St. Patrick’s Day aurora storm strongest in a decade

Using the “day-night band” (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS), the Suomi NPP satellite acquired this view (above) of the aurora borealis around 1:30 a.m. Eastern Daylight Time on March 18, 2015. Auroras appear as white streaks over Hudson Bay, southern Canada, and the northern United States. The DNB sensor detects dim light signals such as auroras, airglow, gas flares, city lights, and reflected moonlight. In the image above, the sensor detected visible light emissions as energetic particles rained down from Earth’s magnetosphere into the gases of the upper atmosphere.

The Suomi NPP satellite photographed the aurora borealis around 12:30 a.m. CDT on March 18, 2015. Auroras appear as white streaks over Hudson Bay, southern Canada, and the northern United States. In the image above, the sensor recorded the emission of light as energetic particles rained down from Earth’s magnetosphere into the gases of the upper atmosphere. Credit: NASA/Suomi NPP – VIIRS

Earth celebrated St. Patrick’s Day on March 17 with vivid red, white and green auroras seen as far south as the southern U.S. and as far north as New Zealand in the southern hemisphere.

It turns out the geomagnetic storm that sparked the lights was the strongest in a decade. On Sunday, March 15, a coronal mass ejection exploded off the Sun towards Earth as seen by the Solar Heliospheric Observatory (SOHO).

The Kp index over the three days starting March 16 tells the story of the geomagnetic storm in red bars of high activity. The times shown are CDT at the height of the storm. Credit: NOAA

The Kp index over the three days starting March 16 tells the story of the geomagnetic storm in red bars of high activity. The times shown are CDT at the height of the storm. Credit: NOAA

By March 17, the burst of solar particles and energy reached Earth and kept the solar wind stream at potent levels for more than 24 hours. The storm reached a G4 or “severe” level on NOAA’s geomagnetic storm scale. Meanwhile, the Kp index, an indicator of global geomagnetic storm activity, fluctuated between 6 to 8 on a scale that goes to 9.

The storm peaked during the daylight hours for observers in the U.S. and Canada. Some observers caught it on the rise in the early morning hours of the 17th while many more saw it rage into the night. Auroras continued to reverberate – albeit on the quieter side – for the remainder of the week.

The Aurorasaurus site was designed by researchers from the New Mexico Consortium, NASA, Pennsylvania State University, and Science Education Solutions to improve chances for people to catch an aurora by collecting real-time tweets and information from other sites. Credit: Aurorasaurus

The Aurorasaurus site was designed by researchers from the New Mexico Consortium, NASA, Pennsylvania State University, and Science Education Solutions to improve chances for people to see an aurora by collecting real-time tweets from aurora watchers. Credit: Aurorasaurus

Many people submitted photos and observations of the display through the Aurorasaurus website, a new citizen science project that aims to improve chances for folks to see an aurora by collecting and sharing tweets and information from other sources in real-time. Aurorasaurus gathered 35,000 aurora-related tweets and reports and confirmed 250 of them as positive sightings.

The project’s designers hope to improve our understanding of the auroral oval, two rings-shaped zones of auroras centered on Earth’s geomagnetic poles.

Auroras may return tonight, Saturday

Aurora near Yellowknife, Northwest Territory, Canada during the big St. Patrick's Day display. Credit: Joe Culler

Amazing curtains of aurora breaking up into rays near Yellowknife, Northwest Territory, Canada during the big St. Patrick’s Day display. Credit: Joe Culler

Thanks to a change-up in the solar wind called a co-rotating interaction region (CIR) followed by more gusty winds from a hole in the Sun’s corona, we have a shot at seeing auroras both tonight and Saturday night. CIRs are compression regions between a slow-flowing solar wind and a fast one. Material can pile up in a CIR, creating delicious auroral havoc upon its arrival at Earth.

Multiple curtains of northern lights float over conifers near Yellowknife during the mid-March aurora storm widely seen across the central and northern U.S. Credit: Joe Culler

Multiple curtains of northern lights float over conifers near Yellowknife during the mid-March aurora storm widely seen across the central and northern U.S. Credit: Joe Culler

NOAA space weather experts are calling for G1 minor geomagnetic storms during the hours leading up to midnight both nights. Minor storms usually mean auroras across the northern parts of the northern states and southern Canada, but as you’re probably aware, the magnetic direction of material coming our way makes a big difference as to whether it creates a storm.

If the south pole of the cloud brushes our magnetic domain, it’s far more likely to connect with Earth’s northward-pointing field. Like magnets snapping together, cloud and Earth-field are drawn to each other. Particles from the Sun can then follow Earth’s magnetic field lines into the polar regions where they strike and excite the atoms that produce the aurora.

