Weird “teardrop” aurora airbrushes the first night of spring

Peculiar teardrop-shaped auroral patch in the northwestern sky this evening near the Pleiades star cluster (upper left). Credit: Bob King

Peculiar teardrop-shaped auroral patch in the northwestern sky this evening near the Pleiades star cluster (upper left). The aurora slowly pulsated in brightness. Credit: Bob King

Just got back from looking at some pretty weird northern lights. A bright teardrop-shaped patch glowed alone low in the northwestern sky around 10:30-11 p.m. 10 minutes later, another oval patch mysteriously appeared in the north. The two swelled in size and length and almost appeared to join … but didn’t . Instead, the teardrop faded away while the oval brightened. Then it slowly disappeared. When I last looked, the oval had returned but was fainter.

The teardrop on the left and oval to the right. Each slowly pulsed, fading and brightening. Credit: Bob King

The teardrop on the left and oval to the right. Each slowly pulsed, fading and brightening. Credit: Bob King

To look at the aurora indicators we’ve tapped into the past few nights — the  Kp index and auroral oval — you’d think there’d be no reason to don hat and coat and go aurora-hunting on cold, windy night. Both indicators are nearly flat, having dropped from minor storm level during the late afternoon (CDT). Yet Earth magnetic bubble keeps on jiggling, shaking out some peculiar forms of aurora.

A closer look at the featureless northern lights oval seen around 11 p.m. in the northern sky. Credit: Bob King

A closer look at the featureless northern lights oval seen around 11 p.m. in the northern sky. Credit: Bob King

One hint that solar excitement still lingers in Earth’s vicinity comes from the live information sent to us by the Advanced Composition Explorer (ACE) satellite, which taps into the Sun’s wind a million miles upstream of our planet. Around 10:30 p.m. (CDT), ACE recorded a southward dip in the magnetic field embedded in the solar wind – perfect for linking into Earth’s field and firing up auroras.

As always, it’s hard to know how long these “glows” may last, but if you’re out, don’t be surprised if you see them. We’re now at five nights in a row and counting for northern lights displays this week. Looks like we’re in for more. The forecast calls for yet another G1 geomagnetic storm Saturday evening (March 21) from about 7-10 p.m. CDT.

Eclipse spectacle / Record-thin moon / Aurora redux?

A total solar eclipse is seen in Longyearbyen on Svalbard, Norway, March 20, 2015. REUTERS/Jon Olav Nesvold/NTB scanpix

A total solar eclipse is seen in Longyearbyen on Svalbard, Norway, March 20, 2015.  The black circle is the moon covering the Sun. The “collar” around the moon is the Sun’s atmosphere called the corona, which is invisible to the eye except during an eclipse. Credit: Reuters/Jon Olav Nesvold/NTB scanpix

I’m told weather was great at Svalbard in Norway for this morning’s total solar eclipse. Completely clear skies. The solar corona, only seen during an eclipse, looks fashionably punk with a head full of beautiful, magnetically-aligned spikes.

A girl uses a welding mask to view a partial solar eclipse from Bradgate Park in Newtown Linford, central England March 20, 2015. A solar eclipse swept across the Atlantic Ocean on Friday with the moon blocking out the sun for a few thousand sky gazers on remote islands with millions more in Europe, Africa and Asia getting a partial celestial show. Reuters / Darren Staples

A girl uses a welding mask to view a partial solar eclipse from Bradgate Park in Newtown Linford, England to watch the eclipse. Millions of skywatchers in Europe, Africa and Asia got to see the partial show. Credit: Reuters / Darren Staples

Because the corona is a million times fainter than the blazing surface of the Sun you can’t see it in the daytime. Only during a eclipse when the moon covers our star can we finally glimpse its hidden crown.

A student observes the partial eclipse cast onto white paper at the Astronomical Observatory in Bialystok, Poland March 20, 2015. Credit: Reuters / Agencja Gazeta

Clouds proved to be the ideal filter for photographing the partial solar eclipse from Trieste, Italy Friday morning. Details: 50mm lens, f/6, 1/100 second at ISO 100. Credit: Giorgio Rizzarelli

Clouds proved to be the ideal filter for photographing the partial solar eclipse from Trieste, Italy Friday morning. Details: 50mm lens, f/6, 1/100 second at ISO 100. Credit: Giorgio Rizzarelli

Every day, the orbiting Solar and Heliospheric Observatory uses a coronagraph to create and artificial eclipse as seen from space. It uses an opaque disk to block the brilliant solar surface called the photosphere, so astronomers can study the corona any time without the expense, time and uncertain weather that can make eclipses on Earth so touch-and-go.

