Meteors Archives

August 31, 2016May 5, 2019 by Matt Williams

On The Origin Of Phobos’ Groovy Mystery

Mars’ natural satellites – Phobos and Deimos – have been a mystery since they were first discovered. While it is widely believed that they are former asteroids that were captured by Mars’ gravity, this remains unproven. And while some of Phobos’ surface features are known to be the result of Mars’ gravity, the origin of its linear grooves and crater chains (catenae) have remained unknown.

But thanks to a new study by Erik Asphaug of Arizona State University and Michael Nayak from the University of California, we may be closer to understanding how Phobos’ got its “groovy” surface. In short, they believe that re-accretion is the answer, where all the material that was ejected when meteors impacted the moon eventually returned to strike the surface again.

Naturally, Phobos’ mysteries extend beyond its origin and surface features. For instance, despite being much more massive than its counterpart Deimos, it orbits Mars at a much closer distance (9,300 km compared to over 23,000 km). It’s density measurements have also indicated that the moon is not composed of solid rock, and it is known to be significantly porous.

(a) Spacecraft image of Phobos (photo credit: ESA/Mars Express) showing the observed catena of interest (red arrows); (b) reimpact map for a primary impact at Grildrig, azimuth ?? [0: ) rendered in three dimensions. Relative sizes and orientations between a and b are similar and may be correlated from Drunlo, Clustril, Grildrig, Gulliver and Roche craters, respectively. From the correlation, the highlighted catena likely originates from sesquinary ejecta from Grildrig. — *Image of Phobos showing the observed catena of interest (left) and reimpact map for a primary impact at Grildrig (right). Credit: ESA/Mars Express*

Because of this proximity, it is subject to a lot of tidal forces exerted by Mars. This causes its interior, a large portion of which is believed to consist of ice, to flex and stretch. This action, it has been theorized, is what is responsible for the stress fields that have been observed on the moon’s surface.

However, this action cannot account for another common feature on Phobos, which are the striation patterns (aka. grooves) that run perpendicular to the stress fields. These patterns are essentially chains of craters that typically measure 20 km (12 mi) in length, 100 – 200 meters (330 – 660 ft) in width, and usually 30 m (98 ft) in depth.

In the past, it was assumed that these craters were the result of the same impact that created Stickney, the largest impact crater on Phobos. However, analysis from the Mars Express mission revealed that the grooves are not related to Stickney. Instead, they are centered on Phobos’ leading edge and fade away the closer one gets to its trailing edge.

For the sake of their study, which was recently published in Nature Communications, Asphaug and Nayak used computer modeling to simulate how other meteoric impacts could have created these crater patterns, which they theorized were formed when the resulting ejecta circled back and impacted the surface in other locations.

*Image showing the Stickney crater (left) and how ejecta from an impact can form patterns (right) and crater chains (catenae). Credit: ESA/DLR/FU Berlin-Neukum*

As Dr. Asphaug told Universe Today via email, their work was the result of a meeting of minds that spawned an interesting theory:

“Dr. Nayak had been studying with Prof. Francis Nimmo (of UCSC), the idea that ejecta could swap between the Martian moons. So Mikey and I met up to talk about that, and the possibility that Phobos could sweep up its own ejecta. Originally I had been thinking that seismic events (triggered by impacts) might cause Phobos to shed material tidally, since it’s inside the Roche limit, and that this material would thin out into rings that would be reaccreted by Phobos. That still might happen, but for the prominent catenae the answer turned out to be much simpler (after a lot of painstaking computations) – that crater ejecta is faster than Phobos’ escape velocity, but much slower than Mars orbital velocity, and much of it gets swept up after several co-orbits about Mars, forming these patterns.”

Basically, they theorized that if a meteorite stuck Phobos in just the right place, the resulting debris could have been thrown off into space and swept up later as Phobos swung back around mars. Thought Phobos does not have sufficient gravity to re-accrete ejecta on its own, Mars’ gravitational pull ensures that anything thrown off by the moon will be pulled into orbit around it.

Once this debris is pulled into orbit around Mars, it will circle the planet a few times until it eventually falls into Phobos’ orbital path. When that happens, Phobos will collide with it, triggering another impact that throws off more ejecta, thus causing the whole process to repeat itself.

The streaked and stained surface of Phobos. (Image: NASA) — *The streaked and stained surface of Phobos, with the Stickney crater shown in the center. Credit: NASA/JPL/Mars Express*

In the end, Asphaug and Nayak concluded that if an impact hit Phobos at a certain point, the subsequent collisions with the resulting debris would form a chain of craters in discernible patterns – possibly within days. Testing this theory required some computer modeling on an actual crater.

Using Grildrig (a 2.6 km crater near Phobos’ north pole) as a reference point, their model showed that the resulting string of craters was consistent with the chains that have been observed on Phobos’ surface. And while this remains a theory, this initial confirmation does provide a basis for further testing.