ACE plot of magnetic field direction or Bz from last night. You can see how the storm dissipated once the magnetic direction of the cloud changed from south (during the storm) to north (above the white horizontal line). Credit: NASA

ACE plot of magnetic field direction or Bz from a storm last September. You can see how the storm dissipated once the magnetic direction of the cloud changed from south (during the storm) to north (above the white horizontal line). Credit: NASA

I always check the Bz, a measure of whether the arriving solar wind is pointing north or south. When the Bz drops below the centerline and especially if it’s at -10 or lower (south), there’s a fair chance you’ll see northern lights. Click over the ACE satellite page to check to get the lowdown on the Bz. Use the topmost graph with the red squiggly line.

The 8-day-old moon will fill your eyes with craters. Credit: Bob King

The 8-day-old moon will fill your eyes with craters. Credit: Bob King

Unlike the recent St. Patrick’s Day display, which happened in a moonless sky, we have an 8-day-moon to contend with tonight. That’s not an aurora killer but it will reduce contrast. Also, don’t be fooled by a lighter horizon in the northern sky. Normally, that’s a sign of aurora, but moonlight can also make the sky near the horizon appear brighter.

Not that there’s anything wrong with the moon. Now’s the best time to see it in a telescope – it’s high in the south and its current phase shows off a spectacular diversity of craters and land forms.

Let’s hope we get a nice aurora sometime this weekend.

One other tidbit for those following the nova in Sagittarius (Nova Sagittarii 2015 No.2). After fading early this week to around 6th magnitude, it’s rebrightened! I was surprised to see it back up to 5.0 this morning.

Nova in Sagittarius brightens / Aurora keeps on truckin’

Photo of the Teapot constellation Sagittarius this morning March 21 with the nova. The best time to see it is at the start of dawn when the star is highest in a dark sky. Credit: Bob King

Photo of the Teapot constellation Sagittarius this morning March 21 with the nova. The best time to see it is at the start of dawn when the star is highest in a dark sky. Credit: Bob King

The nova in Sagittarius discovered last week is on its way UP! Since then, it’s brightened to around magnitude 4.5, making it relatively easy to see with the naked eye if you know just where to look. It’s also been christened Nova Sagittarii 2015 No. 2, a temporary designation.

It surprised me this morning at +4.4 — easy to see from a dark sky alongside the spectacular southern Milky Way. It’s uncommon to see one of these stellar explosions with the naked eye. That’s why I encourage you to seize the opportunity. The last time one was this bright was back in August 2013 when Nova Delphini (V339 Del) popped off at +4.3.

This AAVSO chart will not only help you pinpoint the nova but also has stars labeled with their magnitudes or brightness. Decimals are omitted, so a star marked 47 is magnitude +4.7. Credit: AAVSO

This AAVSO chart will not only help you pinpoint the nova but also has stars labeled with their magnitudes or brightness. Decimals are omitted, so a star marked 47 is magnitude +4.7. The PNV title refers to Possible Nova. The nova’s has since been confirmed. Credit: AAVSO

You can use the photo and the AAVSO chart to take you right there. The nova’s not so bright that you can just walk outside and look up and see it. Find a location with a wide open view to the southeast, get oriented in the Teapot and then use binoculars. Once you’ve located the nova this way, try spotting it with your eyes alone.

Checking the list of recent observations submitted by observers with the American Association of Variable Star Observers (AAVSO) the nova’s been trending upward in brightness since discovery. Who knows? There’s a good chance it could brighten further.

Telescope users should keep an eye out for changes in the nova’s color. Right now it’s pale yellow as we see a mix of light from the bluish explosion on the surface of the white dwarf and the red-light-emitting expanding cloud of debris around it. Over time, many novae redden as the explosion plays out and they cool. As with Nova Delphini, color changes over time can be striking and worth the extra effort to follow.

A short, featureless, pulsating arc of aurora from last night. Credit: Bob King

A featureless auroral arc slowly pulsed in brightness low in the northern sky last night March 20. Credit: Bob King

I also wanted to revisit the aurora, which we’ve been revisiting for days now, since it won’t quit! Last night’s weird, pulsating patches continued through at least 3 a.m. this morning, and the space weather experts predict more minor storming early tonight and Sunday night. We’re stuck in an awesome auroral groove fueled by streams of electrons and protons whooshing from the holes in the Sun’s corona unconstrained by solar magnetic fields.

No complaints here!

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.

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.

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.