I'm a long-time amateur astronomer and member of the American Association of Variable Star Observers (AAVSO). My observing passions include everything from auroras to Z Cam stars. I also write a daily astronomy blog called Astro Bob. My new book, "Wonders of the Night Sky You Must See Before You Die", a bucket list of essential sky sights, will publish in April. It's currently available for pre-order at Amazon and BN.
A screen grab of the new zoomable Milky Way mosaic that uses Microsoft's WorldWide Telescope viewer. Click to use. Credit: NASA
Touring the Milky Way’s a blast with this brand new 360-degree interactive panorama. More than 2 million infrared photos taken by NASA’s Spitzer Space Telescope were jigsawed into a 20-gigapixel click-and-zoom mosaic that takes the viewer from tangled nebulae to stellar jets to blast bubbles around supergiant stars.
Magnetic loops carry gas and dust above disks of planet-forming material circling stars, as shown in this artist’s conception. These loops give off extra heat, which NASA’s Spitzer Space Telescope detects as infrared light. The colors in this illustration show what an alien observer with eyes sensitive to both visible light and infrared wavelengths might see. Credit: NASA/JPL-Caltech/R. Hurt (IPAC)
The new composite, using infrared images taken over the past decade, was compiled by a team led by UW-Madison astronomer Barbara Whitney and unveiled at a TEDactive conference in Vancouver, Canada Thursday. Unlike visual light, infrared penetrates the ubiquitous dust concentrated in the galactic plane to reveal structures otherwise obscured.
Catching a GLIMPSE of the Milky Way in this short video presentation
“For the first time, we can actually measure the large-scale structure of the galaxy using stars rather than gas,” explained Edward Churchwell, UW-Madison professor of astronomy and team co-leader. “We’ve established beyond the shadow of a doubt that our galaxy has a large bar structure that extends halfway out to the sun’s orbit. We know more about where the Milky Way’s spiral arms are.”
Named GLIMPSE360 (Galactic Legacy Mid-Plane Survey Extraordinaire project), the deep infrared survey captures only about 3% of the sky, but because it focuses on the plane of the Milky Way, where stars are most highly concentrated, it shows more than half of all the galaxy’s 300 billion suns.
The Milky Way is a spiral galaxy with several prominent arms containing stellar nurseries swathed in pink clouds of hydrogen gas. The sun is shown near the bottom in the Orion Spur. Credit: NASA
Using your imagination to hover high above the galactic plane, you’d see the Milky Way is a flat spiral galaxy sporting a stubby bar of stars crossing its central bulge. The solar system occupies a tiny niche in a minor spiral arm called the Orion Spur two-thirds of the way from the center to the edge. At 100,000 light years across, the Milky Way is vast beyond comprehension and yet it’s only one of an estimated 100 billion galaxies in the observable universe.
Bubbles of gas and sites of star formation are seen in this close up in a region in the constellation Sagittarius. Credit:
While you and I sit back and marvel at all the stellar and nebular eye candy, the Spitzer images are helping astronomers determine where the edge of the galaxy lies and location of the spiral arms. GLIMPSE images have already revealed the Milky Way to be larger than previously thought and shot through with bubbles of expanding gas and dust blown by giant stars.
Spitzer can see faint stars in the “backcountry” of our galaxy — the outer, darker regions that went largely unexplored before.
Barbara Whitney, co-leader of the GLIMPSE360 team
“There are a whole lot more lower-mass stars seen now with Spitzer on a large scale, allowing for a grand study,” said Whitney. “Spitzer is sensitive enough to pick these up and light up the entire ‘countryside’ with star formation.”
The new 360-degree view will also help NASA’s upcoming James Webb Space Telescope target the most interesting sites of star-formation, where it will make even more detailed infrared observations.
When you play around with the interactive mosaic, you’ll notice a few artifacts here and there among the images. Minor stuff. What took some getting used to was how strikingly different familiar nebulae appeared when viewed in infrared instead of visual light. The panorama is also available on the Aladin viewing platform which offers shortcuts to regions of interest.
Neil deGrasse Tyson, astrophysicist and host of the new Cosmos TV series, gave the third line of our “cosmic address” as the Milky Way after ‘Earth’ and ‘Solar System’. After a few minutes with GLIMPSE360 you’ll better appreciate the depth and breadth of our galactic home.
Zodiacal light tilts upward from the western horizon and points at the Pleiades star cluster in this photo taken March 19, 2009. Clouds at bottom reflect light pollution from nearby Duluth, Minn. U.S. Credit: Bob King
Welcome to the first day of spring! If you have a clear night between now and April 1, celebrate the new season with a pilgrimage to the countryside to ponder the eerie glow of the zodiacal light. Look for a large, diffuse, tapering cone of light poking up from the western horizon between 90 minutes and two hours after sunset. While the zodiacal light appears only as bright as the Milky Way, you’re actually looking at the second brightest object in the night sky. No kidding. If you could crunch it all into a little ball, it would shine at magnitude -8.5, far brighter than Venus and bested only by the full moon.