A view from a plane during the so-called "Eclipse Flight" from the Russian city of Murmansk to observe the solar eclipse above the neutral waters of the Norwegian Sea, March 20, 2015. A partial eclipse was visible on Friday, the first day of northern spring, across parts of Africa, Europe and Asia. The total eclipse of the sun was only visable in the Faroe Islands and the Norwegian archipelago of Svalbard in the Arctic Ocean. REUTERS/Sergei Karpukhin

This is one way to guarantee a cloud-free view of a total eclipse. A view from a plane during an “Eclipse Flight” from the Russian city of Murmansk to observe the event high over the Norwegian Sea. Credit: Reuters / Sergei Karpukhin

While very dilute compared to the Sun itself, the corona is extremely hot, about a 1,800,000° F. During periods of high solar activity, especially during the peak of the 11-year sunspot cycle, the corona is evenly distributed around the solar disk. In “slow” times, it stretches out in long streamers from the Sun’s equator.

The corona’s shape is determined by magnetic fields that originate from within the Sun and extend outward for some 5 million miles. I’ve been fortunate enough to stand under the moon’s shadow during several eclipses, and it’s always the highlight. The Sun’s atmosphere, threaded with delicate loops and spikes, looks electric. Alive. If you’ve never seen a total solar eclipse, make sure to put it on your bucket list.

A very, very young lunar crescent might be viewable this evening just about 20 minutes after sunset nearly due west about 25 degrees (2.5 outstretched fists) below Venus. Source: Stellarium

A very, very young lunar crescent might be viewable this evening just about 20 minutes after sunset nearly due west about 25 degrees (2.5 outstretched fists) below Venus. Source: Stellarium

The moon, responsible for today’s spectacle, will put on a solo encore this evening when it will be just far enough from the Sun to glimpse shortly after sunset.

This truly is a “young” moon, just 14 hours old as seen from the East Coast, 15 from the Midwest, 16 from the mountain states and 17 from the West Coast.

Use the diagram to help you find it. The moon will be just 3° high 20 minutes after sunset. You’ll need a very open, clear sky and a pair of binoculars to attempt the challenge.

If you were out early this morning you might have seen a few rays of northern lights. Credit: Guy Sander

If you were out early this morning you might have seen a few rays of northern lights. Credit: Guy Sander

Ah, the aurora. Hard to believe, but it’s been glimmering in the north for four nights in a row as seen from the northern U.S. and southern Canada. Guy Sander of Duluth spotted it at 1:15 this morning and brought his camera along for the ride.

NOAA space weather forecasters are predicting a G1 or minor geomagnetic storm for this evening before activity tapers off for the weekend. Cause? Another one of those holes in the Sun’s corona that allows subatomic particles to flow as free as the spring breeze from there to here.

Speaking of spring, the vernal equinox begins this evening at 5:45 p.m. (CDT). That’s when the Sun crosses the celestial equator moving north. Day and night are an equal 12 hours apiece across the planet except for the North Pole where the Sun will be up 24 hours now through the first day of fall. The South Pole will see their last day of 24-hour sunlight; starting tomorrow 6 months of night commence.

Unique eclipse to darken North Pole’s first day of sunshine

Eclipse March 20

The path of totality passes over far more water than land during tomorrow’s total solar eclipse.  Areas outside of totality will see a partial eclipse with varying amounts of the Sun visible depending on location. The eclipse happens during mid-morning hours across central Europe. Credit: Larry Koehn / shadowandsubstance.com

Tomorrow March 20, coincidentally the first day of spring, the moon’s shadow will sweep across the Danish Faroe Islands and darken the Norwegian archipelago Svalbard before setting at the North Pole. It’s a little unusual to have a total solar eclipse occur on an equinox, but one that ends at sunset directly at the North Pole makes it unique.

Global map showing where the eclipse will be visible along with times, which are given in UT or Universal Time. Subtract 4 hours for EDT, 5 for CDT and so on. Credit: Fred Espenak

Global map showing where the eclipse will be visible along with times, which are given in UT or Universal Time. Subtract 4 hours for EDT, 5 for CDT and so on. Click for an interactive map with times for your city. Credit: Fred Espenak

Die-hard totalitarians – utterly the wrong word for those who travel the world to see as many total solar eclipses in one lifetime as possible – are already cozied up in a hamlet in the Faroes or on a ship in the Arctic Ocean near Svalbard, where the weather forecast tomorrow is for partly sunny skies and a high of 0° F (-18° C). For a little more money, some will board a special eclipse jet and fly above the clouds directly within the eclipse path.

