Monthly Archives: July 2011

Got dark skies? See a comet this week!

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The Summer Triangle at nightfall in early August. The triangle is large and covers a sizeable chunk of sky. Created with Stellarium

Summer’s best and brightest nighttime asterism sails high over our heads as August opens. The Summer Triangle and the magnificent stretch of Milky Way it contains command the southeastern sky at nightfall. Altair in the constellation Aquila the Eagle forms the triangle’s bottom apex. For observers at mid-northern latitudes, it’s at eye level as you face to the south-southeast. Three fists held at arm’s length above Altair lies Vega in Lyra the Harp. At 10:30 p.m. local time, this prominent white star is nearly overhead.

Vega is the sky’s 5th brightest star, right behind Arcturus, which flashes like a ruby in the western sky. The eastern apex of the Summer Triangle belongs to Deneb in the constellation Cygnus, also near the top of the sky about two fists across from Vega. Once you’re familiar with these three summer sparklers, you can use them as familiar landmarks to navigate to other stars and constellations.

Italian comet observer Rolando Ligustri made this fine image of C/2009 P1 Garradd (left) as it approached the globular cluster M15 in Pegasus last night July 31. He photographed the comet 'remotely' via computer using a wide-field refracting telescope in New Mexico.

We’ll use the Summer Triangle to help us find Comet Garradd, the brightest comet currently visible in the sky. Don’t fret if you don’t have a telescope. You can already see this fuzzball in 7×50 or 10×50 binoculars if you’re observing from a dark site with minimal light pollution. I saw it two nights ago in my 10x50s just above the star Enif near the Great Square of Pegasus. OK, it was only a blob but it gave me a kick just the same.

But wait, there’s more!

The comet will pass very close to the bright globular cluster M15 Monday and Tuesday nights August 1 and 2. That means you’ll see two side by side blobs. Does life get any better? Telescope users will have the best view when the comet and its fat, short tail make a striking contrast with the rich star cluster. I suspect astrophotographers will burn through more than a few gigs of memory recording the event. Try to catch it this week before a bright moon returns to the evening sky.

Comet Garrad climbs from Pegasus near the star Enif up the Summer Triangle during August. On August 1 and 2, it slides just north of the cluster M15. Enif will guide you to the comet the next few days. It's three 'fists' to the lower left or east of Altair. Created with Chris Marriott's SkyMap software

Comet Garradd is 8th magnitude with a head or coma about 1/4 the size of the full moon (~8 arc minutes). Its tail extends better than half a full-moon-diameter from the head to the south. In a telescope, the bright nuclear or central region looks like a star at low magnification. Binoculars squeeze tail and head together into a small, blurry glow.

The comet keeps getting higher and brighter through the remainder of summer as it slices through the Summer Triangle north of Altair. By September, it will drop lower in the west but remain visible in the evening sky until year’s end for observers at mid-northern latitudes. In early 2012, Garradd moves into the morning sky, brightening all the while. While closest approach to the sun (perihelion) occurs on December 24, closest approach to Earth happens next March 5, when Garradd will be 117.7 million miles away. Then the comet will be ideally positioned in the Little Dipper, shining around 6th magnitude and faintly visible with the naked eye to sky watchers at dark sky sites.

Photo of the coronal hole (top) on July 29 that might cook up auroras tonight. Credit: NASA

As long as we’re on comets, the most recent observations of Comet Elenin from July 30 put it at magnitude 9.5 – 10. Nice to see it’s still climbing in brightness. If you’re out looking for Comet Garradd, keep an eye on the northern sky tonight and tomorrow night. That’s when space weather forecasters are predicting a stream of particles from a large gash in the sun’s atmosphere called a coronal hole to strike Earth’s protective magnetic bubble.  Possible modest auroras might be visible at higher latitudes. Look for a greenish glow or spear-like rays just above the northern horizon. Generally, the closer to midnight – 1 a.m. you’re out, the better chance of seeing northern lights.

The three big naked eye sunspot groups are an amazing sight in this photo taken around 10 a.m. today. Credit: NASA

Those big sunspot groups are still busy and very obvious. I saw all three with the naked eye using a safe solar filter earlier this morning. Group 1263, which has the largest spots, was the easiest to see. Compare this photo to their appearances just two days ago.

Now is best time to see asteroid Vesta

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Jupiter (at right) glows brightly through a light fog this morning around 3 a.m. At left is the Seven Sisters or Pleiades star cluster. If you do go out in the wee hours, Jupiter is the brightest object you'll see in the eastern sky. Details: 24mm lens at f/2.8, ,ISO 3200 and 30-second time exposure. Photo: Bob KIng

I am so sleepy right now. Can you blame me? My friends Jon, Greg and I stayed up until the first hint of dawn this morning blissfully hopping from one deep sky object to the next with our telescopes. The mosquitos robbed us of some of the pleasure, but I’m sure that memory will fade with time.

