The Living Force
Meteor hunters know there’s a lot of sky to watch if you’re hoping to see what’s flying toward our planet.
Western University joined a worldwide network of researchers — using about 450 video cameras — to make sure they don’t miss any meteor showers or bits of space rock that make their way to Earth.
“People usually have a picture in their mind that there is a government agency or NASA or someone else who immediately knows what is going on when a meteor happens,” said Denis Vida, a researcher at Western who founded the global meteor network (GMN). “That’s not necessarily true.”
“They do have monitoring satellites in place, but they don’t take as accurate a measure as a camera system does. We are observing fainter meteorites,” Vida said.
Data on meteorites or showers is valuable because it can be used to help build prediction models for where they might fall next, he said.
For NASA astronauts, who may be planning a spacewalk, meteor showers could heighten the danger of injury or death, Vida said.
“A dust particle that is travelling at 20 km per second has a higher kinetic energy than a rifle bullet. So if you have a meteor shower and these particles are entering the atmosphere, we need global coverage to make sure we have guaranteed observations,” he said.
Since a meteorite fireball can drop anywhere in the world, to get the exact location and the orbit, it needs to be observed by at least two cameras in two different locations, Vida said.
Vida envisioned the GMN project when he was an undergrad in computer science and the first system was implemented at Western in 2017.
Meteorite researchers in 30 countries have joined the network.
It was only a few months ago that GMN cameras, with other meteor networks, tracked the Winchcombe meteorite, which led to the discovery of its location on Earth, Vida said.
The locations of the GMN cameras and the latest data is available at tammojan.github.io/meteormap/
More information about the project can be viewed at arXivarxiv.org/abs/2107.12335.
A bright bolide visible for several seconds
14 August, a meteor crossed the Sicilian sky
Ragusa - At about 11.30 p.m., and for an interminable number of seconds, the Sicilian sky was crossed by a very bright trail, caused by the fall of a meteorite that disintegrated on contact with the atmosphere. The phenomenon is also known in astronomy as a 'bright bolide' and has been seen in various parts of Sicily and southern Italy. In the past, such phenomena were considered auspicious signs.
“According to the calculations of NASA experts, the asteroid 2016 AJ193 will approach the Earth as close as possible to about 3.4 million kilometers on August 21. The diameter of the flying asteroid is estimated at about 1.4 kilometers, ”RIA Novosti reports the words of representatives of the Moscow Planetarium.
When we think of the solar system, we tend to think of the Sun and the nine planets that orbit it. But there’s a lot more orbiting the Sun than just planets (and dwarf planets — we see you, Pluto!)
Take asteroids, for example. Asteroids are the debris left over from the formation of the solar system. Four and a half billion years ago, our solar system was nothing more than a rotating cloud of gas and dust. When that cloud collapsed, possibly due to the shockwaves from a nearby exploding star, its enormous gravity pulled in most of the surrounding material in an event so intense that hydrogen atoms fused into helium atoms.
Ninety-nine percent of the cloud’s material became part of a huge nuclear reactor that we now call the Sun. The remaining one percent began to coalesce into planets and settle into regular orbits. But not everything managed to form something big enough to be called a planet — or even a dwarf planet. Today, most people call the bits of rock and metal that didn’t make the cut, but still orbit the Sun, asteroids. (The word ”asteroid” means ”star-like.”) You could also call them planet wannabes, but they’re more technically known as planetesimals or planetoids.
Meet Mr. SpockAccording to NASA’s latest count, there are over a million asteroids zipping around the Sun. Many are less than 10 meters across. Some are pretty big, though. The largest, Vesta, is about twice the area of the state of California. Ceres was previously the largest asteroid with a radius about a third that of our moon’s, but it got an upgrade in 2006 when it was reclassified as a dwarf planet.
When it comes to naming asteroids, the International Astronomical Union is a little more lenient than when naming other celestial objects. For proof, just look to the asteroid named Mr. Spock (actually named after a cat who was in turn named after the Star Trek character), the one named Arthurdent (after the hero from The Hitchhiker’s Guide to the Galaxy), or the one named for late rock
musician Frank Zappa. Most asteroids, however, have more sober names — like Ceres and Vesta.