The zodiacal (Zo-DIE-uh-cull) light is centered on the plane of the solar system called the ecliptic. This is the same band of sky where you’ll find the planets and zodiac constellations, hence the name. On late March nights, you can trace it from near the western horizon more than 45 degrees (halfway up the sky). Created with Stellarium
Sunlight reflecting off countless dust particles shed by comets and spawned by asteroid collisions creates the luminous cone of light. First time observers might think they’re looking at skyglow from light pollution but the tapering shape and distinctive tilt mark this glow as interplanetary dust.
Photo of coronal and zodiacal light taken by the Clementine spacecraft when the sun was hidden by the moon. At right is Venus. Clementine measured the brightness of the light to arrive at an integrated magnitude of -8.5. It also estimated dust particle sizes and origin. Credit: NASA
Like the planets, the dust resides in the plane of the solar system. In spring, that plane (called the ecliptic) tilts steeply up from the western horizon after sunset, “lifting” the chubby thumb of light high enough to clear the horizon haze and stand out against a dark sky for northern hemisphere observers. In October and November the ecliptic is once again tilted upright, but this time before dawn. While the zodiacal light is present year-round, it’s usually tipped at a shallow angle and camouflaged by horizon haze. No so for skywatchers in tropical and equatorial latitudes. There the ecliptic is tilted steeply all year long, and the light can be seen anytime there’s no moon in the sky.
The combined glow of dust particles in the plane of the solar system reaching from the sun’s vicinity out to at least Jupiter is responsible for creating the zodiacal light. Dust closest to the sun glow more brightly, the reason the bottom of the zodiacal light cone is brighter than the tip. Planets are shown as colored disks. Illustration: Bob King
Now through April 1 and again from April 17-30 are the best nights for viewing because the moon will be absent from the sky. The cone is widest near the western horizon and narrows as you direct your gaze upward and to the left. At its apex, where it touches the V-shape Hyades star cluster, it continues into the even fainter zodiacal band and gegenschein, but more about that in a moment. Sweep your gaze in broad strokes back and forth across the western sky to help you discern the Z-light’s distinctive conical shape. And be sure to look for something HUGE. This thing is a monster – indeed, one of the largest entities in the solar system.
Scanning electron microscope photo of an interplanetary dust particle collected by a high-altitude plane. It measures about 8 microns across or a little less than twice the size of a human red blood cell. Scientists recently discovered that dust particles can act as tiny factories to built water molecules. Credit: Donald Brownlee and Elmar Jessberger
Observers fortunate enough to live under or with access truly dark skies can trace the zodiacal light all the way across the sky as the zodiacal band.
Midway along its length, 180 degrees opposite the sun, a slightly brighter circular patch called the gegenschein (German for ‘counter glow’) embedded in the band.
Dust particles there get an extra brightness boost because they face the sun square on, much like the moon does when full. While I usually see only a section of the zodiacal band from my dark observing site, the gegenschein is often visible as a diffuse, hazy patch of light about 6 degree across a little brighter than the sky background.
Incredible 360-degree-wide view of morning and evening zodiacal light cones (far left and right), the fainter zodiacal band and the brighter spot of gegenschein (center) and the Milky Way photographed from Mauna Kea. Click to enlarge. Credit: Miloslav Druckmuller and Shadia Habbal
Dutch astronomer H. C. van de Hulst determined that the dust particles responsible for the zodiacal light and its cousins the zodiacal band and gegenschein are about 0.04 inch (1 mm) in diameter and separated, on average, by about 5 miles (8 km).
The gegenschein, an oval shaped brighter spot within the faint zodiacal band, is easiest to when due south and highest in the sky at local midnight (1 a.m. Daylight Saving Time). Currently it’s in northern Virgo. Since the ‘counter glow’ will always be opposite the sun, it will slide down closer to Spica in April. Created with Stellarium
The particles form a low density, lens-shaped cloud of dust that’s thickest within the plane of the solar system but in reality covers the entire sky but ever so thinly. Sunlight absorbed by the particles is re-emitted as invisible infrared (heat) radiation. This re-radiation robs the dust of energy, causing the particles to spiral slowly into the sun. Fresh dust from the vaporization of cometary ices as well as collisions of asteroids replenishes the cloud.
Zodiacal light cones in the fall morning sky (left) and in late March. Both times of year we see the plane of the solar system tipped at a high angle in the sky. Credit: Bob King
According to a study by Joseph Hahn and colleagues of the Clementine Mission data, comet dust accounts for the majority of the zodiacal dust within 1 a.u. (93 million miles) of the sun; a mix of asteroidal and comet dust makes up the remainder.
Stepping out on a spring evening to look at the zodiacal light, we can appreciate how small things can come together to create something grand.
The bright star Regulus will disappear for observers living along the path between the red lines. The disappearance is longest - up to 14 seconds - along the center green line. Credit: Google Maps / IOTA
North America’s brightest predicted asteroid occultation may be one-upped by a much bigger occultation – a solid blanket of clouds. Asteroid 163 Erigone will cover or occult the bright star Regulus shortly after 2 a.m. Eastern Daylight Time tomorrow morning March 20. Observers along a 45-mile-wide (73-km) belt stretching from the wilderness of Nunavut to the salty seas of Bermuda could see the star vanish for up to 14 seconds. Provided they can find a hole in the clouds.