“The initial main test of the theory is that the patterns match up, ejecta from Grildrig for example,” said Asphaug. “But it’s still a theory. It has some testable implications that we’re now working on.”

In addition to offering a plausible explanation of Phobos’ surface features, their study is also significant in that it is the first time that sesquinary craters (i.e. craters caused by ejecta that went into orbit around the central planet) were traced back to their primary impacts.

The many faces of Mars inner moon, Phobos (Credit: NASA) — *Mosaic of space images showing the many “faces” of Mars inner moon, Phobos. Credit: NASA*

In the future, this kind of process could prove to be a novel way to assess the surface characteristics of planets and other bodies – such as the heavily cratered moons of Jupiter and Saturn. These findings will also help us to learn more about Phobos history, which in turn will help shed light on the history of Mars.

“[It] expands our ability to make cross-cutting relationships on Phobos that will reveal the sequence of geologic history,” Asphaug added. “Since Phobos’ geologic history is slaved to the tidal dissipation of Mars, in learning the timescale of Phobos geology we learn about the interior structure of Mars”

And all of this information is likely to come in handy when it comes time for NASA to mount crewed missions to the Red Planet. One of the key steps in the proposed “Journey to Mars” is a mission to Phobos, where the crew, a Mars habitat, and the mission’s vehicles will all be deployed in advance of a mission to the Martian surface.

Learning more about the interior structure of Mars is a goal shared by many of NASA’s future missions to the planet, which includes NASA’s InSight Lander (schedules for launch in 2018). Shedding light on Mars geology is expected to go a long way towards explaining how the planet lost its magnetosphere, and hence its atmosphere and surface water, billions of years ago.

Further Reading: Nature Communications

August 12, 2016 by Bob King

Perseid Meteor Shower Briefly Storms, Still Has Legs

A brilliant Perseid meteor streaks along the Summer Milky Way as seen from Cinder Hills Overlook at Sunset Crater National Monument—12 August 2016 2:40 AM (0940 UT). It left a glowing ion trail that lasted about 30 seconds. The camera caught a twisting smoke trail that drifted southward over the course of several minutes. — A brilliant Perseid meteor streaks along the Summer Milky Way as seen from Cinder Hills Overlook at Sunset Crater National Monumen at 2:40 a.m. (9:40 UT) August 12. It left a glowing ion trail that lasted about 30 seconds. The camera caught a twisting smoke trail that drifted southward over the course of several minutes. Credit: Jeremy Perez

The Perseid meteor shower must have looked fantastic from 10,000 feet. That’s how high you would have had to go to get past the pervasive fog and overcast skies at my home last night. Tonight looks a little better for weather, so I’ll do what all hopeful amateurs astronomers do. Set the alarm for 2 a.m. and peek out the shade looking for those glimmers of starlight that indicate clear skies.

A composite photo, made from images taken last night August 11-12 from the UK, captures multiple Perseids. Credit: Peter Greig

From observations reported as of mid-afternoon to the International Meteor Observers 2016 Perseids Quick-Look site, it appears the greatest activity or highest meteor counts happened over Europe and points east in two outbursts: a brief but intense display around 23:15 Universal Time (6:15 p.m. CDT in daylight) August 11 when some observers briefly saw up to 15 Perseids a minute (!) with many bright ones, and a second peak starting around 2:00 UT (9 p.m. CDT) and lasting till 5:00 UT (midnight CDT).

90+ Perseid meteors captured on video August 11-12, 2016 by Ohio amateur John Chumack

While Europeans clearly hit the jackpot — some observers calling it the best since the 2002 Leonid storm — U.S. observers varied in their meteor counts. A few thought the shower was a bust, others reported numbers more typical of an “average year” shower. It appears that Earth passed through a dense filament of comet dust while it was night in Europe but late afternoon in the Americas. C’est la vie météore!

We should be past peak by today, but experience shows that tonight should still be a very good time for Perseid watching. Indeed, the next few nights will reward skywatchers with at least a dozen an hour. I’ll be out watching and hopefully not imagining what’s happening 10,000 feet over my head. Good luck to you too!

August 9, 2016 by David Dickinson

Get Ready for the 2016 Perseids

Out camping under the August sky? The coming week gives us a good reason to stay up late, as the Perseid meteor shower graces the summer sky. An ‘old faithful’ of annual meteor showers, the Perseids are always sure to produce.

The 2016 Perseids present a few challenges, though persistent observers should still see a descent show. The Perseids are typically active from July 17^th to August 24^th, with the peak arriving this year right around 13:00 to 15:30 Universal Time on Friday, August 12^th. This will place the radiant for the Perseids high in the sky after local midnight for observers in the northern Pacific, though observers worldwide should be vigilant over the next week. Meteor showers don’t read predictions and prognostications, and an arrival of the peak just a few hours early would place North America in the cross-hairs this coming Friday. The Perseids typically produce an average Zenithal Hourly Rate of 60-200 per hour, and the International Meteor Organization predicts a ZHR of 150 for 2016.

