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August 6, 2015December 23, 2015 by David Dickinson

Stealing Sedna

An artist's conception of Sedna. this assumes that Sedna has a tiny as yet undiscovered moon. Image credit; NASA/JPl-Caltech

Turns out, our seemly placid star had a criminal youth of cosmic proportions.

A recent study out from Leiden Observatory and Cornell University may shed light on the curious case of one of the solar system’s more exotic objects: 90377 Sedna.

Distant Sedna (circled) moving against the starry background). Image credit: NASA/Hubble

A team led by astronomer Mike Brown discovered 90377 Sedna in late 2003. Provisionally named 2003 VB12, the object later received the name Sedna from the International Astronomical Union, after the Inuit goddess of the sea.

From the start, Sedna was an odd-ball. Its 11,400 year orbit takes it from a perihelion of 76 astronomical units (for context, Neptune is an average of 30 AUs from the Sun) to an amazing 936 AUs from the Sun. (A thousand AUs is 1.6% of a light year, and 0.4% of the way to Proxima Centauri, the closest star to our solar system). Currently at a distance of 86 AU and headed towards perihelion in 2076, we’re lucky we caught Sedna as it ‘neared’ (we use the term ‘near’ loosely in this case!) the Sun.

But this strange path makes you wonder what else is out there, and how Sedna wound up in such an eccentric orbit.

Zooming out; the inner solar system (upper left), the outer solar system (upper right), the orbit of Sedna (lower right) and the inner edge of the Oort cloud (lower left). Image credit: NASA

The study, entitled How Sedna and family were captured in a close encounter with a solar sibling looks at the possibility that Sedna may have been snatched from another star early on in our Sun’s career (of interstellar crime, perhaps?) The team used supercomputer simulations modeling 10,000 encounters to discover which types of near stellar passages might result in an ice dwarf world in a Sedna-like orbit.

“We constrained the parent star of Sedna to have between one and two times the mass of the Sun and its closest approach to be 200-400 AUs,” Dr. Lucie Jilkova of Leiden Observatory told Universe Today. “Such a close encounter probably happened while the Sun was still a member of its birth star cluster — a family of about 1,000 stars, so called solar siblings, born at the same time relatively close together — which was about 4 billion years ago.”

The orbit of Sedna. (Note Neptune and Pluto towards the center) Image credit: NASA/JPL

The best fit for what we see today in the outer solar system in the case of Sedna, is a close (340 AU) passage from the Sun — that’s over 11 times Neptune’s distance — of a 1.8 solar mass star inclined at an angle of 17-34 degrees to the ecliptic. Sedna’s current orbital inclination is 12 degrees.

Rise of the Sednitos

The paper assigns the term ‘Sednitos’ (also sometimes referred to as ‘Sednoids’) for these Edgeworth-Kuiper Belt intruders with similar characteristics to Sedna. In 2012, 2012 VP113, dubbed the ‘twin of Sedna,’ was discovered by astronomers at the Cerro Tololo Inter-American Observatory in a similar looping orbit. The ‘VP’ designation earned the as yet unnamed remote world the brief nickname ‘Biden’ after U.S. Vice President Joe Biden… hey, it was an election year.

There’s good reason to believe something(s?) out there shepherding these Senitos into a similar orbit with a comparable argument of perihelion. Researchers have suggested the existence of one or several planetary mass objects loitering out in the 200-250 AU range of the outer solar system… note that this is

a separate scientific-based discussion versus any would-be Nibiru related non-sense, don’t even get

us started…

If researchers in the study are correct, Sedna may have lots of company, with perhaps 930 planetesimals predicted in the ‘Sednito region’ of the solar system from 50 to 1,000 AUs and 430 more additional planetesimals littering the inner Oort cloud from the same early event.

“We focused on a particular example of a stellar encounter with characteristics from the ranges mentioned,” Dr. Jilkova said. “For this example, we estimated that there would be about 430 bodies similar to Sedna in the outer solar system (beyond 75 AU).”

Fun fact: One possible controversial candidate for the birth cluster of Sol and our solar system is the open cluster M67 in Cancer. It’s an intriguing notion to try and track down the star we stole Sedna from 4 billion years ago using spectral analysis, though researchers in the study point out that the other more massive star is probably an aging white dwarf by now.

Astronomy from the surface of Sedna is mind-bending to contemplate. Currently 86 AU from the Sun and headed towards perihelion in 2076, Sol would appear only 20” across from the surface of Sedna, but would still shine at magnitude -17 to -18 near perihelion, about 40 to 100 times brighter than a Full Moon. Fast forward about 5,500 years towards aphelion, however, and the Sun would dim to a paltry magnitude -12, a full magnitude (2.5 times) dimmer than the Full Moon.

The view from Sedna looking towards the inner solar system in 2015. Image credit: Starry Night Education Software. — The view from Sedna looking towards the inner solar system in 2015. Note the five degree red field of view marker. Image credit: Starry Night Education Software.

Shining at magnitude +21 in the constellation Taurus, astronomers know little else about Sedna. Based on brightness estimates, Sedna measures about 1,000 km in diameter. It does appear to be the reddest object in the solar system, and may turn out to be the ‘red twin of Pluto’ as recently revealed by NASA’s New Horizons spacecraft, complete with a surface rich in tholins.

And a new generation of observatories may uncover a treasure trove of Sednitos. The European Space Agency’s Gaia astrometry mission should uncover lots of new asteroids, comets, exoplanets and distant Kuiper Belt objects as a spin-off to its primary mission. Then there’s the Large Synoptic Survey Telescope, set to see first light in 2019.

“The key piece of the puzzle is to actually observe more Sedna-like objects.” Dr Jilkova said. “Currently, we know only of two such bodies. More discoveries are expected in the following years and they will shed light on the origin of Sedna and its family and the ‘criminal record’ of the Sun.”

It’s a fascinating story of interstellar whodunit for sure, as our Sun’s early days of wanton juvenile delinquency unravel before the eyes of modern day astronomical detectives.

