Love at first sight – smitten by a cosmic diamond ring

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

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

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

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

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

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

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

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

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

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

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

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

Strong solar flare creates rare magnetic ripples in Earth’s atmosphere

Energy stored in twisted magnetic fields above sunspot group 2017 was released a as a strong X1-class flare at 12:52 p.m. CDT March 29. Powerful X-rays from the flare sent magnetic currents through Earth’s upper atmosphere minutes later. Credit: NASA

An fast, intense X1-class solar flare yesterday afternoon not only blasted a cloud of solar electrons and protons into space but also sent magnetic ripples across Earth’s upper atmosphere creating what astronomers call a magnetic crochet.

X1 solar flare on March 29, 2014

Normally it takes an average of 4 days for a cloud of fast moving solar particles called a coronal mass ejection or CME to reach the Earth. Fast ones moving at 620 miles per second (1,000 km/sec) arrive in about 42 hours. But energy levels rose so rapidly in yesterday’s flare that Earth’s atmosphere was affected only minutes after the onset of the storm.

How could something from the sun get here so fast? Well, it does everyday. Sunlight traverses the 93 million miles between Earth and sun in just 8.3 minutes. There are many forms of light from radio waves to visible light to X-rays. Flares are so powerful they kick out waves of light energy across the entire spectrum from radio to deadly gamma rays.

The Earth’s ionosphere, divided into layers D, E and F, begins about 37 miles high and extends nearly to space. Solar and cosmic radiation strips electrons from atoms turning them into ions, which respond to electrical and magnetic fields. Credit: Rutherford Appleton Laboratory

A burst of X-rays from sunspot region 2017 arrived 8.3 minutes after the blast and increased the electrical conductivity in the D and E layers of Earth’s ionosphere by stripping electrons from the atoms there, making electric currents flow more easily. Because moving electrical currents create magnetic fields, the flare caused a sudden jump or ripple of magnetic energy to pulse through the ionosphere. As the flare subsided, those layers returned to normal.

You can see for yourself how an electric current creates a magnetic field by holding a compass near an operating electric shaver or hairdryer. As you move the shaver back and forth, the compass needle will swing wildly as it responds to the local magnetic field created by the flow of electrons in the current.

Even though we can’t see them, magnetic fields have very real effects.

Magnetic crochets are rare because they only occur during large flares that peak quickly. They’re also typically recorded at locations where the sun is overhead at the time of the flare.

Just one more way the sun touches our lives. As for the particles propelled by the flare, most of them took off northward of Earth but a glancing blow is expected around April 1 when Arctic observers may see a nice show of northern lights during their rapidly diminishing nighttime hours.

It’s St. Patrick’s Day, so why no green stars?

No one’s ever seen a green star and for good reason. Stars that pour out green light also emit light of every other color. Blended together, they appear white.

Ever wonder why you never see any green stars? Sure, there are plenty of white stars and a fair number tinted orange and red. But green? I’ve never seen one, not even in a telescope. Faith and begorrah, where have they all gone?

To tell the truth, many stars do emit green light. Even the sun. If we were to measure how much light the sun gives off in each color of the rainbow (remembering that white light is made of a rainbow of colors), we’d quickly discover that it radiates most strongly in the yellow-green part of the spectrum. That’s right. Our very own sun should look like a flaming, yellow-green orb. It doesn’t because it’s also sending out substantial amounts of  blue, yellow, orange and red light that combined together appear ‘white’ to our eyes.

Stars much cooler than the sun radiate across the spectrum just like the sun does but emit much more of their light in the red end of the rainbow spectrum and therefore appear orange or red to our eyes. Hotter stars do likewise but pack most of their energy in the blue or even ultraviolet end of the spectrum and appear pale blue.

The horizontal or x-axis represent the wavelength or color of light. The “y” or vertical axis shows the brightness. The curves represent light emitted by the sun (middle) and two other stars. The sun peaks in the green, while a cooler star (bottom curve) peaks in the red. Much hotter stars pour out most of their light in the blue-violet end of the spectrum. Credit: Andrew Fraknoi

Stars like the sun whose peak light emission lies smack in the middle of the visual spectrum also radiate plenty in the blue and red ends. Added up, you get white.

