Morning crescent moon anticipates weekend solar eclipse

The sky facing east tomorrow morning about an hour before sunrise. The moon will appear as a beautiful crescent. Created with Stellarium

As the solar eclipse approaches, we watch with anticipation as the moon slims to a thin crescent in the morning sky. Each day it slips a fist eastward toward the sun as if drawn by a tractor beam toward Sunday evening’s eclipse.

Tomorrow the moon will be appear in the rosy glow of dawn in the east below the familiar Great Square of Pegasus, a baseball-diamond shaped constellation prominent during fall evenings.  Watch for it if you’re up with the birds.

The May 5 full moon occurred when the moon was closest to the Earth or perigee; new moon happens 2 weeks later at apogee, when the moon is farthest away. Illustration: Bob King

A reader asked about why the moon is now so far from Earth (at apogee) when we just had a perigee or unusually close full moon.

If you recall that the moon’s orbit is an ellipse with Earth a little off to one side of center, perigee and apogee are directly opposite one another.  Since the moon orbits the planet in about four weeks, when perigee (closest approach) occurs at full moon, it’s a given that apogee will be half an orbit or about two weeks later.

Total solar eclipse August 11, 1999 occurred when the moon was near perigee. Credit: Luc Viatour

Guess what phase the moon’s in two weeks after full? New moon! And it’s only at new moon, when the moon slides between the Earth and the sun, that a solar eclipse is possible. This month’s new moon happens when it’s most distant from Earth. Its smaller apparent diameter can’t fully hide the sun, giving us an annular eclipse.

When a new moon happens around perigee, it’s more than big enough to cover the sun. That’s why the November 13 eclipse over northern Australia will be a total one. New moon occurs just a day before perigee.

Complete viewing guide to Sunday’s annular solar eclipse

The gray band is the annular eclipse visibility zone. Anyone within it will see the moon completely cross over the sun. If you're on the red line, the moon will pass exactly over the center of the sun leaving a symmetrical ring of sunlight. Other locations in North America will see a partial eclipse except the East Coast. Click map for interactive version. Credit: NASA map / overlays: Bob King

It’s almost here. Time to get ready for Sunday’s annular eclipse of the sun, the first one visible from the U.S. since 1994. Anyone living in the approximately 150-mile-wide band from southern Oregon to northern Texas will see the moon’s black disk silhouetted squarely against the sun’s.

Folks like me, who live outside that band, will witness a partial eclipse. For Duluth, Minn., the moon will cover a maximum of 63% of the sun. Chicago gets a bit more – 69% – and Dallas 94%.

Clicking on Duluth, Minn. on the NASA website map reveals eclipse details. A magnitude of .633 means 63.3% or nearly 2/3 of the sun is covered during maximum eclipse. Click map to read weather prospects for cities located along he eclipse center line. Credit: NASA

To find out circumstances of the eclipse for any town in the U.S., Canada and other regions, click on the map at top. It will take you to NASA’s eclipse website, where you can zoom in to find your town. When you click again on the town name, an info box pops up with times and “eclipse magnitude”. This is the amount of sun covered for your A magnitude of 0.59 means 59% of the sun will be blocked by the moon at maximum eclipse. The times shown in the bubble are Universal Time (UT or Greenwich time). For Eastern Daylight subtract 4 hours, Central 5 hours, Mountain 6 and Pacific 7 hours. In the example, the eclipse starts at 00:17 UT May 21. Subtracting 5 hours we get 7:17 CDT May 20.

94% of the sun will be covered by the moon during this Sunday's eclipse. Illustration: Bob King

Annular eclipses happen when the moon passes directly in front of  the sun just as it does during a total solar eclipse – with one difference. Normally the moon is big enough to completely cover the solar disk, but during this eclipse, it happens to be farthest from Earth and hence a bit smaller than usual. Small enough that it leaves an annulus or ring of sunlight remaining at maximum eclipse.

During a total eclipse (left), the moon is close enough to Earth to cover the sun and casts a shadow called the umbra on Earth. An annular eclipse happens when the moon is farther from Earth than normal. The antumbra defines the path of annularity.

Since some portion of the sun remains visible during the entire eclipse, it’s important to use a safe solar filter to protect your eyes if you plan on watching the event. You can find out where to purchase a filter in this recent blog I wrote on the topic.

