A bright flash of light. Moments pass. Then a rumble. The ground shakes a little. It can be only one thing — thunder and lightning. Right? That’s what most residents of Eastern Michigan thought when they heard a boom just after 8 p.m. on January 16.
The only problem? It was below freezing and there was hardly a cloud in the sky. That’s not the expected environment for a thunderstorm.
Social media lit up as confused natives reported a bright blue explosion followed by ground tremors. About two hours later, the National Weather Service in Detroit announced it could “confirm the flash and boom was NOT thunder.” The most likely culprit was a meteor.
Paul Gross is a meteorologist at WDIV-TV in Detroit. It's been one of his goals to make TV meteorologists a resource for more than just covering the weather. And when “a giant meteor lit up the skies over the Detroit metropolitan area,” he says, it provided him an opportunity to do just that.
“The estimated 6-foot- [1.8-meter-] diameter space rock created a bright fireball that broke up,” he tells Science News for Students. This was due to the intense pressure, he says, “experienced as it raced through our atmosphere.” The meteor travelled at an estimated 45,000 kilometers (28,000 miles) per hour, creating a sonic “boom” that startled many people. That sound shook the ground enough, Gross says, to mimic a magnitude 2.0 earthquake.
The racing meteor’s aerial “flash was so bright that it was detected by the Geostationary Lightning Mapper,” he notes. That’s an instrument on the latest weather satellite — the National Oceanic and Atmospheric Administration’s GOES-16. Friction during the meteor’s flight through the atmosphere caused the space rock to break into pieces. Many of them, Gross notes, were large enough to be detected by the National Weather Service’s Detroit-area Doppler radar.
“Meteorite hunters immediately began searching the area where the radar showed the debris trail,” he says. And several space rocks turned up, he adds, “including one [found] by a cameraman at my television station.”
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Not just a Michigan event
People didn’t have to live in Michigan to witness these all-natural fireworks. The American Meteor Society logged 355 separate reports of a brilliant fireball streaking across the heavens. They came in from seven states. The society pored over the reported observations. It also analyzed video footage and interviewed witnesses about the booms.
Using the visible reports, scientists were able to stitch together the path these falling space rocks likely took. They concluded these must have crashed down somewhere along a line from Brighten to Howell, Mich. That’s only 50 kilometers (30 miles) northwest of Detroit.
The reason people could witness the meteor’s flight was the incredible amount of light the rock produced as it raced through the atmosphere at 11.26 kilometers (7 miles) a second. Friction against the surrounding air slowed it down, converting its energy of motion (kinetic energy) to heat energy (thermal energy) and eventually to light.
This heating becomes so intense that the rock actually began to burn up.
Most meteors, including this one, are chondrites. They are made of tiny chondrules, mineral bits containing silicon. Meteors also have a lot of iron, nickel and magnesium. The latter is the reason they appear to glow blue. Magnesium burns white, but only the blue rays penetrate to the ground.
If a meteor doesn’t totally burn up, parts of it can hit the ground. These remains are known as meteorites. But most meteors explode under the extreme heat of friction as they brush again air molecules in the atmosphere. Such an exploding space rock is known as a bolide. When a meteor transforms into a bolide, bits of the initial rock may now spread out and rain down over the surrounding countryside.
That’s where knowing about the sound becomes useful. The International Meteor Organization notes that “bangs or swishing sounds, or possibly other noises” can be linked with meteors and offer clues to whether they have shattered.
Those sounds may arrive several minutes after sighting the burning space rock. The reason? Sound travels much more slowly than light. Last week’s incoming meteor, for instance, traveled at Mach-37, according to NASA. That’s 37 times the speed of sound. That’s very fast. But the speed of light is 874,030 times the speed of sound.