Animation of the March 20 total solar eclipse. The small black spot is the umbra or core of the moon's shadow. The larger gray area is the penumbra. Credit: NASA

Animation of the March 20 total solar eclipse. The small black spot is the umbra or core of the moon’s shadow. The larger gray area is the penumbra, where a partial eclipse will be visible. The longest duration of totality – 2 minutes 47 seconds – will occur off the coast of the Faroe Islands. Credit: NASA

“Umbraphile” is the real word for those who crave the moon’s shadow. Because of the distant location and lack of land to stand on, their number will be tiny compared to the millions of regular folk who’ll witness a partial eclipse across all of Europe, the northern third of the African continent, north-central Asia and the Middle East. The farther north you live, the deeper the moon will bite into the Sun.

If I could, I’d opt for the North Pole. It’s been in darkness the past six months with only the glow of twilight in recent weeks. Tomorrow, for the first time since the fall equinox, the sun will poke above the horizon. For a couple minutes during its return, the moon will cover the Sun’s face and polar skies will darken for a brief time.

The view from the north pole will be nothing short of amazing with the Sun setting in total eclipse. Source: Stellarium

The view from the North Pole will be nothing short of amazing with the Sun skimming along the horizon while briefly in total eclipse. Source: Stellarium

Now that sounds like an amazing thing to see. Imagine wintering at the North Pole, waiting 6 months for the Sun’s return, only to see it robbed (temporarily) by the moon getting in the way.

I suppose you wouldn’t complain. After all, a total solar eclipse on the first day of spring at the pole happens only once every 400,000-500,000 years!

Solar eclipses usually happen a few times a year when the new moon passes directly between the Earth and Sun, completely blocking the Sun from view for several minutes of totality. Because the moon’s shadow on Earth is rather narrow – about 125 miles wide – only those living within that strip will see a total eclipse. Far more people will witness a partial eclipse, which will be visible across thousands of miles.

During a solar eclipse, the moon gets directly between Sun and Earth and casts its shadow along a narrow band on our planet's surface. Credit: NASA

During a solar eclipse, the moon gets directly between Sun and Earth and casts its shadow along a narrow band on our planet’s surface. Credit: NASA

Would you like to see the total eclipse as it happens and not spend a cent? SLOOH’s online observatory will stream the event starting at 3:30 a.m. CDT.

Sorry, I should have told you about that little catch. The eclipse happens during morning hours across Europe. That translates to very early morning hours from the U.S. You can also watch it at the Virtual Telescope’s site beginning at 3:15 a.m. CDT.

Head to bed early if you want to see it. I hope to share eclipse photos gathered online tomorrow. The next eclipse, a total lunar, will come at the next full moon on April 4th and be widely visible across the Americas.

Northern lights recap and planning for the next show

Northern Lights over Caribou Lake, Minn. by Guy Sander of Duluth, Minn.

How to describe last night’s northern lights? Grand expectations – brief but spectacular display around 9:30 p.m. – long lull till nearly midnight – second blast low in the sky around midnight.

Aurora over an ice-covered lake north of Duluth last night March 17. Credit: Bob King

Aurora over an ice-covered lake north of Duluth last night March 17. Credit: Bob King

If you lived near city lights or in an area where there were trees to your north, you might have wondered what all the fuss was about. At best, you may seen just a big glow in the northern sky. Most of the action from mid-northern latitudes was low enough that buildings, hills and trees would have blocked the view.

Aurora seen over Lake Superior from Wisconsin Point in Superior, Wis. around 11:55 p.m. Credit: Matthew Moses

Aurora seen over Lake Superior from Wisconsin Point in Superior, Wis. around 11:55 p.m. Credit: Matthew Moses

There are two key things to plan in advance of an aurora – a place with a wide open view of the northern sky and one where there are no concentrations of city lights in that direction. When a display is imminent, drive to that spot, watch and wait. I nearly missed last night’s peak because of a commitment till 9. On the way out, the sky broke loose with brilliant, rippling rays while I was still in the car. Luckily I arrived in time to see part of the great unfurling.

Of course, you may get skunked. Either by clouds or a disappointing show. But the longer you hang in there, the better your odds of being present when the sky cuts loose. I try to look at the up side. Even if no aurora appears, the company of the stars, the occasional meteor and sounds of the night are always a welcome break from work or sitting around the house.

Auroras may poke out again tonight. The forecast calls for a G2 geomagnetic storm with any northern lights reaching as far south as New York and Idaho. Last night’s show was visible as far south as southern New Jersey and perhaps further.

