It’s no secret that planet Earth is occasionally greeted by rocks from space that either explode in our atmosphere or impact on the surface. In addition, our planet regularly experiences meteor showers whenever its orbit causes it to pass through clouds of debris in the Solar System. However, it has also been determined that Earth is regularly bombarded by objects that are small enough to go unnoticed – about 1 mm or so in size.
According to a new study by Harvard astronomers Amir Siraj and Prof. Abraham Loeb, it is possible that Earth’s atmosphere is bombarded by larger meteors – 1 mm to 10 cm (0.04 to 4 inches) – that are extremely fast. These meteors, they argue, could be the result of nearby supernovae that cause particles to be accelerated to sub-relativistic or even relativistic speeds – several thousand times the speed of sound to a fraction of the speed of light.
On Wednesday, July 24th, the people of the Great Lakes region were treated to a spectacular sight when a meteor streaked across the sky. The resulting fireball was observed by many onlookers, as well as the University of Western Ontario’s All-Sky Camera Network. This array runs across southern Ontario and Quebec and is maintained in collaboration with NASA’s Meteoroid Environment Office (MEO) at the Marshall Space Flight Center.
What is especially exciting about this event is the possibility that fragments of this meteorite fell to Earth and could be retrieved. This was the conclusion reached by Steven Ehlert at the MEO after he analyzed the video of the meteorite erupting like a fireball in the night sky. Examination of these fragments could tell astronomers a great deal about the formation and evolution of the Solar System.
Since it first formed roughly 4.5 billion years ago, planet Earth has been subject to impacts by asteroids and plenty of meteors. These impacts have played a significant role in the geological history of our planet and even played a role in species evolution. And while meteors come in many shapes and sizes, scientists have found that many become cone-shaped once they enter our atmosphere.
The reason for this has remained a mystery for some time. But thanks to a recent study conducted by a team of researchers from New York University’s Applied Mathematics Lab have figured out the physics that leads to this transformation. In essence, the process involves melting and erosion that ultimately turns meteorities into the ideal shape as they hurl through the atmosphere.
470 million years ago, somewhere in our Solar System, there was an enormous collision between two asteroids. We know this because of the rain of meteorites that struck Earth at that time. But inside that rain of meteorites, which were all of the same type, there is a mystery: an oddball, different from the rest. And that oddball could tell us something about how rocks from space can change ecosystems, and allow species to thrive.
This oddball meteorite has a name: Osterplana 65. It’s a fossilized meteorite, and it was found in a limestone quarry in Sweden. Osterplana 65 fell to Earth some 470 mya, during the Ordovician period, and sank to the bottom of the ocean. There, it became sequestered in a bed of limestone, itself created by the sea-life of the time.
The Ordovician period is marked by a couple thing: a flourishing of life similar to the Cambrian period that preceded it, and a shower of meteors called the Ordovician meteor event. There is ample evidence of the Ordovician meteor event in the form of meteorites, and they all conform to similar chemistry and structure. So it’s long been understood that they all came from the same parent body.
The collision that caused this rain of meteorites had to have two components, two parent bodies, and Osterplana 65 is evidence that one of these parent bodies was different. In fact, Ost 65 represents a so far unknown type of meteorite.
The study that reported this finding was published in Nature on June 14 2016. As the text of the study says, “Although single random meteorites are possible, one has to consider that Öst 65 represents on the order of one per cent of the meteorites that have been found on the mid-Ordovician sea floor. “It goes on to say, “…Öst 65 may represent one of the dominant types of meteorites arriving on Earth 470 Myr ago.”
The discovery of a type of meteorite falling on Earth 470 mya, and no longer falling in our times, is important for a couple reasons. The asteroid that produced it is probably no longer around, and there is no other source for meteorites like Ost 65 today.
The fossil record of a type of meteorite no longer in existence may help us unravel the story of our Solar System. The asteroid belt itself is an ongoing evolution of collision and destruction. It seems reasonable that some types of asteroids that were present in the earlier Solar System are no longer present, and Ost 65 provides evidence that that is true, in at least one case.