National forecast map for 8 p.m. EDT tonight March 19. A low pressure region is expected to bring rain and snow to the Northeast and Ontario today and overnight with clearing skies later tomorrow. Click for latest New York City weather forecast. Credit: NOAA
Overcast skies with a mix of rain or snow are predicted along virtually the entire track from the tiny berg of Cochrane in northern Ontario south through New York City, Connecticut and New Jersey. A sluggish cold front isn’t expected to clear skies until … no surprise here … after the event is over.
Bermuda, perhaps the best place to watch the occultation, crosses the eastern edge (blue line) of the asteroid’s shadow. The red line marks one sigma of uncertainty in the shadow edge. Credit: Google Maps/IOTA
But there is one place where maybe, just maybe, the clouds may part to let Erigone do its job. Bermuda. The Bermuda Weather Service forecast calls for highs in the low 70s mid-week, but that balmy air may come packaged with a partly to mostly cloudy sky at the time of the occultation. A few determined observers are on their way there right now, hoping for better weather. In case the islands are socked in, some plan to rent planes to rise above the low-lying clouds typical this time of year and revel in the shadow of an asteroid. Even if clear, Bermuda lies near the eastern edge of the path. Any occultation there will be brief.
Illustration showing asteroid 163 Erigone about to cover Leo’s brightest star Regulus around 2:07 Eastern Daylight Time Thursday morning March 20, 2014. As the asteroid’s shadow passes over the ground, observers will see Regulus briefly disappear. Illustration: Bob King with ESO/NASA images
Yes, there will be more occultations, but bright ones that the public can enjoy with the naked eye are rare.
Skywatchers are nothing if not hopeful. We believe in the sucker hole, the name given to rogue clearings in an otherwise overcast sky. We are patient and steadfast when it comes to glimpsing the rarest of the rare. I know this because my friends and I have stood outside on winter mornings staring at the western sky, waiting for clouds to peel back that we might glimpse a Martian dust storm or new comet.
If it does clear tomorrow, face southwest shortly before 2 a.m. to find Leo’s brightest star Regulus. The star will be about 40 degrees high (four ‘fists’ held at arm’s length against the sky). Above is the the Sickle of Leo, shaped like a backwards question mark. Brilliant Jupiter shines well to its lower right. Stellarium
If there’s an astronomer’s credo, it’s this: “The sky might clear yet!” The latest weather word (9 a.m. March 19) for U.S. and Canadian observers indicates thinner clouds along the southern end of the track in New Jersey. Many of us considered driving to the event but changed our minds because of work, worries about weather and other commitments. Assuming the credo holds true, you’ll be able to watch Regulus disappear live from the comfort of your home thanks to the efforts of several observers planning to stream the event on the Web.
Here’s a list of streamers so far:
* Brad Timerson plans to go live with audio at 2 a.m. at a rest area along I-90 just west of Syracuse, NY.
A new interactive mosaic from NASA's Lunar Reconnaissance Orbiter covers the north pole of the moon from 60 to 90 degrees north latitude at a resolution of 6-1/2 feet (2 meters) per pixel. Close-ups of Thales crater (right side) zoom in to reveal increasing levels of detail.
Image Credit: NASA/GSFC/Arizona State University
OMG – breathtaking! That was my reaction when I clicked on this incredible new interactive map of the moon’s north polar region. Be prepared to be amazed. It took four years and 10,581 images for the LROC (Lunar Reconnaissance Orbiter Camera) team to assemble what’s believed to be the largest publicly available image mosaic in existence. With over 650 gigapixels of data at a resolution of 2 meters per pixel, you’ll feel like you’re dropping in by parachute to the lunar surface.
Wide view of the 91-km Karpinskiy Crater from the new interactive north pole mosaic. See image below for a zoomed-in view. Credit: NASA/GSFC/Arizona State Univ.
When you call up the map, be sure to click first on the full-screen button below the zoom slider. Now you’re ready for the full experience. With mouse in hand, you’re free to zoom and pan as you please. Take in the view of Whipple Crater shadowed in polar darkeness or zoom to the bottom of Karpinskiy Crater and fly like a bird over its fractured floor.
In this photo, we come in for a closer look at the fracture or rill in Karpinskiy’s floor. Notice the small, lighter-toned boulders on the cliff side. The images were all taken with the Lunar Reconnaissance Orbiter’s Narrow Angle Camera (NAC). Credit: NASA/GFSC/Arizona State Univ.
The images are so detailed and the zoom so smooth, there’s nothing artificial about the ride. Except the fact you’re not actually orbit. Darn close though. All the pictures were taken over the past few years by NASA’s Lunar Reconnaissance Orbiter which can fly as low as 50 km (31 miles) over the lunar surface and resolve details the size of a desk.
Printed at 300 dpi – a high-quality printing resolution that requires you to peer very closely to distinguish pixels – the mosaic map would be larger than a football field. Credit: NASA
There are 10 snapshots along the bottom of the map – click them and you’ll be swiftly carried directly to that feature. One of them is the lunar gravity probe GRAIL-B impact site.
The region the gigapixel map covers superimposed on the outline of the U.S. Credit: NASA
To create the 2-D map, a polar stereographic projection was used in to limit mapping distortions. In addition, the LROC team used information from the LOLA and GRAIL teams and an improved camera pointing model to accurately project each image in the mosaic to within 20 meters. For more information on the project, click HERE.