July 6, 2015December 23, 2015 by David Dickinson

Catching Earth at Aphelion

Do you feel a little… distant today? The day after the 4^th of July weekend brings with it the promise of barbecue leftovers and discount fireworks. It also sees our fair planet at aphelion, or its farthest point from the Sun. In 2015, aphelion (or apoapsis) occurs at 19:40 Universal Time (UT)/3:40 PM EDT today, as we sit 1.01668 astronomical units (AU) from the Sun. This translates to 152.1 million kilometres, or 94.5 million miles. We’re actually 3.3% closer to the Sun in early January than we are today. This also the latest aphelion has occurred on the calendar year since 2007, and it won’t fall on July 6^th again until 2018. The insertion of an extra day every leap year causes the date for Earth aphelion to slowly vary between July 3^rd and July 6^th in the current epoch.

Aphelion sees the Earth 4.8 million kilometers farther from the Sun than perihelion in early January. The eccentricity of our orbit—that is, how much our planet’s orbit varies from circular to elliptical—currently sits at 0.017 or 1.7%.

It is ironic that we’re actually farther from the Sun in the middle of northern hemisphere summer. It sure doesn’t seem like it on a sweltering Florida summer day, right? That’s because the 23.44 degree tilt of the Earth’s rotational axis is by far the biggest driver of the seasons. But our variation in distance from the Sun does play a factor in long term climate as well. We move a bit slower farther from the Sun, assuring northern hemisphere summers are currently a bit longer (by about 4 days) than winters. The variation in solar insolation between aphelion and perihelion currently favors hot dry summers in the southern hemisphere.

But these factors are also slowly changing as well.

The eccentricity of our orbit varies from between 0.000055 and 0.0679 over a span of a ‘beat period’ of 100,000 years. Our current trend sees eccentricity slowly decreasing.

The tilt of our rotational axis varies between 22.1 and 24.5 degrees over 41,000 years. This value is also currently on a decreasing trend towards its shallow minimum around 11,800 AD.

And finally, the precession of the Earth’s axis and apsidal precession combine to slowly move the date of aphelion and perihelion one time around our calendar once every 21,000 years.

These combine to form what are known as Milankovitch Cycles of long-term climate variation, which were first expressed by astronomer Milutin Milankovic in 1924. Anthropogenic climate change is a newcomer on the geologic scene, as human civilization does its very best to add a signal of its very own to the mix.

We also just passed the mid-point ‘pivot of the year’ on July 2nd. More than half of 2015 is now behind us.

Want to observe the aphelion and perihelion of the Earth for yourself? If you have a filtered rig set to photograph the Sun, try this: take an image of the Sun today, and take another on perihelion next year on January 2nd. Be sure to use the same settings, so that the only variation is the angular size of the Sun itself. The disk of the Sun varies from 33’ to 31’ across. This is tiny but discernible. Such variations in size between the Sun and the Moon can also mean the difference between a total solar and annular eclipse.

Should we term the aphelion Sun a #MiniSol? Because you can never have too many internet memes, right?

And did you know: the rotational axis of the Sun is inclined slightly versus the plane of the ecliptic to the tune of 7.25 degrees as well. In 2015, the Sun’s north pole was tipped our way on March 7^th, and we’ll be looking at the south pole of our Sun on September 9^th.

And of course, seasons on other planets are much more extreme. We’re just getting our first good looks at Pluto courtesy of New Horizons as it heads towards its historic flyby on July 14^th. Pluto reached perihelion in 1989, and is headed towards aphelion 49 AU from the Sun on the far off date in 2114 AD. Sitting on Pluto, the Sun would shine at -19th magnitude—about the equivalent of the twilight period known as the ‘Blue Hour’ here on Earth—and the Sun would appear a scant one arc minute across, just large enough to show a very tiny disk.

All thoughts to consider as we start the long swing inward towards perihelion next January.

Happy aphelion!

July 3, 2015December 23, 2015 by Bob King

River of Fire Smoke Darkens Sun and Moon

The waning gibbous moon was still the color of fire even at midnight last night due to heavy smoke from Canadian forest fires. Credit: Bob King

My eyes are burning. The morning Sun, already 40° high, glares a lemony-orange. It’s meteorologically clear, but the sky looks like paste. What’s going on here?

Forest fires! Many in the Midwest, northern mountain states and Canadian provinces have been living under a dome of high altitude smoke the past few days reflected in the ruddy midday Sun and bloody midnight Moon.

On June 29, 2015 NASA’s Terra satellite captured this image of a river of smoke pouring across the Canadian provinces and central U.S. from hundreds of wildfires (seen at upper left) in western Canada. The difference in color between clouds true clouds and smoke is obvious. Credit: NASA image courtesy Jeff Schmaltz, LANCE/EOSDIS MODIS Rapid Response Team at NASA GSFC

Fires raging in the forests of northern Alberta and Saskatchewan have poured tremendous amounts of smoke into the atmosphere. Favorable winds have channeled the fumes into a brownish river of haze flowing south and east across Canada and into the northern third of the U.S. If an orange Sun glares overheard at midday, you’ve got smoke. Sometimes you can smell it, but often you can’t because it’s at an altitude of 1.2 – 3 miles (2-5 km).

The Moon sits at lower right with the star Vega visible at the top of the frame in this 30-second time exposure made last night (July 2) under the pall of forest fire smoke. Credit: Bob King

But the visual effects are dramatic. Last night, the nearly full Moon looked so red and subdued, it could easily have been mistaken for a total lunar eclipse. I’ve never seen a darker, more remote-looking Moon. Yes, remote. Without its customary glare, our satellite looked shrunken as if untethered from Earth and drifting away into the deep.

And nevermind about the stars. Try as I might, I could only make out zero magnitude Vega last night. The camera and a time exposure did a little better but not much.