Ultimately, it comes down to how the cone cells in the retina perceive color. There are three different kinds: those sensitive to red, those to blue and those to green. An apple looks red because the red cones respond strongly to red light while the blue and green ones don’t. When the signal from the trio goes to our brain we see a ‘red’ apple.

If the green and red cones are active but blue is not, we see yellow. To perceive green, the object must be strongly emitting only green light. Since the sun and stars like it also emit red and blue, all three types of cones fire up and we see white.

Thor’s Helmut also known as NGC 2359 in the constellation Canis Major emits green light from excited oxygen atoms much like the Orion Nebula. Credit: Jim Misti

Oh well, no green stars. But don’t hang your head. There’s plenty of green in the cosmos. When oxygen in huge gas clouds like the Orion Nebula gets ionized by ultraviolet light streaming from newborn stars, it emits a strong green light. Even a small telescope will show the nebula’s eerie green connection to St. Pat’s Day.

Aurora alert for northern U.S. tonight Feb. 27-28

Click image to watch video of the X4.9 flare on Feb. 25 in multiple wavelengths of light / Solar Dynamics Observatory

Lots of movement in the northern lights over Hamburg, Germany this evening Feb. 27-28, 2014. Submitted by Daniel Fischer

A spectacular solar X4.9 solar flare from returning sunspot group AR 1967 on Feb. 25 wasn’t supposed to have much affect on Earth. Surprise! Even though the plasma blast shot off to one side of the sun’s disk, our planet’s magnetic bubble received a glancing blow from the explosion this afternoon. Talk about explosion – swarms of electrons and protons left the sun at an estimated 4.4 million mph!

Still image of the X4.9 flare on Feb. 25. Notice that it’s aimed well off to the left. If it had occurred near the center of the disk, its effects on Earth would be more severe. This flare is the strongest yet this year and one of the strongest in the current sunspot cycle. Credit: NASA

As of 5 p.m. CST, a moderate G2 geomagnetic storm is in progress with strong auroras flaring up over across Europe as far south as southern Germany. Should the activity continue, skywatchers in the northern U.S. and possibly farther south will have a good chance at seeing the northern lights tonight. With no moon present, conditions will be ideal for aurora watching. Start looking as soon as possible after twilight ends this evening.

Click HERE to see the extent of the auroral oval, which will help you determine if northern lights might be visible from your location. I’ll update as needed. Good luck!

A quiet affair. The aurora from north of Duluth, Minn. U.S. Thursday night Feb. 27, 2014. Temperature -30 F. Credit: Bob King

UPDATE 9 p.m. CST: Aurora out here in Duluth as a so-far quiet bright arc low in the northern sky.

Daylight forces the hand of night as we surge toward spring

Animation showing the Earth – with tipped axis – revolving around the sun. Seasons are shown for the northern hemisphere.

It happens every mid-winter. I wake up earlier and earlier, unconsciously responding to the daylight that spills beneath the window shade as the pace of the season quickens.

We’ve been putting seconds and minutes in our sunny-day piggy bank every since the winter solstice last Dec. 21. Those deposits are now accumulating rapidly as February gives way to March. Where I live, days were as short as 8 hours 32 minutes in late December. Today that time has swelled to 10 hours 24 minutes.

As Earth revolves around the sun, its 23.5 degree-angled axis points toward, perpendicular to and away from the sun over the year to make the seasons. Credit: Tao’olunga with additions by B. King

While a half hour of extra light may not be enough to notice, 1 hour and 52 minutes is a revelation. Many of us now drive home in bright twilight at the end of a work day. This has beneficial effects like seeing more sunsets and full moon rises. We also feel more connected with the world because we can see it. Humans weren’t born to live as troglobites in dark caves. We crave sunlight as much as clear,dark nights.

I like the extra daylight for hiking and skiing. Shorter nights also mean less time for the Earth to loose heat and the temperature to dip below zero. If you’d like to see how your day/night account is coming along, check out the UNSO’s Duration of Daylight/Darkness Table.

