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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

Ghost of SOHO’s comet still lives!

That faint streak is all that's left of C/2015 D1 (SOHO). It was taken on Feb. 25, 2015. Details: Stack of 31 8-second-long exposures at ISO 1600, shot with a Nikon D5100 + 70-300mm telephoto at 135mm f/4.7. A tracking mount kept the stars from trailing. See below for a "blinking" version. Credit: Justin Cowart

That faint streak is all that’s left of C/2015 D1 (SOHO). It was taken on Feb. 25, 2015. Details: Stack of 31 8-second-long exposures at ISO 1600, shot with a Nikon D5100 + 70-300mm telephoto at 135mm f/4.7. A tracking mount kept the stars from trailing. See below for a “blinking” version. Credit: Justin Cowart

A comet that probably shouldn’t have survived its close encounter with the Sun last week appears made it out alive. If ailing a bit. C/2015 D1 SOHO, discovered in photos taken by the Solar and Heliospheric Observatory (SOHO), somehow stayed together in one piece after its near-death solar pass.

This photo taken on Feb. 25 in late evening twilight by geologist and amateur astronomer Justin Cowart of Alto Pass, Illinois, is the first of the comet’s ghostly remnant. It was taken on Feb. 25 during late evening twilight. Cowart didn’t have much hope after hearing speculation that the comet may have been “ISON-ized”. In late 2013, Comet ISON frittered away to little more than an expanding cloud of dust after a similar close pass by our star.

Animation showing the possible D1 SOHO comet and its position marked on an atlas based on its orbit. Credit: Justin Cowart / José Chambo

Animation showing the possible D1 SOHO comet and its position marked on an atlas based on its orbit. Credit: Justin Cowart / José Chambo

But rather than give up, he set up a camera and tracking mount and waited for the sky to clear in the west after sunset Wednesday evening. Comet SOHO was then located about 10° above the horizon near the star Theta Piscium at the time the photo was taken.

“I was able to see stars down to about 6th magnitude in the raw frames, but no comet,” wrote Cowart.  “I decided to stack my frames and see if I could do some heavy processing to bring out a faint fuzzy. To my surprise, when DeepSkyStacker spit out the final image I could see a faint cloud near Theta Picsium, right about where the comet expected to be!”

Stacking is a method of adding multiple pictures taken of the same object together to create a brighter, less grainy and more detailed image. Software programs make it easy.

Cowart sent the picture off to astronomer Karl Battams, who initially brought the comet into the limelight, for his opinion. Meanwhile, comet observer José Chambo got involved in the discussion and plotted D1’s position on a star atlas (in the blinking photo above) based on a recent orbit calculation. Bingo! Justin’s photo was dead on with the predicted position.

This photo was taken on Feb. 27 from Germany. Jost Jahn stacked 59 15-second exposures (ISO 1600, f/2.4) taken with an 85mm telescope. Credit: Jost Jahn

This photo, which confirms Cowart’s observation, was taken on Feb. 27 from Germany. Jost Jahn stacked 59 15-second exposures (ISO 1600, f/2.4) taken with an 85mm telescope. Credit: Jost Jahn

Two night later on the 27th, Jost Jahn of Armrum, Germany set up a small telescope and photographed the SOHO D1 which had by then moved a little higher in the western sky. No question about it – that’s the comet. But like the headless horseman in the Legend of Sleepy Hollow, it’s returned without its head! After a thorough toasting by the Sun, all that remains is an expanding, elongated dust cloud. ISON-ization indeed!

Watch Comet Lovejoy C/2011 W3 rise in this beautiful video by Stephane Guisard

Readers may remember that Comet Lovejoy (C/2011 W3) suffered a similar fate in late 2011, yet remained a remarkable sight in the dawn sky.