Mars photographed during part of its rotation from Melbourne, Australia on March 8. The bright "cap" marks Hellas, now covered in wintertime frost and clouds. Credit: Maurice Valimberti
Earth’s changing weather always makes life interesting. Seeing weather on other planets through a telescope we sense a kinship between our own volatile world and the fluttering image in the eyepiece. With the April 8 opposition of Mars rapidly approaching, you won’t want to miss a striking meteorological happening right now on the Red Planet.
Map showing the most prominent dark features on Mars. Hellas is at upper right. Credit: A.L.P.O.
Winter’s already well underway in the planet’s southern hemisphere and there’s no better place to see it than over Hellas, Mars’ biggest impact crater. Hellas formed some 4 billion years when a small asteroid crashed into the young planet and left a scar measuring 1,400 miles (2,300 km) wide and 26,465 feet (7,152 meters) deep. Point your telescope in its direction in the next few weeks and you’ll see what looks at first like the planet’s south polar cap. Don’t be deceived. That’s Hellas coated in dry ice frost and filled with wintertime clouds.
The Hellas impact basin, also known as Hellas Planitia, is 1,400 miles wide. After Mars’ Utopia Planitia and the moon’s South Pole-Aitken Basin, Hellas is the third largest confirmed crater in the solar system.
Right now, Mars’ northern hemisphere, along with the north polar cap, are tipped our way. Though the cap is rapidly vaporizing as the northern summer progresses, you can still spot it this month as a small dab of white along the northern limb in 6-inch (15 cm) and larger telescopes. Use a magnification upwards of 150x for the best views. The south polar cap can’t be seen because it’s tipped beyond the southern limb.
Mars from Athens, Greece on March 14, 2014 with Hellas (top), Syrtis Major and both morning and evening limb water clouds. The winter-whitened Hellas impact basin is best seen using magnifications of 150x or higher. Credit: Manos Kardasis
Along with nearby Syrtis Major, Hellas was one of the first features discovered with the telescope. Even in summer its pale floor stands out against the darker volcanic features of the planet. Though windswept and bitter cold now, Hellas’ great depth makes it one of the warmest places on Mars during the summer months. Mid-summer atmospheric pressure has been measured at more than 10 millibars, more than twice the planet’s mean. Afternoon high temperatures reach near the freezing point (32 F / 0 C) with nighttime lows around -50 F (-45 C). Winter temperatures are much more severe with lows around -22o F (-140 C). Carbon dioxide condenses as frost and whitens the floors of many craters during this time.
Mars photographed by the Mars Global Surveyor shows the equally prominent Syrtis Major and the Hellas impact basin. Syrtis Major is an ancient, low relief shield volcano. Credit; NASA/JPL/Malin Space Systems
We can only see Hellas when that hemisphere is turned in our direction; this happens for about a week and a half approximately once a month. European observers are favored this week with Hellas well placed near the planet’s central meridian from 1 – 4 a.m. local time. Why the outrageous hour? Mars rises around 10 p.m. but typically looks soft and mushy in the telescope until it’s high enough to clear the worst of atmospheric turbulence 2 – 3 hours later. North and South American observers will get their turn starting this Saturday March 22nd around 12:30 – 1 a.m. Good Hellas viewing continues through early April.
Mars at 1 a.m. CDT on successive nights starting March 21, 2014. Notice how planetary features appear to rotate slowly eastward night to night. Created with images from Meridian
Like Earth, Mars revolves from west to east on its axis, but because it rotation period is 37 minutes longer than Earth’s, Hellas and all Martian features appear to drift slowly eastward with each succeeding night. A feature you observed face-on at midnight one night will require staying up until 2:30 a.m. a week later for Mars to “rotate it back” to the same spot. To keep track of the best times to look for Hellas or anything else on Mars, I highly recommend the simple, free utility called Meridian created by Claude Duplessis. Set your time zone and you’ll know exactly the best time to look.
Mars on March 8, 2014 shows clouds over Hellas and evening limb clouds. Credit: Chin Wei Loon
While you’re out watching the Martian winter at work, don’t forget to also look for the shrinking north polar cap and bright, patchy clouds along the planet’s morning (east) and evening limbs. You can use the map above to try and identify the many subtle, gray-toned features named after lands in classic antiquity by 19th century Italian astronomer and Mars aficionado Giovanni Schiaparelli.
I will you success in seeing Hellas and encourage you to share your observations with us here at Universe Today.
Comet C/2014 E2 Jacques photographed from Siding Spring Observatory on March 14, 2014. Credit: Rolando Ligustri
Congratulations to Cristovao Jacques and the SONEAR team! On March 13 they snared C/2014 E2 (Jacques) in CCD images taken with a 0.45-meter (17.7-inch) wide-field reflector at the SONEAR (Southern Observatory for Near Earth Asteroids Research) observatory near Oliveira, Brazil. A very preliminary orbit indicates its closest approach to the sun will occur on June 29 at a distance of 56 million miles followed two weeks later by a relatively close flyby of Venus of 0.09 a.u. or 8.4 million miles (13.5 million km). If a comet approached Earth this closely so soon after perihelion, it would be a magnificent sight. Of course, watching from Venus isn’t recommended. Even if we could withstand its extreme heat and pressure cooker atmosphere, the planet’s perpetual cloud cover guarantees overcast skies 24/7.