All things warm and fuzzy (and cold and spiky) come our way because of Earth’s axial tilt. The axis remains fixed at an inclination of 23.5 degrees, but as the planet revolves about the sun during the year, the northern hemisphere tilts toward the sun in summer and away in winter. These are the extremes. In between, we have the spring and fall equinoxes, when both hemispheres are “face on” to the sun and receive equal amounts of daylight and night.

There are mini-seasons too. Mid-February is as good a time as any to call by that name. We’re moving away from winter toward spring with night on the run and daylight gaining the upper hand. A month from today, on the verge of the spring equinox, daylight will have increased an additional 1 1/2 hours to 12 hours. For a moment day and night will balance. The next moment day surpasses night and won’t relinquish its lead until after the fall equinox.

The sun’s always high in the sky at low tropical latitudes, so the seasons don’t vary much. This diagram shows the sun’s position around noon on the winter and summer solstices and equinoxes. Stellarium

Daylight length depends upon your latitude. If you took a tropical vacation this winter, you probably noticed that the sun rose around 6 a.m. and set around 6 p.m. Closer to the equator, the sun’s path is steeply inclined to the horizon every day of the year with little change in sunrise and sunset times. The sun’s always high in the sky there at the noon hour, bringing with it those consistently warmer temperatures we’re willing to pay big bucks for.

A mid-winter sun shines through an icicle formation on Lake Superior. Credit: Bob King

At mid and high latitudes, the yearly variation in sun’s position in the sky puts it high in the sky during summer and low in the sky during winter. Low means less time above the horizon, shorter daylight hours and cold temperatures.

To better understand this, consider that on the first day of spring and fall on the equator, the sun rises due east, passes directly overhead and sets due west. On the first day of summer, the sun at noon passes 23.5 degrees ( a little more than two fists held at arm’s length) north of the overhead point, while on the winter solstice it’s 23.5 degrees south of overhead. No matter the season, the sun will always shine down from a high altitude at noon.

This view shows the sun from a mid-northern latitude city like Minnepolis, Minn. Notice how the sun’s yearly elevation spread take it much closer to the horizon (wintertime) and also quite high (summertime). The scale of this map is different from the one above because it doesn’t need to include as much sky near the overhead point. Stellarium

In Minneapolis, halfway between the equator and north pole at latitude 45 degrees north, the sun is 45 degrees high at noon on the first day of spring and fall or halfway between the overhead point and southern horizon. Come the first day of summer, it’s way up there at 68.5 degrees and roasts the back of your neck, but on the winter solstice it peaks out at just 21.5 degrees high. Better protect that neck with a scarf.

The full range of the sun’s yearly motion – 23.5 degrees north to 23.5 degrees south of the celestial equator – is the same no matter where you are on Earth, but if you live far from the equator, the sun’s altitude reaches greater extremes, making the seasons more pronounced.

Big sunspot convulses but all quiet on the aurora front … for now

Sunspot region 1967 is so big it easily popped into view through a “cloud filter” Sunday afternoon Feb. 2. The group is visible with the naked eye properly shielded by a safe solar filter. Details: 350mm lens at f/11, ISO 200 and 1/2000″. Credit: Bob King

What a crazy sunspot cycle. Weeks go by with only a few tiny spots freckling the sun, then all at once a monster group big enough to swallow 10 Earths rounds the eastern limb and we’re back in business. I’m happy to report we’ve got another behemoth snapping and crackling with M-class (moderately strong) flares. That would be Active Region 1967, the hunk a hunk of burnin’ sun we checked out a few days ago.

NOAA weather forecasters predict an 80% chance of continued M-flares and a 50% chance over the next 3 days for considerably more powerful X-class flares. This sunspot group has a delta classification magnetic field, the Facebook equivalent of “it’s complicated”.