Photo taken last night (Feb. 26) with a 200mm lens at f/2.8 showing where the comet should have been found. I've marked a tenuous suspect. Details: 2-seconds at ISO 3200. Stars visible to about magnitude +10. Credit: Bob King

Photo taken last night (Feb. 26) with a 200mm lens at f/2.8 showing where the comet should have been found. I’ve marked a tenuous suspect. Details: 2-seconds at ISO 3200. Stars visible to about magnitude +10. Credit: Bob King

Inspired by Cowart’s possible capture, I set up my own camera two nights ago and photographed the comet’s position with a 200mm telephoto lens under a cold but very transparent twilight sky. Shot “raw” with no stacking, I’m not convinced the image shows a comet. It was still fun to give it a try, and I look forward to the moon leaving the sky next week for a go at seeing Comet SOHO D1 with a telescope.

Comet C/2015 D1's path now through March 3 as it tracks from Pisces into Andromeda in the western sky at dusk. Time is 7 p.m. CST and stars are shown to magnitude +8. Created with Chris Marriott's SkyMap software

Comet C/2015 D1’s path now through March 3 as it tracks from Pisces into Andromeda in the western sky at dusk. Time is 7 p.m. CST and stars are shown to magnitude +8. Created with Chris Marriott’s SkyMap software

Here’s a fresh map based on the most recent orbit published by the Minor Planet Center. Go out and give a try yourself at photographing it. Stacking images is preferred to enhance what’s obviously a faint and diffuse object. Cowart shot his photos between 60 and 70 minutes after sunset when the comet’s altitude ranged from 10° and 6° high. Mine were taken between 70 and 80 minutes after sundown.

Cross your fingers and make appropriate sacrifices to the god of your choice. The comet may be visible in telescopes as it climbs higher into a dark sky after the moon departs the scene around March 6-7.

Dark Energy Camera sees universe through a comet’s tail

At the time this image was taken, the comet was passing about 51 million miles from Earth – a short distance for the Dark Energy Camera, which is sensitive to light up to 8 billion light years away. Each of the rectangular shapes above represents one of the 62 individual fields of the camera. Click to explore the original, hi-res image. Credit:

Comet Q2 Lovejoy on December 27, 2014. At the time this image was taken, the comet was passing about 51 million miles from Earth – a short distance for the Dark Energy Camera, which is sensitive to light up to 8 billion light years away. Each of the rectangular shapes above represents one of the 62 individual fields of the camera. Click to explore the original, hi-res image. Credit:

Not a bad photo considering no one planned to shoot this picture of Comet Lovejoy with the  world’s most powerful digital camera. That’s right. The comet just happened to “be in the way” during a scan made by the Dark Energy Camera. A member of the observing team said it was a “shock” to see the comet appear on the computer screen.

An assortment of galaxies including this spiral appear through the tail of Comet Q2 Lovejoy on December 27, 2014 during one of the new Dark Energy Camera's scans of the sky. Credit: Fermilab’s Marty Murphy, Nikolay Kuropatkin, Huan Lin and Brian Yanny

An assortment of galaxies including this pretty spiral appear shine through a small section of Lovejoy’s tail on December 27, 2014 during one of the Dark Energy Camera’s scans of the sky. Credit: Fermilab’s Marty Murphy, Nikolay Kuropatkin, Huan Lin and Brian Yanny

While the detail in the comet is spectacular, what’s behind it is equally amazing. The image represents a narrow but deep slice into the body of the cosmos, revealing hundreds of distant galaxies beyond the green veil of Lovejoy’s tail. I’ve sectioned off a few portions, but I encourage you to download and explore the original file and see the rest for yourself. We’ve all read there are billions of galaxies out there, but seeing them twinkling beyond the comet gives us a visceral feel of how deep the universe goes.

The camera, a 570 megapixel beast with lenses up to a yard across, is mounted on the 157-inch (4-meter) Victor M. Blanco telescope at the National Science Foundation’s Cerro Tololo Inter-American Observatory in the Andes Mountains in Chile. With a 2.2° field of view (much larger than most professional telescopes) and the ability to see light from more than 100,000 galaxies up to 8 billion light-years away in each snapshot, it forms the heart of the Dark Energy Survey (DES).