Looking to the northeast from latitude 50 degrees north at 1AM local on the morning of August 12th. Image credit: Stellarium.

The nemesis of the 2016 is the Moon, which reaches Full on August 18^th, six days after the shower’s peak. The time to start watching this shower is now, before the waxing Moon becomes a factor. The farther north you are, the earlier the Moon sets this week:

Moonset on the evening of August 11/12^th:

Latitude versus Moonset ( in local daylight saving time)

20 degrees north – 1:30 AM

30 degrees north – 1:14 AM

40 degrees north – 0:56 AM

50 degrees north – 0:30 AM

Early morning is almost always the best time to watch any meteor shower, as the Earth-bound observer faces in to the meteor stream head on. The December Geminids only recently surpassed the Perseids in annual intensity in the past few years.

The orientation of the Earth's shadow versus, the Sun, Moon and the radiant of the Perseids at the start of the projected peak on August 12th. Image credit: Orbitron. — The orientation of the Earth’s shadow versus the Sun, Moon and the radiant of the Perseids at the start of the projected peak on August 12th. Image credit: Orbitron.

The radiant of the Perseids drifts through the constellations of Cassiopeia, Perseus and Camelopardalis from late July to mid-August. The Perseids could just as easily have received the tongue-twisting moniker of the ‘Cassiopeiaids’ or the ‘August Camelopardalids.’ The source of the Perseids is comet Comet 109P/Swift-Tuttle discovered by Lewis Swift and Horace Tuttle in 1862. Comet Swift-Tuttle reached perihelion on 1992, and visits the inner solar system once again in 2126.

The Perseids are also sometimes referred as the “Tears of Saint Lawrence” who was martyred on a hot grid iron on August 10th, 258 AD.

The Perseids have been especially active in recent decades, following the perihelion passage of Comet Swift-Tuttle. Meteor showers come and go. For example, the Andromedids were a shower of epic storm proportions until the late 19^th century. We have records of the Perseids back to 36AD, but on some (hopefully) far off date, the debris path of Comet Swift-Tuttle will fail to intersect the Earth’s orbit annually, and the Perseids will become a distant memory. During previous years, the Perseids exhibited a peak of ZHR= 95 (2015), 68 (2014), 110 (2013), 121 (2012) and 58 (2011). Keep in mind, the Perseids have also sometimes displayed a twin peak during previous years, as well.

An early snapshot of the activity for the 2016 Perseids. image credit: The International Meteor Organization. — An early snapshot of the activity for the 2016 Perseids. Image credit: The International Meteor Organization.

Observing the Perseids

The best instrument to observe the Perseids with is a pair of old fashioned, ‘Mk-1 eyeballs.’ Simply lay back, warm drink in hand, and watch. Remember, the quoted ZHR is an ideal rate that we all strive for, though there are strategies to maximize your chances of catching a meteor. Watching early in the morning when the radiant rides highest (around sunrise in the case of the Perseids), seeking out dark skies, and enlisting a friend to watch in an opposite direction can raise your hourly meteor count.

Keep a pair of binoculars handy to examine any persistent glowing trains and lingering smoke trails from bright fireballs. Monitoring the FM band for the pings of accompanying radio meteors can add another dimension to an observation session. The ionized trail of a meteor can very occasionally reflect the signal of a distant radio station, bringing it through clear for a few seconds before fading out.

@Astroguyz I wasn’t aiming for #Perseid images, wanted to grab Milky Way shots and it sneaked into one of the frames pic.twitter.com/BuGE8xrsVH

— irv (@irvb) August 9, 2016

Also, keep an ear out for an even stranger phenomenon, as bright meteors are sometimes accompanied by a hissing or crackling sound. Long thought to be a psychological phenomenon, a team of Japanese astronomers managed to catch recordings of this strange effect during the 1988 Perseid meteors.

Imaging meteors is also pretty straight forward. Simply tripod mount a DSLR with a wide field lens, take some test exposures of the sky to get the ISO, f-stop and exposure combination just right, and begin taking exposures 30 seconds to five minutes long. An intervalometer can automate the process, freeing you up to kick back and watch the show.

Got science? Be sure to send those meteor counts into the International Meteor Organization (IMO) and watch their live updated graph as the shower progresses.

Also, be sure to tweet those meteor sightings to #Meteorwatch.