Comet Jacques travels across the deep southern sky in early spring as seen from mid-northern latitudes. Approximate positions are shown through April 4. Stellarium
It’s the team’s second comet discovery this year after turning up C/2014 A4 (SONEAR) in January. Comet Jacques has been tracking across northern Centaurus since discovery. Over the next few nights, it straddles the border with Hydra where it will be visible low in the southern sky around for northern hemisphere observers from about midnight to 2 a.m. If you live on a Caribbean island and points south your view will be even better.
Steven Tilley’s animation of Comet C/2014 E2 Jacques over 35 minutes on March 13, 2014
Comet Jacques exhibits a dense, fairly bright 2-arc-minute coma or cometary atmosphere with a short northward-pointing tail. Brightness estimates have been hard to come by, but it appears the comet may be around magnitude +11.5 – 12 or within range of an 8-inch (20-cm) or larger telescope. One thing’s for certain. In the coming weeks, E2 will be approaching both the Earth and the sun and brightening as it slowly gains altitude in the evening sky.
Another view of the comet on March 13 through a 0.5-meter (19.5-inch) telescope. Credit: Ernesto Guido, Nick Howes, Martino Nicolini
Shortly after perihelion, Comet Jacques will shine brightest at around magnitude +10-10.5 (though it could be brighter) and remain nearly this bright as it swings north from Orion into Perseus from mid-July to mid- August. Closest approach to Earth occurs on Aug. 29-30 at 54 million miles (87 million km). It will join Comet Oukameiden – predicted to reach binocular visibility in late August – to offer comet lovers much to look forward to as the summer wanes.
Lambda Geminorum at 10:43 p.m. March 11 just two minutes before disappearing behind the moon as seen from Minneapolis, Minn. US. Stellarium
Ever dabbled in the occult? You’ll have your chance Monday night March 10 when the waxing gibbous moon glides in front of the star Lambda Geminorum for much of North America, occulting it from view for an hour or more. Occultations of stars by the moon happens regularly but most go unnoticed by casual skywatchers. Lambda is an exception because it’s one of the brighter stars that happens to lie along the moon’s path. Shining at magnitude +3.6, any small telescope and even a pair of 10×50 or larger binoculars will show it disappear along the dark edge of the moon.
Map showing where the disappearance (right half of tube-like figure) and reappearance of Lambda Gem will be visible. Credit: International Occultation Timing Assn. (IOTA)
With a telescope you can comfortably watch the star creep up to the moon’s edge and better anticipate the moment of its disappearance. The fun starts a few minutes before the impending black out when the moon, speeding along its orbit at some 2,280 mph (3,700 km/hr), draws very close to the star. During the final minute, Lambda may seem to hover forever at the moon’s invisible dark limb, and then – PFFFT – it’s gone! Whether you’re looking through telescope or binoculars, the star will blink out with surprising suddenness because the moon lacks an atmosphere.
Disappearance and reappearance seen from Minneapolis, Minn. Monday night. I’ve lightened the moon so you can see the dark limb. You’ll likely not see this edge in a telescope because of glare. Stellarium
If there was air up there, Lambda would gradually dim and disappear. Even without special instruments, early astronomers could be certain the moon had little if anything to protect it from the vacuum of space by observing occultations.
As the moon moves approximately its own diameter in an hour, you can watch Lambda re-emerge along the bright limb roughly an hour later, though its return will lack the drama and contrast of a dark limb disappearance. While occultations allow us to see how swiftly the moon moves in real time as well as provide information on its atmosphere or lack thereof, real science can be done, too.
Planets also are occasionally occulted by the moon. Time lapse of Venus’ disappearance on May 16, 2010
Observers along the occultation boundary in the southern U.S. can watch the star pop in and out of view as it’s alternately covered and uncovered by lunar peaks jutting from the moon’s limb. Before spacecraft thoroughly mapped the moon, careful timings made during these “grazing occultations” helped astronomers refine the profile of the moon’s limb as well as determine elevations of peaks and crater walls in polar regions. They can still be useful for refining a star’s position and motion in the sky.
The moon’s limb can also be used much like a doctor’s scalpel to split unsuspected double stars that otherwise can’t be resolved by direct observations. Take Lambda Gem for instance. We’ve known for a long time that it totes around a magnitude +10.7 companion star 10 arc seconds to its north-northeast, but previous occultations of the star have revealed an additional companion only a few hundredths of an arc second away orbiting the bright Lambda primary. The star plays a game of hide-and-seek, visible during some occultations but not others. Estimated by some as one magnitude fainter than Lambda, keep an eye out for it Monday night in the instant after Lambda goes into hiding.
Lunar occultation and reappearance of Antares Oct. 21, 2009
I watched just such a “two-step” disappearance of Antares and it fainter companion some years back. With brilliant Antares briefly out of view behind the moon’s limb, I easily spotted its magnitude +5.4 companion just 2.5 arc seconds away – an otherwise very difficult feat at my northern latitude.