Another serving of galaxy salad. Credit:

Serving up another helping  of galaxy salad. Credit: Marty Murphy, Nikolay Kuropatkin, Huan Lin and Brian Yanny

Dark energy is the name given to whatever is causing the universe to accelerate. No one went looking for it, but studies of the brightnesses of extremely distant supernovae in the 1990s turned up a phenomenal increase in the expansion rate of the universe when viewed across billions of light years. Now we’re stuck trying to figure out what it is. If anything, most astronomers expected cosmic expansion to slow down as predicted by Einsteins’ Theory of Relativity. Nope.

Overall, dark energy is thought to comprise 73% of all the mass and energy in the universe. 23% is unseen dark matter known only through its gravitational prowess, leaving just 4% ordinary matter for hamburgers, stars and cars.

How the universe divvies up its energy/matter. Credit: NASA

How the universe divvies up its energy/matter. Credit: NASA

The DES designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. The survey will probe dark energy on four fronts:

* Counting galaxy clusters: Dark matter and galaxies’ own gravity hold clusters together, but dark energy tries to pull the clusters apart. The camera will photograph 100,000 clusters across billions of light years of space and time. Counting clusters and mapping their distribution will help us understand how dark energy battles gravity for the fate of the universe.

* Measuring supernovae brightnesses and distances to better determine the expansion rate of the universe. 4,000 new supernovae are expected to be found with the camera.

Fermilab astrophysicist Tom Diehl inspects the Dark Energy Camera.

Fermilab astrophysicist Tom Diehl inspects the 570-megapixel Dark Energy Camera. A high-end consumer camera like the Canon D5 has a full-frame 22.3 megapixel “chip”. Credit: Fermilab

* Studying how dark energy interacts with dark matter. The light of distant galaxies is bent and distorted when it passes around dark matter, warping their shapes. The survey will measure those shapes to see what role dark energy plays in the interaction.

* When the universe was less than 400,000 years old, matter and light interacted to set off a series of sound waves which left an imprint on how galaxies are distributed throughout the universe. The survey will measure the positions in space of 300 million galaxies to find this imprint and use it to infer the history of cosmic expansion.

Even if we don’t track down the nature of dark energy in our lifetime, we can sure enjoy the side benefits of pictures like this one.

Watch Io snuff out Ganymede at Jupiter tonight

The moon kisses up to Aldebaran last night (Feb. 25) during evening twilight seen from Duluth, Minn. Credit: Clint Austin

The moon kisses up to Aldebaran last night (Feb. 25) during evening twilight seen from Duluth, Minn. Credit: Clint Austin

First, my apologies. I so wanted to alert you to the half moon’s pass of the bright star Aldebaran last night. But there were network problems with the blog, and I wasn’t able to post.

No doubt many of you noticed it all the same. A quick look up at the moon and you couldn’t help but see the star a little more than one lunar diameter to the southwest. The farther north you lived, the closer they drew together. In far northeastern Canada the moon occulted Aldebaran. Checking the moon several times overnight, it was amazing to see how quickly it departed Aldebaran, forced by its perpetual orbital motion to “go east, young moon, go east”.

Tonight our satellite moves a fist further east in Taurus the Bull and beams atop Orion the mighty hunter at nightfall. It’s 8 days past new phase and absolutely resplendent with craters. Sic your telescope on it and marvel at the ruggedness of all that ancient terrain bludgeoned by forgotten meteorites and asteroids.

The view through the telescope this evening just before Ganymede is eclipsed by Io's shadow. Created with Stellarium

The view through the telescope this evening just before Ganymede is eclipsed by Io’s shadow. The deepest part of the eclipse will occur around 9:35 p.m. Created with Stellarium

East of Orion you’ll find the blazingly bright planet Jupiter right along the border of Leo and Cancer. I’ve written before about this being a special season for Jupiter’s moons. Because Earth’s equator is aligned with Jupiter’s, and the brightest moons orbit above the planet’s equator, we can see them eclipse and occult one another in what astronomers call “mutual events”.

Tonight, little Io will cast its shadow on the largest Jovian moon, Ganymede. While not a total eclipse, it’s close, with a good deal of Ganymede in shadow at maximum (although not 97% as I wrote earlier). This should be easily visible in a small telescope at low to medium magnification. The eclipse begins at 9:31 p.m. CST (3:31 UT) and ends at 9:40 p.m. (3:40 UT). Jupiter will be very well placed for viewing across all of the Americas at the time.