Beautiful rays returned at midnight seen here over Boulder Lake north of Duluth, Minn. Credit: Clint Austin

Beautiful rays returned at midnight seen here over Boulder Lake north of Duluth, Minn. Credit: Clint Austin

Aurora colors always fascinate. All the green and most of the reds you see are caused by oxygen atoms in our atmosphere. When high-speed particles from the Sun come racing down Earth’s magnetic fields lines towards the geomagnetic poles, they eventually strike the upper atmosphere anywhere from about 70 to 200 miles overhead. There they strike and transfer their energy to oxygen and nitrogen atoms. As the atoms return to their “rest states” they release the energy as tiny zaps of green and red light called photons.

Nature is so generous it swells me up inside. Good luck to you with clear skies in your forecast tonight.

Aurora’s out tonight as forecast – take a look!

After all the mush, a gorgeous outbreak of the northern lights around 9:30 p.m. (CDT) this evening. Here the lights are reflected off the ice in a lake north of Duluth, Minn. Credit: Bob King

After all the mush, a gorgeous outbreak of the northern lights around 9:30 p.m. (CDT) this evening. Here the lights are reflected off the ice in a lake north of Duluth, Minn. Credit: Bob King

Good news! So far the forecast has been accurate. The aurora’s out right now filling the entire northern sky. It massive but still rather faint, soft and with little structure. I’m picking up a few dim rays. Many potentially strong aurora start this way but eventually break out into amazing lights.

The aurora returns to its soft, mushy state around 10:30 p.m. Tuesday night. Credit: Bob King

The aurora returns to its soft, mushy state around 10:30 p.m. Tuesday night. Credit: Bob King

Well, it happened. The mush congealed into a long curtain across the northern sky and shattered into a display of brilliant rays around 9:30 p.m. This lasted till around 10 when the lights died back to glows and soft rays. As of 11 p.m. it’s still out there but quiet for the moment. I wouldn’t be surprised at all if a rerun happened around midnight.

Auroras paint the sky green (and red!) on St. Patrick’s Day

Wow! Tall green and red rays of northern lights fill the northern sky earlier this morning. More may arrive tonight. "It was great to see the color in them - green and red - appropriate for the day," said Schaff said

Wow! Tall green and red rays of northern lights fill the northern sky earlier this morning. More may arrive tonight. “It was great to see the color in them – green and red – appropriate for the day,” said Schaff. Credit: Jim Schaff

What a colorful coincidence! On the morning of St. Patrick’s Day an unexpected and HUGE geomagnetic storm blew our way. And it’s still blowing. If it wasn’t for that new nova in Sagittarius, I would have slept through the whole thing. Maybe some of you rose before dawn to see the nova and turned around in surprise at what was going on behind your back.

Deliciously delicate "paws" of aurora leave temporary impressions in the northern sky this morning around 5:45 a.m. Credit: Bob King

Deliciously delicate “paws” of aurora leave temporary impressions in the northern sky this morning around 5:45 a.m. Credit: Bob King

Jim Schaff of Duluth happened to be up around 2:30 and wisely set up camera on tripod to capture the magnificent and colorful display. Even as the sky blued at the coming of dawn, the northern lights wouldn’t quit. I stood and watched two bands of green toss out rays like clowns throwing candy in a parade. Beautiful.

The Sagittarius Teapot with the new nova arrowed photographed yesterday morning March 16. Credit: Justin Cowart

The Sagittarius Teapot with the new nova arrowed photographed yesterday morning March 16. Credit: Justin Cowart

Oh and yes, there was the nova. Caught up in a green auroral haze, I nearly forgot to look, but when I did, the news was good. Reports from late yesterday indicated our new “guest star” had already faded a bit, but I saw it plainly in 10×50 binoculars at magnitude +5.6, a little brighter.

Then came another surprise – the crescent moon. The slender slipper rose above the rose ribbon of an impending sunrise. But the light was gaining. Sagittarius soon faded away as did the aurora.

The Kp or K-index measures the amount of magnetic activity high in Earth's atmosphere. Kp=8 means a severe storm. Minor auroras show up when Kp = 4 or 5. Click to see the live version which is updated every 3 hours. Credit: NOAA

The Kp or K-index measures the amount of magnetic activity high in Earth’s atmosphere. Kp=8 means a severe storm. Minor auroras show up when Kp = 4 or 5. Click to see the live version which is updated every 3 hours. Times are CDT. Credit: NOAA

Not so fast. Just because the sky turned blue didn’t mean the aurora wasn’t still in the house. Throughout the morning it continued and blossomed from a strong G3 geomagnetic storm into rather rare G4 or severe storm. G4 storms can cause electrical currents in oil pipelines, fading of shortwave radio frequencies, problems with satellite navigation and auroras as far south as Alabama. Too bad it’s daytime!