June 13, 2016July 21, 2016 by Evan Gough

Mammals Were Already Flourishing When The Axe Fell On The Dinosaurs

It's long been thought that a giant asteroid, which broke up long ago in the main asteroid belt between Mars and Jupiter, eventually made its way to Earth and led to the extinction of the dinosaurs. New studies say that the dinosaurs may have been facing extinction before the asteroid strike, and that mammals were already on the rise. Image credit: NASA/JPL-Caltech

It’s an apocryphal image. The ignorant faces of the dinosaurs, roaring helplessly at their fate, and looking skyward as an asteroid plunged to Earth. And the sneaky, clever little mammals coming out of their hiding holes to take their rightful place. If you grew up reading about this version of things, you’re not alone.

The line of reasoning says that mammals were present during the dinosaur’s reign, but their potential to thrive was suppressed by the dinosaurs, which were supremely evolved to dominate conditions on Earth at the time. It took the extinction of the dinosaurs to allow mammals to flourish. But according to new studies, that might not have been the case. As it turns out, mammals may have been well on their way to displacing the dinos long before the Chicxulub meteor hastened the dinosaur’s demise.

One such study, from researchers at the Universities of Southampton and Chicago, focused on hundreds of fossilized mammal teeth. As you know if you’ve been paying attention to how you eat, different teeth have different purposes. Carnivores have sharp teeth designed to rip and shred flesh, while herbivores have duller teeth for grinding up vegetation. Omnivores, like us, have a bit of both. That’s a simplification, of course, but its generally true.

What this study showed is that mammals with varied diets began to appear 10 to 20 million years before the dinosaurs were extinguished. It focused on early therian mammals, which are the ones that gave rise to the modern marsupials (ones with pouches) and placentals (ones where a fetus is carried inside the uterus). The third class of mammal, monotremes, were egg-laying mammals like the platypus.

In recent years, more and more early mammal fossils have been discovered, and they show that mammals were well on their way to diversifying long before the dinosaurs disappeared. The mammal fossil record also shows that mammal diversity suffered from the meteor strike, but mammals recovered and diversified into a greater number of species in the new conditions.

Another study, by Manabu Sakamoto and Chris Venditti from the University of Reading, and by Michael Benton from the University of Briston, shows that the opposite is true for dinosaurs. For tens of millions of years before their extinction, dinosaur species were becoming extinct and new species were not taking their place. This made the dinosaurs more vulnerable to extinction, whereas the diversifying mammals were in a better position to thrive, regardless of dinosaur extinction.

The main threat posed by the asteroid strike was the climate change that followed it. With greater species diversity in place immediately preceding the strike, mammals had a greater probability to survive the changing climate than did their dinosaur counterparts.

Evolutionary biologist and co-author of the study, Dr. Chris Venditti, told BBC News, “The current widespread view is that dinosaurs were reigning strong right up to the impact that hit the Earth – and it’s the impact that drove their final extinction,” he said. “And while that’s certainly true, what we found was that they were on the decline long before that.”

This image shows a very faint circular outline of the Chicxulub crater, site of the asteroid strike that finished off the dinosaurs. After 65 million years, it is barely visible. Image: NASA/JPL

“If they were reigning strong perhaps they would have fared much better than they did,” said Venditti. Dinosaurs had been around for 160 million years and had faced pressures and had dips in their diversity before.

This begs the question, why were dinosaurs in decline?

It likely all revolves around the environmental conditions. At the dawn of the dinosaurs 230 million years ago, Earth was a warm, lush place. Not just near the equators, but all the way to the poles. And there was one single continent, called Pangaea. But it’s the nature of things to change, and change it did.

The climate cooled, the sea level changed, and the dinosaurs were facing new environmental pressures. And as the record shows, the dinosaurs were losing species faster than they could replace them. Chicxulub was more than they could recover from.

Study co-author Mike Benton also talked to the BBC about this study. He said, “World climates were getting cooler all the time. Dinosaurs rely on quite warm climates and mammals are better adapted to the cold.”

“So there might have been a switch over in any case without the asteroid impact.”

Looking back on the older narrative, that the asteroid strike wiped out the dinosaurs, and mammals took their place and became dominant, it looks a little simplistic. But it has a nice narrative hook, and there is the matter of the cataclysmic asteroid strike, which no doubt had a huge effect on life on Earth, any way you want to slice it.

It’s possible that had the asteroid not struck, or had struck a few million years earlier or later, Earth would be a much different place. Perhaps we would not be here, and maybe intelligent dinosaurs would be in our place.

We’ll never know, of course, but it’s a fun narrative.

May 21, 2016June 13, 2016 by Evan Gough

Massive 400 Ft. Tsunamis On Ancient Mars

An artist's impression of the ancient Martian ocean. When two meteors slammed into Mars 3.4 billion years ago, they triggered massive, 400 ft. tsunamis that reshaped the coastline. Image: ESO/M. Kornmesser, via N. Risinger

About 3.4 billion years ago, (according to a new study) when the Late Heavy Bombardment had ended, and the first cells resembling prokaryotes were appearing on Earth, two enormous meteoroids slammed into the ancient, frigid ocean on Mars. These impacts generated massive 400 ft. high tsunamis that reshaped the shoreline of the Martian ocean, leaving behind fields of sediments and boulders.