On rare occasions, it’s possible to hear sound at the same time you see the meteor high in the sky. This may seem crazy, but it has to do with radio waves. Scientists have speculated that rapidly moving meteors may emit very-low-frequency (VLF) radio waves. VLF waves move at the speed of light and then interact with conducting bodies at the surface. These conducting bodies can be any structures or even the ground itself — anything that permits miniscule electrical currents to pass through. Sometimes this produces a shrill chirping sound. Similar phenomena are sometimes observed beneath an aurora. Research into such sounds is still ongoing, as the electrical structure of the atmosphere remains poorly understood.
It made the Earth quake
The 1.8-meter wide meteor would have weighed a whopping 1,000 kilograms (2,200 pounds) before it exploded. The sound of its breakup would produce a substantial shock wave through the atmospheric. Imagine throwing a rock into a pond. It would send ripples outwards in concentric rings. That’s exactly how the sound waves would have spread. That sound was so loud and Earth rattling that it tricked some people into thinking it was an earthquake.
Stephen Szulborski is a meteorologist and weather observer at Detroit Metropolitan Airport. It’s his job to take and log hourly observations of conditions on the runways. This information helps air-traffic-control teams make decisions that keep pilots and passengers safe.
“I was not expecting something so exciting to happen during my weather watch,” he says of this past January 16. Szulborski was facing south, so he only caught the meteor — which fell to the west — out of the corner of his eye. “I caught the flash,” he says. “But I didn’t think much of it because of all the planes moving around as usual.”
Then, seconds later, the building shook. That’s when he knew something big had happened. “We thought a plane had rammed the building,” he recalls.
Only later, when reviewing social media, did he realize he had seen a meteor.
The shaking was even picked up by seismometers (Size-MAH-meh-turz). These are instruments that measure the movement of Earth’s surface. They registered the seismic waves as equal to those produced by a magnitude 2.0 earthquake. The trembling ground was felt more than 70 kilometers (43 miles) away, according to the U.S. Geological Survey.
As seen from space
NOAA has a series of Geostationary Operational Environmental Series (GOES) satellites in orbit around Earth. The 16th in that series launched last November 19 from Cape Canaveral, Fla. Roughly two months into its career, GOES-16's lightning mapper accidentally witnessed the Michigan meteor’s pyrotechnics.
This instrument records lightning flashes by the light they produce high up in the clouds. The meteor illuminated the landscape so intensely that the satellite mistook this for lightning, despite there being no storms in the area.
A National Weather Service station in White Lake, Mich., runs a Doppler radar system about 35 kilometers (22 miles) from where the meteor entered the atmosphere. As the meteor broke apart, the radar beam bounced off the pieces. The returning signal tricked the radar into thinking something was there.
But the radar is “smart.” It knew the signal wasn’t from rain, snow or other precipitation. That’s because this is dual-polarization device. That means it radiates waves that alternate between horizontal and vertical orientations. These send a pulse to bounce off an object, which then returns an echo back to the radar. If more of one type of signal is returned than the other, the system can gauge something about the shape of an object.
The round, normal shapes that typically fall from clouds — raindrops, snowflakes or hail — tend to return just as many echoes from the vertical pulses as from the horizontal radar waves. But the same is not true for objects whose shape is jagged, bumpy or otherwise weird. And meteors qualify in that last category.
The White Lake radar system picked up echoes of the debris at 8:07 p.m. The beam passed through the atmosphere in slices oriented at 4.5º, 3.5º and 2.5º above the horizon, respectively. That means the beam scans for things higher up and gradually for ones lower.
The first sweep (at 4.5º) recorded 8 bizarre pixels about 3,000 meters (10,000 feet) above the ground. That was the meteor! This was near Whitmore Lake. Then one scan lower showed the debris a bit farther northwest. When the radar was set to 2.5º, one of the lowest levels, the space rock had moved much farther northwest. More importantly, this echo was more diffuse. It showed bolide debris spreading out as a spattering of broken rocks raining down from the night sky.
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A horizontal slice taken by the radar showed the trail of debris left as the meteor hurtled downward.