Wide open view of this morning's aurora shows two active rayed arcs. Credit: Bob King

Wide open view of this morning’s aurora shows two active rayed arcs. Credit: Bob King

Tonight, NOAA space weather forecasters are calling for G1 level or minor storms (check update below). That usually means auroras only visible from the northern tier of states and points north. You never know. The Earth’s magnetic environment is highly disturbed after being hit with blasts of solar particles from recent explosions related to the supercharged sunspot group 2297 as well as a large coronal hole. The best time to look tonight will be from about 7 p.m. to 1 a.m. CDT. Watch for low bright arcs or occasional feather-like rays in the northern sky.

The auroral oval this morning just before 5 a.m. CDT. Intense auroras were seen in the red area. Click to go to the current view of the oval. Credit: NOAA

The auroral oval this morning just before 5 a.m. CDT. Intense auroras were seen in the red area. Click to go to the current view of the oval. Credit: NOAA

Another great tool to help you predict or know when the aurora’s out is the Aurora – 30 Minute Forecast put out by NOAA. It shows the extent of the permanent aurora that’s centered on Earth’s geomagnetic pole. When the Sun’s magnetic field links up with Earth’s magnetic bubble, particles get funneled into this beanie-cap affair, causing it to expand southward. During a big aurora, it expands far enough south that folks in the Midwest and southern states can see the northern lights.

Things weren't too bad in Alaska either. This spectacular photo was taken early this morning from Donnelly Creek. Nothing like a little green on St. Patrick's Day. Credit: Sebastian Saarloos

Things weren’t too bad in Alaska either. This spectacular photo was taken early this morning from Donnelly Creek. Nothing like a little green on St. Patrick’s Day. Credit: Sebastian Saarloos

May the luck of the Irish be with you tonight.

**UPDATE: The new forecast is much better. Strong to severe storms (G3-4) are now in the forecast for the remainder of the day and tonight. Start looking as soon as it gets dark.

New binocular nova discovered / Jupiter event tonight / Aurora update

Animation showing the star field before the nova appeared and after. It's currently bright enough to see from a dark sky site with the naked eye. Credit: Ernesto Guido and Nick Howes

Animation showing the star field before the nova appeared and after. It’s currently bright enough to see from a dark sky site with the naked eye. Credit: Ernesto Guido and Nick Howes

A star undergoing a massive thermonuclear explosion called a nova was discovered yesterday (March 15) in the constellation Sagittarius the Archer by Australian amateurJohn Seach. He found it in photos he took with a digital SLR camera and low-light 50mm lens.

It’s the second nova to whistle from the Teapot constellation this year. The first appeared in mid-February and became faintly visible in larger binoculars. Seach found nova #2 shining at magnitude +6, the naked eye limit. Other observers later confirmed the sighting at magnitude 5.3, dim but easily visible with the naked eye from a rural site, and 5.8.

This view shows the sky facing south-southeast just before the start of dawn in mid-March from the central U.S. The nova’s located squarely in the Teapot constellation. Source: Stellarium

This view shows the sky facing south-southeast around the start of dawn from the central U.S. at mid-month. The nova’s located almost in the center of of the Teapot constellation about 15° high. Source: Stellarium

Whether it brightens or begins to fade only time will tell, but any nova bright enough to see in binoculars is exciting news. I plan to be out looking at the next opportunity. I’ve included maps here you can use to point you to the “new star”.

Be aware that Sagittarius is rather low in the sky from mid-northern latitudes this time of year. To spot the nova you’ll need an open view toward the southeast. Start looking just before the start of dawn or about 1 hour 40 minutes before sunrise. Sagittarius is the next zodiac constellation to the east (left) of Scorpius.

Use this map along with a pair of binoculars to pinpoint the nova's location. Neighboring stars are numbered with their magnitudes (decimals omitted for clarity) to help you estimate the nova's brightness. Source: Stellarium

Use this map along with a pair of binoculars to pinpoint the nova’s location. Neighboring stars are numbered with their magnitudes (decimals omitted for clarity) to help you estimate the nova’s brightness. Source: Stellarium

Novae always occur in very close double stars, where one of the stars is a tiny but dense white dwarf and the other a more familiar sun-like star. The dwarf draws matter from the atmosphere of the normal star, which ultimately accumulates on its surface. There it’s heated to tens of thousands of degrees until igniting and burning explosively in a thermonuclear explosion.

Suddenly, a dim unnoticed star brightens 50,000-100,000 times in a matter of hours, luminous enough for someone back here on Earth to spot it in binoculars. Simply remarkable.