I’ve seen two annular eclipses in my time and enjoyed them both immensely. Sure, it’s not the same as a total, where you can stare at the sun directly and watch pink flames lick its circumference beneath a quivering corona. But make no mistake, there’s still plenty to see and enjoy during this eclipse.

Here’s what to watch for with naked eye, binoculars and small telescopes. Again, I can’t emphasize enough how important it is to do your looking through a safe solar filter:

* Daylight perception – When about 75% or more of the sun is covered, you’ll notice a change in the quality of daylight. The sky will be darker and a steelier shade of blue than before the eclipse.

* Weird shadows – Again, in places where about 3/4 of the sun will be covered, the quality of your shadow will change from soft and fuzzy-edged to sharp as the disk of the sun narrows to a thin arc.

Simulated view of moon's edge approaching a sunspot group. Background image: NASA

* The serrated edge – For those with small telescopes, take a look at the silhouetted edge of the moon against the sun. If you look closely, you’ll notice it’s irregular in places like a serrated knife. Those are the tops of mountains and crater rims seen in profile. While an interesting sight in itself, it gets even better (see farther down).

* Sunspot hide and seek – If the sun has any sunspots – very likely – it’s fun to watch the moon’s edge approach, slice into and then cover the spots. See if you can tell which is darker – the silhouetted moon or the dark sunspot cores called umbrae.

Mountains "biting" into the edge of the sun (lower left) during annularity. Credit: W. Van Kerkhoff

* Sticky mountains – For anyone within the annular zone or very close to it, the mountains along the moon’s edge will appear to “stretch” and briefly “stick” to the inner circumference of the sun, breaking it into short segments.

This wonderful sight happens for several seconds at second and third contacts and is caused by atmospheric effects on the moon’s bumpy profile.

Second contact occurs the moment the entire moon is visible against the sun. Third contact occurs the moment the leading edge of the moon touches the inner edge of the sun as it exits the disk. During a total solar eclipse, the same mountains create the sparking “diamond ring” effect.

The Ring of Fire seen during maximum eclipse. Credit: Sancho_Panza

* Ring of fire effect -For many this will be the climax of the eclipse when observers in the path of annularity will be able to see the moon surrounded by a fiery ring of sunlight for about 4 minutes. Be sure to look take your eye away from the scope for a minute to appreciate the sight with the (filtered) naked eye. It’s eery to see nothing but a ring up there, almost like you’re living on a planet orbiting a distant sun.

Venus should be easy to see during the eclipse as long as the sky's transparent all along the eclipse path. Albuquerque is shown here. Created with SkyMap

* Planetary bonus – For those in the annular zone or near it, the sky should get dark enough to see Venus high above the moon in the western sky. Those watching from California and especially from Japan and China, where the sun will be much higher, can also look for Jupiter and Mercury below the it.

* Live Webcast – If you’re not able to see the annular eclipse, check out AstronomyLive’s live webcast.

One of the best things about an annular eclipse is seeing how quickly the moon glides from one side of the sun to the other through a telescope. Unless you witness a total eclipse, you’ll probably never feel it move faster. Now let’s just hope it’s clear. Good luck to all of you!

Bye, bye Venus, see you on the other side

A colorful 22-degree halo, the most common variety, rings the sun yesterday afternoon. Like a prism, the ice crystals spread white light out into a rainbow spectrum giving the inner edge a red-orange tint and outer edge a pale blue. Photo: Bob King

A reminder to keep an eye out for halos around the moon and sun. We’re outside more often during the warmer months with more opportunities to notice things in the sky. Yesterday I caught the bottom edge of a colorful solar halo while making that first buzz with the lawnmower through a jungle of dandelions. Halos are created when light is bent or refracted by billions of microscopic, pencil-shaped ice crystals in cirrostratus clouds. Most have a radius of 22 degrees, making them 44 degrees or “four fists” in diameter. If you see thin, wispy clouds that stretch like a veil across the sky, halos may be in the offing.

Bye, bye Venus! Watch as Venus departs the evening sky in the next two weeks. These maps show the view facing northwest about 45 minutes after sunset. Created with Stellarium

Being outside in warmer weather also makes it easy to follow Venus’ quickening exit from the evening sky. Remember when it set at midnight? No more. 45 minutes after sunset tonight, the shining planet will be only 15 degrees high (a fist and a half held at arm’s length) in the northwest. A week from now that shrinks to 10 degrees and by late May, it’ll be lost in twilight’s glow.