This image taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard the Terra satellite on June 30, 2015. Residents of the states affected by the smoke will notice much more vivid sunsets during the time the smoke is in the air. The size of the smoke particles is just right for filtering out other colors meaning that red, pink and orange colors can be seen more vividly in the sky. NASA image courtesy Jeff Schmaltz, MODIS Rapid Response Team. Caption: NASA/Goddard, Lynn Jenner — This image was taken by the Terra satellite on June 30, 2015. Residents of the states affected by the smoke will notice much more vivid sunsets during the time the smoke is in the air. The size of the smoke particles is just right for filtering out other colors meaning that red, pink and orange colors can be seen more vividly in the sky. NASA image courtesy Jeff Schmaltz, MODIS Rapid Response Team. Caption: NASA/Goddard, Lynn Jenner

These days of deep red suns in the middle of the day fiery moons at night are an occasional occurrence across Canada and the northern half of the U.S. during the summer. Our previous bout with fire haze happened in early June as a result of massive wildfires in the Northwest Territories and northern Alberta. A change in wind direction and thorough atmospheric-cleaning by thunderstorms returned our blue skies days later.

Using a prism, we can take white light and spread it apart into its component colors. Credit: NASA

While the downsides of fire haze range from poor air quality to starless nights, the upside is a more colorful Sun and Moon.

Back in grade school we all learned that white light is made up of every color of the rainbow. On a sunny day, air molecules, which are exceedingly tiny, scatter away the blue light coming from the Sun and color the sky blue. Around sunset and sunrise, when the Sun’s light passes through the lowest, thickest, haziest part of the atmosphere, greens and yellows are also scattered away, leaving an orange or red Sun.

Fire smoke adds billions of smoke particles to the atmosphere which scatter away purples, blues, greens and yellows to turn an otherwise white Sun into a blood red version smack in the middle of the day.

A ring-billed gull is silhouetted against a yellow sky and orange sun early Monday afternoon. Smoke from forest fires across Canada’s Northwest Territories and northern Alberta drifted over the region and colored the the sun orange long before sunset. Credit: Bob King — A ring-billed gull is silhouetted against a yellow sky and orange Sun in Duluth, Minn. a few weeks back during the previous series of smoky days.This photo was taken around 3 p.m. local time. Credit: Bob King

Keep an eye on the color of the blue sky and watch for red suns at midday. Forest fires are becoming more common and widespread due to climate change. If you’ve never seen this eerie phenomenon, you may soon. For more satellite images of forest fires, check out NASA’s Fires and Smoke site.

I’ve often wondered what it would look like if Earth orbited a red dwarf star instead of the Sun. These smoky days give us a taste.

June 2, 2015December 30, 2015 by Jason Major

This Video About Solar Superstorms is Narrated by Benedict Cumberbatch and It Looks Awesome.

What’s better than a full 180-degree digital theater experience that takes you into the heart of our Sun to see how solar storms form? Why, all of that accompanied by a rumbling narration by Benedict Cumberbatch, of course.

The video above is a trailer for “Solar Superstorms,” a digital planetarium presentation distributed by Fulldome Film Society and co-produced by Spitz Creative Media, NCSA’s Advanced Visualization Lab, and Thomas Lucas Productions. It uses the monster Blue Waters supercomputers at the National Center for Supercomputing Applications at the University of Illinois to visualize the complex processes occurring in, on, and around the Sun. It might look a little weird in the flat 2D format above, but I can only imagine what it will be like to see it from inside a digital dome (and have the disembodied voice of Smaug/Sherlock/Khan thundering through the room!)

The film itself is still in production so I couldn’t find an official release date. But keep an eye out for it at your nearest planetarium and visit the FulldomeFilm.org catalog page for other films from the same distributor.

You can find a database of fulldome theaters and digital planetariums around the world here.

Video credit: Spitz Creative Media

May 31, 2015December 23, 2015 by Bob King

Allergies? Must Be Pollen Corona Season Again

A multi-ringed, oval shaped corona around the Sun on May 30, 2015 seen from northern Minnesota. The white spots are aspen seeds better known as "cotton fluff". Credit: Bob King

Don’t be surprised if you look up in the Sun’s direction and squint with itchy, watery eyes. You might be staring into billows of tree pollen wafting through your town. It’s certainly been happening where I live.

When conditions are right, billions of microscopic pollen grains consort to create small, oval-shaped rings around a bright Moon during the peak of the spring and early summer allergy season. With the Full Moon coming up this week, there’s no better time to watch for them.

Pollen grains from a variety of different common plants including sunflower, morning glory, prairie hollyhock and evening primrose. Credit: Dartmouth Electron Microscope Facility, Dartmouth College — Pollen grains from a variety of different common plants including sunflower, morning glory, prairie hollyhock and evening primrose magnified 500x and colorized. The green, bean-shaped grain at lower left is 0.05 mm across. Credit: Dartmouth Electron Microscope Facility

Because they’re often lost in the glare of the Sun or Moon, the key to finding one is to hide the solar or lunar disk behind a thick tree branch, roof or my favorite, the power pole. Look for a telltale oval glow, sometimes tinted with rainbow colors, right up next to the Moon or Sun’s edge. Common halos, those that form when light is refracted by ice crystals, span 44° compared to pollen coronas, which measure just a few degrees in diameter.

To see or photograph coronas, you need plenty of light. The Sun’s ideal, but so is the Moon around full. Fortunately, that happens on June 2, neatly fitting into the sneezing season. Last night, the same grains — most likely pine tree pollen — also stoked a lunar corona. Once my eyes were dark adapted and the Moon hidden by an arboreal occulting instrument (tree branch), it was easy to see.

A lunar pollen corona on May 30, 2015. The Moon was hidden by a utility pole. Like the solar version, this one is elongated too. The shape is caused by pollen grains' elongated shape and the fact that they tend to orient themselves as they drift in the wind. Credit: Bob King — A lunar pollen corona on May 30, 2015. The Moon was hidden by a utility pole. Like the solar version, this one was also oval and measured about 3.5° across. The shape is caused by elongated pollen grains fact that orient themselves as they drift in the wind. Credit: Bob King

One of things you’ll notice right away about these biological bullseyes is that they’re not circular. Pollen coronas are oval because the pollen particles are elongated rather than spherical like water droplets. When light from the moon or sun strikes pollen, the minute grains diffract the light into a series of closely-spaced colored rings. I’ve read that pine and birch produce the best coronas, but spruce, alder and and others will work, too.

