101 geysers erupt from Enceladus’ salty deeps

At least 20 geysers blast icy particles and water vapor from cracks in the icy crust of Saturn’s moon Enceladus. Scientists recently confirmed the geyser material derives from a salty ocean beneath the moon’s surface. Credit: NASA/JPL

Future astronauts better watch where their step when exploring the south polar terrain of Saturn’s icy moon Enceladus. A geyser could pop up anywhere.

This graphic shows a 3-D model of 98 geysers whose source locations and tilts were found in a Cassini imaging survey of Enceladus’ south polar terrain by the method of triangulation. Credit: NASA/JPL-Caltech/Space Science Institute

NASA’s Cassini spacecraft have identified 101 distinct geysers erupting on Saturn’s icy moon Enceladus. Cassini has studied and photographed the moon’s intriguing ‘tiger stripe’ fractures for over 7 years and discovered that each of them coincides with a particular hot spot within a fracture.

Three competing hypotheses were put forward to explain how geysers might happen on an ice-covered moon nearly a billion miles from the warmth of the sun.

#1 – Tidal flexing: As Enceladus revolves around Saturn, the planet’s enormous gravity flexes the little moon, heating up its interior and melting ice into water which escapes as vapor through openings in the icy crust.
#2 – Frictional heating: Back-and-forth rubbing of opposing walls of the fractures generate frictional heat that turns ice into geyser-forming vapor and liquid. Same principle as rubbing your hands together to create heat.
#3 – Jaws of ice: The opening and closing of the fractures caused by Saturn’s gravitational might exposes water from below when then quickly vaporizes in the moon’s vacuum.

This artist’s rendering shows a cross-section of the ice shell immediately beneath one of Enceladus’ geyser-active fractures, illustrating how water works its way to the moon’s surface. Credit: NASA/JPL-Caltech/Space Science Institute

But a detailed study by Cassini in 2010 appears finally to have netted the correct explanation. The probe’s heat-sensing instruments matched the geysers’ locations with small-scale hot spots only a few dozen feet across - too small to be produced by frictional heating, but the right size to be the result of condensation of vapor on the near-surface walls of the fractures.

“Once we had these results in hand, we knew right away heat was not causing the geysers, but vice versa,” said Carolyn Porco, leader of the Cassini imaging team and lead author of the first scientific paper on the discovery. “It also told us the geysers are not a near-surface phenomenon, but have much deeper roots.”

Researchers concluded the only logical source of the material forming the geysers is the sea now known to exist beneath the ice shell. They also found that narrow pathways through the ice shell can remain open from the sea all the way to the surface, if filled with liquid water. This implies, at least in my mind, that liquid water might exist as pools in hot spots encircled by thick rims of ice (condensed water vapor) on the moon’s chill -330° F (-201° C) surface.

Imagine standing nearby watching fountains of vapor turn to ice crystals before your eyes and sparkling like diamond dust against the black starry sky.

Source: JPL

Seeing meteors? Delta Aquarids peak this week!

Meteors from Delta Aquarid meteor shower radiate from near the star Delta Aquarii not far from the bright star Fomalhaut in the Southern Fish low in the south before dawn. Stellarium

With the Southern Delta Aquarid meteor shower peaking tomorrow morning, the summer meteor season’s officially underway. While not a spectacular shower from mid-northern latitudes, why not chance  a look anyway. With a rate of 10-15 per meteors an hour from a dark sky you’re bound to catch at least a few.

The farther south you live, the better it gets. Observers in the southern hemisphere can expect double that number because the shower’s radiant will be much higher in the sky. Any meteors flashing south of the radiant won’t get cut off by the southern horizon like they do further north.

The annual shower gets its name from Delta Aquarii, a dim star in the dim zodiac constellation Aquarius. You don’t need to know the constellations to enjoy a meteor shower but it doesn’t hurt to know the general location of the radiant, the point in the sky from which the meteors appear to radiate. If you can trace the path of a meteor backward toward Aquarius, chances are it’s an Aquarid.