Now here's something cool - a double mutual event. Europa eclipses then occults Io on January 28 captured by Theo Ramakers of Oxford, Georgia.

In this double mutual event, Europa eclipses then occults Io on January 28 captured by Theo Ramakers of Oxford, Georgia. The eclipse is quick in the time lapse, occurring about 1/2 second in. Look for the shadow passing across the top of Io.

Get that scope out at least a half hour beforehand and let it cool down if you’re in a cold climate otherwise Jupiter will look all mushy. Then start watching about five minutes before the eclipse begins, so you can get familiar with Ganymede’s normal brightness.

During the eclipse you won’t be able to see Io’s shadow with your eye, but Ganymede will fade by one magnitude and then re-brighten as the shadow first covers and then departs its 3,275-mile-wide globe.

Wishing you clear or at least partly cloudy skies tonight!

Bizarre bright spot on Ceres has shiny companion

Ceres bright tight

This image was taken by NASA’s Dawn spacecraft of dwarf planet Ceres on Feb. 19 from a distance of nearly 29,000 miles (46,000 km). It shows that the brightest spot on Ceres has a dimmer companion, which apparently lies in the same basin. See below for the wide view. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

What the? The bright spot on Ceres, the subject of much speculation, apparently has a smaller “companion” spot. Both glow brightly from inside a good-sized crater on the dwarf planet. The larger looks like a central peak or spot on a peak.

Certainly a most curious feature. Some scientists think the spots might be related to volcanic activity on Ceres. Credit:

Certainly a most curious feature. Some scientists think the spots might be related to volcanic activity on Ceres. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Fascinating to look at, but the Dawn space probe is still too far away to give us the resolution we need to answer our questions. But watch out. The Internet may soon hum with talk of aliens, mirrors and lasers. I mean, come on, it just looks weird. The contrast between the rest of the asteroid and the spots is remarkable.

These images of dwarf planet Ceres, processed to enhance clarity, were taken on Feb. 19, 2015, from a distance of about 29,000 miles (46,000 kilometers), by NASA's Dawn spacecraft. Dawn observed Ceres completing one full rotation, which lasted about nine hours. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

This and the photo below were taken on Feb. 19, 2015 and processed to enhance clarity. Notice the very large but shallow crater below center. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

The pseudoscience-makers better hurry though. Dawn is fewer than 29,000 miles (46,000 km) away and closing fast. In little more than a week on March 6, the probe will be captured by Ceres gravity and begin a slow dance lasting some 6 weeks settling into a comfortable polar orbit around this intriguing world. That’s when even clearer pictures of the phantom lights will stream their way to Earth. They’re expected to have 100x the resolution of the images seen here.

A different hemisphere of Ceres photographed on Feb. 19. Credit:

A different hemisphere of Ceres photographed on Feb. 19. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Chris Russell, principal investigator for the Dawn mission, thinks it’s possible that the spots may point to a volcano-like origin. That’s just an educated guess at this point. Hang on to your hats – I suspect Ceres will be full of surprises.

Did SOHO’s comet survive? The hunt is on!

Newly-named Comet C/2015 D1 (SOHO) will share the sky with Venus and Mars at dusk. For the next few nights it will be quite low and nearly impossible to see. Its situation improves over time as the comet moves rapidly northward into Pegasus and Andromeda. Tick marks show the comet's position each evening. Stars are shown to magnitude +6.5. Created with Chris Marriott's SkyMap software

Newly-named Comet C/2015 D1 (SOHO) will share the sky with Venus and Mars at dusk. For the next few nights it will be quite low and nearly impossible to see. Its situation improves over time as the comet moves rapidly northward into Pegasus and Andromeda. Tick marks show the comet’s position each evening. Stars are shown to magnitude +6.5. Created with Chris Marriott’s SkyMap software

There’s no telling whether anyone will yet see the “phoenix comet” that survived a close encounter with the Sun last week and continued to keep it together until it exited the coronagraph on the orbiting Solar and Heliospheric Observatory (SOHO).