Material gets blasted into space at tremendous speeds – already astronomers have measured gas moving away from the nova at speeds of over 6.2 million mph (10 million kph)!

Jupiter's four brightness moons shown for tonight (March 16) around 9:50 p.m. CDT just before Ganymede eclipses Europa. Created with Stellarium

Jupiter’s four brightness moons shown for tonight (March 16) around 9:50 p.m. CDT just before Ganymede eclipses Europa. South is up like the view shown in many telescopes. Created with Stellarium

Things must heating up again in the sky. Not only do we have a bright nova but tonight Jupiter’s moon Ganymede eclipses Europa. The event will be one of the best of the Jupiter observing season and easily viewable in a small telescope.

The key to seeing an eclipse is for the moon to be covered in as much shadow as possible. The deeper a moon moves into another’s shadow, the fainter it gets and the more easily we can see its brightness plummet.  Tonight’s eclipse is the best remaining of the year for the Americas; when fully eclipsed by Ganymede, Europa’s light will fade by 2.4 magnitudes or 59%.

A weak display of aurora Saturday evening March 14. Credit: Bob King

Clouds finger a weak display of aurora Saturday evening March 14. Credit: Bob King

The eclipse is short! It begins at 9:51 p.m. (CDT) and ends at 9:55 p.m. just four minutes later. Set your scope up a half hour beforehand and let it cool down so your views will be sharp. Then about 5 minutes before eclipse start focus on Jupiter and get familiar with the uneclipsed appearance of Europa. Now just watch as Europa dims (in comparison to the other moons) and then re-brightens.

There was a lot of potential aurora in the forecast over the weekend, but skywatchers in the U.S. may have looked in vain for it.  But … we did see some. On Saturday evening around 10:30 p.m. a weak aurora raised its head low in the northern sky. Mike Sangster of Duluth, Minn. reported an hour later that a few bright rays appeared.

Guess what? Minor geomagnetic storms are back in the forecast for tomorrow night St. Patrick’s Day. Wouldn’t it be nice if the northern sky wore a little green for the occasion.

Gemini twins grab a phone, snap a “selfie”

The constellation Gemini is easily found at nightfall (around 8:45 p.m. CST) high in the southern sky to the right of brilliant Jupiter. Created with Stellarium

The constellation Gemini is easily found at nightfall (around 8:45 p.m. CST) high in the southern sky to the right of brilliant Jupiter and above Orion the Hunter. Created with Stellarium

The 88 constellations’ number and boundaries were set almost 100 years ago, so we won’t see any new ones added in our lifetimes. But that doesn’t mean we can’t picture them doing things our ancestors never would have never dreamed of.

Castor holds out his arm to snap a selfie of the twin stick-figure brothers. Illustration: Bob King

Castor holds out his arm to snap a selfie of the twin stick-figure brothers. Illustration: Bob King

That’s what happened recently while showing a group of students the nighttime sky at our local planetarium. As we made the rounds from Orion to Sirius and up to Gemini the Twins, it occurred to me that Castor’s arm reached out in the same manner as someone holding a mobile phone to snap a selfie.

Sculptures of the twin brothers Castor and Pollux.

Sculptures of the twin brothers Castor and Pollux.

And why not? The two are the famous twin brothers Castor and Pollux who joined up with Jason and the Argonauts in search of the golden fleece.

Castor was renowned for his skills as a warrior and his ability to tame and train horses; Pollux was a champion boxer. Their travels often took them to many faraway places, so it’s not unreasonable to suppose they’d crack off a few selfies to post on Facebook or Papyrusbook as it might have been known back then.

M35 is a rich and bright star cluster in Castor's foot in Gemini. A pair of 7x35 or 10x50 binoculars will show many of its stars. Just to its right (west) is the equally rich but much fainter star cluster NGC 2158. Credit: Bob King

M35 is a rich and bright star cluster in Castor’s foot in Gemini. A pair of 7×35 or 10×50 binoculars will show many of its stars. Just to its right (southwest) is the equally rich but much fainter star cluster NGC 2158. Credit: Bob King

OK, so I’m just having a little fun here. Let’s get serious for a moment. Castor’s foot is buried in a celestial treasure called M35, one of the winter/spring’s finest star clusters. From a dark sky you can see it as a hazy spot with the naked eye; binoculars will show lots of stars concentrated in a hazy, round glow the diameter of the full moon. Located 2,800 light years from Earth, M35 is relatively nearby.

Mythological view of the Gemini twins with bow and arrow instead of a cell phone. From Urania's Mirror

Mythological view of the Gemini twins with bow and arrow instead of a cell phone. From Urania’s Mirror

See that little clump to the lower right of M35? That’s another unrelated rich star cluster called NGC 2158. It requires a telescope to see. It’s fainter because it’s four times as far away, tucked deep in one of our galaxy’s spiral arms over 11,000 light years from your door.