The asteroid Vesta, imaged by NASA’s Dawn spacecraft. (Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA)
Heads Up!Most asteroids are found in the main asteroid belt, orbiting the Sun between Mars and Jupiter. They don’t always stay in a regular orbit, however. The effects of Jupiter’s immense gravity, combined with the ever-present possibility of crashing into other orbiting objects, can sometimes hurl asteroids out of orbit and send them careening wildly into space.
Sometimes they crash into planets. Earth has been battered by asteroids plenty of times, perhaps most famously when an asteroid crashed into the Yucatán Peninsula and created a disaster that wiped out all non-avian dinosaurs — along with three-quarters of the species on Earth.
One of the biggest asteroid impacts in human history, the Tunguska Event, is still a bit of a mystery. On the morning of June 30, 1908, an explosion ripped through the skies above the Tunguska River in Siberia. Over a hundred times stronger than the atomic bomb that destroyed Hiroshima, the explosion flattened trees and created a pressure wave and intense heat that were felt 40 miles away. However, no impact crater, nor fragments of meteorite, were ever found.
The most likely solution to the puzzle is that the asteroid itself was consumed in the explosion. In 2020, a team of Russian scientists published a study suggesting the possibility that the event was caused by shockwaves from an asteroid passing through Earth’s atmosphere (but not crashing to its surface).
Cause for Concern?Apophis, an asteroid estimated to be about 340 meters across, caused some concern when it was discovered in 2004. However, after careful study of the object’s trajectory, NASA announced this year that we’re safe from Apophis for at least the next 100 years.
How often does space debris hit Earth? According to NASA’s Jet Propulsion laboratory (JPL), our little blue marble is pelted with more than a hundred tons of dust and sand-sized bits of space debris every day. About once a year, an asteroid the size of a car slams into the atmosphere and explodes on arrival, creating some cool fireworks, before harmlessly disintegrating far from Earth’s surface. About once every two millennia, a really big one — the size of a football field — makes it to the surface and does significant damage.
It wouldn’t take something as large as the dino-killing asteroid to cause serious damage to life on Earth, including humans. Anything larger than one or two kilometers, NASA says, could have worldwide effects… and not good ones. That’s why the JPL’s Center for Near Earth Object Studies keeps an eye on any asteroids that look to be heading our way.
More information regarding the Canadian fireball that was filmed, observed and heard near Ottawa and Montreal city:
This footage is of a fireball over Germany.
South AfricaUsing the powerful 570-megapixel Dark Energy Camera (DECam) in Chile, astronomers just ten days ago discovered an asteroid with the shortest orbital period of any known asteroid in the Solar System. The orbit of the approximately 1-kilometer-diameter asteroid takes it as close as 20 million kilometers (12 million miles or 0.13 au), from the Sun every 113 days. Asteroid 2021 PH27, revealed in images acquired during twilight, also has the smallest mean distance (semi-major axis) of any known asteroid in our Solar System — only Mercury has a shorter period and smaller semi-major axis. The asteroid is so close to the Sun’s massive gravitational field, it experiences the largest general relativistic effects of any known Solar System object.
The asteroid designated 2021 PH27 was discovered by Scott S. Sheppard of the Carnegie Institution of Science in data collected by the Dark Energy Camera (DECam) mounted on the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory (CTIO) in Chile. The discovery images of the asteroid were taken by Ian Dell’antonio and Shenming Fu of Brown University in the twilight skies on the evening of 13 August 2021. Sheppard had teamed up with Dell’antonio and Fu while conducting observations with DECam for the Local Volume Complete Cluster Survey, which is studying most of the massive galaxy clusters in the local Universe . They took time out from observing some of the largest objects millions of light-years away to search for far smaller objects — asteroids — closer to home.
One of the highest-performance, wide-field CCD imagers in the world, DECam was designed for the Dark Energy Survey (DES) funded by the DOE, was built and tested at DOE’s Fermilab, and was operated by the DOE and NSF between 2013 and 2019. At present DECam is used for programs covering a huge range of science. The DECam science archive is curated by the Community Science and Data Center (CSDC). CTIO and CSDC are programs of NSF’s NOIRLab.