Venus is a thin crescent through binoculars and small telescopes.

Venus is rapidly closing in on Earth, growing larger all the time. You should now be able to see the planet as a tiny crescent moon in 10 power binoculars. Make sure to focus sharply and observe in early twilight, when the planet’s glare is reduced. Venus undergoes phases just like the moon.

When it’s on the opposite side of the sun from Earth, it looks “full”, but as the planet catches up with ours, Venus’ phase shrinks to half and finally a crescent before gliding between the Earth and sun.  If you observe Venus regularly through the end of the month, you’ll see the crescent enlarge and grow thinner as the distance between the two planets shrinks.

Venus as a "reverse" crescent on June 15

After crossing the solar disk on June 5 during a rare transit, Venus will swing west of the sun and pop out days later in the morning sky at dawn. It will still be a crescent, but because it will then be on the other side of the sun as seen from Earth, the “left” or side of the planet will be illuminated as a thin crescent. The flip-flopping crescents are fun to see in binoculars and telescope; there’s no better demonstration of how Venus keeps on truckin’ along its orbit. As for the June 5 transit, I’ll have more on how to view it soon. It will be the last time in our lives we’ll be able to see one.

As Venus orbits, its changing angle with Earth and sun lets us see it in different phases like the moon. In the evening sky, the planet is to the left or east of the sun; when visible at dawn, it's to the right or west of the sun. Illustration: Bob King.

A journey from Cassiopeia to the Southern Cross

The W of Cassiopeia the Queen is due north and low in the sky at mid-northern latitudes in May. Created with Stellarium

Walking with my older daughter the other night, we noticed how low Cassiopeia had dropped in the  northern sky. It’s also back to looking like a “W”  instead of a zigzag. The familiar constellation reaches its nadir or lowest point above the northern horizon around 11 p.m. in mid-May. For most sky watchers that means it’s lost in the trees or hidden by buildings.

Cassiopeia’s height also depends on one’s latitude. From Duluth, Minn. the W never sets, but from Phoenix, Arizona it nearly scrapes the horizon. Travel further south to Miami and you won’t see it at all on May and June evenings.

The North Star is as high above the horizon as your latitude. In Duluth, that’s 47 degrees or more than halfway between the horizon and the overhead point or zenith.  Since Cassiopeia is only 30 degrees from the pole star, it cycles around it as the Earth rotates and misses the horizon by 17 degrees, ie. never sets. Constellations that never set are called circumpolar. In addition to Cassiopeia, the Big Dipper, Little Dipper, Cepheus, Draco and parts of others are all circumpolar from where I call home.

Cassiopeia is below the horizon in May and June for Florida skywatchers. This map shows the view looking north from Miami around 11 o'clock. Credit: Chris Marriott's SkyMap software

Now let’s pretend we’re in Miami. Its latitude is 26 degrees (21 degrees south of Duluth, Minn.). That means the North Star is just 26 degrees above the horizon in the northern sky. Since the W is 30 degrees from the pole star, it’s below the northern horizon this time of year.

Before we pity the poor Miamians, let’s expand our view. While the northern sky is cut short by their southerly latitude, they’re well compensated by a deeper look into the southern sky.

In Duluth, our southern horizon cuts off constellations not far below the trapezoid-shaped Corvus the Crow. Floridians get to see another 20-plus degrees of sky beyond that.

From southern Florida and points south, the Southern Cross (Crux) and the brightest stars of Centaurus the Centaur are visible. Sky shown around 11 p.m. local time.

And guess what’s there? Only one of the starriest lots of real estate in the sky. From a boat on the Gulf, you’d be able to look due south and spy the Southern Cross just cresting above the horizon with bright Alpha and Beta Centauri in tow on May nights. You’ll recall that  the triple star Alpha is the closest star to Earth after the sun with a distance of 4.3 light years or 26 trillion miles.

In my opinion that more than makes up for the loss of the W. Besides, all Miamians need do to see Cassiopeia is go out at dawn, when Earth’s rotation brings the constellation back up in the northeastern sky.