It was long thought that ancient Mars had oceans. Sedimentary deposits discovered in the Martian north by radar in 2012 helped make the case for Martian oceans. 3.4 billion years ago, this ocean covered most of the Northern Martian lowlands. It’s thought that the ocean itself was fed by catastrophic flooding, perhaps fuelled by geothermal activity on Mars at the time.

These catastrophic tsunamis would have dwarfed most Earthly disasters. Waves 120 meters high would have swamped landmarks like the Statue of Liberty (93 m. high), and caused enormous destruction along the Martian coastline. If the research behind this new study stands up to scrutiny, then it will help prove the existence of the ancient Martian ocean.

The blue area in the above image is thought to be the location of a primordial ocean Mars. Image: NASA/JPL-Caltech/GSFC - Public Domain — The blue area in the above image is thought to be the location of a primordial ocean Mars. Image: NASA/JPL-Caltech/GSFC – Public Domain

The Martian surface shows the remains of an ancient ocean. In some areas, radar data shows a layer of water-borne sediment on top of a layer of volcanic rock. There’s also evidence of a shoreline, described by some scientists as being like a bathtub ring. The problems is, the shoreline can’t be seen everywhere it should be.

The tsunami hypothesis helps explain this missing shoreline.

According to the new study, led by Alexis Rodriguez, a Mars researcher at the Planetary Science Institute in Tucson Arizona, the tsunamis would have wiped away portions of the coastline, and left behind fields of sediment and boulders, and large backwash channels cut into the Martian surface.

The study is focussed on a specific region on Mars where a highland feature called Arabia Terra abuts the Chryse Planitia lowlands. This area was part of the shoreline of the Martian ocean. In that area, the team behind the study identified two separate geological formations that they say were created by two separate tsunami events.

The top image shows the shoreline of the ancient Martian shoreline at two separate times. The bottom images show debris left behind by the two tsunamis. Image: Alexis Rodriguez.

The first formation, and older of the two, looks every bit like a disturbed shoreline. An enormous wave washed over the beach, and in its wake deposited boulders over 10 meters across. Then, as the water drained back down into the ocean, it cut large backwash channels through its debris and boulder field.

A sequence of zoomed in images of the Martian surface in the study. A shows distances and elevations of backwash channels. B shows some of the channel-scoured, north-sloping highland mesas in blue. C shows the channelled surface, and D shows them in closer detail. Finally, E is zoomed in to show boulders as much as 10 m. in diameter. (Yellow bars are 10m.) Image: A,B:MOLA Science Team, MSS, JPL, NASA. C,D,E: NASA/JPL/University of Arizona — A sequence of zoomed in images of the Martian surface in the study. (A) shows distances and elevations of backwash channels. (B) shows some of the channel-scoured, north-sloping highland mesas in blue. (C) shows the channelled surface, and (D) shows them in closer detail. Finally, (E) is zoomed in to show boulders as much as 10 m. in diameter. (Yellow bars are 10m.) Image: A,B:MOLA Science Team, MSS, JPL, NASA. C,D,E: NASA/JPL/University of Arizona

Then, some time passed. Millions of years, probably, until the second meteor hit, triggering another enormous tsunami. But this one behaved a little differently.

Conditions on Mars had changed by then, with temperatures dropping, and glaciers marching across the landscape, gouging out deep valleys on the surface of Mars. When the second tsunami hit the shore, its effect was different.

This time, the tsunami was more like an icy slurry, according to the team. Because of the cold temperatures, the icy water froze in place in some areas, before it could wash back into the ocean. The result? Deposits of frozen debris formed in dense lobes on the surface.

This long lobe of dark material on the surface of Mars was left behind when a tsunami of icy slush washed over the Martian coastline, freezing in place before it could wash back into the sea. Image: Alexis Rodriquez — This long lobe of dark material on the surface of Mars was left behind when a tsunami of icy flush washed over the Martian coastline, freezing in place before it could wash back into the sea. Image: Alexis Rodriquez

But according to Rodriguez, this is just a snapshot of a process that likely occurred multiple times in the history of Mars. Successive meteors could have caused successive mega-tsunamis that would have repeatedly wiped away evidence of a shoreline. This could have happened as often as every 3 million years.

This study isn’t the knockout blow that proves the existence of a Martian ocean in ancient times. But it is certainly intriguing, and is a reasonable hypothesis that explains missing shorelines.

Rodriguez intends to keep looking for other evidence of tsunamis on the Martian surface. If he finds more, it will help make the case for the meteor-tsunami explanation.