And here’s another amazing thing about these coronas. You don’t need a transparent medium to produce them. No ice, no water. All that’s necessary are very small, similarly-shaped objects. Light waves are scattered directly off their surfaces; the waves interfere with one another to create a diffraction pattern of colored rings.

A lunar pollen corona photographed on June 22, 2008 displays “bumps” or extensions at approximately 90° angles around its periphery. Credit: Bob King

Pollen coronas tend to become more elongated when the Sun or Moon is closer to the horizon, so look be on the lookout during those times for more extreme shapes. For some reason I’ve yet to discover, pollen disks sometimes exhibit “bumps” or extensions at their tops, bottoms and sides.

So many of us suffer from allergies, perhaps the glowing presence of what’s causing all the inflammation will serve as partial compensation for our misery.

April 30, 2015December 23, 2015 by Jason Major

Watch an Enormous “Plasma Snake” Erupt from the Sun

SOHO LASCO C2 (top) and SDO AIA 304 (bottom) image of a solar filament detaching on April 28-29, 2015

Over the course of April 28–29 a gigantic filament, briefly suspended above the surface* of the Sun, broke off and created an enormous snakelike eruption of plasma that extended millions of miles out into space. The event was both powerful and beautiful, another demonstration of the incredible energy and activity of our home star…and it was all captured on camera by two of our finest Sun-watching spacecraft.

Watch a video of the event below.

Made from data acquired by both NASA’s Solar Dynamics Observatory (SDO) and the joint ESA/NASA SOHO spacecraft, the video was compiled by astronomer and sungrazing comet specialist Karl Battams. It shows views of the huge filament before and after detaching from the Sun, and gives a sense of the enormous scale of the event.

At one point the plasma eruption spanned a distance over 33 times farther than the Moon is from Earth!

Filaments are long channels of solar material contained by magnetic fields that have risen up from within the Sun. They are relatively cooler than the visible face of the Sun behind them so they appear dark when silhouetted against it; when seen rising from the Sun’s limb they look bright and are called prominences.

When the magnetic field lines break apart, much of the material contained within the filaments gets flung out into space (a.k.a. a CME) while some gets pulled back down into the Sun. These events are fairly common but that doesn’t make them any less spectacular!

Also read: Watch the Sun Split Apart

This same particularly long filament has also been featured as the Astronomy Picture of the Day (APOD), in a photo captured on April 27 by Göran Strand.

For more solar news follow Karl Battams on Twitter.

Image credits: ESA/NASA/SOHO & SDO/NASA and the AIA science team.

*The Sun, being a mass of incandescent gas, doesn’t have a “surface” like rocky planets do so in this case we’re referring to its photosphere and chromosphere.

March 31, 2015December 23, 2015 by Bob King

Don’t Blink! April 4th Lunar Eclipse Shortest of the Century

The phases of a total lunar eclipse. Credit: Keith Burns / NASA

Get ready for one awesome total lunar eclipse early Saturday morning April 4th. For the third time in less than a year, the Moon dips into Earth’s shadow, its dazzling white globe turning sunset red right before your eyes. All eclipses are not-to-miss events, but Saturday’s totality will be the shortest in a century. Brief but beautiful – just like life. Read on to find out how to make the most of it.

Four total lunars in succession is called a tetrad. During the 21st century there are nine sets of tetrads. Credit: NASA — Four total lunar eclipses in succession with no partials in between is called a tetrad. The April 4th eclipse is part of a tetrad that started last April and will wrap up on September 28. During the 21st century there will be eight sets of tetrads. Credit: NASA

Lunar eclipses don’t usually happen in any particular order. A partial eclipse is followed by a total is followed by a penumbral and so on. Instead, we’re in the middle of a tetrad, four total eclipses in a row with no partials in between. The final one happens on September 28. Even more remarkable, part or all of them are visible from the U.S. Tetrads will be fairly common in the 21st century with eight in all. We’re lucky — between 1600 and 1900 there were none! For an excellent primer on the topic check out fellow Universe Today writer David Dickinson’s “The Science Behind the Blood Moon Tetrad“.

The Moon moves out of total eclipse and into partial phases during the second of the four tetrad eclipses on October 8, 2015. Credit: Bob King — The partially eclipsed Moon on October 8, 2015. For skywatchers across the eastern half of North America, this is about how the Moon will appear shortly before it sets. Those living further west will see totality. Credit: Bob King

Lots of people have taken to calling the tetrad eclipses Blood Moons, referring to the coppery color of lunar disk when steeped in Earth’s shadow and the timing of both April events on the Jewish Passover. Me? I prefer Bacon-and-Eggs Moon. For many of us, the eclipse runs right up till sunrise with the Moon setting in bright twilight around 6:30 a.m. What better time to enjoy a celebratory breakfast with friends after packing away your gear?

Map showing where the April 4 lunar eclipse will be penumbral, partial and total. Inset shows a world map. Credit: Larry Koehn / shadowandsubstance.com — Map showing where the April 4 lunar eclipse will be penumbral, partial and total. World map shown in inset. Credit: Larry Koehn / shadowandsubstance.com Inset: Fred Espenak

But seriously, Saturday morning’s eclipse will prove challenging for some. While observers in far western North America, Hawaii, Japan, New Zealand and Australia will witness the entire event, those in the mountain states will see the Moon set while still in totality. Meanwhile, skywatchers in the Midwest and points East will see only the partial phases in a brightening dawn sky. Here are the key times of eclipse events by time zone:

A total lunar eclipse occurs only during Full Moons when the Sun, Earth and Moon form a straight line. The Moon slips directly behind Earth into its shadow. The outer part of the shadow or penumbra is a mix of sunlight and shadow. The inner cone, called the umbra, the Sun is completely blocked from view. However, light refracted by Earth's atmosphere is bent into the umbra where it colors the eclipsed Moon red. — A total lunar eclipse occurs only during full moon phase when the Sun, Earth and Moon lie in a straight line. The Moon slips directly behind Earth into its shadow. The outer part of the shadow or penumbra is a mix of sunlight and shadow and only partially dark. From the inner shadow, called the umbra, the Sun is completely blocked from view. A small amount of sunlight refracted or bent by Earth’s atmosphere into the umbra, spills into the shadow, coloring the eclipsed Moon red.