As morning dawned, meteorite hunters came out in force. People scanned the area furiously to claim their piece of the prize. Indeed, some meteors are worth their weight in gold — or more!
One international auctioning group offered a $20,000 prize for the first person turning in a stone weighing at least one kilogram (2.2 pounds). That may be tough, however. The force of the explosion likely dashed most stones that size to pieces. Still, dozens of people armed with metal detectors targeted the town of Hamburg as one of the most likely places to find a bit of the space rock.
The first reported findings came in on January 18. A pair of professional searchers spied two fragments on a frozen lakebed.
Jacob Nagel is a news photographer at WDIV-TV. He seized the meteor as an opportunity to teach his kids a lesson about science. They headed out to scout for space rocks with high hopes. And they were rewarded. Shockingly, they found a meteorite.
Astronomer Todd Slisher is executive director of the Sloan Museum and Longway Planetarium in Flint, Mich. “I didn’t see the meteor itself,” he reported at a news briefing. However, he added, “I have cameras at my house.” They picked up light from the meteor, putting the house in shadows. “And by using the shadows of the house, I was able to calculate the rough location of where the meteor should have come down.”
Then he turned to American Meteor Society data. This group had used all of those sighting reports to help triangulate the flight path of the meteor. “Their data matched up with my data from pictures of the house,” Slisher says. This scientist then reached out to a friend at NASA. “He clued me in to the fact that weather radar can actually show you the pieces of debris falling down after the meteor explodes.” So Slisher and his colleagues started looking at weather data. Based on where all of those data pointed them, they launched a hunt. And they quickly retrieved three meteorites that had rained down from the Tuesday night bolide.
Even with all those meteorite hunters, there may still be more space rocks left to find. Who knows? If you live in Michigan and have a free afternoon, you too might just find something “out of this world.”
(for more about Power Words, click here)
aerial Of or taking place in the air.
atmosphere The envelope of gases surrounding Earth or another planet.
aurora A light display in the sky caused when incoming energetic particles from the sun collide with gas molecules in a planet’s upper atmosphere. The best known of these is Earth’s aurora borealis, or northern lights. On some outer gas planets, like Jupiter and Saturn, the combination of a fast rate of rotation and strong magnetic field leads to high electrical currents in the upper atmosphere, above the planets’ poles. This, too, can cause auroral “light” shows in their upper atmosphere.
chondrite A stony meteorite, usually one that has chondrules — tiny embedded minerals containing silica that formed at high temperatures as droplets of molten rock and then collected and fused together.
chondrule (in geology) A type of small, rounded particle. Most are only about a millimeter (0.04 inch) in diameter. They tend to be comprised mostly of silicon-based minerals, such as olivine and pyroxene. Chondrules show up embedded in most stony meteorites, known as chondrites.
concentric A series of circles or rings that have a common center point.
debris Scattered fragments, typically of trash or of something that has been destroyed. Space debris, for instance, includes the wreckage of defunct satellites and spacecraft.
degree (in geometry) A unit of measurement for angles. Each degree equals one three-hundred-and-sixtieth of the circumference of a circle.
diameter The length of a straight line that runs through the center of a circle or spherical object, starting at the edge on one side and ending at the edge on the far side.
diffuse Spread out thinly over a great area; not concise or concentrated.
earthquake A sudden and sometimes violent shaking of the ground, sometimes causing great destruction, as a result of movements within Earth’s crust or of volcanic action.
echo To bounce back. For example, sound bouncing off walls of a tunnel, and returning to their source. Radio waves emitted above the surface can also bounce off the bedrock underneath an ice sheet — then return to the surface.
environment The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of components in some electronics system or product).
fireball A lump of rock or metal from space that hits the atmosphere of Earth. Fireballs are meteors that are exceptionally bright and large.
footage (in movies and videos) A term for the uncut or unprocessed motion pictures or video imagery taken by a camera. It takes its name from the fact that it took several feet of film to capture a few seconds of motion-picture photography.