Ost 65 shows us that the diversity in the population of meteorites was greater in the past than it is today. And Ost 65 only takes us back 470 mya. Was the population even more diverse even longer ago?
The Earth is largely a conglomeration of space rocks, and we know that there are no remnants of these Earthly building blocks in our collections of meteorites today. What Ost 65 helps prove is that the nature of space rock has changed over time, and the types of rock that came together to form Earth are no longer present in space.
Ost 65 was found in amongst about 100 other meteorites, which were all of the same type. It was found in the garbage dump part of the quarry. It’s presence is a blemish on the floor tiles that are cut at the quarry. Study co-author Birgen Schmitz told the BBC in an interview that “It used to be that they threw away the floor tiles that had ugly black dots in them. The very first fossil meteorite we found was in one of their dumps.”
According to Schmitz, he and his colleagues have asked the quarry to keep an eye out for these types of defects in rocks, in case more of them are fossilized meteorites.
Finding more fossilized meteorites could help answer another question that goes along with the discovery of Ost 65. Did the types and amounts of space rock falling to Earth at different times help shape the evolution of life on Earth? If Ost 65 was a dominant type of meteorite falling to Earth 470 mya, what effect did it have? There appear to be a confounding number of variables that have to be aligned in order for life to appear and flourish. A shower of minerals from space at the right time could very well be one of them.
Whether that question ever gets answered is anybody’s guess at this point. But Ost 65 does tell us one thing for certain. As the text of the study says, “Apparently there is potential to reconstruct important aspects of solar-system history by looking down in Earth’s sediments, in addition to looking up at the skies.”
Every now and then we look up and see bright fiery balls falling from the sky. Don’t panic, these are just bolides. Sometimes they leave trails, sometimes they explode, and sometimes they survive all the way to the ground.
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.
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.
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.
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.
“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:
Shooting the night sky from an area filled with canyons and towering trees might sound like a challenge, but Gavin Heffernan and his crew at Sunchaser Pictures have “majestically” succeeded with this new timelapse from Kings Canyon and Sequoia National Parks in California. They spent three days and two nights around the summer solstice, covering the 1,353 square miles of the two parks. They captured gorgeous night sky views, star trails, bright meteor streaks, and satellite passes — all framed by the magnificent landscape of the area.
“It was undoubtedly one of the most beautiful places I’ve ever seen, with incredible canyons, mountains, and vistas out of a fantasy novel,” Gavin told UT via email. “Far removed from any light pollution, the skies were equally stunning, with some epic milky ways, star trails, and the brightest meteor picture I’ve ever captured.” Image above — and see the new timelapse video below, with the meteor trails coming at 1:41 & 2:26:
Gavin said most night shots were captured with 25 second exposures on two Canon EOS 6D’s with a variety of wide, fast lenses, including a 24mm f1/4 and 28mm f1/8. The stunning star trails effect is created by tracing rotations of the Earth’s axis, using long exposures.
Find out more about this video on Vimeo and you can watch a “behind the scenes” video of what it took to make this video — including an encounter with a brown bear! — here.
At any given moment, it seems, the sky is sizzling with celestial phenomena waiting to be stumbled upon. New research using the Long Wavelength Array (LWA), a collection of radio dishes in New Mexico, found quite the surprise. Fireballs — those brilliant meteors that leave behind glowing streaks in the night sky — unexpectedly emit a low radio frequency, hinting at new unexplored physics within these meteor streaks.
The LWA keeps its eyes to the sky day and night, probing a poorly explored region of the electromagnetic spectrum. It’s one of only a handful of blind searches carried out below 100 MHz.
Over the course of 11,000 hours, graduate student Kenneth Obenberger from the University of New Mexico and colleagues found 49 radio bursts, 10 of which came from fireballs.
Most of the bursts appear as large point sources, limited to four degrees, roughly eight times the size of the full Moon. Some, however, extend several degrees across the sky. On January 21, 2014, a source left a trail covering 92 degrees in less than 10 seconds (see above). The end point continued to glow for another 90 seconds.
The only known astrophysical object with this ability is a fireball. So Obenberger and colleagues set out to see if NASA’s All Sky Fireball Network had detected anything at the same location and time as the bursts.