Rodriguez will also be visiting places on Earth that are analogues for the Martian surface of ancient times. This summer he plans on visiting high-altitude, cold, alpine lakes in Tibet, where he hopes to learn something about the processes and geological formations involved.

Even better would be a mission to Mars, to sample the area where the tsunamis came ashore. A group of small craters near the shore that were drenched by the tsunamis is of particular interest to Rodriguez and his team. Martian ocean water could have been trapped there for millions of years. This site could provide evidence about the briny nature of the ancient ocean on Mars, and possibly tell us something about the evolution of life there.

May 17, 2016May 22, 2016 by Jason Major

Super Bright Fireball Spotted Across U.S. Northeast

Bright meteor captured on a webcam in Portsmouth, New Hampshire on May 17, 2016. Via www.portsmouthwebcam.com

It came from outer space—literally! On Tuesday, May 17, 2016, the early morning sky briefly lit up with the brilliant flash of a fireball—that is, an extremely bright meteor—over much of eastern New England states and even parts of southeastern Canada.

The event, which occurred around 12:50 a.m. EDT (04:50 UTC), was reported by witnesses from Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut, New York, Ontario, and Québec, and captured on several automated cameras like a webcam in Portsmouth, NH (seen above) and a police dashcam in Plattsburgh, NY (below).

The fireball appeared to be moving from southwest to northeast and for some witnesses created an audible sonic boom, heard (and felt) several minutes later.

See more videos of this event from local news stations WMTW and WGME (Maine) and WMUR (New Hampshire) and from the Ogunquit police department on Twitter.

Meteors are the result of debris in space rapidly entering Earth’s upper atmosphere, compressing the air and causing it to quickly release energy in the form of heat and optical light. If the entering object is massive enough it may violently disintegrate during its fall, creating both light and sound. This particular meteor technically classifies as a bolide, due to its brightness, eruption, and visible fragmentation. Learn more about the various types of meteors here.

No reports of a meteorite impact at ground level have been made although I must assume there will be individuals who go on the hunt—meteorite fragments, especially those associated with witnessed events, can be quite valuable.

Full-frame image of the May 17, 2016 fireball from Portsmouth, NH (www.portsmouthwebcam.com) — *Full-frame image of the May 17, 2016 meteor from Portsmouth, NH* (portsmouthwebcam.com)

Did you witness the event or capture it on camera? Report your sighting of this or any other fireballs on the AMS site and be sure to send your fireball videos or images to the American Meteor Society here.

Source: American Meteor Society

Added May 18: here’s a beautiful video of the same bolide captured from Saint-Jacques-le-Mineur, Québec by Dany Bilodeau (ht to Massimo on Twitter)

May 4, 2016 by Bob King

2016 Eta Aquarid Meteor Shower Peaks May 5-6

A bright Eta Aquarid earthgrazer streaks across the northern lights in May 2013. Credit: Bob King

The Eta Aquarid meteor shower peaks shortly before dawn on Friday and Saturday mornings. The radiant lies in Aquarius near the star Eta. Diagram: Bob King, source: Stellarium — The Eta Aquarid meteor shower peaks shortly before dawn on Thursday and Friday mornings. The radiant lies in Aquarius near the star Eta. Diagram: Bob King, source: Stellarium

Itching to watch a meteor shower and don’t mind getting up at an early hour? Good because this should be a great year for the annual Eta Aquarid (AY-tuh ah-QWAR-ids) shower which peaks on Thursday and Friday mornings May 5-6. While the shower is best viewed from tropical and southern latitudes, where a single observer might see between 25-40 meteors an hour, northern views won’t be too shabby. Expect to see between 10-15 per hour in the hours before dawn.

Most showers trace their parentage to a particular comet. The Perseids of August originate from dust strewn along the orbit of comet 109P/Swift-Tuttle, which drops by the inner solar system every 133 years after “wintering” for decades just beyond the orbit of Pluto.

Photo of Haley's Comet crossing the Milky Way, taken by the Kuiper Airborne Observatory in New Zealand on April 8th/9th, 1986. Credit: NASA — Halley’s Comet crossing the Milky Way, taken by the Kuiper Airborne Observatory in New Zealand on April 8-9, 1986. Credit: NASA

The upcoming Eta Aquarids have the best known and arguably most famous parent of all: Halley’s Comet. Twice each year, Earth’s orbital path intersects dust and minute rock particles strewn by Halley during its cyclic 76-year journey from just beyond Uranus to within the orbit of Venus.

Our first pass through Halley’s remains happens this week, the second in late October during the Orionid meteor shower. Like bugs hitting a windshield, the grains meet their demise when they smash into the atmosphere at 147,000 mph (237,000 km/hr) and fire up for a brief moment as meteors. Most comet grains are only crumb-sized and don’t have a chance of reaching the ground as meteorites. To date, not a single meteorite has ever been positively associated with a particular shower.