force Some outside influence that can change the motion of a body, hold bodies close to one another, or produce motion or stress in a stationary body.
frequency The number of times a specified periodic phenomenon occurs within a specified time interval. (In physics) The number of wavelengths that occurs over a particular interval of time.
friction The resistance that one surface or object encounters when moving over or through another material (such as a fluid or a gas). Friction generally causes a heating, which can damage a surface of some material as it rubs against another.
gauge A device to measure the size or volume of something. For instance, tide gauges track the ever-changing height of coastal water levels throughout the day. Or any system or event that can be used to estimate the size or magnitude of something else. (v. to gauge) The act of measuring or estimating the size of something.
geological Adjective to describe things related to Earth’s physical structure and substance, its history and the processes that act on it. People who work in this field are known as geologists.
GOES satellite A type of weather satellite that collects images of severe storms, hurricanes, wildfires and other weather hazards in near real-time, every hour of the day. Each is “geostationary,” meaning it appears to hover permanently over the same spot on Earth’s surface. The newest version of these orbiters — GOES-16 and -17 (that last one due to launch in early 2018) — provide four times the image resolution of NOAA’s older GOES satellites, and at five times the speed.
horizontal A line or plane that runs left to right, much as the horizon appears to do when gazing into the distance.
International Meteor Organization Founded in 1988, it has more than 250 members, including amateur meteorite hunters. Members study meteor showers and their relation to comets and interplanetary dust.
iron A metallic element that is common within minerals in Earth’s crust and in its hot core. This metal also is found in cosmic dust and in many meteorites.
kinetic energy The energy held by an object due to its being in motion. The amount of this energy contained will depend on both the mass (usually weight) of the object and its speed.
lightning A flash of light triggered by the discharge of electricity that occurs between clouds or between a cloud and something on Earth’s surface. The electrical current can cause a flash heating of the air, which can create a sharp crack of thunder.
magnesium A metallic element that is number 12 on the periodic table. It burns with a white light and is the eighth most abundant element in Earth’s crust.
magnitude (in geology) A number used to describe the relative size of an earthquake. It runs from 1 to more than 8 and is calculated by the peak ground motion as recorded by seismographs. There are several magnitude scales. One of the more commonly used ones today is known as the moment magnitude. It’s based on the size of a fault (crack in Earth’s crust), how much the fault slips (moves) during a quake, and the energy force that was required to permit that movement. For each increase in magnitude, an earthquake produces 10 times more ground motion and releases about 32 times more energy. For perspective, a magnitude 8 quake can release energy equivalent to detonating 6 million tons of TNT.
meteor A lump of rock or metal from space that hits the atmosphere of Earth. In space it is known as a meteoroid. When you see it in the sky it is a meteor. And when it hits the ground it is called a meteorite.
meteorite A lump of rock or metal from space that passes through Earth’s atmosphere and collides with the ground.
meteorologist Someone who studies weather and climate events.
mineral Crystal-forming substances that make up rock, such as quartz, apatite or various carbonates. Most rocks contain several different minerals mish-mashed together. A mineral usually is solid and stable at room temperatures and has a specific formula, or recipe (with atoms occurring in certain proportions) and a specific crystalline structure (meaning that its atoms are organized in regular three-dimensional patterns).
molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
NASA Short for the National Aeronautics and Space Administration. Created in 1958, this U.S. agency has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It also has sent research craft to study planets and other celestial objects in our solar system.