The last we heard, SOHO-2875, now formally named C/2015 D1 (SOHO), still glowed around magnitude +4 on Feb. 21.

Now the hunt is on to see if enough of the comet remains after its perilous journey to make an appearance in evening twilight. After many position measurements from photos taken by SOHO, an orbit has been calculated that was just published today. Using those numbers, I made a map showing the comet’s nightly progress as it travels up from the western horizon not far from Venus and Mars through the constellations Pisces and Andromeda over the next couple weeks.

Don’t expect to see it tonight. It’s likely no brighter than the naked eye limit (magnitude +6) and swamped in the glow of twilight very low in the western sky. Still, by good fortune, it just happens to hover very close to the star Gamma in Pisces about 5° above the horizon near the end of dusk.Those with crystal clear skies and an open view to the west should give it a try.

The situation soon improves as SOHO’s northward movement carries it higher into a darker sky. It’s uncertain if the comet is a tight, dense ball or a ballooning bag of dust. Until the first observations come in, we won’t know how the comet’s fairing. Also keep in mind that the orbit is preliminary, meaning C/2015 D1 may not exactly follow the path shown. Do sweeps around the positions, moving left and right and up and down from each nightly spot.

I’m as eager as you to see our new visitor.

Planetary traffic jam lookback / Speedy comet update

To capture the planet Uranus (at lower right) I had to overexpose the bright, sunlight lunar crescent. Naturally, this made the earth-lit portion stand out very clearly. Credit: Bob King

To capture the planet Uranus (at lower right) I had to overexpose the bright, sunlight lunar crescent. Naturally, this made the earth-lit portion stand out very clearly. Credit: Bob King

Wow, we had quite a weekend. The moon visited every evening sky planet while Venus and Mars squeezed together for their closest approach of the year. We’ve already looked at the “triple play” conjunction that occurred Friday. I thought it would be fun to look at the other alignments that have made the past few nights so memorable.

The moon (top) along with Venus and Mars Saturday evening Feb. 21, 2015. Credit: Guy Sander

The moon (top) along with Venus and Mars Saturday evening Feb. 21, 2015 from near Duluth, Minn. Credit: Guy Sander

Here, Guy has enlarged portions of the image to better see all three planets involved. Credit: Guy Sander

Here, Guy has enlarged portions of the image to better see all three planets involved. Credit: Guy Sander

Venus and Mars were still close Sunday night Feb. 22, but they will part in the coming days as Venus moves up and Mars slides closer to the Sun. Credit: Bob King

Venus and Mars were still close Sunday night Feb. 22, but they will part in the coming days as Venus moves up and away from the Sun while Mars slides closer. Credit: Bob King

As for that fast-moving comet discovered last week and en route to the evening sky, Karl Battams, an astrophysicist and computational scientist based at the Naval Research Laboratory (NRL) in Washington DC, is right now at his computer measuring positions of the comet from photos made with the orbiting Solar and Heliospheric Observatory (SOHO).

Comet SOHO-2875 survived its close passage of the Sun and may make an appearance in the evening sky soon. This photo montage was made using the coronagraph (Sun-blocking device) on SOHO. Click to watch a movie of the comet. Credit: NASA/ESA

Comet SOHO-2875 survived its close passage of the Sun and may make an appearance in the evening sky soon. This photo montage was made using the coronagraph (Sun-blocking device) on SOHO. Click to watch a movie of the comet. Credit: NASA/ESA

Once enough positions are known, he’ll send the data off to the Minor Planet Center where a preliminary orbit will be determined. With that information I can make a nice map showing us where to look for it. Stay tuned.

Mars mystery plumes might be auroras

Mystery plume in Mars' southern hemisphere photographed by amateur astronomer Wayne Jaeschke on March 20, 2012

Mystery plume in Mars’ southern hemisphere photographed by amateur astronomer Wayne Jaeschke on March 20, 2012. The feature extended between 310-620 miles and lasted for about 10 days.

Strange plumes in Mars’ atmosphere first recorded by amateur astronomers two years ago have planetary scientists still scratching their heads.