Want to know more about things that disappear (and reappear) in the night? Make a visit to the International Occultation Timing Association’s websitewhere you’ll find lists of upcoming events, software and how to contribute your observations. If you’re game for Monday night’s occultation, click HEREfor a list of cities and times. Remember that the time show is Universal or Greenwich Time. Subtract 4 hours for Eastern Daylight, 5 for Central, 6 for Mountain and 7 for Pacific. Wishing you clear skies as always!
On March 3, 2014 the The Ground-to-Rocket Electrodynamics – Electron Correlative Experiment (GREECE) sounding rocket launched straight into an aurora from the Poker Flat Research Range in Poker Flat, Alaska. Credit: NASA
If you’ve ever wondered what makes the aurora take on the amazing forms it does you’ve got company. Marilia Samara and the crew of aurora researchers at Alaska’s Poker Flat Range head up the NASA-funded Ground-to-Rocket Electrodynamics-Electrons Correlative Experiment, or GREECE. Their mission is to understand what causes the swirls seen in very active auroras.
Robert Michell, who built some of the instruments on the sounding rocket, and Marilia Samara, the principal investigator for the GREECE project. Credit: NASA
“Our overarching goal is to study the transfer of energy from the sun to Earth,” said Samara, a space scientist at the Southwest Research Institute, or SwRI, in San Antonio, Texas. “We target a particular manifestation of that connection – the aurora.”
Here’s what we know. Electrons and protons from the sun come charging into Earth’s magnetic domain called the magnetosphere and strike and energize molecules of oxygen and nitrogen in the atmosphere between 60 and 200 miles overhead. The molecules release that extra energy as the greens, reds and purples of the northern lights.
Earth has a magnetic field much like an ordinary refrigerator magnet but shaped by charged particles flowing from the sun called the solar wind. When those particles travel down the planet’s magnetic field lines and excite atmospheric gases, they create the familiar parallel rays seen in auroras. Credit: Greg Shirah and Tom Bridgman, NASA/Goddard Space Flight Center Scientific Visualization Studio (left); Bob King (right)
And those picket-fence, parallel rays that can suddenly spring from a quiet arc are created by billions of electrons spiraling down individual magnetic field lines, crashing into atoms and molecules as they go. Because the lines of magnetic force are closely bunched, as shown in the illustration above, we see side-by-side, tightly spaced rays.
What we less about is how the twists, swirls and eddies form.
Wave clouds forming over Mount Duval, Australia from a Kelvin-Helmholtz Instability. Credit: GRAHAMUK / English language Wikipedia
Scientists suspect the swirls may take shape as a result of Kelvin-Helmholtz instabilities or Alfven waves. The first occurs when two fluids or gases moving at different rates of speed flow by one another. In a familiar example, wind blowing over water creates ripples that are amplified into curling, white-topped waves.
Alfven waves are created when flows of electrified particles from the sun (plasma) interact with Earth’s magnetic field. To study the structures, sounding or research rockets are launched directly into an active display of northern lights to gather electrical and magnetic measurements. At the same time, cameras on the ground record the dance of rays and arcs above. Samilla and her team at GREECE then compare the aurora’s shifting shapes with real-time data gathered during the rocket’s 600 seconds of flight.
Still and video cameras on the ground simultaneously image the aurora as the instrument-laded rocket flies into the aurora to gather data. Credit: Marilia Samara / Robert Michell / SwRI
“Auroral curls are visible from the ground with high-resolution imaging,” said Samara. “And we can infer from those observations what’s happening farther out. But to truly understand the physics we need to take measurements in the aurora itself.”
Poker Flat rocket launch – Jason Ahrns
And that’s exactly what the team did this past Monday morning March 3. Conditions looked good from Poker Flat the previous evening with a flurry of red and green arcs after sunset. At about 2:10 a.m. Alaska time, after careful monitoring of activity, the order was given to launch.
“It was a wonderful auroral event,” said Kathe Rich, Poker Flat Range manager. “We got good data throughout the flight, and all the instruments worked.”
Time exposure showing the trail of the rocket after it was launched into the aurora over Poker Flat early Monday morning March 3, 2014. Credit: Jason Ahrns
The rocket soared to an altitude of 220 miles (354 km) and recorded data as the video and still cameras whirred on the ground during the 10 minute 15 second long flight.
There must be a bunch of happy scientists at the Range this week. They have their work cut out for them; those few minutes of data collecting will mean years of work to track down the cause of the beautiful curlicues that make our hearts leap at the sight.
Happy researchers at the Poker Flat Research Range. Credit: Lex Wingfield / NASA
Poker Flat Research Range, the world’s only scientific rocket launching facility owned by a university, is located about 30 miles north of Fairbanks, Alaska and is operated by the University of Alaska’s Geophysical Institute under contract with NASA. Most of the research there involves the aurora with sounding rocket launches done about once a year. While waiting for the right moment to launch, members of the team exercise their poetic side by writing and sharing haikus about their beloved aurora. Here’s a sampling, and there are more HERE.