We looked at supernovas, nebulas, great balls of stars called globular clusters and even dropped in on the asteroid Vesta, now in the public eye with fresh closeup photos posted every few days on the Dawn website. Vesta was bright enough but challenging to see with the naked eye. Binoculars made it instantly easy. We were all a bit surprised at its distinctly yellow tint when viewed at low power through a telescope. The whole time, a modest sprinkling of meteors shot across the sky — mostly southern Delta Aquarids and a couple early Perseids. I counted more than a dozen.

Use this map to guide you to Vesta, currently located in southern Capricornus and best seen between about midnight and dawn now through mid-August. The flattened triangle of stars I've nicknamed the "Pointer" will help point you to the asteroid. Vesta is only a little fainter than these three. Created with SkyMap

If you’d like to see Vesta with your own eyes, copy the updated map above and use it along with a pair of binoculars. The best time for Vesta viewing will be in the next week or two, when the 330-mile-diameter asteroid is closest to Earth and reaches its peak brightness of magnitude 5.7 on August 6. That’s when it lines up with Earth on the other side of the sun in opposition.

Capricornus is low in the southeast around 11 p.m. but reaches a respectable height around midnight. Click the map above for a wide-angle version to navigate to Capricornus. For light from Vesta to reach our eyes, it currently has to travel 114 million miles, a feat accomplished in no more than 10 minutes!

Spectacular sunspots plus meet Earth’s newest friend, asteroid 2010 TK7

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Three large sunspot groups are getting solar observers' attention. Group 1260 has the potential for powerful flares. This photo was taken earlier today by NASA's Solar Dynamics Observatory. Click image to watch a movie of the spots as they've developed over the past few days. Credit: NASA/SDO

After a brief lull, solar activity is back in full swing. The largest sunspot groups look like showy parade floats wheeling across the sun’s northern hemisphere. The three largest spots are approximately the size of the planet Jupiter. Using a safe solar filter this morning, I saw Groups 1260 and 1263 with the naked eye. Even more exciting, Group 1260 has a ‘delta class’ magnetic field, where dark sunspot cores called umbrae of different magnetic polarities are closely packed together inside the larger penumbrae. In the photo above, the umbrae are the dark dots surrounded by the paler penumbrae.

Like a bunch of Democrats and Republicans squeezed into a small room, the atmosphere in a delta configuration can get testy. The jumble of north and south magnetic fields in close proximity can lead to sudden connections between them, releasing vast amounts of energy in the form of X-class solar flares. X- flares can damage sensitive satellite electronics, cause radio blackouts and initiate spectacular displays of northern and southern lights.

If you have a scope with a safe filter, have a look at the home star in the coming days. Sunspots are very dynamic. Groups can change shape, number and extent day by day as they move westward with the sun’s rotation.

Earth's newly-discovered Trojan asteroid, 2010 TK7, orbits about a stable point near Earth in a loping orbit (green) that takes it well above and below Earth's orbital plane, shown by the blue dots. Credit: NASA

In case you haven’t heard the news, Earth’s got a new little buddy named 2010 TK7, a 1,000 foot long Trojan asteroid orbiting in a stable region called the L4 Lagrangian point just ahead of our planet. Trojans are asteroids that share an orbit with a planet at two stable points 60 degrees ahead and 60 degrees behind it. These areas are where the sun and the planet’s gravity balance out neatly, allowing small objects like asteroids to remain there relatively undisturbed.

Trojans are named for characters in Homer’s epic The Iliad and The Odyssey, thus we have Achilles, Icarion and Hektor, three of the many hundreds of thousands of Trojans orbiting in giant Jupiter’s stable zones.

2010 TK7 is the very first Earth Trojan. It was discovered by the Wide-Field Infrared Survey Explorer (WISE) during its grand survey of the entire sky in infrared light. Astronomers using WISE have observed 155,000 asteroids in the main
belt between Mars and Jupiter, and more than 500 near-Earth asteroids and discovered
132 that were previously unknown.


This animation illustrates the orbit of 2010 TK7 as it performs a large looping motion around the stable Lagrangian point ahead of Earth.

Earth Trojans are difficult to find, because they lie in the same direction as the sun in the daytime sky. But 2010 TK7 orbits around the L4 stable point well above and below Earth’s orbit, so it appears farther from the sun than a routine Trojan, making it an easier catch. It’s located a nominal 50 million miles from our planet, but its unusual looping orbit means its distance from us varies over time. Not to worry. The asteroid’s orbit is well-defined and for at least the next 100 years, it won’t come closer to Earth than 12.4 million miles.