Sunspots are made of a dark umbra and lighter penumbra. Very tiny spots with no penumbrae are called pores. A close up of the sun’s photosphere shows a finely granulated texture. Granules are cells of hot gas about the size of Texas that rise from below, cool and sink. Each lasts from 8 to 20 minutes. Credit: NASA

Sunspots have two parts: a dark core (or cores) called an umbra surrounded by a paler skirt of magnetic energy, the penumbra. They can look impressive like this one, but it’s hard to call a sunspot a “thing”. It’s really more of a location on the sun’s bright white photosphere where bundles of powerful magnetic energy bob up from below the surface and insulate a region of the sun’s fiery hydrogen gas from the rest of the flaming globe.

We’re talking insulate as in staying cool. While the photosphere cooks at around 11,000 degrees Fahrenheit, sunspots are some 3,000 degrees cooler. That’s why they appear dark to the eye. If you could rip them away from the sun and see them alone against the sky, they’d be too bright to look at.

Close up of AR 1967 photographed by the Solar Dynamics Observatory at 6:45 p.m. CST Feb. 3, 2014. The group’s shape reminds me of the Big Dipper. Credit: NASA

A delta-class spot group has umbrae of both polarities, north and south, corralled within the penumbra. Like bringing opposite poles of a two magnets so close they snap together, something similar happens inside delta-class groups. Only instead of a snap, a titanic thermonuclear explosion called a flare goes kaboom.The biggest flares release the equivalent of more than a billion hydrogen bombs.

We thank our lucky stars for the 93 million miles separating sun and Earth. AR 1967 has paraded right in front of our noses as it rotated with the sun. Today it squarely faced the Earth – a good thing when it comes to the particle blasts that fire up the northern lights. Let’s hope it showers us with a magnetic goodness in the coming days. I really miss seeing the aurora. You too?

Big sunspot livens up a quiet sun / Chance for auroras overnight Feb. 1-2

Sunspot region 1967 dominates the solar disk in this photo made late Jan. 31 by the Solar Dynamics Observatory. Credit: NASA

Sunspot group 1967 burst onto the scene on Jan. 28. Now it’s big enough to easily see with the naked eye through a safe solar filter. The group’s twisty, complex magnetic field has already ignited a significant M6 flare on the 30th with a 60% chance for more M-class flares in the next three days.

The expanding cloud of solar plasma called a coronal mass ejection caught blasting away from sunspot group 1967 on Jan. 30 photographed by the Solar Heliospheric Observatory. Credit: NASA/ESA

The Jan. 30 event kicked out a high-speed proton-electron soup called a coronal mass ejection, a part of which will graze Earth overnight tonight (Feb. 1-2) and may spark a northern light display at high latitudes. Of course there’s always a chance southern Canada and the northern border states of the U.S. will see some action, too.

Since there’s been such a dearth of auroras of late, I wanted to share this bit of potentially good news. I’ll post updates if the lights make an appearance.

Polar vortex returns, paints sky in prismatic sparkles

A beautiful halo with accompanying sun dogs (bright spots left and right of the sun) and an upper tangent arc at top photographed earlier this morning Jan. 27. A second much larger and fainter halo ringed this one but doesn’t show in this picture. Credit: Bob King

Pardon my obsession with ice. It’s one of the ways I’ve come to accept this coldest of cold winters. Sparkling halos, sun dogs and ice pillars ornamenting our favorite luminaria – the sun and moon – make it hard to stay indoors.

Looking like some portal into the heavenly realms, the last week’s moon displays an oval corona and tall, wide moon pillar from light reflecting from plate-shaped hexagonal ice crystals floating horizontally in the air. Credit: Bob King

Many of these spectacular prismatic light displays have come to the U.S. and Canada by way of bitter cold polar air bundled with face-freezing winds. One word of advice. If you run out to shoot pictures, don’t do it in your slippers like I did this morning. Wear warm boots. It’s easy to shoot photos of astronomical events in daylight with any kind of camera. Just point, compose and shoot.

This is the top end of a hexagonal column-shaped ice crystal. Light refracting (bending) through billions of these crystals spreads out to form a typical solar halo. Sun dogs form when horizontal plate-shaped crystals refract sunlight.

Although we often can’t see them, the air is laced with microscopic, six-sided plate and column-shaped ice crystals that swirl about and refract the light into wonderful arcs and glows.

Light refracting through column crystals is responsible for halos; refraction through horizontally-floating plate crystals fires up those brilliant sun dogs on either side of the halo.