A Southern Delta Aquarid meteor captured on July 30, 2013. Credit: John Chumack

There are actually two meteor showers in Aquarius active this time of year – the northern and southern Delta Aquarids. The northern version sports fewer meteors and peaks in mid-August.

The Southern Deltas peak over the next two mornings – July 29 and 30. Both serve as warm-ups for the upcoming Perseid meteor shower that climaxes on August 12.

Tonight’s shower will suffer no interference from moonlight, making this an ideal time for meteor watching. Unfortunately, Perseid rates will be reduced by a bright waning gibbous moon. Don’t be surprised though if you see a few Perseids while you’re out. The shower’s just become active. If you can draw a meteor’s trail back to the northeastern sky, it just might be one. Perseids are also known for leaving bright streaks in their wake called trains.

Nearly all meteor showers originate from clouds of sand to seed-sized bits of debris spewed by vaporizing comet ice as they swing near the sun. The Delta Aquarids may trace its origin to dust boiled off Comet 96P/Machholz.

The best time to watch the shower is in the early morning hours before dawn when the radiant rises in the south-southeastern sky above the bright star Fomalhaut. Try to get away from city lights. Point your lawn chair south and spend some time in heavenly contemplation as you wait for Aquarius to toss a few javelins of light your way.

Sunrise and sunset – nature’s most beautiful illusions

Earth turns on its axis to greet the sun at sunrise each morning of the year. Credit: Bob King

Every day the sun rises, crosses the sky and sets. And it does it again and again and again like the perpetually repeating cycle of events in the movie Groundhog Day.

Except perhaps for a few remaining Flat-Earthers, we know what’s going on here. The sun’s not doing the moving. Instead, the Earth’s rotation causes the apparent motion of the sun across the sky. Yet the sense of the sun’s movement is so powerfully ingrained in our experience you might balk if I told you it’s essentially sitting still in the sky.

Every day the turning Earth causes the nearly static sun to rise in the east at sunrise and set in the west at sunset. Credit: Canadian Space Agency

For you to see a sunrise, Earth must rotate on its axis until your location faces the sun as it crests above the planet’s curvature. The following morning, when Earth rolls around after another 24 hours, the sun is very nearly in the same place in the celestial sphere as the previous morning. Once again, we see the sun ‘rise’. Ditto for the next morning and the next. It’s like turning over in your bed each and every morning and seeing your spouse in the same spot. Or very nearly.

If the Earth spun but stood in one spot never circling the sun, we would meet the rising sun at precisely the same time and place every day ad infinitum – a true Groundhog Day scenario. But the Earth orbits or revolves around the sun as surely as it rotates. Just like our daily spin, our planet’s revolution is reflected in the sun, which appears to slowly crawl across the sky, inching its way from one background zodiac constellation to the next, during the course of a year.

The orbiting and titled Earth cause slow but continuous changes in the times of sunrise and sunset during the course of a year. Credit: Thomas G. Andrews, NOAA Paleoclimatology

The ever-changing times of sunrise and sunset stem from the Earth’s orbital travels combined with the shifting seasonal tilt of the planet. From December 21 until June 21, as the amount of daylight increases in the northern hemisphere, the sun appears to travel slowly northward in the sky and we meet its welcome rays a couple minutes earlier each morning.

The sun’s yearly motion across the sky during the year traces out a path called the ecliptic. The top of the curve, at right, is the sun’s position during the summer. The low part of the curve is the sun’s location during winter. The up-and-down path is a reflection of the 23 1/2-degree tilt of the Earth’s axis. Illustration and animation by Dr. John Lucey, Durham University

Then from June 22 to December 20, Earth’s orbital motion causes the north polar axis to slowly point away from the sun. The sun appears to slide south as the hours of daylight wane, and we meet the sunrise a minute or two later each morning.