Twilight, just after sunset or before sunrise, is the best time to hunt for asteroids that are interior to Earth’s orbit, in the direction of the two innermost planets, Mercury and Venus. As any stargazer will tell you, Mercury and Venus never appear to get very far from the Sun in the sky and are always best visible near sunrise or sunset. The same holds for asteroids that also orbit close to the Sun.
Following 2021 PH27’s discovery, David Tholen of the University of Hawai‘i measured the asteroid’s position and predicted where it could be observed the following evening. Subsequently, on 14 August 2021, it was observed once more by DECam, and also by the Magellan Telescopes at the Las Campanas Observatory in Chile. Then, on the evening of the 15th, Marco Micheli of the European Space Agency used the Las Cumbres Observatory network of 1- to 2-meter telescopes to observe it from CTIO in Chile and from South Africa, in addition to further observations from DECam and Magellan, as astronomers postponed their originally scheduled observations to get a sight of the newly found asteroid.
“Though telescope time for astronomers is very precious, the international nature and love of the unknown make astronomers very willing to override their own science and observations to follow up new, interesting discoveries like this,” says Sheppard.
Planets and asteroids orbit the Sun in elliptical (or oval-shaped) orbits, with the widest axis of the ellipse having a radius described as the semi-major axis. 2021 PH27 has a semi-major axis of 70 million kilometers (43 million miles or 0.46 au), giving it a 113-day orbital period on a elongated orbit that crosses the orbits of both Mercury and Venus .
It may have begun life in the main Asteroid Belt between Mars and Jupiter and got dislodged by gravitational disturbances from the inner planets that drew it closer to the Sun. Its high orbital inclination of 32 degrees suggests, however, that it might instead be an extinct comet from the outer Solar System that got captured into a closer short-period orbit when passing near one of the terrestrial planets. Future observations of the asteroid will shed more light on its origins.
Its orbit is probably also unstable over long periods of time, and it will likely eventually either collide with Mercury, Venus or the Sun in a few million years, or be ejected from the inner Solar System by the inner planets’ gravitational influence.
Astronomers have a hard time finding these interior asteroids because they are very often hidden by the glare of the Sun. When asteroids get so close to our nearest star, they experience a variety of stresses, such as thermal stresses from the Sun’s heat, and physical stresses from gravitational tidal forces. These stresses could cause some of the more fragile asteroids to break up.
“The fraction of asteroids interior to Earth and Venus compared to exterior will give us insights into the strength and make-up of these objects,” says Sheppard. If the population of asteroids on similar orbits to 2021 PH27 appears depleted, it could tell astronomers what fraction of near-Earth asteroids are piles of rubble that are loosely held together, as opposed to solid chunks of rock, which could have consequences for asteroids that might be on a collision course with Earth and how we might deflect them.
“Understanding the population of asteroids interior to Earth’s orbit is important to complete the census of asteroids near Earth, including some of the most likely Earth impactors that may approach Earth during daylight and that cannot easily be discovered in most surveys that are observing at night, away from the Sun,” says Sheppard. He adds that since 2021 PH27 approaches so close to the Sun, “...its surface temperature gets to almost 500 degrees C (around 900 degrees F) at closest approach, hot enough to melt lead”.
Because 2021 PH27 is so close to the Sun’s massive gravitational field, it experiences the largest general relativistic effects of any known Solar System object. This reveals itself as a slight angular deviation in the asteroid’s elliptical orbit over time, a movement called precession, which amounts to about one arcminute per century .
The asteroid is now entering solar conjunction when from our point of view it is seen to move behind the Sun. It is expected to return to visibility from Earth early in 2022, when new observations will be able to determine its orbit in more detail, allowing the asteroid to get an official name.
Notes The Local Volume Complete Cluster Survey (LoVoCCS) is an NSF’s NOIRLab survey program that is using DECam to measure the dark matter distribution and the galaxy population in 107 nearby galaxy clusters. These deep exposures will allow a clean comparison of faint variable objects when combined with data from Vera C. Rubin Observatory.