When not refracting light, plate-shaped crystals hovering with their flat sides parallel to the ground can also reflect the light of sun and moon to create tall columns called ice pillars.

Horizontal plate crystals reflect light to create pillars pointing up and down. On the ground and when the sun or moon is low in the sky, we see only the top pillar, but under the right conditions, when sun or moon is up high, both are visible. Credit: Keith C. Heidorn

Keep an eye out for these sights this week as we get a taste of what its like to live in the Arctic.

Mammoth sunspot erupts with X1-flare

Huge sunspot region 1944 rotated to the center of the sun’s disk today Jan. 7. This photo was taken at noon by the Solar Dynamics Observatory. The largest spot in the group is big enough to see with the naked eye using a safe solar filter like a #14 welder’s glass. Credit: NASA

That huge sunspot we talked about two days ago erupted today at 12:32 p.m. with a powerful X-class flare. I love solar fireworks because there’s always a possibility for a nice aurora display in the wake of a large flare. Good news this time around – the cloud of subatomic particles called a coronal mass ejection appears to be directed toward the Earth.

An X1-class flare erupts from within the large sunspot group 1944 this afternoon Jan. 7. Photo taken in far ultraviolet light by the Solar Dynamics Observatory. Credit: NASA

If it does blow past our planet and forge a connection with our magnetic field we might expect chances for aurora to sharply increase in a couple of days. Already, the NOAA space weather forecast is calling for minor auroral storms at tonight and tomorrow night. I’ll be monitoring from my home and update with the latest information. Be on the lookout!

Big Sunspot Group Turns Earth’s Way / Comet ISON Photo a False Alarm

Sunspot region 1944 has a complicated beta-gamma magnetic field making it prone to producing flares. Photo taken by the Solar Dynamics Observatory at 9:15 a.m. CST today. Click to enlarge. Credit: NASA

We knew it was big even when it rounded the sun’s limb two days ago, but now that sunspot group 1944 has rotated into clear view, we can truly appreciate its enormity. Based on my rough estimate, the largest spot in the group is now easily 40,000 miles across or five times the diameter of Earth and one of the largest of the current solar cycle.

Sunspot group photographed through a “cloud filter” with a 300mm lens this morning Jan. 4, 2014. With a safe solar filter, the group is big enough to see with the naked eye. Credit: Bob King

The group has banged off several moderate M-class flares in the past 24+ hours. NOAA space weather forecasters are calling for a 75% chance of additional M-flares and a 30% chance for powerful X-flares in the days ahead.

Given that the group’s predicted arc across the rotating sun will soon place it squarely in Earth’s direction, we hope that it continues to percolate with flares, potentially sparking auroras in the nights ahead.

Earth and moon size illustration compared to today’s photo of the large sunspot group. Credit: NASA

Using a #14 welder’s glass I could easily see the sunspot region as a dark dot in the lower right corner of the sun with my naked eye this morning. If you have a safe solar filter or a telescope equipped with one, take a look and be impressed.

The sausage-shaped glow running from upper left to lower right in the left-side negative image was suspected to be Comet ISON’s remnant. Photo at right shows nothing at ISON’s position on Jan. 1, 2014. The blue dot marks the predicted position of the comet; the green type gives the names of stars. Click for more images and information. Credit: Hisayoshi Kato

In other news, Japanese amateur astronomer Hisayoshi Kato made a deep image of Comet ISON’s location on December 29 using a 180mm f/2.8 telephoto lens near the Mauna Loa Observatory in Hawaii, recording a possible sausage-shaped dust remnant. Because long time exposures and electronic image processing can sometimes introduce artifacts into an image, Kato photographed ISON’s position again on Jan. 1 but came up empty handed.

No similar remnant stood out on the second try indicating his original photo didn’t capture the comet after all. Some of us were hopeful he had. So what is that dusty sausage? Possibly a strand of the Integrated Flux Nebula, a flock of dust clouds threading the galaxy that glow not by the light of a nearby star(s) but instead from the integrated flux of all the stars in the Milky Way. Think of it as stellar light pollution.