The sun, located some 26,000 light years from the center of the Milky Way galaxy, takes about 220 million years to make one revolution around its core moving at 483,000 mph. Credit: ESO

Earth moves along its orbit at an average speed of 67,000 mph (108,000 km/hr).

How about the sun? If I left the impression that it’s totally static I apologize. Yesiree, it’s moving too – at the astonishing speed of 483,000 miles per hour (792,000 km/hr) around the center of the galaxy.

Don’t look now, but you and I are going on the ride of our lives.The only reason stars remain static in the sky over the span of many generations despite the sun’s hurry is because nearly all of them are too far away to show a shift in position with the human eye. Telescopes, which magnify everything including motion, do show very subtle changes in the positions of nearby stars over much shorter time intervals.

Rising each morning to the same old sun, I try to remind myself that with every rotation comes a new opportunity to spin some joy into the day.

A comely cometary coincidence / New camera to record cargo ship’s fiery reentry

In this happy alignment, perfectly composed and exposed by Italian amateur astronomer Rolando Ligustri, Comet Jacques pairs up with IC 405, the Flaming Star Nebula on July 26. The comet will be visible in binoculars now until the moon returns to brighten the sky around August 8. Credit: Rolando Ligustri

A stunning photo! It’s comet C/2014 E2 Jacques, tail as straight as a Q-tip, forming a cosmic question mark with the glowing cloud of hydrogen gas called the Flaming Star Nebula. Two tails stand out. The one reaching beyond the frame is made of carbon monoxide gas fluorescing in the sun’s ultraviolet light. To the left of the bright head a meeker dust tail shines by reflected sunlight.

This close-up photo taken July 25 reveals that the glowing gas tail (right) is made of multiple streamers. Heat from the sun vaporizes ices which stream back to form a comet’s tails. Credit: Damian Peach

The nebula’s 1,500 light years away in the direction of the constellation Auriga the Charioteer, while Jacques plies the solar system just 112 million miles from Earth. Discovered by a group of Brazilian amateur astronomers last March, a study of its orbit hinted it might wax bright enough to see with binoculars after making its closest approach to the sun in late May.

That’s exactly what happened, and you can see it right now – assuming you’re willing to rise at 4 a.m. – low in the northeastern sky just before the start of morning twilight. I caught it in 8×40 and 10×50 binoculars Saturday from home. No tail stood out but the comet’s head looked like a small, fuzzy spot compared to the sharp points of nearby stars. Through a telescope I saw a dense, bright cotton ball and hint of a tail.

Follow Jacques in a small telescope or binoculars in its travels across Auriga into Perseus during the next two weeks. Comet positions are shown for 4 a.m. CDT every 5 days. Stars to magnitude +8.0. Click to enlarge. Source: Chris Marriott’s SkyMap

Comet Jacques glows at magnitude 6.5 and will remain about that bright through early August. Because the comet’s moving up and away from the sun, it’s getting higher in the east and easier to see with each passing morning.

If you need another reason to arise so early, the International Space Station will light your path all this week and next. Head over to Heavens-Above and click on the ISS link to get times for passes over your city. Simultaneous evening passes begin on or around August 2.

The last of the European Space Agency’s five automated space freighters, ATV-5, is being prepared for launch to the ISS on Tuesday, July 29. Named “Georges Lemaître” in honor of the Belgian astronomer who first proposed the idea of the Big Bang, the ship will ferry six tons of supplies including lots of drinking water and food to the astronauts. If there’s an opportunity to see it ‘chase’ the space station, I’ll provide an update.

Artist’s view of ATV-5’s destructive reentry into Earth’s atmosphere over the Pacific Ocean. A special camera will record the scene from inside. Copyright: ESA–D. Ducros

ATV-5 is the last of the European cargo ships and will burn up like the others during atmospheric reentry once its mission is complete. But this one ends with a twist. The fiery burn-up and disintegration will be recorded from the inside by a unique infrared camera. Before the camera becomes toast, it will transmit the images to a ‘black box’ called the Reentry SatCom, a spherical capsule protected by a heatshield. The SatCom will relay the data to a nearby Iridium satellite and from there back to mission control. Can’t wait to see that video!