Dim, wide green madness Electromagnetic ghost Surrender your soul – EM
Hey elusive arc Zenith is over there, dude It’s about damn time -EM
Oh Oh Oh Oh Oh Oh Oh Oh Oh Oh Oh Oh So ready to launch! -JC
While the cause of auroras is understood, what causes the swirl shapes is an open question. University of Alaska researchers at Poker Flat hope to find an answer. Aurora photographed on Dec. 15, 2012 from Tromso, Norway. Credit: Ole Salomonsen
Somewhere in this image there should be a static point of light that is the asteroid 2000 EM26. Based on orbital data from NASA/JPL, this is where it should have been. Credit: Slooh
Yesterday evening you may have dropped by to watch Slooh’s live coverage of asteroid 2000 EM26 as it passed just 8.8 lunar distances of Earth. Surprise – the space rock never showed up! Slooh’s robotic telescope attempted to recover the asteroid and share its speedy travels with the world but failed to capture an image at the predicted position.
Now nicknamed Moby Dick after the elusive whale in Herman Melville’s novel of the same name, the asteroid’s gone missing in the deep sea of space. Earthlings need fear no peril; it’s not headed in our direction anytime soon. Either the asteroid’s predicted path was in error or the object was much fainter than expected. More likely the former.
Last night’s coverage attempt of 2000 E26’s close flyby of Earth
2000 EM26’s predicted brightness at the time was around magnitude 15.4, not bright but well within range of the telescope. Rather than throwing their hands up in the air, the folks at Slooh are calling upon amateur astronomers make a photographic search for the errant space rock in the next few nights.
Since the asteroid was last observed 14 years ago for only 9 days, it isn’t too surprising that uncertainties in its position could add up over time, shifting the asteroid’s position and path to a different part of the sky by 2014. According to Daniel Fischer, German amateur astronomer and astronomy writer, the positions were off by 100 degrees! As Paul Cox, Slooh’s Observatory Director, points out:
“Discovering these Near Earth Objects isn’t enough. As we’ve seen with 2000 EM26, all the effort that went into its discovery is worthless unless followup observations are made to accurately determine their orbits for the future. And that’s exactly what Slooh members are doing, using the robotic telescopes at our world-class observatory site to accurately measure the precise positions of these asteroids and comets.”
If a determined, modern-day Ahab doesn’t find this asteroidal Moby Dick, one of the large scale robotic telescope surveys probably will. Here’s a link to the NASA/JPL particulars including brightness, coordinates and distance for 2000 EM26.
Similar sized asteroids, including ones passing even closer to Earth, zip by every month. 2000 EM26 received a lot of coverage yesterday likely because it arrived near the time of the anniversary of the Chelyabinsk meteorite fall over Russia. Though it remains scarce for now, eyes are on the sky to find the asteroid again and refine its orbit. Hopefully the beast won’t get away next time.
Chelyabinsk fireball recorded by a dashcam from Kamensk-Uralsky north of Chelyabinsk where it was still dawn. A study of the area near this meteor air burst revealed similar signatures to the Tall el_Hammam site.
Wonder and terror. Every time I watch the dashcam videos of the Chelyabinsk fireball it sends chills down my spine. One year ago today, February 15, 2013, the good citizens of Chelyabinsk, Russia and surrounding towns collectively experienced these two powerful emotions as they witnessed the largest meteorite fall in over 100 years.
Incredible compilation of dashcam and security camera videos of the fireball
The Chelyabinsk fall, the largest witnessed meteorite fall since the Tunguska event in 1908, exploded with 20-30 times the force of the atomic bomb over Hiroshima at an altitude of just 14.5 miles (23 km). Before it detonated into thousands of mostly gravel-sized meteorites and dust, it’s estimate the incoming meteoroid was some 66 feet (20-meters) end to end, as tall as a five-story building. The shock wave from the explosion shattered windows up and down the city, injuring nearly 1,500 people.
Atmospheric friction pressure on the Chelyabinsk meteoroid caused it to explode to pieces and send a shock wave across the land below. Pictured is a selection of typical small, fusion-crust covered Chelyabinsk meteorites recovered shortly after the fall. The U.S. penny is 9mm in diameter. Credit: Bob King
For nearby observers it briefly appeared brighter than the sun. NASA Meteorite researcher Peter Jenniskens conducted an Internet survey of eyewitnesses and found that eye pain and temporary blindness were the most common complaints from those who looked directly at the fireball. 20 people also reported sunburns including one person burned so badly that his skin peeled:
Map showing the trajectory of the main fireball in yellow (and two additional explosions at top left). The pink oval, called the strewnfield, is where the densest concentration of meteorites were found. Click to see additional maps. Credit: Svend Buhl and K. Wimmer
“We calculated how much UV light came down and we think it’s possible,” Jenniskens said. Perhaps surprisingly, most of the meteoroid’s mass – an estimated 76% – burned up and was converted to dust during atmospheric entry. It’s estimated that only 0.05% of the original meteoroid or 9,000 to 13,000 pounds of meteorites fell to the ground.
No video I’ve seen better captures the both the explosion of the fireball and ensuring confusion and chaos better than this one.
The largest fragment, weighing 1,442 lbs. (654 kg), punched a hole in the ice of Lake Chebarkul. Divers raised it from the bottom muck on Oct. 16 last year and rafted it ashore, where scientists and excited onlookers watched as the massive space rock was hoisted onto a scale and promptly broke into three pieces. Moments later the scale itself broke from the weight.