 2021 PH27 is only one of around 20 known Atira asteroids that have their orbits completely interior to the Earth’s orbit.
 Observation of Mercury’s precession puzzled scientists until Einstein’s general theory of relativity explained its orbital adjustments over time. 2021 PH27’s precession is even faster than Mercury’s.
More informationThis research was reported to the Minor Planet Center.
NSF’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory), the US center for ground-based optical-infrared astronomy, operates the international Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (operated in cooperation with the Department of Energy’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O'odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.
The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time.
Abundant streaks of light have raced across the night sky this week during the peak of the Perseid meteor shower. The light show happens every year in mid- to late-August when Earth’s orbit intersects with the trail of debris left by Comet Swift-Tuttle.
While the Perseids and other major showers (Geminids, Orionids, and Leonids) draw the most attention, meteors are visible any time of the year, albeit at a slower rate. That’s because Earth is bombarded with heaps of dust and sand-sized particles every day. Sometimes, an object is large enough to produce a brilliantly bright spectacle known as a fireball. Fireballs are meteors that have an apparent magnitude of at least -5, making them brighter than Venus.
“More people see meteors during a shower because there are so many of them. For the Perseids, there are up to 100 meteors per hour,” said Paul Chodas, director of the Center for Near Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory. “Fireball events, on the other hand, are quite rare and can happen on any day of the year.”
Data compiled by CNEOS scientists were used to produce the map above, based on an interactive version created by Alan Chamberlin. The map shows the locations of large fireballs detected by government sensors between 1988 and 2021. The size of each dot is proportional to the impact energy (kinetic energy) of each fireball; that is, the total energy the meteoroid brought into the atmosphere due to its velocity.
As a meteoroid cruises into Earth’s atmosphere, some of its kinetic energy is converted into radiated energy—the bright optical flash detected by the sensors. The rest is converted into sound waves and energy at other wavelengths. Some goes into a blast shock wave. By observing many such events, scientists established a way to determine the total energy of an event based its optical flash. From this, scientists can derive the original size of the object before it entered Earth’s atmosphere.
Using such calculations, scientists have estimated that the asteroid that lit up the sky in February 2013 over Chelyabinsk, Russia, initially measured 20 meters across. This is by far the largest fireball in the CNEOS database, which focuses on larger fireball events. All fireballs in the database stem from asteroids measuring at least one meter across.
In contrast, the meteoroids associated with a meteor shower—the stream of debris released from a comet or asteroid—are much smaller, generally ranging from the size of a grain of sand to tens of centimeters. Fireballs associated with meteor showers are possible but infrequent. Still, some Perseids can appear quite bright.
Meteors need not be fireballs to be photogenic. NASA photographer Bill Ingalls captured this photograph of a meteor zipping across the night sky on August 11, 2021, during the peak of the Perseid shower. Ingalls shot the 30-second exposure from the summit of Spruce Mountain in West Virginia. A few thin clouds lingered, reflecting light from distant urban areas.
Notice that part of the meteor appears green. According to Bill Cooke, lead at the NASA Meteoroid Environment Office, this is due to the way the meteoroid excited oxygen molecules during its impact with the atmosphere.
Cooke also noted that the Perseid shower is especially rich in bright meteors. He points to data from NASA’s network of all-sky meteor cameras , which can detect meteors that are brighter than Jupiter. “The number of bright meteors in the Perseids dwarfs all other meteor showers—30 percent more than the Geminid shower, which has better rates and is also noted for bright meteors,” Cooke said.
The peak of the shower occurred from August 11-13, but it’s not too late to catch a glimpse of the summer phenomenon. The meteors should remain relatively abundant in the nighttime sky for a few days after the peak. Beyond that, keep looking up; you never know when a rare fireball might brighten the night or even the day.
NASA Earth Observatory image by Joshua Stevens, using data from the Center for Near Earth Object Studies/NASA/JPL-Caltech. Photograph by Bill Ingalls/NASA. Story by Kathryn Hansen.