On two occasions in 2012 amateurs photographed cloud-like features rising to altitudes of over 155 miles (250 km) above the same region of Mars. By comparison, similar features seen in the past haven’t exceeded 62 miles (100 km). Back then, no one was certain of the cloud’s nature; it was thought ice crystals or even dust whirled high into the Martian atmosphere by seasonal winds could be the cause.

Mars High-altitude_plume_on_Mars

The top image shows the location of the mysterious plume on Mars (yellow circle)  along with different views of the plume’s changing shape taken by Wayne Jaeschke and Don Parker on March 21, 2012

But a recent paper by scientist Agustin Sanchez-Lavega of the Universidad del País Vasco in Spain explores other possibilities. One problem with dust or ice is altitude – 155 miles is way, way up there where Mars’ atmosphere grazes outer space. Just how clouds could form so high is unknown.

“One idea we’ve discussed is that the features are caused by a reflective cloud of water-ice, carbon dioxide-ice or dust particles, but this would require exceptional deviations from standard atmospheric circulation models to explain cloud formations at such high altitudes,” said Agustin.

Another idea is even more intriguing. The wisps could be Martian auroras linked to regions on the surface with stronger-than-usual magnetic fields.

 

The small protrusion extending into the night sky of Mars in this 1997 Hubble photo is probably a high cloud catching sunlight. Credit: NASA/ESA

The small protrusion extending into the night sky of Mars in this 1997 Hubble photo resembles the March 2012 plumes in appearance and altitude. Credit: NASA/ESA

Once upon a very long time ago, Mars may have had a global magnetic field generated by electrical currents in a liquid iron-nickel core much like the Earth’s does today. In the current era, the Red Planet has only residual fields centered over regions of magnetic rocks in its crust.

Instead of a single, planet-wide field that funnels particles from the Sun into the atmosphere to generate auroras, Mars is peppered with pockets of magnetism, each potentially capable of connecting with the wind of particles from the Sun to spark auroras.

Mars has magnetized rocks in its crust that create localized, patchy magnetic fields (left). In the illustration at right, we see how those fields extend into space above the rocks. At their tops, auroras can sometimes form. Credit: NASA

Mars has magnetized rocks in its crust that create localized, patchy magnetic fields (left). In the illustration at right, we see how those fields extend into space above the rocks. At their tops, auroras can form. Credit: NASA

Auroras were first discovered on Mars in 2004 by the European Space Agency’s Mars Express orbiter. NASA’s MAVEN spacecraft, which has been orbiting Mars since last September, is well-equipped to study the planet’s upper atmosphere and auroras, so perhaps we’ll have a more definitive answer soon on the makeup of the mysterious plumes.

Moon meets Uranus next / Oddball comet update

Wow! What a fine photo from last night's conjunction. Venus, Mars and waxing crescent Moon over sculpture "Calling The Power" by Larry Bechtel at Vic Thomas Park. Credit: Terry Aldhizer

Wow! What a fine photo from last night’s conjunction. Venus, Mars and the waxing crescent Moon over the sculpture “Calling The Power” by Larry Bechtel at Vic Thomas Park in Roanoke, Virginia. Credit: Terry Aldhizer

Close-up of the moon, Venus, Mars gathering last night. The earthshine on the moon is amazing! Credit: Terry Aldhizer

Close-up of the moon, Venus, Mars gathering last night. The earthshine on the moon is amazing! Credit: Terry Aldhizer

We were  hopelessly cloudy for last night’s conjunction. You were luckier I hope. Don’t forget, tonight’s thicker crescent passes very close to the planet Uranus, occulting it from the far northeastern U.S. and southeastern Canada. Venus and Mars will also be in conjunction today and a smidge closer that they were yesterday evening.

Wide view of Uranus and the moon on tonight (Feb. 21)  as seen from the Midwest about an hour and a quarter after sunset. Source: Stellarium

For the Central Time Zone, Uranus will lie 0.5° west of the moon in twilight, 1° away the Mountain States and 1.5° for the West Coast. What a great opportunity to spot the 7th planet in binoculars. Not only that, but a simple time exposure with a tripod-mounted camera will easily show it. Wait till late twilight and try a range of exposures starting around 5 seconds at ISO 800 with the lens wide open to f/2.8 or 3.5.