Eclipse Events EDT CDT MDT PDT

Penumbra eclipse begins	5:01 a.m.	4:01 a.m.	3:01 a.m.	2:01 a.m.
Partial eclipse begins	6:16 a.m.	5:16 a.m.	4:16 a.m.	3:16 a.m.
Total eclipse begins	——–	——–	5:58 a.m.	4:58 a.m.
Greatest eclipse	——–	——–	6:00 a.m.	5:00 a.m.
Total eclipse ends	——–	——–	6:03 a.m.	5:03 a.m.
Partial eclipse ends	———	——–	——–	6:45 a.m.
Penumbra eclipse ends	———	———	——–	——–

* During the penumbral phase, shading won’t be obvious until ~30 minutes before partial eclipse.

Partial eclipse, when the Moon first enters Earth's dark, inner shadow called the umbra, begins at 5:16 a.m. CDT near the start of morning twilight. Totality begins at 6:58 a.m. with the Moon already set for the eastern half of the country. Credit: Fred Espenak — Partial eclipse, when the Moon first enters Earth’s dark umbral shadow, begins at 5:16 a.m. CDT near the start of morning twilight. Totality begins at 6:58 a.m. with the Moon already set for the eastern half of the country. Credit: Fred Espenak

This eclipse will also be the shortest total eclipse of the 21st century; our satellite spends just 4 minutes and 43 seconds inside Earth’s umbra or shadow core. That’s only as long as a typical solar eclipse totality. Ah, the irony.

Better have your camera ready or you’ll miss it. The maps below show the maximum amount of the Moon visible shortly before setting from two eastern U.S. cities and the height of the totally eclipsed Moon from two western locations. Click each panel for more details about local circumstances.

The Earth's shadow will take only a small bite out of the Moon before sunrise (6:47 a.m.) as seen from Washington D.C. Source: Stellarium — The Earth’s shadow will take only a small bite out of the Moon before sunrise (6:47 a.m.) as seen from Washington D.C. From all mainland U.S. locations Virgo’s brightest star Spica will appear about 10° to the left of the Moon. Source: Stellarium

Here's the view from Chicago where sunrise occurs at 6:27 a.m. Source: Stellarium — Here’s the view from Chicago where sunrise occurs at 6:27 a.m. Source: Stellarium

Totality will be visible From Denver, Colorado with the Moon low in the western sky. Source: Stellarium — Totality will be visible From Denver, Colorado with the Moon low in the western sky in morning twilight. Sunrise is 6:42 a.m. Source: Stellarium

Seattle and the West Coast get a great view of totality in a dark sky. The final partial phases will also be visible. Sunrise there is 6:40 a.m. Source: Stellarium

Now that you know times and shadow coverage, let’s talk about the fun part — what to look for as the event unfolds. You’ll need to find a location in advance with a good view to the southwest as most of the action happens in that direction. Once that detail’s taken care of and assuming clear weather, you can kick back in a folding chair or with your back propped against a hillside and enjoy.

During the early partial phases you may not see the shadowed portion of the Moon with the naked eye. Binoculars and telescopes will show it plainly. But once the Moon's about 50% covered, the reddish-orange tint of the shadowed half becomes obvious. Credit: Jim Schaff — During the early partial phases you may not see the shadowed portion of the Moon with the naked eye. Binoculars and telescopes will show it plainly. But once the Moon is about 50% covered, the reddish-orange tint of the shadowed half becomes obvious. During total eclipse (right), the color is intense. Credit: Jim Schaff

The entire eclipse can be enjoyed without any optical aid, though I recommend a look through binoculars now and then. The eclipsed Moon appears distinctly three-dimensional with only the slightest magnification, hanging there like an ornament among the stars. The Earth’s shadow appears to advance over the Moon, but the opposite is true; the Moon’s eastward orbital motion carries it deeper and deeper into the umbra.

Nibble by nibble the sunlit Moon falls into shadow. By the time it’s been reduced to half, the shaded portion looks distinctly red even to the naked eye. Notice that the shadow is curved. We live on a spherical planet and spheres cast circular shadows. Seeing the globe of Earth projected against the Moon makes the roundness of our home planet palpable.

Artist view of Earth totally eclipsing the sun as viewed from the moon. Low angled sunlight filtered by our atmosphere is reddened in exactly the same way a setting sun is reddened. That red light bathes the moon’s surface which reflects a bit of it back toward Earth, giving us a red moon during totality. — A simulated view looking back at Earth from the Moon during a total lunar eclipse on Earth. Sunlight grazing Earth’s circumference gets filtered by our atmosphere in exactly the same way the setting or rising Sun looks red. All the cooler colors have been scattered away by air and Red light, bent into the umbra by atmospheric refraction, bathes the lunar surface in red. As you might have guessed, when we see a total lunar eclipse on Earth, lunar inhabitants see a total eclipse of the Sun by Earth. Source: Stellarium

When totality arrives, the entire lunar globe throbs with orange, copper or rusty red. These sumptuous hues originate from sunlight filtered and bent by Earth’s atmosphere into the umbral shadow. Atmospheric particles have removed all the cooler colors, leaving the reds and oranges from a billion sunrises and sunsets occurring around the planet’s circumference. Imagine for a moment standing on the Moon looking back. Above your head would hang the black disk of Earth, nearly four times the size of the Moon in our sky, ringed by a narrow corona of fiery light.

Color varies from one eclipse to the next depending on the amount of water, dust and volcanic ash suspended in Earth’s atmosphere. The December 30, 1982 eclipse was one of the darkest in decades due to a tremendous amount of volcanic dust from the eruption of the Mexican volcano El Chichon earlier that year.

The more particles and haze, the greater the light absorption and darker the Moon. That said, this eclipse should be fairly bright because the Moon does not tread deeply into Earth’s shadow. It’s in for a quick dip of totality and then resumes partial phases.