Happy Pi Day! Find Pi in the Sky

A lovely lemon angel meringue pie in honor of Pi Day. Who knew math could make you hungry? Credit: Bob King

A lovely lemon angel meringue pie in honor of Pi Day. Pi, denoted by the symbol in the photo, has the unique power of stirring up an appetite. Credit: Bob King

Happy Pi Day! Pi is one of the few mathematical constants that immediately conjures up thoughts of food. Pies in particular. My wife Linda, inspired by this important day, prepared a lemon angel meringue pie I can’t wait to taste.

The parts of a circle – the encompassing circumference, the radius and diameter, equal to 2x the radius. Pi is the ratio between the circumference and diameter of a circle

The parts of a circle – the encompassing circumference, the radius and diameter, equal to 2x the radius. Pi is the ratio between the circumference and diameter of a circle

Exactly what is pi? It’s the ratio of the circumference of a circle to its diameter or the number you get when you divide the circumference of any circle by its diameter. It starts with 3.1415 and goes on forever in a never-repeating pattern. Mathematicians call it an infinite decimal. Unlike 3.57 or 7.5, which have a finite number of numbers after the decimal point, pi continues on into infinity. Divide C by D and you’ll never get to the end.

Not that math geeks with computers haven’t tried. By October 2011 two Japanese guys calculated 10 trillion digits of pi, a world record. Nice work, but still far from infinity.

Pi Day happens every March 14 because the calendar date 3/14 is the same as pi’s first three digits. But this year’s pi celebration is an exceptional one. When you add on the last two digits of the year you get 3.1415. As you might guess, this date alignment happens just once a century.

Let’s go further. When the clocks strikes  9:26:53 a.m. and 9:26:53 p.m. today we can add an additional five digits to make 3.141592653. If you find yourself in a bar or pub this evening, see if you can convince the crowd to celebrate the world of mathematics with a toast to the moment.

How about 6 slices of pi? The brighter stars in constellations are named for the letters of the Greek alphabet with Alpha typically denoting the brightest star. Much of Orion's shield is composed of similarly bright stars neatly lined up, so each received the "pi" designation with a number. Created with Stellarium

Help yourself to six slices of Orion pi if you’re out tonight. The brighter stars in constellations are named for the letters of the Greek alphabet with Alpha typically denoting the brightest. Most of the stars in Orion’s shield are of similar brightness and neatly lined up, so each received the “pi” designation with an individual number. Created with Stellarium

If you’re not out sipping suds but find yourself instead at the telescope, consider celebrating the special moment with a hefty helping of Orion’s “pi stars” and the very attractive double star Pi Bootis. After proper names, the brighter stars in the constellations are labeled with Greek letters, meaning most groups have a “pi star”.

Pi Bootis, a beautiful double star comes up in the east around 11 p.m. local time. You'll find the magnitude 4.5 star not far below brilliant Arcturus, the brightest star in Bootes. Created with Stellarium

Pi Bootis, a beautiful double star comes up in the east around 11 p.m. local time. You’ll find the magnitude 4.5 star not far below brilliant Arcturus, the brightest star in Bootes. Created with Stellarium

Pi Bootis is a striking, close double star that looks like pair of headlights approaching from interstellar space. The brighter star is magnitude 5 with a mag. 5.8 companion star just 5.5″ due east. Even a small telescope will split this beauty so long as you use a magnification around 60x or higher.

Pi shows up in more places than your oven or neighborhood greasy spoon. Anything involving circles, spheres and ellipses feature pi front and center which is why astronomy and architecture require healthy servings of pi for sustenance. Galileo, Copernicus and Kepler used pi in their calculations of the sizes, distances from Earth, and orbits of the planets. It pops up in statistics, mechanics, cosmology and even in Einstein’s Theory of Relativity equations.

Coincidentally it’s also the wild-haired Einstein’s birthday today. Happy E=mc² Day, too!

PS. I have to admit I ate my pie as I wrote this entry. Truly delicious. I like Pi Day.

Lucky Friday the 13th for auroras? / Ganymede auroras hint at hidden ocean

Close-up of the complex sunspot group behind the recent CMEs arriving at Earth yesterday and today. Credit: NASA

Close-up of the complex sunspot group behind the recent CMEs arriving at Earth yesterday and today. Italian amateur spotted it with the naked eye using a safe solar filter today. Credit: NASA

Before we look in on Jupiter’s moon Ganymede to see what we can learn from its auroras, I wanted to update you on what’s going on with our own greeny lights here on Earth. The anticipated minor storm arrived late – around 5 a.m. Central time today but didn’t dip deeply enough into the U.S. for a good show.

Don’t give up hope yet. Activity from all the coronal mass ejections kicked out by sunspot group 2297 this week combined with streams of high speed particles from recent solar coronal holes should make for more storming tonight.  NOAA space weather forecasters are calling for a G1 (minor) geomagnetic storm which usually means skywatchers in the northern U.S. should be alert for northern lights. Maybe our luck will change – I can’t think of a better day for it to happen.

Meanwhile, 422 million miles away, a cyclical shift in the position of auroral ribbons on Jupiter’s largest moon Ganymede hint at a hidden ocean buried under 95-miles (150 km) of icy crust.

In this artist’s concept, the moon Ganymede orbits the giant planet Jupiter. NASA’s Hubble Space Telescope observed aurorae on the moon generated by Ganymede’s magnetic fields. A saline ocean under the moon’s icy crust best explains shifting in the auroral belts measured by Hubble. Credit: NASA/ESA

In this artist’s concept, the moon Ganymede orbits the giant planet Jupiter. NASA’s Hubble Space Telescope observed auroras on the moon generated by Ganymede’s magnetic fields. A salty ocean under the moon’s icy crust best explains shifting in the auroral belts measured by Hubble. Credit: NASA/ESA

Ganymede is the largest moon in the solar system and the only moon with its own magnetic field. The magnetic field causes aurorae, which are ribbons of glowing, hot electrified gas, in regions circling the north and south poles of the moon. Because Ganymede is close to Jupiter, it’s also embedded in Jupiter’s magnetic field. When Jupiter’s magnetic field changes, the auroras on Ganymede also change by “rocking” back and forth.

To generate a magnetic field a planet or moon must have material moving beneath its crust that’s able to conduct an electric current. On Earth that’s iron in our planet’s liquid outer core, on Ganymede it appears to be a salty subterranean ocean.

To see and photograph auroras you need an atmosphere. Incoming solar or Jovian energetic particles strike the air, excite the atoms and cause them to release light in response – this is what we see as the aurora.  Ganymede possesses a very thin atmosphere of oxygen.

NASA Hubble Space Telescope images of Ganymede's auroral belts (colored blue in this illustration) are overlaid on a Galileo orbiter image of the moon. The amount of rocking of the moon's magnetic field suggests that the moon has a subsurface saltwater ocean. Image Credit: NASA/ESA

Images of Ganymede’s auroral belts (colored blue in this illustration) are overlaid on a Galileo orbiter image of the moon. The amount of rocking of the moon’s magnetic field suggests that the moon has a subsurface saltwater ocean. The new observations were done in UV light, which can be seen by the Hubble in its orbit above Earth’s atmosphere. Credit: NASA/ESA

By watching the rocking motion of the two auroras, scientists were able to determine that a large amount of saltwater exists beneath Ganymede’s crust affecting its magnetic field.

Here’s how it works. If Ganymede DIDN’T have an ocean, changes in Jupiter’s magnetic field would cause the auroras to rock back and forth by 6°. But the conductive ocean fights Jupiter’s field so much, it reduces the rocking of the auroras to just 2°.

Jupiter’s magnetic field creates a secondary magnetic field within Ganymede’s soggy interior counter to the planet’s. Call it magnetic friction, but what a wonderfully imaginative way to probe a moon’s interior through study of its faint auroras.

Scientists studying how Ganymede's magnetic field (shown here as curved lines of magnetic force similar to iron filings around a magnet) NASA/European Space Agency

Scientists studying how Ganymede’s magnetic field (shown here as curved lines of magnetic force similar to iron filings around a magnet) interacts with Jupiter’s in the form of shifting auroras believe the moon harbors a large ocean. Credit: NASA/European Space Agency

“I was always brainstorming how we could use a telescope in other ways,” said Joachim Saur of the University of Cologne in Germany, who headed up the study using the Hubble Space Telescope. “Is there a way you could use a telescope to look inside a planetary body? Then I thought, the aurorae! Because aurorae are controlled by the magnetic field, if you observe the aurorae in an appropriate way, you learn something about the magnetic field. If you know the magnetic field, then you know something about the moon’s interior.”

“Brilliant!” as the Harry Potter character would say.

Scientists estimate the ocean is 60 miles (100 km) thick or 10 times deeper than Earth’s oceans. Now we can add Ganymede to the roster of extraterrestrial planets and moons – Mars, Europa and Enceladus – known to possess liquid water, one of life’s essential essences.