A bright, earthgrazer Eta Aquarids streaks across Perseus May 6, 2013. Because the radiant is low for northern hemisphere observers, earthgrazers - long, bright meteors that come up from near the horizon and have long-lasting trails. Credit: Bob King — A bright, earthgrazing Eta Aquarid streaks across Perseus and through the aurora on May 6, 2013. Because the radiant is low for northern hemisphere observers, earthgrazers – long, bright meteors that come up from near the horizon and have long-lasting trails. Credit: Bob King

The farther south you live, the higher the shower radiant will appear in the sky and the more meteors you’ll spot. A low radiant means less sky where meteors might be seen. But it also means visits from “earthgrazers”. These are meteors that skim or graze the atmosphere at a shallow angle and take many seconds to cross the sky. Several years back, I saw a couple Eta Aquarid earthgrazers during a very active shower. One other plus this year — no moon to trouble the view, making for ideal conditions especially if you can observe from a dark sky.

From mid-northern latitudes the radiant or point in the sky from which the meteors will appear to originate is low in the southeast before dawn. At latitude 50° north the viewing window lasts about 1 1/2 hours before the light of dawn encroaches; at 40° north, it’s a little more than 2 hours. If you live in the southern U.S. you’ll have nearly 3 hours of viewing time with the radiant 35° high.

At some personal peril, I grabbed a photo of snow in the headlights while driving home in a recent storm. Meteors in a meteor shower appear to radiate from a point in the distance in identical fashion. Photo: Bob King — Meteors in a meteor shower appear to radiate from a point in the distance in identical fashion to the way snow or rain radiates from a point in front of your car when you’re driving. Credit: Bob King

Grab a reclining chair, face east and kick back for an hour or so between 3 and 4:30 a.m. An added bonus this spring season will be hearing the first birdsong as the sky brightens toward the end of your viewing session. And don’t forget the sights above: a spectacular Milky Way arching across the southern sky and the planets of Mars and Saturn paired up in the southwestern sky.

Meteor shower members can appear in any part of the sky, but if you trace their paths in reverse, they’ll all point back to the radiant. Other random meteors you might see are called sporadics and not related to the Eta Aquarids. Meteor showers take on the name of the constellation from which they originate.

Aquarius is home to at least two showers. This one’s called the Eta Aquarids because it emanates from near the star Eta Aquarii. An unrelated shower, the Delta Aquarids, is active in July and early August. Don’t sweat it if weather doesn’t cooperate the next couple mornings. The shower will be active throughout the weekend, too.

Happy viewing and clear skies!

December 8, 2015December 22, 2015 by Bob King

Viewing Guide to the 2015 Geminid Meteor Shower

A brilliant Geminid flashes below Sirius and Orion over Mount Balang in China. Credit: NASA/Alvin Wu

2015 looks like a fantastic year for the Geminids. With the Moon just 3 days past new and setting at the end of evening twilight, conditions couldn’t be more ideal. Provided the weather cooperates! But even there we get a break. With a maximum of 120 meteors per hour, the shower is expected to peak around 18:00 UT (1 p.m. EST, 10 a.m. PST) December 14th, making for two nights of approximately equal activity: Sunday night Dec. 13-14 and Monday night Dec. 14-15. Continue reading “Viewing Guide to the 2015 Geminid Meteor Shower”

November 18, 2015December 23, 2015 by David Dickinson

Hunting Unicorns: Is an Alpha Monocerotid Outburst Due in 2015?

What’s rarer than a unicorn? Perhaps, its spying a a elusive meteor outburst from the heart of one…

Ready for more meteor shower action? Thus far this season, we’ve covered the Orionids, Taurid fireballs, and the Leonid meteors…

Up for one more? Well, this week’s offering is a bit chancy, but we ‘may’ be in for a minor outburst from a usually quiescent shower. On any given year, the Alpha Monocerotid meteors wouldn’t rate a second look.

A confirmed 2014 Alpha Monocerotid. Image credit: The United Kingdom Meteor Observation Network (UKMON)

First, however, a caveat is in order. Meteor showers never read prognostications and often prove to be fickle, and wild card meteor storms doubly so.

Not to be confused with the straight up Monocerotids which peak in early December, the Alpha Monocerotids are moderately active from November 15th through the 25^th, with a soft peak on the 22^nd. And though the radiant derives its name from the brightest star in the rambling constellation of Monoceros the Unicorn, the radiant is actually located at its peak at right ascension 7 hours 46 minutes and declination +00 degrees 24 minutes, just across the border in the constellation Canis Minor.