Uranus in early twilight (left) just before its dramatic disappearance behind the earth-lit edge of the moon tonight Feb. 21 as seen from Portland, Maine. 36 minutes later Uranus emerges at the bright crescent’s edge. Both disappearance and reappearance occur in a dark enough sky to see in a small telescope. Source: Stellarium

Map showing where the occultation of Uranus by the moon will be visible. Between the white lines, it’ll be visible in a dark sky. Blue is twilight and the red dotted line is daytime. Uranus is too faint to see in the daytime sky. Click the map to get a list of disappearance and reappearance times for a variety of cities. Credit: IOTA/Occult

Most of the time the moon occults stars along its path since there are a lot more of those than planets. Because they’re so remote, stars are little more than points of light; as the moon moves over them they disappear with surprisingly suddenness. Since Uranus displays a real, measurable disk it will take a second or two to disappear behind the moon’s edge.

SOHO-8275 comet about 7 east of the Sun this morning at 9:06 a.m. (CST) this morning. Credit: NASA/ESA

SOHO-2875 comet about 7 east of the Sun this morning at 9:06 a.m. (CST) this morning. Credit: NASA/ESA

The little comet we discussed yesterday continues trekking away from the Sun after its searing encounter two days ago. SOHO-2875 still shows a short tail and hangs in there around magnitude +3.5. It reached the edge of the field of view of the Solar and Heliospheric Observatory’s C3 wide-field coronagraph this morning headed east-northeast.

Since the field of view of the coronagraph is 15°, the comet’s presently about 7° east of the Sun, too close to spot yet in twilight. Give it 4-5 more days and someone may see it in a telescope in evening twilight. As soon as an orbit becomes available I’ll put together a chart to help you find it.

New Fast-Moving Comet May Become Visible from Earth

SOHO-2875 seen SOHO's LASCO C3, wide-field coronograph called LASCO C3 at 11:02 a.m. (CST) today Feb. 20. It's already moved a good distance to the east-southeast of the Sun and still displays a short tail. Credit: NASA/ESA

SOHO-2875 seen SOHO’s LASCO C3, wide-field coronograph called LASCO C3 at 11:02 a.m. (CST) today Feb. 20. It’s already moved a good distance to the east-southeast of the Sun and still displays a short tail. Credit: NASA/ESA

A newly-discovered comet may soon make an appearance in the evening sky. Dubbed SOHO-2875, it was spotted in photos taken by the Solar and Heliospheric Observatory (SOHO) earlier this week. Astronomer Karl Battams, who maintains the Sungrazer Project website, originally thought this little comet would dissipate after its close brush with the Sun. To his and our delight, it’s now outperforming expectations. Given the comet’s rapid movement away from the Sun, we won’t have to wait long to find out whether it might be visible in a telescope.

Composite of Comet SOHO-2875 crossing the C2 coronagraph field yesterday. Credit: NASA/ESA/Barbara Thompson

Composite of Comet SOHO-2875 crossing the C2 coronagraph field yesterday. Credit: NASA/ESA/Barbara Thompson

Most sungrazing comets discovered by SOHO are members of the Kreutz family, a group of icy fragments left over from the breakup of a single much larger comet centuries ago. We know they’re all family by their similar orbits. The newcomer, SOHO’s 2,875th comet discovery, is a “non-group” comet or one that’s unrelated to the Kreutz family or any other comet club for that matter. According to Battams these mavericks appear several times a year.

Photo taken at 20:00 UT (2 pm. CST) Feb. 19 with the SOHO C2 coronagraph, a device that blocks the Sun, allowing a view of the area close by. A faint tail can be seen just below the comet's bright head. Credit: NASA/ESA

Photo taken at 20:00 UT (2 pm. CST) Feb. 19 with the SOHO C2 coronagraph, a device that blocks the Sun, allowing a view of the area close by. A faint tail can be seen just below the comet’s bright head. Credit: NASA/ESA

What’s unusual about #2,875 is how bright it is. At least for now, it appears to have survived the Sun’s heat and gravitational tides and is turning around to the east headed for the evening sky. I’m no expert but having looked at many SOHO photos over the years, I’d estimate the comet is presently about magnitude +2.5 and some 5° from the Sun. No one can say for sure whether it has what it takes to hang on, so don’t get your hopes up just yet.