The Moon's color can vary from yellow-orange to dark, smoky brown during totality depending on the state of the atmosphere. You can also see lots of stars in the sky right up to the Moon's edge when it's in Earth's shadow. This photo from last April's eclipse. Credit: Bob King — The Moon’s color can vary from yellow-orange to dark, smoky brown during totality depending on the state of the atmosphere. You can also see lots of stars in the sky right up to the Moon’s edge when it’s in Earth’s shadow. This photo from last April’s eclipse. Spica is below the Moon and Mars to the right. Credit: Bob King

It’s northern edge, located close to the outer fringe of Earth’s umbra, should appear considerably brighter than the southern, which is closer to the center or darkest part of the umbra.

Earth's shadow exposed! During a lunar eclipse that occurs at dusk or dawn (like the April 4th one and this one last October) we have the rare opportunity to see Earth's shadow on the distant Moon at the same time it's visible as a dark purple band cast on the upper atmosphere as seen here on October 8, 2015. Credit: Bob King — Earth’s shadow exposed! When a lunar eclipse occurs at dusk or dawn we have the rare opportunity to see Earth’s shadow on the distant Moon at the same time it’s visible as a dark purple band cast on the upper atmosphere as seen here on October 8, 2015. Credit: Bob King

Besides the pleasure of seeing the Moon change color, watch for the sky to darken as totality approaches. Eclipses begin with overwhelming moonlight and washed out, star-poor skies. As the Moon goes into hiding, stars return in a breathtaking way over a strangely eerie landscape. Don’t forget to turn around and admire the glorious summer Milky Way rising in the eastern sky.

Lunar eclipses remind us we live in a Solar System made of these beautiful, moving parts that never fail to inspire awe when we look up to notice.

In case you can’t watch the eclipse from your home due to weather or circumstance, our friends at the Virtual Telescope Project and SLOOH will stream it online.

March 27, 2015October 10, 2016 by David Dickinson

Living with a Capricious Star: What Drives the Solar Cycle?

Solar energy energizes the drama of life on Earth, such as the bird caught transiting the solar disk as seen here. Image credit and copyright: Roger Hutchinson

You can be thankful that we bask in the glow of a relatively placid star. Currently about halfway along its 10 billion year career on the Main Sequence, our Sun fuses hydrogen into helium in a battle against gravitational collapse. This balancing act produces energy via the proton-proton chain process, which in turn, fuels the drama of life on Earth.

Looking out into the universe, we see stars that are much more brash and impulsive, such as red dwarf upstarts unleashing huge planet-sterilizing flares, and massive stars destined to live fast and die young.

Our Sun gives us the unprecedented chance to study a star up close, and our modern day technological society depends on keeping a close watch on what the Sun might do next. But did you know that some of the key mechanisms powering the solar cycle are still not completely understood?

One of the exceptionally active sunspot groups seen for Cycle #24 in early 2014. Image credit: David Dickinson

One such mystery confronting solar dynamics is exactly what drives the periodicity related to the solar cycle. Follow our star with a backyard telescope over a period of years, and you’ll see sunspots ebb and flow in an 11 year period of activity. The dazzling ‘surface’ of the Sun where these spots are embedded is actually the photosphere, and using a small telescope tuned to hydrogen-alpha wavelengths you can pick up prominences in the warmer chromosphere above.

This cycle is actually is 22 years in length (that’s 11 years times two), as the Sun flips polarity each time. A hallmark of the start of each solar cycle is the appearance of sunspots at high solar latitudes, which then move closer to the solar equator as the cycle progresses. You can actually chart this distribution in a butterfly diagram known as a Spörer chart, and this pattern was first recognized by Gustav Spörer in the late 19^th century and is known as Spörer’s Law.

Sunspot_butterfly_graph — The ‘Butterfly diagram’ of sunspot distribution by latitude over previous solar cycles. Image credit: NASA/Marshall Spaceflight Center

We’re currently in the midst of solar cycle #24, and the measurement of solar cycles dates all the way back to 1755. Galileo observed sunspots via projection (the tale that he went blind observing the Sun in apocryphal). We also have Chinese records going back to 364 BC, though historical records of sunspot activity are, well, spotty at best. The infamous Maunder Minimum occurred from 1645 to 1717 just as the age of telescopic astronomy was gaining steam. This dearth of sunspot activity actually led to the idea that sunspots were a mythical creation by astronomers of the time.

But sunspots are a true reality. Spots can grow larger than the Earth, such as sunspot active region 2192, which appeared just before a partial solar eclipse in 2014 and could be seen with the unaided (protected) eye. The Sun is actually a big ball of gas, and the equatorial regions rotate once every 25 days, 9 days faster than the rotational period near the poles. And speaking of which, it is not fully understood why we never see sunspots at the solar poles, which are tipped 7.25 degrees relative to the ecliptic.

Other solar mysteries persist. One amazing fact about our Sun is the true age of the sunlight shining in our living room window. Though it raced from the convective zone and through the photosphere of the Sun at 300,000 km per second and only took 8 minutes to get to your sunbeam-loving cat here on Earth, it took an estimated 10,000 to 170,000 years to escape the solar core where fusion is taking place. This is due to the terrific density at the Sun’s center, over seven times that of gold.

Another amazing fact is that we can actually model the happenings on the farside of the Sun utilizing a new fangled method known as helioseismology.

Another key mystery is why the current solar cycle is so weak… it has even been proposed that solar cycle 25 and 26 might be absent all together. Are there larger solar cycles waiting discovery? Again, we haven’t been watching the Sun close enough for long enough to truly ferret these ‘Grand Cycles’ out.

Are sunspot numbers telling us the whole picture? Sunspot numbers are calculated using formula that includes a visual count of sunspot groups and the individual sunspots in them that are currently facing Earthward, and has long served as the gold standard to gauge solar activity. Research conducted by the University of Michigan in Ann Arbor in 2013 has suggested that the orientation of the heliospheric current sheet might actually provide a better picture as to the goings on of the Sun.