The 26-foot-wide (8-meter) hole punched in the ice of Chebarkul Lake by the largest fragment of the Chelyabinsk meteorite. Credit: Eduard Kalinin
There were plenty of meteorite to go around as local residents tracked down thousands of fragments by looking for holes pierced in the snow cover by the hail of space rocks. Working with hands and trowels, they dug out mostly small, rounded rocks covered in fresh black fusion crust, a 1-2 mm thick layer of rock blackened and melted rock from frictional heating by the atmosphere. According to the Meteoritical Bulletin Database entry, the total mass of the recovered meteorites to date comes to 1,000 kg (2,204 lbs.) with locals finding up to more than half of that total.
Animation of the orbit Chelyabinsk meteoroid via Ferrin and Zuluaga. Meteoroid is the name given a meteor while still orbiting the sun before it enters Earth’s atmosphere.
Thanks to the unprecedented number of observations of the fireball recorded by dashcams, security cameras and eyewitness accounts, astronomers were able to determine an orbit for Although some uncertainties remain, the object is (was) a member of the Apollo family of asteroids, named for 1862 Apollo, discovered in 1932. Apollos cross Earth’s orbit on a routine basis when they’re nearest the sun. Chelyabink’s most recent crossing was of course its last.
Chelyabinsk meteorites tell the tale of an earlier impact with another asteroid 4.452 billion years ago. Many specimens are pale white with small chondrules typical of LL5 chondrites. A closer look shows fine, dark shock veins of melted glass. Other fragments are made of pure impact melt, rock shocked-heated, melted and blackened by impact. Credit: Bob King
Chelyabinsk belongs to a class of meteorites called ordinary chondrites, a broad category that includes most stony meteorite types. The chondrites formed from dust and metals whirling about the newborn sun some 4.5 billion years ago; they later served as the building blocks for the planets, asteroids and comets that populate our solar system. Chondrites are further subdivided into many categories. Chelyabinsk belongs to the scarce LL5 class — a low iron, low metal stony meteorite composed of silicate materials like olivine and plagioclase along with small amounts of iron-nickel metal.
Most of the Chelyabinsk meteorites were shattered and broken during the explosion / shock blast, revealing brecciation, metal and shock veins in their interiors. Credit: Bob KingA thin slice of Chelyabinsk impact melt breccia. Flows of once-molten rock (paler gray) surround islands of less altered material. A small iron nickel nodule is seen at lower left. Credit: Bob King
A closer look at Chelyabinsk meteorites reveals a fascinating story of ancient impact. Remarkably, the seeds of the meteoroid’s atmospheric destruction were sown 115 million years after the solar system’s formation when ur-Chelyabinsk was struck by another asteroid, suffering a powerful shock event that heated, fragmented and partially melted its interior. Look inside a specimen and the signs are everywhere – flows of melted rock, spider webby shock veins of melted silicates and peculiar, shiny cleavages called “slickensides” where meteorites broke along pre-existing fracture planes.
Slickensides on a Chelyabinsk meteorite fragment where the fragment broke along a pre-existing fracture plane. Credit: Bob King
Jenniskens calculated that the object may have come from the Flora family of S-type or stony asteroids in the belt between Mars and Jupiter. Somehow Chelyabinsk held together after the impact until nearly the time it met its fate with Earth’s atmosphere. Researchers at University of Tokyo and Waseda University in Japan discovered that the meteorite had only been exposed to cosmic rays for an unusually brief time for a Flora member – just 1.2 million years. Typical exposures are much longer and indicate that the Chelyabinsk parent asteroid only recently broke apart. Jenniskens speculates it was likely part of a loosely-bound, rubble pile asteroid that may have broken apart during a previous close encounter with Earth in the last 1.2 million years. The rest of the rubble pile might still be orbiting relatively nearby as part of the larger population of near-Earth asteroids.
Rivulets of melted rock line the fusion crust of melted rock on this small Chelyabinsk meteorite. Credit: Bob King
Good thing Chelyabinsk arrived pre-fractured. Had it been solid through and through, more of the original asteroid might have survived its fiery descent and wreaked even more havoc in in its wake.
We’re fortunate that Chelyabinsk contains a fantastic diversity of features and that we have so many pieces for study. Surveys have found some 500 near-Earth asteroids. No doubt some are part of the parent body of Chelyabinsk and may grace our skies on some future date. Whatever happens, Feb. 15, 2013 will go down as a very loud “wake-up call” for our species to implement more asteroid-hunting programs both in space and on the ground. Enjoy a few more photos of this incredible gift from space:
This Chelyabinsk “nosecone” or “bullet” weighs just 0.35g. It displays a beautiful streamlined form from its flight through the atmosphere. Credit: Bob KingCheck out the bubble texture on this one. Heated by friction with the air, this fragment shows bubbly crust from escaping gases. Credit: Bob KingSlice of Chelyabinsk showing mildy shocked areas (light brown) cut by thick dark veins of shock-darkened material. Credit: Bob KingSome Chelyabinsk individuals show interesting variations in color that have nothing to do with rusting. It’s believed that varying amounts of oxygen available to the speeding rocks during the meteorite break up created the brownish-red coloration on some fusion crusts. Credit: Bob KingI saved the weirdest for last – a smaller Chelyabinsk meteorite appears to have followed closely enough behind the larger for their still-molten fusion crusts to have welded them together. Just my speculation. Credit: Bob King