The Alpha Monocerotids have a curious history. They first caught the keen eye of observers in 1925, when F.T. Bradley watching from rural Virginia noted 37 meteors over a 13 minute span. In the 20^th century, small outbursts seemed to ply the skies around November 22^nd on the fifth year of each decade, with brief outbursts seen in 1935 and 1985. NASA astronomer and SETI Institute research scientist Peter Jenniskens predicted a 1995 outburst, and as predicted, a brief 30 minute display greeted members of the Dutch Meteor Society based under dark skies in southern Spain. The shower had a brief 5-minute climax in 1995, with an extrapolated zenithal hourly rate of 420.

6AM local radiant. image credit — The location of the Alpha Monocerotid meteor shower radiant at 6AM local from about 30 degrees latitude north. Image credit: Stellarium

Prospects for the shower in 2015

As of this writing, a major outburst from the Alpha Monocerotids isn’t predicted for 2015… but you just never know. It’s always worth watching for an outburst on the night of November 21/22^nd, especially in years ending in five.

In 2015, the Moon phase for the night of Saturday/Sunday November 21^st/22^nd is waxing gibbous and about 79% illuminated and setting at around 1:00 AM local, putting it safely out of view.

The predicted peak for the 2015 Alpha Monocerotids is centered on 4:25 UT/11:25 PM EST as per the International Meteor Organization (IMO), favoring western European longitudes in a similar fashion as 1995 at dawn on Sunday, November 22^nd.

Thus far, the source comet for the Alpha Monocerotids remains a mystery, though a prime contender is Comet C/1943 W1 van Gent-Peltier-Daimaca. Discovered during the Second World War, this comet has an undefined long period orbit, and reached perihelion 0.87 AU from the Sun on January 12^th, 1944.

Jenniskens notes that orbital configurations of Jupiter and Saturn may play a role in the long term modification of meteor streams such as the Alpha Monocerotids. A fascinating discussion on predicting meteor outbursts and the evolution of meteor streams by Mr Jenniskens can be read here.

The stream seems to have a very brief burst of activity of less than an hour, reminiscent of the elusive January Quadrantids. The Alpha Monocerotid radiant sits highest in the sky at around 4 AM local, and the incoming speed of the meteors is a very respectable 65 kilometers a second, making for brief swift trails.

Meteor Watching and Reporting

But beyond just observing, many sky watchers choose to log what they see and report it. Meteor shower streams—especially obscure ones such as the Alpha Monocerotids—are often poorly understood, and observers provide a valuable service by counting and reporting the number of meteors seen over a particular period of time.

Imaging meteors is as simple as setting up a DSLR on a tripod for wide angle shots, and taking repeated exposures of the sky. We generally take a few test shots to get the ISO/f-stop mix just right for the current sky conditions, then set our intervalometer to take repeated 30-second exposures while we visually observe. Aim about 45 degrees away from the radiant to catch meteors in profile, and check the camera lens periodically for morning dew. We generally keep a hair dryer handy to combat condensation under moisture-laden Florida skies.

Maybe a vigil for an Alpha Monocerotid outburst is an exercise in hunting unicorns… but watching an outburst would be an unforgettable sight. Perhaps, the Alpha Monocerotid stream is on the wane in the 21^st century… or a new outburst is still in the wings, waiting to greet dawn residents of the Earth.

November 13, 2015December 23, 2015 by Nancy Atkinson

‘Explody’ Taurid Meteors Produce Persistent Trains

A bright Taurid meteor falls over Deadfall Basin, near the base of Mount Eddy in California. Credit and copyright: Brad Goldpaint.

“The landscape was just at the verge of trying to silently explode with vibrant colors of red, gold and oranges,” said photographer Brad Goldpaint as he described the autumn view during his hike to Deadfall Basin in California to set up his cameras to try and capture a few Taurid meteors.

But the landscape wasn’t the only thing about to explode.

Later that night Brad captured a few “exploding” meteors that produced what are called persistent trains: what remains of a meteor fireball in the upper atmosphere as winds twist and swirl the expanding debris.

Brad created a time-lapse video from the event and slowed down the footage to highlight the trains.

Persistent trains have been difficult to study because they are rather elusive. But lately, with the widespread availability of ultra-fast lenses and highly sensitive cameras, capturing these trains is becoming more common.

Phil Plait still has the best description out there of what happens when persistent trains are produced:

As a meteoroid (the actual solid chunk of material) blasts through the air, it ionizes the gases, stripping electrons from their parent atoms. As the electrons slowly recombine with the atoms, they emit light — this is how neon signs glow, as well as giant star-forming nebulae in space. The upper-level winds blowing that high (upwards of 100 km/60 miles) create the twisting, fantastic shapes in the train.

The consensus among our Universe Today Flickr pool photographers who posted images of the Taurids this year is that the 2015 Taurids weren’t entirely remarkable. Most astrophotgraphers reported they saw one or two per hour. Here are a few more Taurid meteor shower images from our photographer friends: