by the close moon will make for unusually high tides. High tides occur when the Sun, moon and Earth are all in a line as they during both new moon phase and at full moon.

The moon, still very close to perigee, pops up in the western sky at dusk on Thurs. Feb. 19 well below Venus and Mars, now in close embrace. This map shows the sky about 35-45 minutes after sunset facing west. Source: Stellarium

So tomorrow morning you can catch the moon near Mercury at dawn, and on Thursday the 19th you’ll have the chance to enjoy the delicate grin of a one-day-old crescent in the west at dusk. Finally, on Friday, don’t miss the close conjunction of the moon with Mars and Venus.

Our satellite has a busy schedule this week!

 

A triple-scoop conjunction with a cherry on top!

Venus and Mars (at right) are drawing closer every night. This photo was taken at dusk Thursday Feb. 12 an hour and 15 minutes after sunset. On Feb. 20-21 they’ll be just half a degree apart or 8 times closer. The moon joins the pair on the 20th. Details: 35mm lens, f/3.5, ISO 800, 12 second exposure. Credit: Bob King

Get ready. One week from tonight fate has arranged a celestial spectacle. That night (Feb. 20) a two-day-old crescent moon will “triple up” with the planets Venus and Mars after sundown.

The entire bunch will fit within a circle 1.5° wide or just three times the diameter of the full moon. Like a glittering pendant around your sweetheart’s neck the trio will dangle above the western horizon in the afterglow of sunset. This is a not-to-miss event and one that should be fairly easy to photograph.

Moon, Mars and Venus around 6:45 p.m. (CST) on Feb. 20 in the western sky. Be sure to look for the darkly-lit part of the moon illuminated by sunlight reflecting off Earth called earthshine. It’s a beautiful sight in binoculars. Source: Stellarium

Look toward the west in the direction of the setting Sun; the best viewing time will be 45 to 90 minutes after sunset. With plenty of light to work with, taking a picture of the scene shouldn’t be too difficult. Attach your camera to a tripod and use the information in the photo caption as a place to start. Try to keep your exposure times to 20 seconds or less. Any longer and the planets will stretch into short trails instead of compact dots due to Earth’s rotation.

When you look at the LCD screen on the back of your camera, don’t be surprised if the crescent moon is completely filled out. Time exposures in semi-darkness necessarily overexpose the bright sunlit crescent. The rest of the moon is illuminated by dimmer earthshine, sunlight reflected from the Earth to the moon and back.

From the East Coast, the moon will lie a little farther to the right of Venus and Mars than depicted in the map; from the West Coast, it sits above the pair. Conjunction with Venus occurs around 5 p.m. (CST) and with Mars an hour later.

Venus and Mars will be close conjunction the following night (Feb. 21) only 0.5° or one moon diameter apart. If the weather doesn’t cooperate on the 21st, don’t sweat it – the two planets will be close from the 19th through the 22nd. You’ll easily tell the two apart. Venus is SO much brighter than Mars (about a hundred times) and the lunar crescent brighter yet. This promises to be one of the best moon-planet gatherings of the year.

Uranus in early twilight (left) just before its dramatic disappearance behind the earth-lit edge of the moon on Feb. 21 as seen from Portland, Maine. 36 minutes later Uranus emerges at the bright crescent’s edge. Both disappearance and reappearance occur in a dark enough sky to see in a small telescope. Source: Stellarium

Here’s a wider view of Uranus and the moon on Feb. 21 as seen from the Midwest about an hour and a quarter after sunset. Source: Stellarium

Ah, but the moon won’t be quite finished with its magic. There’s still the cherry on top. The very same night – Feb. 21 – the crescent covers up or occults the planet Uranus for skywatchers in northeastern U.S. and southeastern Canada during twilight. For the Central Time Zone Uranus will lie 0.5° west of the moon, 1° from the Mountain States and 1.5° for the West Coast. Amazing stuff – yet another opportunity to easily spot planet #7 in binoculars.

Map showing where the occultation of Uranus by the moon will be visible. Between the white lines, it’ll be visible in a dark sky. Blue is twilight and the red dotted line is daytime. Uranus is too faint to see in the daytime sky. Click the map to get a list of disappearance and reappearance times for a variety of cities. Credit: IOTA/Occult

Most of the time the moon occults stars along its path since there are a lot more of those than planets. Because they’re so remote, stars are little more than points of light; as the moon moves over them they disappear with surprisingly suddenness. Since Uranus displays a real, measurable disk it takes a second or two to disappear behind the moon’s edge. This should be a very fun occultation for those lucky skywatchers living out East. Maybe it will help take their minds off the unrelenting snow.