Another major mystery is why the Sun has this 22/11 year cycle of activity in the first place. The differential rotation of the solar interior and convective zone known as the solar tachocline drives the powerful solar dynamo. But why the activity cycle is the exact length that it is is still anyone’s guess. Perhaps the fossil field of the Sun was simply ‘frozen’ in the current cycle as we see it today.

There are ideas out there that Jupiter drives the solar cycle. A 2012 paper suggested just that. It’s an enticing theory for sure, as Jupiter orbits the Sun once every 11.9 years.

The motion of the solar barycenter through the last half of the 20th century. Image credit: Carl Smith/Wikimedia Commons

And a recent paper has even proposed that Uranus and Neptune might drive much longer cycles…

Color us skeptical on these ideas. Although Jupiter accounts for over 70% of the planetary mass in the solar system, it’s 1/1000th as massive as the Sun. The barycenter of Jupiter versus the Sun sits 36,000 kilometres above the solar surface, tugging the Sun at a rate of 12.4 metres per second.

Rigs to view the Sun in both hydrogen-alpha and visible light. Credit: David Dickinson

I suspect this is a case of coincidence: the solar system provides lots of orbital periods of varying lengths, offering up lots of chances for possible mutual occurrences. A similar mathematical curiosity can be seen in Bode’s Law describing the mathematical spacing of the planets, which to date, has no known basis in reality. It appears to be just a neat play on numbers. Roll the cosmic dice long enough, and coincidences will occur. A good test for both ideas would be the discovery of similar relationships in other planetary systems. We can currently detect both starspots and large exoplanets: is there a similar link between stellar activity and exoplanet orbits? Demonstrate it dozens of times over, and a theory could become law.

That’s science, baby.

March 17, 2015December 23, 2015 by Bob King

Green and Red Auroras Light Up St. Patrick’s Day Dawn

Just in time for St. Patrick's Day - a — A spectacular green and red aurora photographed early this morning March 17, 2015, from Donnelly Creek, Alaska. Credit: Sebastian Saarloos

A strong G3 geomagetic storm surged across the planet this morning producing a spectacular display of the northern lights. Some of you may who may have risen to see the new nova were no doubt as surprised as the NOAA space weather folks, whose overnight forecast did not include an alert for even a minor storm.

So what happened? Let’s just say the Sun isn’t always as predictable as we’d like. An interplanetary shock wave in the form of a sudden increase in the solar wind speed from 250 miles per second to 375 mph (400-600 km/sec) began blasting Earth shortly before midnight. It appears the combined effects of earlier coronal mass ejections (CMEs) and an outpouring of high-speed solar particles from a gaping hole in the Sun’s magnetic canopy crashed through Earth’s magnetic defenses.

Particle-wise, all hell broke loose. You can start looking for more as soon as it gets dark tonight.

A powerful X2.2-class flare from sunspot region 2297 glows fiery yellow in this photo taken by NASA’s Solar Dynamics Observatory on March 11, 2015. Credit: NASA — A powerful X2.2-class flare from sunspot region 2297 glows intensely in this photo taken in short wavelength ultraviolet light by NASA’s Solar Dynamics Observatory on March 11, 2015. Credit: NASA Goddard SDO

We know that recent flares from sunspot group 2297 have sent more than a few billows of solar particles our way called CMEs or coronal mass ejections. Weekend forecasts called for minor storms but little materialized. Only when we thought it was safe to go back to bed did the aurora pounce. Reading the magnetospheric tea leaves, better known as the Kp index, a measure of magnetic activity high overhead in Earth’s ionosphere, quiet conditions gave way to auroral abandon starting around 1 a.m (CDT) today.

A wall of colorful red and green aurora met the eye and camera of Jim Schaff of Duluth this morning around 3 a.m. CDT. Credit: Jim Schaff

Like a spring grassfire the northern lights took off from there and burned till dawn, peaking between 2 and 4 a.m. Most of us are usually asleep during those deep hours of the night, but I’m hoping those who arose to see the nova or catch the lunar crescent at dawn may have been as surprised and delighted as I was to see auroras.

Like paw prints made by a cat, pale green auroral rays mark the northern sky around 5:45 a.m this morning March 17. Credit: Bob King

More are in the offing. The latest space weather forecast calls for continued severe storms (G3 or higher) to continue through tonight. G1 or minor storms are normally only visible as arcs or low rays across the north from the northern tier of states, but if tonight’s forecast holds, a fair portion of the U.S. should see auroras. Keep an eye peeled for bright, moving glow and arcs across the northern sky.

The awesome 30-minute aurora forecast map updates the shrinking and expanding of Earth's northern auroral oval due to changes in the solar wind from CMEs, flares and the like. This view is from this morning around 4:55 a.m. Red indicates intense aurora. Credit: NOAA — The awesome 30-minute aurora forecast map updates the shrinking and expanding of Earth’s northern auroral oval due to changes in the solar wind from CMEs, flares and the like. This view is from this morning around 4:55 a.m. Red indicates intense aurora. Credit: NOAA

There are lots of tools available you can use yourself to know if auroras are lurking about. First, check the NOAA 3-day space weather forecast. There you’ll see a list of times along with a Kp index number indicating magnetic activity. Number “1-4” means no storm and little likelihood you’ll see an aurora. “5” indicates a minor storm; the higher the number the more severe the storm and more widespread the northern lights will be.

Curtains of aurora still pushed through the growing light of dawn. Credit: Bob King — Curtains of aurora still pushed through the growing light of dawn (blue sky at top). Credit: Bob King

There’s also a nice visual representation of the numbers on the Planetary K-index site, where magnetic activity is updated every 3 hours. The dashed line on the bar chart represents 0 UT or 7 p.m. CDT. One of my favorites and the ultimate visual feast of an aurora indicator is NOAA’s Aurora 30-minute Forecast. Here you get a birds-eye representation of the current aurora based on satellite data. When the permanent auroral oval expands southward and intensifies, put on your coat and head out for a look. For education and entertainment, click on the gray arrow below the graphic and you’ll see a whole day’s worth of activity play out before your eyes. Totes cool.