The Southern Cross (center) and Alpha and Beta Centauri (left) are embedded in a rich section of the southern Milky Way. The dark patch to the left of the Cross is dark nebula called the Coalsack, composed of interstellar dust. Credit: Mike Salway

While clearly unfair to northerners, the Southern Cross and its cohorts are motivation for the astronomically-inclined to make a trip to the far south. After living most of one’s life where the North Star is always forever in one place in the sky, you’ll feel like a newborn babe under the southern stars.

Chance to own a piece of Sutter’s Mill meteorite

This Sutter's Mill meteorite struck Suzi Matin's garage and broke into two fragments weighing 10.3 grams and 1.4 grams. The 10.3 gram has been broken into fragments for sale. Credit: Greg Hupe

Two of the meteorite hunting community’s most respected hunters, Greg Hupe and Mike Farmer, are selling small fragments from the 10.3 gram Sutter’s Mill meteorite (provisional name) that hit Suzie Matin’s garage. The price isn’t cheap – $2000 per gram – but they’ve divided the stone into very small pieces, so that a fraction of a gram becomes more affordable.

I found out about the offer tonight and wanted to pass it along. I wouldn’t normally promote a particular sale, but this meteorite has been the focus of extraordinary public and scientific interest due to its spectacular fall and rare nature. Sutter’s Mill appears now to be something other than the “usual” carbonaceous chondrite, though a complete analysis is still underway.

To date, the total weight of Sutter’s Mill meteorites comes to about 421 grams. The largest stone, a 44 gram individual, was found Thursday by Robert Ward, who also holds the distinction of finding one of the smallest pieces — 0.1 gram.

If you’re interested or would like more information, e-mail Greg Hupe at gmhupe@centurylink.net


Video of NASA’s hunt for Sutter’s Mill meteorites using a zeppelin. One caveat: the video seems to imply they found a specimen from the air, but the one shown was found instead by a ground search.

For the record, no one asked me to advertise this sale and I will not benefit from it in any way. There have been and will be other sales of Sutter’s Mill fragments in the future. If the number of pieces is large enough to “go around” like this one, I will post them here.

Here is the list of fragments available as of 10 p.m. CDT. All weights in grams:

0.0046 no crust $20.00
0.0062 no crust $20.00
0.0062 no crust $20.00
0.0162 25% crust $33.00
0.0240 30% crust $48.00 (on hold)
0.0278 15% crust $56.00 (on hold)
0.0302 no crust $61.00
0.0558 no crust $112.00
0.0670 no crust $134.00
0.0672 no crust $135.00
0.0710 no crust $142.00
0.0888 no crust $178.00
0.0898 no crust $180.00
0.0942 no crust $189.00
0.0988 no crust $198.00
0.1000 no crust $200.00
0.1292 no crust $259.00
0.2004 30% crust $400.00
0.0882 fragments & dust $200.00
0.1924 fragments & dust $436.00

Jupiter’s disappearing act plus exciting news from Vesta

Jupiter approaches conjunction with the sun in this photo taken by the SOHO's C2 coronagraph this morning. A coronagraph uses a disk to block direct sunlight. Credit: NASA/ESA

Back in the day before orbiting telescopes and 24/7 sky surveillance, when a planet got too near the sun, it was invisible in the solar glare. Not anymore. Thanks to the two coronagraphs aboard the Solar and Heliospheric Observatory (SOHO), we can follow planets right through conjunction with the sun.

SOHO is located at a stable point some 930,000 miles sunward of Earth. With no atmosphere to contend with, SOHO studies the sun from the spotless window of outer space.

Jupiter reaches solar conjunction tomorrow when it will be closest to the sun. You can see from the photo that today it’s already very close – less than one degree away or one “pinkie” finger held at arm’s length against the sky. Notice that Jupiter is a little below or south of the sun. Tomorrow it will be even closer but still travel south and miss the solar disk. Rarely do planets line up exactly with the sun during conjunction. That’s why next month’s transit of Venus is so special.

Keep in mind as you look at the picture that Jupiter lies in the distant background on the opposite side of the sun from Earth. It’s currently 558 million miles away or six times the Earth-sun distance. As you might guess, if Jupiter precisely lined up, it would be hidden behind the sun. As for that big sunspot group, it’s still lively but no X-class flares yet.


Virtual flyover of the asteroid Vesta based on hundreds of actual photographs. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

After almost a year’s study by the orbiting Dawn space probe, NASA shared new insights about the asteroid Vesta this week. We now know that the 326-mile-diameter orb was on its way to becoming a planet 4.6 billion years ago. It developed an iron core measuring 136 miles across, a dense, rocky mantle and crust made of lava flows that were soon battered by meteorite impacts.

Bright and dark craters on Vesta. Like everything else in the solar system, the asteroid was bombarded heavily by meteorites at the dawn of the solar system. Credit: NASA/JPL-Caltech

Terrestrial planets also possess these three basic layers. With Vesta, the decay of a radioactive form of aluminum around in the early solar system generated the heat that melted the asteroid. As it cooled, heavier elements like iron and nickel sunk to form a core, while lighter elements floated to the top and solidified into the mantle and crust.

The layering, known as differentiation, make Vesta more like a small planet or Earth’s moon than most asteroids. Smaller bodies never had enough radioactive material to melt and layer-cake.

The Rheasilvia Basin dominates Vesta's southern hemisphere. The crater is 90 percent as wide as the entire asteroid. Fragments from the collision have reached Earth over the ages as HED meteorites. Credit: NASA/JPL-Caltech

By counting craters, scientists determined the age of Vesta’s biggest crater, the 314-mile-wide Rheasilvia Basin in the southern hemisphere. The impact, which removed a sizable portion of the asteroid’s southern polar region, happened only about a billion years ago, long after Vesta formed and when most meteorite bombardment had ceased

Scientists were also able to determine what minerals are in Vesta’s crust by examining how they reflect sunlight. Here’s where things really get exciting. They discovered that the meteorites in the HED clan – howardites, eucrites and diogenties – are the same materials seen in Vesta’s crust. We’ve suspected this for years because the two reflect light in almost the same way, but this is the first time we’ve visited a source of meteorites found on Earth.

A slice of Vesta! This eucrite meteorite named NWA 2724 was found in the Sahara Desert . It represents a small cross section of an ancient lava flow on the asteroid. Photo: Bob King

Eucrites are similar to lava flows on Earth; diogenites are coarse-grained crystalline rocks from the mantle and howardites are a mix of the two, created when meteorites bash, mix and cement together fragments of both crust and mantle.

It sends a chill up my spine to touch the meteorite in the photo above and know that it came directly from Vesta, launched by an impact perhaps a billion years ago. Too bad Vesta never grew larger than it is today. You can blame Jupiter. Its dominating gravitational influence stirred up material in the asteroid belt, where Vesta resides, and prevented any large body from forming.

Read more about the new Vesta results HERE.

Purple aurora majesties

The summer Milky Way rises along the eastern horizon last night around 11:30 p.m. The slight green glow at bottom is airglow, caused by air molecules emitting light after being excited to higher energy levels by sunlight during the day. Photo: Bob King

Last night a stranger approached me in the dark. I was out in the country in a pullout along a gravel road just setting up my telescope. You never know what to expect when someone drives up to you and steps out of their car. I make the assumption their motivation is curiosity and not harm. So far, that’s been true.

We approached each other, gave names, shook hands. Both of us relaxed. Over the next half hour Tony and I shared looks at Saturn, Venus, a globular cluster, two galaxies, a meteor and one of the brightest Iridium satellite flares I’ve ever seen in my life.  At magnitude -8 or nearly as bright as a half moon, the flare demonstrated how bright a nearby supernova might look.

Unusual purple auroral rays briefly stripe the northern sky last night about 10:30 p.m. The more common green aurora is below. Photo: Bob King

We asked questions about each others interests and professions and remarked about the lone wolf howling a mile away. Then he decided it was time to go and offered an apology for disturbing me. None was needed. There’s always joy in sharing the sky. By connecting to something larger than ourselves, we find we’re more alike than different.

Later I was happy to see the smouldery glow of aurora beyond the trees to the north. Nothing bright or spectacular, just a few patches and rays. But I soon learned this was no ordinary aurora. Most auroras are pale green to the eye and shine a vivid green in time exposure photos. These rays appeared colorless, but as soon as I pressed the button to check the exposure, my jaw dropped. Purple!