Tomorrow’s new moon foretells October’s solar eclipse

Tomorrow July 26, 2014, the invisible new moon will pass a few degrees south of the sun in the daytime sky. Stellarium

New moons aren’t much to look at. You can’t even see them most months of the year. That’s true for tomorrow’s new moon which will invisibly accompany the sun in its journey across the sky.

New moons occur about once a month when the moon passes between the sun and Earth. We can’t see them for two reasons: first, no sunshine touches the Earth-facing side when the moon lies in the same direction as the sun. It’s completely dark. From our perspective, the out-of-view lunar farside gets all the sunlight. Second, since the moon is nearly in line with the sun, it’s utterly lost in the glare of daylight.

The moon seesaws 5 degrees north and south of Earth’s orbit during its monthly cycle because its orbit is tilted with respect to Earth’s. Only when the moon crosses the plane of Earth’s orbit at the same time as a new moon do we see a solar eclipse. Illustration: Bob King

We normally have to wait two days after new moon – when the moon’s orbital motion carries it to the left (east) of the sun – to see it as a thin crescent at dusk.

Most of the time the moon passes north or south of the sun at new phase because its orbit is tilted 5 degrees with respect to Earth’s. But 2.4 times a year on average, new moon coincides with the time the moon’s seesawing path slices through the plane of Earth’s orbit. For a brief time during that crossing, all three bodies are aligned and happy earthlings witness a solar eclipse.

If the alignment is imprecise, the moon blocks only a part of the sun, giving us a partial solar eclipse.  If dead-on, we see a rarer total solar eclipse.

View of the partial solar eclipse across the Upper Midwest a half hour before sunset on October 23. By coincidence, Venus will be near conjunction at the same time and only a couple moon diameters north of the pair. Seeing the planet in a telescope will still be challenging because of daylight glare.  Stellarium

On October 23 this year, the lineup at new moon will be a good if imperfect one with a maximum of 81% of the sun covered. The partial eclipse will be visible across much of North America; from the eastern half of the U.S. and Canada the event will occur near sunset, adding a touch of drama to the scene.

I wrote earlier that we can’t see a new moon. That’s only partly true. We mostly pay attention to the sun’s changing shape during solar eclipses, but the dark, curving bite working its way slowly across the sun’s disk is none other than the new moon seen in silhouette.

Rosetta’s comet shows off new bumps, bruises and bright collar

New views of Comet 67P/C-G show more surface features including a bright collar. The dark band in the middle and right images is the shadow cast by one part of the comet on its other half during rotation. Each picture is separated by 2 hours. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Pictures taken July 20 of comet 67P/Churyumov-Gerasimenko by the Rosetta spacecraft show cool new stuff. They include several tantalizing depressions in both lobes of the comet and a bright collar where the two dissimilar halves meet.

3-D model of the comet’s shape based on July 14 images. Credits:ESA/Rosetta/MPS for OSIRIS Team MPS

What makes the comet’s ‘neck’ bright might help us understand how 67P/C-G got its strange shape. It could be a region of freshly exposed ice, differences in the composition of the material where the two lobes meet or a change in elevation in the landscape. More detailed studies including examination with a spectrograph to nail down its composition will have to wait until August 6th and beyond, when Rosetta parks itself in orbit.

Look closely and you’ll also see several depressions. One of the largest is a shallow bowl at the top of the smaller lobe. No one knows if these are impact craters or some kind of collapse pits created where ice below the surface vaporized away during the comet’s regular swings past the sun every 6.5 years.

More and more observations of the 67P/C-G are being made every day. Everything from determining its mass and volume, which will be used to arrive at the comet’s density, to measuring the rate at which gas and dust boils off the icy nucleus.

The animation above covers one full 12.4 hour rotation of the nucleus. The next batch of pictures is expected on July 31 with the first high resolution images arriving on August 6.


Chandra’s X-ray eyes behold catastrophe

To mark the 15th anniversary of NASA’s Chandra X-ray Observatory, four newly processed images of supernova remnants illustrate Chandra’s ability to explore high-energy processes in the cosmos. See end of article for detailed explanations of each. Click to enlarge. NASA/CXC/SAO

15 years ago to the day, NASA’s Chandra X-ray Observatory opened its eyes to the high-energy universe. It was launched aboard the space shuttle Columbia and entered a long elliptical orbit that takes it more than a third of the distance to the moon before returning to its closest approach to Earth of 9,942 miles. This specially tailored path keeps it above the Van Allen radiation belts – which would interfere with its X-ray vision – more than 85% of the time.

Chandra’s long elliptical orbit around the Earth keeps it away from the Van Allen belts and allows the telescope to study an object up to 55 hours without interference. NASA

Chandra, named for Indian-American astrophysicist Subrahmanyan Chandrasekhar who did groundbreaking work on white dwarf stars, is specially designed to detect X-rays emitted by hot and energetic objects in the universe. What we feel as heat – infrared light – is low-energy radiation. Planets, comets and asteroids warmed by the sun emit infrared as surely as our own bodies do.

Radio waves, some infrared and visible light penetrate the atmosphere and make it to the ground. Shorter wavelength light from energetic UV to gamma rays are stopped by the atmosphere. A good thing.

As we move to light of shorter wavelengths, energy content rises. Visible light is more energetic than infrared, UV light more so (it can give us a painful sunburn) and X-rays very much more so. To spew X-rays, something very powerful must be happening in space like a supernova explosion or matter heated to incandescence as it disappears down a black hole.

Earth’s atmosphere acts to filter out dangerous much of the more energetic particles and light waves careening around the cosmos, the reason Chandra had to be pitched into the vacuum of space to use its X-ray specs.

Chandra has observed objects ranging from the closest planets and comets to the most distant known quasars. It has imaged the remains of exploded stars, or supernova remnants, observed the region around the supermassive black hole at the center of the Milky Way, and discovered black holes across the universe.

To celebrate the anniversary, NASA released  four newly processed pictures of supernova remnants, the dusty, gassy leftovers of stars blown to smithereens. Let’s take a look at each in turn:

Chandra view of the Crab Nebula expansion in just 7 months

* Crab Nebula: At its center is a city-sized, extremely compact, rapidly rotating neutron star left after the original sun went supernova in 1054 A.D. Also called a pulsar, the star spews zillions of high-speed particles that plow into the expanding debris field to create a ghostly X-ray nebula.

* G292.0+1.8:  One of only three supernova remnants in the Milky Way known to contain large amounts of oxygen. These oxygen-rich supernovas are of great interest to astronomers because they are one of the primary sources of elements heavier than hydrogen and helium that are necessary to form planets and people. The image shows a rapidly expanding debris field that contains, along with oxygen (yellow and orange), other elements such as magnesium (green) and silicon and sulfur (blue) that were forged in the star before it exploded.

* Tycho’s remnant: The supernova that created the remnant was first noticed by Danish astronomer Tycho Brahe in 1572 as a brand new star in the constellation Cassiopeia. The supersonic expansion of the exploded star produced a shock wave moving outward into the surrounding interstellar gas, and another, reverse shock wave moving back into the expanding stellar debris. Heated to millions of degrees, the gas and debris produce copious X-rays.

* 3C58: 3C58 is the remnant of a supernova observed in the year 1181 AD by Chinese and Japanese astronomers. It contains a rapidly spinning neutron star surrounded by a thick ring of X-ray emission. The pulsar also has produced jets of X-rays blasting away from it to both the left and right, and extending trillions of miles. These jets are responsible for creating the elaborate web of loops and swirls.

As a kid, we used to joke about wishing we had X-ray vision. Now we really do.

How to find the center of the Milky Way … and what lurks there

Want to know where the center of our galaxy is? Face south around nightfall in late July and find the Teapot of Sagittarius about ‘two fists’ to the left of bright Antares in Scorpius. The core is a blank bit of sky just above the spout near the 4.5 magnitude star 3 Sagittarii.  Stellarium

Ever stared straight at the heart of the Milky Way galaxy? Give it a try this coming week. With dark skies and no moon, the time is right.

Artist’s view of the 4 million mass black hole at the center of the Milky Way. The hole measures about 28 million miles in diameter. Credit: NASA

Notice I didn’t say into the heart. No human eyes can penetrate the veil of interstellar dust that cloaks the galactic central point 26,000 light years away in the direction of the constellation Sagittarius. Only X-ray, gamma ray and radio telescopes can ‘part the way’ and expose the galaxy’s dark secret which astronomers call Sagittarius A*.

There, at the center of it all, lies a black hole with a mass of 4 million suns. The innermost 3.2 light years centered on the black hole swarms with thousands of aged stars and about 100 fresh-born ones, some in very tight orbits about the hole. Gas clouds abound, and there’s at least another smaller black hole nearby.

NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, captured these first, focused views of the supermassive black hole at the heart of our galaxy in high-energy X-ray light. Known as Sagittarius A* (A star), the bright flare formed when Sgr A* was consuming and heating matter. The background image, taken in infrared light, shows its location. Credit: NASA

Occasionally the central black hole flares to life when a random asteroid, gas cloud or stray star passes too close and gets ripped to pieces before disappearing down the gullet of the beast. Heated by friction, the material sends out every type of light from visible to X-rays and gamma rays. But no one can see all the excitement because it’s hidden by light years of dust grains. To the eye, the center looks nondescript and static, but nothing could be further from the truth.

The Milky Way is beautiful to gaze at this time of year. Take a drive to the country and park your car where the sky is dark and open to the south. At nightfall, you’ll see a fiery-hued star a few fists up from the southern horizon at nightfall. That’s Antares in Scorpius. Now shift your gaze two fists to the left or east and see if you can spot the outline of the Teapot. Once you’ve found it, galactic center lies just above the spout.

Closeup of the Spout showing a couple bright star clusters and the Lagoon Nebula, a rich star-forming region. Credit: Bob King

Though the center remains hidden, large chunks of the Milky Way hover like clouds against the black sky. Every puffy piece is comprised of billions of distant stars the light of which blends together to form a misty haze. Here and there are smaller knots. These are individual gas clouds called nebulae and bright star clusters. A pair of 40-50mm binoculars will show many of these wonders and countless fainter stars plainly. If we could magically remove the dust between us and the galactic center, the rich intensity of stars in the Sagittarius direction would be bright enough to cast shadows at night.

Take it all in. Let your eyes follow the arc from the southern horizon clear up across the eastern sky and back down to the northeastern horizon. We live here – can you believe it?

Moon nestles in Hyades then departs for Venus

The crescent moon slips in front of the Hyades star cluster only a degree from Aldebaran tomorrow morning. Don’t miss the other bright star cluster, the Pleiades, just above. Look low in the northeastern sky about an hour before sunrise to catch the scene. Stellarium

That old devil moon’s up to its old tricks again. Tomorrow morning, early risers will see it tucked inside the V-shaped face of Taurus the Bull. Better known as the Hyades star cluster, look for the crescent to pass just 1° north of the bright star Aldebaran. A pair of binoculars will enhance the view by pulling in more stars and revealing details in the spooky, earth-lit moon. Sunlight illuminates the lunar crescent, but the remainder is light reflecting off Earth out to the moon and back again.

The crescent is lit by the sun while the remainder glows dimly from twice-reflected light called earthshine. Credit: Bob King

To the eye, ‘earthlight’ looks smoky gray and nearly featureless though binoculars will show the lunar seas and larger craters. The quality of the light mimics a lunar eclipse but instead of red we see the pale blue glow of sunlight reflecting back from our planet’s oceans.

At 153 light years, the Hyades is the nearest star cluster to our solar system, one of the reasons you can see it without a telescope. Aldebaran appears to be a full-fledged cluster member, but it’s a ruse. The bright, ruddy star lies much closer to us along the same line of sight.

Venus and a very thin crescent moon on July 24 about 45 minutes before sunrise low in the northeast. Stellarium

The Hyades were born in a dense cloud of interstellar dust and gas 625 million years ago around the time underwater life flourished in the late Precambrian era. When you gaze at the cluster tomorrow, the light that touches your retinas left the Hyades the same time Abraham Lincoln took office.

The moon moves on toward Venus after vacationing in the Hyades, passing south of the planet on Thursday morning. It will be extremely thin that morning and should make a pretty sight for anyone looking low in the northeastern sky 45 minutes before sunrise.

Shhh! Don’t wake the sun

Contrast these views of the nearly spotless sun on July 16-17, 2014 with a picture taken about two weeks earlier (below). Credit: Giorgio Rizzarelli

Who doesn’t enjoy a nap on a lazy summer afternoon? That’s what the sun’s been up to past few days. Instead of a steady parade of sunspots, it put its pencils away and went to sleep. For a time on July 17 not a singe magnetic blemish marred the entire Earth-facing hemisphere. The last time that happened was nearly 3 years ago on Aug. 14, 2011.

Ten groups including three visible with the naked eye dot the sun on July 8, 2014. Credit: NASA

The solar blank stare lasted but a day; by the 18th two small groups emerged. Today three little spot clusters have emerged but again, they’re on the small side.

I think the reason the sun looks so stark is that only two weeks ago nearly a dozen sunspot regions freckled the disk including three visible with the naked eye with a safe solar filter.

These ups and downs aren’t unusual unless this downturn continues for weeks. Expect more bubbles of magnetic energy to rise from beneath the glaring surface of the sun called the photosphere and spawn fresh groups soon. Because we now have eyes on the farside of the sun courtesy of the dual STEREO solar probes, we know the complete story. There are at least seven spotted regions in hiding there today.

Sunspot numbers are plotted for the last three solar cycles through the present. The double peak of the current cycle is shown. Credit: NASA

Sunspots and flares peak approximately every 11 years. We’re still riding the roller coaster near the top of the arc after the most recent solar maximum in late 2013. Some maxima are strong, others weak. The current max – Cycle 24 – is the weakest since Cycle 14 in February of 1906 and one of the wimpiest on record. Occasionally a cycle will have two peaks like the current one. The first peak occurred in Feb. 2012 and the second just this past June. What makes Cycle 24 even more unusual is that the second peak is higher than the first – the first time this has ever been recorded. Like people, every maximum has a personality of its own.

Doug Bieseker of the NOAA Space Weather Prediction Center has analyzed historical records of solar activity and he finds that most large events such as strong flares and significant geomagnetic storms typically occur in the declining phase of solar cycles—even weak ones, so don’t give up hope for some great auroral displays ahead.

A coronal mass ejection blew off on the farside of the sun early this morning July 20. It appears to envelop Jupiter, but the planet is 490 million miles in the background. SOHO uses an occulting disk to block the brilliant sun. Credit: NASA/ESA

The sun’s got a buddy this week – Jupiter! We can’t see the planet from the ground because it’s swamped by solar glare, but the Solar and Heliospheric Observatory (SOHO) has a great view from space. Watch the sun approach from the right and pass the planet over the next few days. After the 24th, Jupiter will move into the morning sky.