While the network shares only a portion of the sky with the LWA, the fireballs seen in this direction matched fireballs caught by NASA. Additionally, most bursts did occur directly after the peak of a bright meteor shower.
The fireballs detected here are extremely energetic, traveling with an average velocity of 68 km/s, near the upper end of the meteorite velocity spectrum (from 11 km/s to 72 km/s).
They can be seen in the radio due to radio forward scattering. When fast-moving meteoroids strike Earth’s atmosphere they heat and ionize the air in their path. The luminous ionized trails reflect radio waves. During a meteor shower these waves can not only be picked up by vast arrays, such as the one in New Mexico, but by your TV and AM/FM radio transmitter.
Whereas most fireballs have been detected well over 100 MHz, “we’ve discovered that they also produce a low frequency pulse,” says Obenberger’s PhD advisor, Gregory Taylor.
This pulse is telling us something about the physical conditions in the plasma created by the meteor. “It could be cyclotron radiation (emitted from moving charges in a magnetic field), or perhaps some sort of plasma wave leakage from the trail, or maybe something completely different,” says Obenberger. “It’s too early to tell at the moment.”
Meteors come in a range of energies and sizes. So investigating this unexpected signature further will yield new insights into the interaction between meteors and our atmosphere.
“This is just the beginning,” says Taylor. “Now we have to put this new technique to use — find out more about the spectrum of the pulse and the meteors that produce it. It’s an entirely new way of looking at meteors and how they interact with our atmosphere.”
If you’re curious what’s currently emitting radio waves in the New Mexico sky check out the LWA’s live radio cam.
The paper was published in Astrophysical Journal Letters today and is available for download here.
So how were the ‘Cams’ by you? Based on a few reports via e-mail and my own vigil of two and a half hours centered on the predicted maximum of 2 a.m. CDT (7 UT) Saturday morning the Camelopardalid meteor shower did not bring down the house. BUT it did produce some unusually slow meteors and (from my site) one exceptional fireball with a train that lasted more than 20 minutes.
I saw 10 meteors in all, most of them slow and colorful with orange and yellow predominating. My hopes were high when the shower started with a bang. At 12:34 CDT, a brilliant, very slow moving meteor flashed below Polaris at about magnitude -1. A prominent train glowed many seconds after burnout and continued to show for more than 20 minutes in the camera and telescope. At low magnification in my 15-inch reflector (37-cm) the persistent glow looked like a brand new sausage-shaped diffuse nebula in Cassiopeia.
Trains form when a meteoroid’s hypersonic velocity through the upper atmosphere ionizes the air along the object’s path. When the atoms return to their rest states, they release that pent up energy as a glowing streak of light that gradually fades. The train in the photos expands and changes shape depending on the vagaries of upper atmospheric winds. Absolutely fascinating to watch.
Most activity occurred between 12:30 and 2 a.m. for my time zone in the U.S. Midwest. Surprisingly, the action dropped off around 2 and stayed that way until 3. I did get one ‘farewell Cam’ on that last look up before turning in for the night.
The team working with Gianluca Masi at the Virtual Telescope Projectreported a number of bright meteors as well but no storm. We share several of their photos here. As more information comes in, please drop by for a more complete report. You can also check out Dirk Ross’s Latest Worldwide Meteor News for additional first hand reports.
Before signing off for the moment, I’d like to ask your help in explaining a strange phenomenon I saw while out watching and photographing the shower. Around 1 a.m. I looked up and noticed a comet-like streak about 15-degrees long drifting across northern Leo. My first thought was meteor train – a giant one – but then I noticed that the center of the streak was brighter and contained a starlike object that moved in tandem with the wispy glow. I quickly took a couple pictures as the streak traveled north and expanded into a large, nebulous ray that persisted for about 1o minutes. There were no other clouds in the sky and the aurora was not active at the time.
Can anyone shed light on what it was??
UPDATE: According Mike McCants, satellite tracking software developer, the plume is fuel dump connected to the launch of a new Japanese mapping satellite. One never knows sometimes what the night has in store.