Besides Jupiter’s hoard of Trojans, Mars has four and Neptune eight. Watch the video and you’ll see how the newly-discovered asteroid precedes Earth in its orbit. Our two worlds perform an orbital ballet for all to marvel. You can read more about 2010 TK7 HERE.

NASA's Dawn spacecraft obtained this image with its framing camera on July 23, 2011. It was taken from a distance of about 3,200 miles. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

One last news note. The Dawn space probe has returned a new closeup photo of the asteroid Vesta. Science operations and detailed mapping should begin in early August. Scientists are hoping to learn the origin of its totally ‘groovy’ surface.

Lowell’s Mars proves we might just see what we wish for

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The tough-to-spot supernova SN 2011ef in the dim galaxy UGC 12640 photographed on July 22. Credit: William Wiethoff

Sometimes you just can’t trust your eyes. That’s why I’m always careful to examine objects, especially faint ones, multiple times through the telescope until my confidence level rises to the certainty of “Yes, I see it!”

That happened two nights ago when searching for a newly discovered supernova in the faint galaxy UGC 12640  in the constellation Pegasus. Embedded as it was near the galaxy’s center, the star’s light was partly masked by the galaxy’s hazy core, making it very tricky to see. Only after 20 minutes of looking – first with my right eye and then with the left – and employing every technique I knew for squeezing the last photon of light from a faint object was I certain of seeing it.

Other nights, I can persevere even longer, looking for a faint comet or galaxy detail and still not find my quarry. That’s when it’s time to move on to something a little less challenging. It’s so easy to see the thing you really want to see, especially when it’s at the limit of observation. One’s expectations and assumptions can literally make things materialize from the background noise.

That brings me to Mars. Seeing fine details on planets is always challenging. Mars, Jupiter and Saturn look great in photos, but their globes are small and flutter about when viewed through Earth’s tremulous atmosphere. To see beyond the gross features, you need a quality instrument, high magnification and calm air. While it’s theoretically possible to use high magnifications with even small telescopes, the more power you use, the fainter and softer the image. Magnification’s a beautiful thing until you realize you’re also magnifying air turbulence between you and the object. Only on nights when the ‘seeing’ conditions are calm do fine details rise above the noise.

Map of Mars by Giovanni Schiaparelli made in 1888 showing his 'canali'.

Back in the early 20th century, a wealthy Bostonian named Percival Lowell got a bad case of Mars fever after learning of Italian astronomer Giovanni Schiaparelli’s observations of Mars. During its favorable approach to Earth in 1877, Schiaparelli observed a series of linear features on its surface that he dubbed ‘canali’, the Italian word for ‘channels’. A channel is a natural feature as opposed to a ‘canal’ which is a man-made waterway. Schiaparelli imagined them as broad, shallow water courses that extended thousands of miles across the planet’s vast desert-like landscape.

Percival Lowell, circa 1904. Credit: J.E. Purdy

Back in America and elsewhere, his channels were mistranslated into English as ‘canals’. When the reports appeared in the popular press, it led to much speculation about Martian life and the function of the ‘canals’. Percival Lowell was inspired by Schiaparelli’s drawings to build an observatory just outside of Flagstaff, Arizona dedicated to studying the planet Mars. Lowell Observatory, on Mars Hill, is still open today. On public observing nights,  you can still look through Percival’s beautiful 24-inch refracting telescope. I stood in line on a lovely evening there a few years back. When it was finally my turn at the eyepiece, I got an most satisfying eyeful of the planet Jupiter.

Lowell’s drawings of Mars and his interpretation of the dark markings went a step beyond those of Schiaparelli’s. In place of curving channels, Lowell saw straight, linear features connecting continents and ‘oases’ on Mars. In his mind, their precise, geometrical shapes clearly indicated they’d been built by intelligent beings. Furthermore, Lowell hypothesized that a dying race of Martians created the network of canals to carry water from the poles to the parched equatorial regions to water crops. Their planet was drying up and the canals were an effort to deal with what we would call global climate change.

Mars and its canals as seen and drawn by Percival Lowell

It’s no surprise canals were on everyone’s mind in the late 19th century. The Suez Canal connecting the Mediterranean Sea and Red Sea opened in 1869, and the Panama had long been on the drawing board. It opened in 1914.

The public loved Lowell’s ideas. He wrote a book about his observations in 1895 called “Mars” as well as articles for Popular Astronomy and Atlantic Monthly and lectured widely. Thanks to strong convictions and an intense presence, Lowell gained a large following. More books followed — “Mars and Its Canals” in 1906  and “Mars as he Abode of Life” in 1908. He was on a hot streak.

Percival Lowell observing through the 24-inch refracting telescope at Lowell Observatory

Astronomers however were skeptical. Only a few saw Lowell’s canals. Most, like the famous American astronomer E.E. Barnard, spied lots of things that Lowell missed but never discerned a single linear feature. Even observers using the 100-inch Hooker telescope on Mt. Wilson, then the largest in the world, failed to see them. Lowell countered that larger scopes were more plagued by atmospheric turbulence than his. Astronomer William Campbell used a new spectroscope to search for water vapor in Mars’ atmosphere during its close approach to Earth in 1894 and found none. Over time, it became obvious that the canals were illusions caused by an active imagination grasping at faint and tenuous details visible at the telescope’s resolution limit.

To rescue his reputation, Lowell worked on other projects including irregularities in the orbit of Uranus that led him to predict a ninth planet beyond Neptune. He called it Planet X. Although his idea later proved wrong, he inspired the search that led ultimately to the discovery of Pluto at Lowell Observatory by Clyde Tombaugh in 1930.

Lowell's and Schiaparelli's channels/canals and ideas about Mars helped inspire H.G. Wells' 1898 book "War of the Worlds" about an invasion from Mars.

Lowell’s fascination with Mars and possible Martian life lived on. The thread was not only picked up by science fiction writers but many amateur and some professional astronomers, who continued to look for evidence of some ‘low’ form of plant or microbial life on the Red Planet. I still recall drawings of the canals in the astronomy books I perused as a kid. Until the Mariner 4 probe returned photos of a barren, crater-ridden Mars in 1964, many of us still secretly hoped Mars had life. We’d screw up our eyes at the telescope eyepiece hoping to see the planet’s dark markings turn a pale green during Martian spring and summer.

It still seemed possible, even as late as the early 1960s, that water from melting polar ice soaked the dry land beyond, perhaps stimulating the growth of Martian versions of moss and lichens.

No evidence of artificial canals or any other alien structures are known on Mars today, however you’ll find plenty of evidence of past water in the form of dry stream beds and enormous outflow channels. Perhaps there was even time for life to fire up and evolve. The two Viking landers, Phoenix lander, three rovers and numerous orbiters are a start, but we’ve really only scraped the surface of the Red Planet. There’s a whole world of discovery out there, and the possibility of Martian life lingers in the air in every discussion about Mars, much as it must have during Lowell’s time.

Streamlined islands formed where long-ago water flowing on the surface of Mars encountered obstacles along its path. Here water was diverted by two 5-6-mile-diameter craters lying near the mouth of Ares Vallis. Credit: NASA

In light of all the unsubstantiated ideas flying around the Internet about Comet Elenin, wayward stars, 2012 and the like, there’s a lesson we can all learn from Lowell’s foibles: Maintain a healthy skepticism and avoid leaping to fantastic conclusions based on scanty data and wishful thinking.

Tiny Mars draws closer to Earth

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The moon will guide sky watchers to the planet Mars tomorrow morning. Aldebaran is slightly brighter than the planet. This map shows the sky facing east-northeast near the start of dawn or about 2 hours before sunrise. Created with Stellarium

The little planet Mars is slowly climbing the morning sky in the constellation Taurus the Bull. It’s still far from Earth – nearly 200 million miles away or better than twice our planet’s distance from the sun – and on the faint side. Thanks to the crescent moon, however, the Red Planet will be easy to spot tomorrow morning at the start of dawn. Look for it low in the northeastern sky.

Mars photographed through a 14-inch telescope this past Sunday morning July 24. It's currently winter in Mars' northern hemisphere (bottom) and summer in the southern. Credit: Brian Combs

Mars and nearby Aldebaran, Taurus’ brightest star, are nearly the same color. Mars’ hue originates from the abundant iron oxide (rust) in its soils and Aldebaran’s to its status as an orange giant star with a cooler, redder outer envelope than the sun’s.

While the photo (left) looks a bit fuzzy, it’s an amazing accomplishment considering how far and tiny Mars is. The disk is only 4.3 arc seconds across or less than 1/400 the size of the moon as seen with the eye. On it you can see lots of dark markings as well as a white glow along the bottom. That’s the North Polar Hood, a vast canopy of clouds that stretches over Mars’ north pole and polar regions during the winter months. It will break up as the Martian year progresses and reveal a blazing white polar cap beneath. At the same time, the planet is slowly drawing nearer to Earth on the way to its next opposition in early March 2012. Matter of fact, tomorrow morning, it will be about 279,000 miles closer than it is today.

The North Star (Polaris) stands nearly still last night as the stars of the northern sky circle around it during a 20-minute time exposure, 24mm lens and ISO 800. Photo: Bob King

Near Mars and the moon are two of the winter sky’s best known star clusters, the V-shaped Hyades, which precede Aldebaran, and the ‘little dipper’ of stars best known as the Seven Sisters of Pleiades.

We had a rare cloudless night in Duluth last night and I stayed up late enough to catch sight of both lunar crescent and the Seven Sisters low in the eastern sky. Despite the mosquitos, it was hard to drag myself home. The Milky Way totally ruled the sky with the Summer Triangle front and center.

If you’re looking for a great time to see our galaxy in all its soft, stellar grandeur, take a drive to the country sometime in the next week before the moon returns and just look up!

Uptick in meteors as summer ripens

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Look northwest at nightfall in late July to find the Big Dipper. Following the arc of its handle will take you to the brilliant star Arcturus. From Arcturus, hop from star to star to see the kite-shaped constellation Bootes. Below the Dipper's handle is the diminuitive Canes Venatici, pair of stars that represent Bootes' hunting dogs. Created with Stellarium

Like the raspberries in the woods, summer is ripening. Stars that were once prominent in June are on their way westward. And if you’re out at dawn, be prepared for a shock -  the early winter constellations of Taurus and Auriga have returned. Last night I noticed that the Big Dipper has dropped considerably in the northwestern sky. It’s tipped at the same angle I tipped the little rubbed-coated  spoon we used to feed our daughters when they were babies.

Once the Dipper is in your sights, it’s simple to “Arc to Arcturus” and bop into Bootes. Don’t forget to make a stop at the small, two-star constellation of Canes Venatici (KAY-nees ven-AT-iss-see). I know it’s a meager group, but if you own a small telescope, the brighter of the two stars, called Cor Caroli, is one of the prettiest double stars in the sky.

A brilliant fireball meteor photographed in 2009 above the constellation Orion. Credit: Wally Pacholka

While you’re out, you may notice more meteors than usual this time of year. We’re now in a multi- meteor shower season with contributions from several different minor showers. Meteor showers occur when Earth’s orbit intersects a debris trail left by a comet (or rarely, an asteroid). Meteors or ‘shooting stars’ are the glowing trails left by bits of comet dust when they strike our atmosphere at speeds of many thousands of miles per hour and vaporize in a flash. Each meteor shower has its own ‘parent’ comet. The familiar Perseid shower of mid-August originates from dust left by Comet Swift-Tuttle.

* Alpha Capricornids: this shower appears to radiate from near the star Alpha in Capricornus about three outstretched fists to the lower left of the Summer Triangle. It’s active from mid-July to mid-September and peaks around August 1. With only about a half dozen meteors per hour, it’s definitely in the ‘minor’ category, but it has a saving grace – the shower’s known for its slow, bright meteors. Best viewing time is from 11:30 p.m. until the start of dawn. The 169P/NEAT.

The southern Delta Aquarid meteor shower peaks the night of July 29-30. The radiant, or point in the sky from which the meteors appear to radiate, lies in the dim constellation Aquarius, the brightest stars of which are outlined above. You can also use much brighter Fomalhaut to help you find it. The map shows the sky facing south around 2 a.m. local time July 30.

* Southern Delta Aquarids (SDA): Active from mid-July to mid-August. This shower is the best of the bunch with a peak on the night of July 29-30 (Friday night-Saturday morning).  From a dark sky site, especially from the southern U.S. where the radiant is higher up, an observer would expect to see 15-20 meteors per hour. Face south or southeast for the best view.

Because the radiant lies in Aquarius, the best time for viewing the shower is from about midnight until dawn, when the constellation is high enough in the south for meteors to clear the horizon. The parent comet is one of the ‘sungrazers’ that closely approach the sun, often breaking up or partially vaporizing under the influence of its gravity and heat. The SDA produces medium-speed meteors that speed into our atmosphere at 26 miles per second or over 93,000 mph!

* Northern Delta Aquarids: This weaker shower radiates from northern Aquarius and is active from mid-July into September with a maximum of 10 meteors per hour in mid-August.

Credit: NASA/MFSC

You can tell which is which by following a meteor’s path backward in the sky. If it points to below the Summer Triangle, it’s probably an Alpha Capricornid. If you can trace it back to a spot in the sky above the bright star Fomalhaut, it’s a southern Delta Aquarid.

Granted, with all these meteoric dribs and drabs, it might be hard to know exactly which meteor belongs to which shower, but it’s still fun watching them. Sharpening your meteor-watching skills will prepare you for the bigger Perseid shower due to peak in a little more than two weeks. Hey, you might even see a few early Perseids later this week. If so, they’ll originate from Perseus in the northeastern sky.

Space station returns to view. Little Mars robot strides toward Endeavour

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Astronaut Tracy Caldwell Dyson reflects as she looks out the International Space Station's cupola window during a mission in September 2010. Credit: NASA/Doug Wheelock

No more shuttles, that’s for sure, but you can still watch the International Space Station (ISS) cruise 245 miles high over your neighborhood. A new round of bright dawn passes begins this weekend and continues for the next several weeks. You’ll find a list of times and expectations below for the Duluth, Minn. region. For times for your town, please click HERE and key in your zip code or log in to Heavens-Above. The ISS looks like a very bright star with a steady light (not flashing) and travels from the western direction to the east. Its eight large, orange-colored solar arrays give the station a yellow hue to the naked eye.

* Monday morning July 25 starting at 5:09 a.m. very low (a fist high at best) across the southeastern sky
* Tues. July 26 at 4:48 a.m. A little higher in the S.East than yesterday’s pass.
* Weds. July 27 at 3:53 a.m. Another very low pass in the S. East
* Thurs. July 28 at 4:29 a.m. It gets better! Excellent pass from S.West to N.East. The ISS will glide under Jupiter at 4:32 a.m. and rival the planet in brightness.
* Fri. July 29 at 5:06 a.m. Cruises almost directly overhead moving west to east. Brilliant!
* Sat. July 30 at 4:10 a.m. Another bright one. Travels from S.West to N.East under the Great Square of Pegasus.

The Opportunity rover sent this photo taken on Friday from Mars showing part of the rim of Endeavour crater in the distance about a kilometer away. It will probably be a month or so until the rover reaches its destination. Credit: NASA

The Mars Opportunity rover continues to make great progress in its drive to the 14-mile-diameter crater Endeavour. After more than seven years of operation, the little robot has traveled 20.20 miles. Currently it’s less than 3/4 mile from ‘Spirit Point’ on the crater’s rim. Because of the crater’s size, scientists expect to study rocks excavated from deep beneath the Martian crust that landed around the rim after the impact. The larger the crater, the deeper the excavation and the older the rocks available for study. Large meteorites become, in effect, giant drills.

Endeavour and neighboring craters on Mars. Credit: NASA

Although Opportunity has had technical problems, mission controllers continue to figure out ways to guide it from one destination to the next. The motor in its right front wheel has been drawing more current than it should for some time now. To help extend the motor’s life, controllers have been driving the rover backwards.

According to JPL’s Bill Nelson, chief of the mission’s engineering team,
“Opportunity has an arthritic shoulder joint on her robotic arm and is a
little lame in the right front wheel, but she is otherwise doing
remarkably well after seven years on Mars — more like 70 in ‘rover
years.’ The elevated right front wheel current is a concern, but a
combination of heating and backwards driving has kept it in check over
the past 2,000-plus sols.” (A ‘sol’ is the length of a day on Mars or 24 hours 37 minutes).

This computer-generated view based on multiple orbital observations shows Mars' Gale crater as if seen from an aircraft northwest of the crater. The oval indicates the landing area. Credit: NASA

NASA’s next Mars rover, named Curiosity, will launch sometime between Nov. 25 and Dec. 18 and land at the foot of a layered mountain inside Gale crater in August 2012. The large crater is home to a 3-mile-high mountain, the lower layers of which contain minerals formed in water. A fan-shaped deposit of sediments likely left by a long-ago stream lies within the landing area. Curiosity, which is twice the size of Opportunity, will use its tools to determine if conditions in the area were once favorable for supporting life.

Comet Elenin brightening a hopeful sign

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Seen from this angle, Vesta resembles a walnut shell. The grazing angle of the sunlight highlights many fine textural details in the terrain. The smallest features visible are about 1.2 miles across. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Vesta’s looks positively groovy in this most recent photo taken by the orbiting Dawn spacecraft from 6,500 miles away. Dawn was traveling toward the nightside of the asteroid when the picture was taken, the reason why so much of the little world is in shadow. The large bump or mountain that you’ve seen in previous images is at center, while a portion of the towering rim of Vesta’s 285 mile diameter impact basin is seen at top at the 1 0′clock position.

Comet Elenin (C/2010 X1) on July 21 photographed through an 11-inch telescope. The bright condensation is the comet's nuclear region, an area of denser gas and dust. Within this but shrouded from view is the actual comet nucleus.The outer glow is the coma or tenuous 'atmosphere' made visible by sunlight reflecting off dust. Credit: Michael Mattiazzo

I’ve got good news about Comet Elenin. Southern hemisphere observers report it’s brightened up to a healthy magnitude 10. This puts it within easy range of 6-inch telescopes. Michael Mattiazzo of Victoria, Australia reports magnitude 10.5 on July 21 with a moderately condensed coma 3.5 minutes across (30 minutes equal one full moon diameter). He was using an 8-inch reflecting telescope and magnification of 45x. David Seargent, another Australian amateur astronomer and discover of Comet Seargent in 1978, reports Elenin’s brightness at magnitude 9.9 using a 25 x 100 binocular telescope. After lagging in brightness for several months, Elenin’s back in the game. I’m still hopeful it will rise to naked eye brightness in October.

Comet Elenin is shown for an observer in the southern U.S. (specifically Phoenix at latitude 33 degrees N) every five days tonight through August 22 about an hour and a half after sunset. Stars are plotted to 8th magnitude with the brighter ones labeled to help in navigating. Created with Chris Mariott's SkyMap software

Since the comet has perked up in brightness, that means observers in the southern U.S. will now have a good shot at seeing it in the next few weeks with the moon gone from the sky. Comet Elenin is currently in the constellation Leo. For a sky watcher in say, Phoenix, Arizona., it hovers about 10 degrees above the western horizon an hour and a half after sunset. Observers further south will have even better viewing opportunities with the comet higher up still.

If you’re new to the sky and don’t have a telescope, don’t bother looking for Elenin yet. It’s still too faint. But if you’re versed in the constellations, have a good view of the western horizon, a 6-inch or larger scope and know how to use a detailed star map, it’s worth the hunt. Should you find it, please share your observation with us.

There’s a moon looking over your shoulder

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The last quarter moon hangs high in the sky at breakfast time this month. Maps created with Stellarium

This morning the last quarter moon peered down over my house from high up in the southwestern sky. It was very plain to see. Have you noticed the moon lately in the daytime? For northern hemisphere observers, it’s out nearly all morning long if your sky is clean and blue.

There are two reasons for the moon’s easy visibility. The first has to do with phase. At full phase, it’s exactly opposite the sun – as far as it can get. When the sun sets, the moon rises, and when the moon sets the next morning, the sun rises. Each day after full moon, the moon moves about one outstretched fist eastward (left) in the direction of the sun as it orbits the Earth. 7 days after full – last quarter phase – it rises around midnight and set around noon the following day. That means it’s still up in the west well after sunrise.

The second reason for the moon’s easy visibility has to do with the direction of its path after full phase. Earlier this month, you might recall how low the full moon was in the southern sky. From my home it skirted the tree tops. That’s because it reached the lowest point in its path around the sky. The sun occupies the same spot in late December at the start of winter.  Recall that both it and the moon follow the same path in the sky called the ecliptic.

The last quarter moon joins the planet Jupiter in the constellation Aries at dawn tomorrow and Sunday.

Having hit its lowest point, the moon had nowhere to go but up. Now at last quarter phase, it’s positioned in Aries, halfway to the summer solstice point. Not only is the moon at a higher altitude, but like the spring sun vs. the winter sun, it hangs around longer in the sky. Over the coming mornings, the moon will wane to a crescent, get closer to the sun and also higher up in the sky. Watch for it.

If you prefer your moon observing in a dark sky, it will be passing the planet Jupiter this weekend. Watch for a nice pairing of the two tomorrow (Saturday) and Sunday mornings. You can either go out around 1:30-2 a.m. when they first come up in the east or wait until dawn to see them nicely placed in the southeastern sky.

A member of the Expedition 28 crew aboard the space station caught this spectacular photo showing the space shuttle Atlantis actually hurtling through the Earth's atmosphere on its way back to Kennedy Space Center, Florida early yesterday. Airglow is visible in the background. Credit: NASA/Johnson Space Center

In case you didn’t see this cool photo of Atlantis, here it is. Be sure to click the image to see the BIG version. It shows the shuttle’s glowing plasma trail from superheated air as it re-entered the Earth’s atmosphere traveling at thousands of miles per hour. Look carefully to follow the trail all the way down to the cloud tops. Stars show in the picture, because it was taken in twilight before sunrise.

Atlantis touches down. How to see spectacular Iridium satellite flares

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Space shuttle Atlantis lands for the final time at NASA’s Kennedy Space Center in Florida earlier this morning. Image credit: NASA/Bill Ingalls

The space shuttle Atlantis landed at 4:57 a.m. CDT today at Kennedy Space Center in Florida after 200 orbits around Earth and a journey of 5,284,862 miles. Now that it’s back home, Atlantis won’t be going far. It’s slated to spend its retirement years on display at Kennedy’s Visitor Complex.

The shuttle crew delivered more than 9,400 pounds of spare parts, spare equipment and other supplies in the Raffaello multi-purpose logistics module – including 2,677 pounds of food – that will sustain space station operations for the next year. As part of space station ‘closet cleaning’, Raffaello brought back nearly 5,700 pounds of unneeded materials. Staring this weekend, the International Space Station, home at the moment to six astronauts, will begin making passes across the dawn sky for much of the U.S. In Sunday’s blog, I’ll post a table of times when to watch for it.

The Iridium 96 satellite looks like a fireball as it briefly flares while passing over the neighborhood in July 2008. Photo: Bob King

The return of the space station got me thinking about Iridium satellites and the spectacular flares they produce when sunlight hits them just so. I’ve written about Iridium flares in the past, but now is a good time to revisit the topic. Summer weather brings more of us outside under the night sky, increasing the chance we’ll see one of one of these jaw-dropping events.

There are some 66 active Iridium satellites orbiting the Earth like electrons around the nucleus of an atom. They form a global ‘constellation’ 485 miles high used for relaying voice and data communications. The name ‘Iridium’ comes from the element iridium which is number 77 on the periodic table. The constellation was originally to consist of 77 satellites, but more have been launched over the years.

A mirror-like reflection of a bright light source off one of the antenna arrays on an Iridium satellite. Credit: SeeSat-L

Normally Iridiums are too faint to see except in binoculars, but they have silver-coated Teflon antenna arrays that reflect sunlight like a mirror. When the angle between satellite and observer is right, a brilliant reflection of the sun from the antennas causes an Iridium to suddenly and spectacularly brighten for between 5 and 20 seconds. Unlike a meteor, the satellite does not dash across the sky as it flares. It moves very slowly due to its high altitude, more than twice that of the space station.

Flares range in brightness from that of the Sirius, the brightest star in the sky at magnitude -1.4, all the way up to about -8, which is 20 times brighter than Venus (-4.5)! I’ve seen a few -8 flares, and they’re so intense, you think the object’s going to explode. Almost as suddenly as it appeared, the satellite fades back to invisibility 15 seconds later. Crazy.

There is one caveat, well, two really. Make sure your watch or cellphone is set to the correct time so you don’t miss the brief event. Secondly, flares are only visible with a range of less than 50 miles. The flares I see at my house will be brighter or fainter than the same seen across town.  That means you’ll need to find when they’re visible for exactly where you live.

The best and easiest to use resource is the Heavens Above website. Once there, login and select your location. Under the Satellites heading on the left side of the page, look for Iridium flares and click on the Next 7 days link. You’ll be taken to a page that shows a table of dates, times, intensities (the higher the negative number, the brighter the flare), the satellite’s number and its altitude and azimuth. Altitude tells you how high to look. If it’s 90 degrees, that’s overhead. If 45 degrees, that’s halfway between the horizon (0 degrees) and overhead.

This time exposure shows the how a flare from Iridium 75 evolved from invisibility (right) through peak brightness and then fadeout. Photo: Bob King

Azimuth tells you what direction to look. Due north is 0 degrees azimuth, east is 90, south is 180 and west 270. The final bit of information is how far you are from the flare’s center, where it reaches peak brightness. Click on the time link to see where the center is. For example, tonight there’s a nice -3 magnitude flare for my location at 9:44 p.m., but I see from the table that I’m 17.7 km west of the flare’s center. If I drove 17.7 km to the east, I’d see a humongous -8 magnitude flare instead. Will I do this? Only if I were able to drive my car on Lake Superior.

Heavens-Above even has a listing of flares visible in broad daylight. Too cool. However you see Iridium flares, bring a friend along and surprise them by ‘predicting’ that a brilliant object will appear shortly in the sky above.

Here are some times to watch for flares in the Duluth area for the coming evenings. Wherever you live, please drop us a line if you spot any.

* Tonight Thursday at 9:44 p.m. 2/3 the way up (59 degrees) in the northeastern sky (azimuth 63 degrees). Iridium 22 satellite.
* Friday July 22 at 9:38 p.m. again in the northeastern sky. Iridium 25. Second flare at 11:13 p.m.  from Iridium 31 27 degrees high (1/3 the way up)  in the northeast.
* Saturday at 9:32 p.m. 61 degrees high in the east-northeast from Iridium 47. This flare will be intensely bright at magnitude -7! A second flare from Iridium 90 at 11:07 p.m. 27 degrees high in the northeast.