National Oceanic and Atmospheric Administration (or NOAA) A science agency of the U.S. Department of Commerce. Initially established in 1807 under another name (The Survey of the Coast), this agency focuses on understanding and preserving ocean resources, including fisheries, protecting marine mammals (from seals to whales), studying the seafloor and probing the upper atmosphere.
native Associated with a particular location; native plants and animals have been found in a particular location since recorded history began. These species also tend to have developed within a region, occurring there naturally (not because they were planted or moved there by people). Most are particularly well adapted to their environment.
nickel Number 28 on the periodic table of elements, this hard, silvery element resists oxidation and corrosion. That makes it a good coating for many other elements or for use in multi-metal alloys.
phenomena Events or developments that are surprising or unusual.
pixel Short for picture element . A tiny area of illumination on a computer screen, or a dot on a printed page, usually placed in an array to form a digital image. Photographs are made of thousands of pixels, each of different brightness and color, and each too small to be seen unless the image is magnified.
polarization (in physics) The condition — or creation of a condition — in which rays of wavelengths of light exhibit different properties when viewed from different directions.
precipitation (in meteorology) A term for water falling from the sky. It can be in any form, from rain and sleet to snow or hail.
pressure Force applied uniformly over a surface, measured as force per unit of area.
pyrotechnics A term for fireworks.
radar A system for calculating the position, distance or other important characteristic of a distant object. It works by sending out periodic radio waves that bounce off of the object and then measuring how long it takes that bounced signal to return. Radar can detect moving objects, like airplanes. It also can be used to map the shape of land — even land covered by ice.
radiate (in physics) To emit energy in the form of waves.
radio waves Waves in a part of the electromagnetic spectrum. They are a type that people now use for long-distance communication. Longer than the waves of visible light, radio waves are used to transmit radio and television signals. They also are used in radar.
satellite A moon orbiting a planet or a vehicle or other manufactured object that orbits some celestial body in space.
seismic wave A wave traveling through the ground produced by an earthquake or some other means.
seismometer (also known as a seismograph ) An instrument that detects and measures tremors (known as seismic waves) as they pass through Earth.
silicon A nonmetal, semiconducting element used in making electronic circuits. Pure silicon exists in a shiny, dark-gray crystalline form and as a shapeless powder.
social media Internet-based media, such as Facebook, Twitter and Tumblr, that allow people to connect with each other (often anonymously) and to share information.
sonic Of or relating to sound.
sound wave A wave that transmits sound. Sound waves have alternating swaths of high and low pressure.
speed of light A constant often used in physics, corresponding to 1.08 billion kilometers (671 million miles) per hour.
survey (v.) To ask questions that glean data on the opinions, practices (such as dining or sleeping habits), knowledge or skills of a broad range of people. Researchers select the number and types of people questioned in hopes that the answers these individuals give will be representative of others who are their age, belong to the same ethnic group or live in the same region. (n.) The list of questions that will be offered to glean those data.
thermal Of or relating to heat. (in meteorology) A relatively small-scale, rising air current produced when Earth’s surface is heated. Thermals are a common source of low level turbulence for aircraft.
U.S. Geological Survey (or USGS) This is the largest nonmilitary U.S. agency charged with mapping water, Earth and biological resources. It collects information to help monitor the health of ecosystems, natural resources and natural hazards. It also studies the impacts of climate and land-use changes. A part of the U.S. Department of the Interior, USGS is headquartered in Reston, Va.
vertical A term for the direction of a line or plane that runs up and down, as the vertical post for a streetlight does. It’s the opposite of horizontal, which would run parallel to the ground.
wave A disturbance or variation that travels through space and matter in a regular, oscillating fashion.
weather Conditions in the atmosphere at a localized place and a particular time. It is usually described in terms of particular features, such as air pressure, humidity, moisture, any precipitation (rain, snow or ice), temperature and wind speed. Weather constitutes the actual conditions that occur at any time and place. It’s different from climate, which is a description of the conditions that tend to occur in some general region during a particular month or season.
Website: P. Gross. New information about Fireball 2018 in Metro Detroit. WDIV ClickOnDetroit. January 17, 2018.
Website: L. Colvin and H. Dudar. Meteorite hunter finds 3 rocks from Michigan meteor in Hamburg Township. Detroit Free Press. January 18, 2018.
Website: American Meteor Society Twitter