We’ll be watching and waiting. I’ll have an update on SOHO-2875’s progress soon.

Spectacular fireball over Pittsburgh / Juvenile moon alert


Pittsburgh fireball February 17

A fireball meteor at least as bright as the full moon flared over the Pittsburgh region around 4:50 a.m. Eastern time Tuesday morning. The object, detected by three NASA meteor cameras, was moving at a speed of 45,000 miles per hour. Based on its brightness, NASA’s Meteoroid Environment Office estimated the object at 2 feet across with a weight of 500 pounds. Something like a very heavy TV falling out of the sky.

“I’ve seen many meteor showers and this wasn’t anything like that. Instead of crossing the upper atmosphere, this feel almost directly down and brighter than any thing I’ve ever seen of this nature,” reported John D. of Elyria, Ohio. “It looked so big that my son and I expected to hear or see an impact.”

Based on data from pictures taken by multiple cameras, an orbit for the Pittsburgh fireball could be made. Originating in the asteroid belt between Mars and Jupiter, it came a long way to get to PA.Copyright David L. Clark, prepared by NASA MEO

Based on pictures taken by multiple cameras, NASA scientists determined an orbit for the Pittsburgh fireball. Originating in the asteroid belt between Mars and Jupiter, it came a long way to get to PA. Copyright David L. Clark, prepared by NASA MEO

“The entire landscape was lit up like daytime. Startling experience. I was very fortunate to be looking out window at the time.” So wrote Robert M. of Clarion, Penn. in his report to the American Meteor Society’s fireball reporting website.

Map showing reported sightings of the fireball. To date, 125 reports have been received. Credit: AMS

Map showing reported sightings of the fireball. To date, 125 reports have been received. Credit: AMS

NASA’s cameras first spotted the meteor at an altitude of 60 miles northwest of Pittsburgh and last saw it 13 miles above Kittanning, northeast of Pittsburgh. Around 13 miles altitude, the meteoroid entered its “dark flight” phase, when the air slowed it down enough to drop in free fall.

When we see a meteor, we don’t actually see the object itself but rather a brilliant “tube” of ionized air caused by the rock’s incredibly speedy passage through the atmosphere. Once a meteoroid loses sufficient speed, it no longer has the energy to ionize or make the air glow around it and falls in dark flight.

Earth seen from the perspective of the meteoroid moments before it entered our atmosphere to become a fireball. Click to see the movie. Credit:

Earth seen from the perspective of the meteoroid moments before it entered our atmosphere to become a fireball. Click to see the movie. Credit: Copyright David L. Clark, prepared by NASA MEO

Some people heard sonic booms during the fall, a good sign that the meteoroid (what you call a meteorite before it hits the ground) fragmented and dropped pieces on the ground east of Kittanning. According to Bill Cooke of the Meteoroid Office, seismographs in the region recorded the pressure wave created by the meteoroid’s flight.

Like most meteors and meteorites, this one’s a visitor from the main asteroid belt located between Mars and Jupiter. If pieces did survive the atmosphere’s ferocity, may I be the first to welcome them to their new home.

Watch for a 1-day-old super-thin crescent moon below the duo of Venus and Mars tonight. This map shows the sky about 35 minutes after sundown. Source: Stellarium

Watch for a 1-day-old super-thin crescent moon below the duo of Venus and Mars tonight. This map shows the sky about 35 minutes after sundown. Source: Stellarium

On another note, I wanted to remind moon lovers that a very young, very thin 1-day-old moon will be visible during early twilight in the western sky this evening starting about 25 minutes after sundown.

The moon’s about about one fist held at arm’s length below the pair of Mars and Venus. Tonight’s act is a warm-up for tomorrow night’s very close gathering of the moon with the two planets. For more information on that event, click HERE.