A striking purple ray from last night caused by excited nitrogen molecules high in Earth's atmosphere. Photo: Bob King

Auroral colors are generated when those frisky electrons from the sun follow Earth’s magnetic field lines straight into the polar atmosphere. There they strike the the atoms and molecules of oxygen and nitrogen and pump them up to an excited state.

In the atomic world, excitement means an electron that orbits close to the nucleus of the atom gets bumped up to a higher energy level. These higher energy states don’t last for long. An excited atom typically crashes into neighboring atoms and loses its energy, but in the near vacuum of the upper atmosphere, atoms don’t meet up very often. Instead, the excited electron returns to its “rest” state, releasing a particle of light called a photon in the process. Photons are packets of energy that make up a beam of light.

Oxygen in the lower atmosphere, from about 50 miles to 120 miles high, emits photons of green light when pounded by solar electrons. Since the element is plentiful and our eyes particularly sensitive to green light, the color dominates most auroras. Picture billions of oxygen atoms beaming bits of green light and you’ve got a typical northern lights display.

Oxygen atoms from 100 miles to as high as 375 miles, where the air is even more rarefied, create the less often seen red auroras. Picture energy levels in an atom as floors in a hotel. When hit by a solar particle, an electron in an oxygen atom “takes the elevator” to a higher floor. Green light is emitted when the electron rides the elevator down from the third to second floor; red light when electrons ride from second floor to first (ground level).

Oxygen atoms are primarily responsible for the greens and reds of the aurora; nitrogen gives us red-bottomed arcs and tall purple rays. Credit: WebExhibits

Nitrogen atoms and molecules give off several colors when stimulated by incoming material from the sun, most of which we can’t see with the naked eye. A few nitrogen atoms emit a faint green that gets lost in oxygen’s brighter colors, but in intense auroras, you’ll sometimes see an intense deep red-purple fringe along the bottom of rays and arcs. This captivating color is caused by nitrogen.

Last night’s aurora was even more unusual because it not only came from very high up but also involved sunlight. Purple light is cast off in a two-step process. First, nitrogen molecules got whacked by electrons, rise to an excited state and then dump their light as purple photons. Second, the excited nitrogen absorbes energy from sunlight shining onto the very top of the atmosphere, exciting the molecules to pump out even more purple. All this happens some 600 miles high!

Too bad our eyes aren’t very sensitive to the blue-purple end of the spectrum, otherwise nitrogen-producing auroras would be much more spectacular. As it was, I saw only a faint hint of blue in the brightest ray last night.

Let’s think about the aurora process again. Electrons stream from the sun and their energy of movement (kinetic energy) is transformed into light via the elevator process described earlier. Second, once the nitrogen molecules get into their excited state, sunlight itself was enough to do the job. That boggles the mind. Simple things like atoms and molecules are a type of machine able to transform one form of energy into another.

Speaking of rarefied, the air is nearly a vacuum at the height the aurora takes place with a pressure one-millionth what it is at sea level. Were it not for the fact that we look through hundreds of miles of light-emitted oxygens and nitrogens, these tiny emissions be far too faint to see.

Just in time, the NOAA space weather forecast predicts possible auroral activity over the next three days.

Solar blowout and a wicked star-planet alignment

Sunspot group 1476 "blemishes" the sun this morning as it rose over Lake Superior in Duluth, Minn. Photo: Bob King

It’s always worth getting up to see a sunrise. Sure, you can’t concentrate and your eyes weigh a pound a piece by afternoon, but it’s worth the lift you feel watching a star rise out of a lake. I saw the sun slowly ease out of Lake Superior in Duluth this morning, and for a few minutes it was safe enough to take pictures with a telephoto lens.

I enjoy imperfections. Matter of fact, I’m built on flaws both inherited and accumulated over the years. Once the solar disk freed itself from the horizon, I could see it also had a blemish, a piece of crud that wouldn’t wipe off. A monster sunspot!

That spot group was plainly visible in the camera once the sun was up. An hour later I easily saw it from home with the naked eye from behind a pair of eclipse glasses.

The sun photograhed this morning through a 3-inch refractor with solar filter later this morning. The big group is 1476; smaller 1477 is at bottom. Photo: Bob King

Now spanning more than 12 Earths, the group is magnificent to view in a small telescope. The main spot has a long string of followers and reminds me of mother goose and her goslings.  Exquisitely small black umbral spots contrasted with the pale, encircling penumbra around the main or lead spot in the group. The photo only hints at the beauty and complexity of the group.

Because the sun rotates on its axis about once every four weeks, we can watch the evolution of this group with each passing day.

In active sunspot groups like 1476, new spots form and evolve quickly. Some expand rapidly and last days or weeks. Others appear and disappear in just a day. Day to day changes are obvious through a small telescope and show us just how dynamic a star can be. As always, you’ll need a safe filter to look directly at the sun. Here’s a link to a recent blog listing good sources.


Must-see video of last night’s M5.7 flare from Region 1476. The best part is the audio. Crank it up!

At 11:18 p.m. Central time last night, sunspot region 1476 blasted off a significant M5-class flare. Though large, it’s not directed toward Earth. For the moment, none of the more powerful X-class flares have made an appearance.

All the activity with more to come is because 1476 is a delta group, where positive and negative magnetic fields (north and south poles) are packed so close together, there’s great potential for instability and the release of energy in the form of solar flares. While there’s only a small chance of auroras for the far north this evening from effects not related to these spots, let’s cross our fingers for possible weekend auroras related to the big group.

From top to bottom: Arcturus, Saturn and Spica form a straight line in the sky last night. Photo: Bob King

Last night when members of our local astronomy club departed the planetarium after the monthly meeting, we instinctively all looked up. Aha! The sky was clear. High up in the southeast was a most striking arrangement: Arcturus, Saturn and Spica all lay in a straight line.

Being humans, we can’t help but be drawn to patterns, and this one you couldn’t miss. Try spying it yourself the next clear night. Go out from 9:30 p.m. on and look well up in the southeastern sky. Arcturus is the bright, orange-red star; below it you’ll find the duo of Saturn and Spica. It’s just cool.

The line will remain straight for about the next several nights. After that, Saturn’s motion to the right (west) will break the pattern. When will you first notice this?

Spitzer sniffs out alien super-Earth

Artist impression of the steamy super-Earth 55 Cancri e compared to our own planet. Credit: NASA

Astronomers have spied the light of big, Jupiter-sized alien planets but never one as small as 55 Cancri e,  a “super-Earth” orbiting the star 55 Cancri 41 light years away in Cancer the Crab. Super-Earths are extrasolar planets more massive than Earth that bridge the gap between little planets like our own and larger ones like Neptune and Uranus.

55 Cancri e is twice as big and 8 times as massive as Earth. It’s believed to have a rocky core surrounded by an ocean that’s simultaneously liquid and vapor and topped with a layer of steam. Orbiting in just 18 hours, the planet is tidally locked in its host star’s gravitational embrace. One hemisphere faces the chill of outer space while the other roasts in starlight.

With a surface temperature of 3,140 degrees Fahrenheit on the sun-facing side, “e” will probably never be an oasis for life.

Extrasolar planet 55 Cancri e is too faint to see in the glare of its host star, but using the Spitzer Space Telescope, which picks up the planet's intense heat, astronomers were able to measure its light and temperature. Credit: NASA/JPL-CalTech

The Spitzer Space Telescope, built to observe in the infrared or heat-radiating end of the spectrum, picked up the planet’s light signature because it blazes like a bonfire. Humans are also warm creatures. If our eyes were adapted to see infrared light, we’d easily spot one another at night  from blocks away. 55 Cancri e’s infrared outpouring makes it stand out from the glare of its host star. In visible light, it’s invisible.

The plot shows how the infrared light from the 55 Cancri system changed as the planet passed behind its star. When the planet disappeared, the total light dropped, and then increased back to normal levels as the planet circled back into view. Credit: NASA

Spitzer can’t actually see the planet as a separate point of light next to the star. The two are much too close for that. Instead it measures the dip in brightness of the entire system as “e” passes behind the star during half of its orbit. Based on how the system’s light changes, astronomers can determine the planet’s temperature, apparent brightness and sometimes even its composition.

55 Cancri e is very dark and very hot. “It could be very similar to Neptune, if you pulled Neptune in toward our sun and watched its atmosphere boil away,” said Michaël Gillon of Université de Liège in Belgium, principal investigator of the research.

The “e’ by the way tells us this is the 5th planet discovered around 55 Cancri. Extrasolar planets are named after the letters of the alphabet starting with “a”.

Globular cluster M55 photographed in infrared light by the 4.1-meter (161-inch) Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal Observatory in Chile. The time exposure also recorded many background galaxies - the easiest to see is at upper right at 2 o'clock. See closeup below. Credit: ESO/J. Emerson/VISTA. Acknowledgment: Cambridge Astronomical Survey Unit

Someday we’ll find planets inside the massive balls of stars called globular clusters that dot the outskirts of the Milky Way galaxy. Globulars contains hundreds of thousands up to 10 million stars. Although photographs show the clusters as flat, try to picture them as they really are – great spheres of stars all in motion around the center like a swarm of bees. Think of all those potential planets!

This cropped version of the photo above shows the background galaxy more clearly. Click the image for a large version where you can explore for more galaxies. Credit: ESO

The European Southern Observatory (ESO) released pictures today of one of the largest, richest globular clusters, M55 in Sagittarius the Archer. At 2/3 the diameter of the full moon, this gemmy bunch is one of the largest in the sky and easy to resolve into stars in a 6″-8″ inch telescope.

M55 packs approximately 100,000 stars into a sphere about 100 light years across or 25 times the distance between the sun and Alpha Centauri, the nearest star system. To learn more about M55 and globular clusters in general, click HERE.

Sutter’s Mill meteorite tally at nearly 60; auroras possible tonight

Venus and El Nath are reflected in a puddle in the neighborhood last night. Details: 35mm lens at ISO 800 and 15-second exposure. Photo: Bob King

Nothing but clouds since May began until last night, when the sky cleared for an hour during twilight. It was wonderful to see Venus again and its close “companion”, the star El Nath in Taurus. One benefit of the frequent rain and clouds is a proliferation of puddles, one of which caught Venus and cast it back at me.

Two sunspot groups currently busy producing flares are regions 1476 and 1471. Photo taken by the Solar Dynamics Observatory this morning. Credit: NASA

Looks like there’s chance for auroras anywhere from around midnight tonight through tomorrow afternoon Central time for the northern U.S. and Canada. The stimulus for this round comes from a coronal mass ejection shot our way on May 7 by sunspot group 1471, which will soon depart the disk.

Meanwhile the much bigger, more active group 1476 continues to produce significant flares, though none are Earth-directed yet. Here’s the latest NOAA magnetic storm forecast.

The current "main mass" of the Sutter's Mill meteorite - a 35.1g rock found over the weekend by Mitch Carey. Click photo to see a detailed tally of all pieces found to date. Credit: Mitch Carey

Over the past two weeks, meteorite hunters in California have sent photos my way of what they thought might be meteorites from the April 22 fireball. Some of them are clearly not meteorites, while with others it’s to say for certain without a “live” inspection. Not so with the pictures Mitch Carey took of a 35.1 gram beautiful, unbroken specimen he found while spraying for poison oak on his land near Lotus. You can even see dirt on one side from the impact.

Meteorite drop zone map or strewnfield marked with the locations and weights of meteorites found so far. The labeling scheme is based on Peter Jenniskens site (see below). Click map to enlarge. Thanks and credit to Marc Fries and his radarmeteorites site

I contacted a couple well-known meteorite hunters in the area and Mitch’s find was soon confirmed as the real thing.  What’s more, it’s the largest piece or “main mass” of Sutter’s Mill (provisional name) found to date. He’s currently taking offers on the piece.

No word yet on whether NASA researchers have found any meteorites from their ride aboard the zeppelin. More flights are underway. About 60 meteorites weighing 364 grams (0.8 lb) have been found to date.

For regular updates on new finds and their locations in the Sutter’s Mill strewnfield, make sure you visit meteorite hunter Jim Wooddell’s Meteorite Strewn Field for Lotus / Coloma area page.

If you’re out hunting and find a meteorite from this fall, please take the proper care to keep it clean, especially if you want to submit it for scientific analysis. That means not handling it with your bare hands and keeping it away from high humidity and plastics. For more on proper handling, see NASA researcher Peter Jenniskens’ guide near the end of his Sutter’s Mill page.