ACE plot from a June 2013 aurora. Note the steep drop in the Bz. Credit: NOAA — ACE plot from a June 2013 aurora. Note the steep drop in the Bz. ACE orbits around the L1 Lagrange point about a million miles ahead of Earth in the direction of the Sun. There it studies the incoming particle streams from the Sun hours before they reach Earth. Credit: NOAA

I’m also in big believer in the the Advanced Composition Explorer (ACE) Bz plot. Bz is the direction of the embedded solar magnetic field that gift-wraps the streams of high-speed particles sent our way by the Sun. Like a magnet, it has a south pole and a north pole. When the south pole of the field sweeps by – what scientists call a negative Bz – the blast is more likely to link up with Earth’s magnetic field and spark auroras. When you see the Bz “head south” to -5 or lower, there’s a chance for auroras.

Now that you’re armed with information, cross your fingers all the indicators will point in the right direction for the aurora to continue tonight. And yes, Happy St. Patrick’s Day!

Skiing stop to take in the northern lights near Fairbanks Monday night. Credit: John Chumack — Skywatchers stop to take in the northern lights near Fairbanks Monday night. Credit: John Chumack

UPDATE: The storm continues and is now rated G4 or severe as of 10 a.m. CDT. Lucky for you if you live somewhere where it’s dark right now.

March 12, 2015December 23, 2015 by David Dickinson

Will the March 20th Total Solar Eclipse Impact Europe’s Solar Energy Grid?

The first eclipse of 2015 is coming right up on Friday, March 20^th, and may provide a unique challenge for solar energy production across Europe.

Sure, we’ve been skeptical about many of the websites touting a ‘blackout’ and Y2K-like doom pertaining to the March 20th total solar eclipse as of late. And while it’s true that comets and eclipses really do bring out the ‘End of the World of the Week’ -types across ye ole web, there’s actually a fascinating story of science at the core of next week’s eclipse and the challenge it poses to energy production.

But first, a brief recap of the eclipse itself. Dubbed the “Equinox Eclipse,” totality only occurs over a swath of the North Atlantic and passes over distant Faroe and Svalbard Islands. Germany and central Europe can expect an approximately 80% partially obscured Sun at the eclipse’s maximum.

The magnitude of the March 20th solar eclipse across Europe. Credit: Michael Zeiler/GreatAmericanEclipse.com

We wrote a full guide with the specifics for observing this eclipse yesterday. But is there a cause for concern when it comes to energy production?

A power grid is a huge balancing act. As power production decreases from one source, other sources must be brought online to compensate. This is a major challenge — especially in terms of solar energy production.

Residential solar panels in Germany. Credit: Wikimedia Commons/ Sideka Solartechnik.

Germany currently stands at the forefront of solar energy technology, representing a whopping quarter of all solar energy capacity installed worldwide. Germany now relies of solar power for almost 7% of its annual electricity production, and during the sunniest hours, has used solar panels to satisfy up to 50% of the country’s power demand.

We recently caught up with Barry Fischer to discuss the issue. Fischer is the Head Writer at Opower, a software company that uses data to help electric and gas utilities improve their customer experience. Based on Opower’s partnerships with nearly 100 utilities worldwide, the company has amassed the world’s largest energy dataset of its kind which documents energy consumption patterns across more than 55 million households around the globe.

A study published last week by Opower highlights data from the partial solar eclipse last October over the western United States. There’s little historical precedent for the impact that an eclipse could have on the solar energy grid. For example, during the August 11^th, 1999 total solar eclipse which crossed directly over Europe, less than 0.1% of utility electricity was generated using solar power.

What they found was intriguing. Although the 2014 partial solar eclipse only obscured 30 to 50% of the Sun, solar electric production dropped over an afternoon span of nearly three hours before returning to a normal pattern.

Examining data from 5,000 solar-powered homes in the western United States, Opower found that during the eclipse those homes sent 41% less electricity back to the grid than normal. Along with a nearly 1,000 megawatt decline in utility-scale solar power production, these drop-offs were compensated for by grid operators ramping up traditional thermal power plants that were most likely fueled by natural gas.

No serious problems were experienced during the October 23^rd, 2014 partial solar eclipse in terms of solar electricity production in the southwestern United States, though it is interesting to note that the impact of the eclipse on solar energy production could be readily detected and measured.

How does the drop and surge in solar power output anticipated for the March 20^th eclipse differ from, say, the kind presented by the onset of night, or a cloudy day? “The impact of an eclipse can register broadly – and unusually rapidly – across an entire region,” Fischer told Universe Today. On a small scale, one area many be cloudy, while on a larger regional scale, other areas of clear or partly sunny skies can compensate. An eclipse — even a partial one — is fundamentally different, because the sudden onset and the conclusion are relatively uniform over a large region.

The March 20^th event offers an unprecedented chance to study the effects of an eclipse on large-scale solar production up close. A study (in German) by the University of Applied Sciences in Berlin suggests that solar power production will fall at a rate 2.7 times faster than usual as the eclipse progresses over a span of 75 minutes. This is the equivalent of switching off one medium-sized power plant per minute.

The anticipated slingshot might be just as challenging, as 18 gigawatts of power comes back online at the conclusion of the eclipse in just over an hour. And as opposed to the 2014 eclipse over the U.S. which ended towards sunset, the key rebound period for the March 20^th eclipse will be around local noon and during a peak production time.

Fischer also noted that “the second half of the partial solar eclipse will also pose a notable challenge” for the grid, as it is flooded with solar power production 3.5 times faster than normal. This phenomenon could also serve as a great model for what could occur daily on a grid that’s increasingly solar power reliant in the future, as energy production ramps up daily at sunrise. Such a reality may be only 15 years away, as Germany projects installed solar capacity to top 66 gigawatts by 2030.

What’s the anticipated impact projected for a future eclipse such as, say, the 2017 and 2024 total solar eclipses over the U.S.?

This eclipse may serve as a great dry run for modeling what could occur as reliance on solar energy production grows.

Such is the modern technical society we live in. It’s fascinating to think that eclipses aren’t only a marvelous celestial spectacle, but their effects on power production may actually serve as a model for the smart grids of tomorrow.