Why We Track Asteroids Like the One That Flew by This Week


Earlier this week, on March 8, asteroid 2013 TX68 came within about 3.1 million miles of Earth, astronomers estimate. Original predictions suggested its closest approach might be within the orbits of geostationary satellites around the Earth, or it could be as far away as 9.5 million miles. Additional data changed the distance range to between 3 million and 15,000 miles. At about 100 feet in diameter, the object was too small to be seen at the 3.1 million-mile distance, but it clearly did not hit Earth.

We keep an eye on such space debris. NASA’s Center for Near-Earth Object Studies at the Jet Propulsion Laboratory in California currently tracks 13,947 near-Earth objects, defined as those coming within 130 million miles of our planet’s orbit. The center considers about 12 percent of those potentially hazardous, according to Paul Chodas, manager of the center. That means they come within 5 million miles and pose about a one in 1 billion chance of hitting Earth in the next 100 years. (TX68 isn’t one of them.)

Asteroids travel on elliptical orbits around the Sun, explains Judit Györgyey Ries, an asteroid observer and researcher at the University of Texas at Austin’s McDonald Observatory. An asteroid’s path changes slightly from the effect of gravity when it passes close to a planet or from the energy of it absorbing and emitting sunlight.

The orbit of asteroid TX68. Image credit: NASA/JPL-Caltech

The more data scientists collect on a specific asteroid, the more accurate their predictions of its path and probability of colliding with Earth. TX68 is a perfect example. It was first observed by the Catalina Sky Survey in October 2013, while approaching Earth at night. Three days later, the asteroid passed into the daytime sky and could no longer be observed. Based on those three days of data, TX68 appeared to have a four in 1 billion chance of hitting Earth.

That may sound like a long shot, but the odds were nevertheless four times higher than the threshold NASA has set for potentially hazardous objects. “That caught our attention,” Chodas says. Then Italian astronomer Marco Micheli, with the European Space Agency, noticed faint traces of the asteroid in archived telescope images, which directed a search for more archived images. Based on that additional data, TX68’s potential for impact dropped back to the more acceptable one-in-a-billion chance.

All calculations come with uncertainty, of course, and with asteroids, that uncertainty grows the farther into the future the orbit projection. At the scale of the Earth, this uncertainty equals large distances, on the order of millions of miles. (For perspective, the average distance from Earth to the Moon is about 239,000 miles.) That makes it important for scientists to continue to monitor known objects.

Now scientists know where to look for TX68 when it returns to our part of the solar system. If it turns up where expected, that will decrease uncertainty about its future orbit. If not, says Györgyey Ries, the uncertainty will grow.

Three years ago, a meteor about 60 feet wide broke up in the atmosphere over Chelyabinsk, Russia. Observers didn’t see it coming because of its small size and approach from the direction of the Sun, but the dashcam and smartphone recordings of its fiery descent and glass-shattering sound wave were subsequently seen worldwide.

Any object between about 100 and 165 feet should burn up and disintegrate in the atmosphere, Chodas says, with some small meteorites reaching the ground, as they did in Chelyabinsk. NASA mostly worries about roughly 1000 known objects measuring at least one kilometer, or about six-tenths of a mile.

NASA-funded surveys began scanning the night sky in 1998 for near-Earth objects, and about 1500 NEOs are now detected each year. The strategy, according to Chodas, is to find as many of these objects measuring 330 feet and larger as possible, to provide as much time as possible for attempts to deflect a potential impact. For example, preparations for diverting a large asteroid of 650 to 1000 feet might involve building and launching a rocket, which would take years.

“You would just have to nudge it,” Chodas says. “Presumably, we could launch as heavy a rocket as we possibly could to run into the asteroid and change its velocity slightly. A change of one meter per second would likely be enough to divert it from impact.” NASA has plans for two missions to test deflection methods.

In January, NASA announced that its NEO detection and tracking project, now called the Planetary Defense Coordination Office, will supervise all NASA-funded projects working to find and characterize asteroids and comets passing near Earth's orbit and also coordinate response to potential impact threats.

For Chodas, TX68’s fly by presented an opportunity. “We know this particular asteroid can’t impact Earth in the next 100 years,” he says. “It is more of an opportunity to remind people we are working on the problem so that, if an asteroid should be headed for Earth, we would have enough warning time, possibly decades, to do something about it.”

But as Györgyey Ries notes, “I only worry about the ones we don’t know of.” 

15 Facts About Nicolaus Copernicus

Polish astronomer and mathematician Nicolaus Copernicus fundamentally altered our understanding of science. Born in 1473, he popularized the heliocentric theory that all planets revolve around the Sun, ushering in the Copernican Revolution. But he was also a lifelong bachelor and member of the clergy who dabbled in medicine and economics. Dive in to these 15 facts about the father of modern astronomy.


Some historians believe that Copernicus's name derives from Koperniki, a village in Poland named after tradesmen who mined and sold copper. The astronomer's father, also named Nicolaus Copernicus, was a successful copper merchant in Krakow. His mother, Barbara Watzenrode, came from a powerful family of merchants, and her brother, Lucas Watzenrode the Younger, was an influential Bishop. Two of Copernicus's three older siblings joined the Catholic Church, one as a canon and one as a nun.


Growing up, Copernicus likely knew both Polish and German. When Copernicus's father died when he was around 10, Lucas Watzenrode funded his nephew's education and he started learning Latin. In 1491, Copernicus began studying astronomy, math, philosophy, and logic at Krakow University. Five years later, he headed to modern Italy's Bologna University to study law, where he likely picked up some Italian. During his studies, he also read Greek, meaning modern historians think he knew or understood five languages.


 A page from the work of Copernicus showing the position of planets in relation to the Sun.
A page from the work of Copernicus showing the position of planets in relation to the Sun.
Hulton Archive, Getty Images

Copernicus is credited with introducing heliocentrism—the idea that the Earth orbits the sun, rather than the sun orbiting the Earth. But several ancient Greek and Islamic scholars from various cultures discussed similar ideas centuries earlier. For example, Aristarchus of Samos, a Greek astronomer who lived in the 200s BCE, theorized that Earth and other planets revolved around the Sun.


To be clear, Copernicus knew of the work of earlier mathematicians. In a draft of his 1543 manuscript, he even included passages acknowledging the heliocentric ideas of Aristarchus and other ancient Greek astronomers who had written previous versions of the theory. Before submitting the manuscript for publication, though, Copernicus removed this section; theories for the removal range from wanting to present the ideas as wholly his own to simply switching out a Latin quote for a "more erudite" Greek quote and incidentally removing Aristarchus. These extra pages weren't found for another 300-some years.


He's known for math and science, but Copernicus was also quite the economist. In 1517, he wrote a research paper outlining proposals for how the Polish monarch could simplify the country's multiple currencies, especially in regard to the debasement of some of those currencies. His ideas on supply and demand, inflation, and government price-fixing influenced later economic principles such as Gresham's Law (the observation that "bad money drives out good" if they exchange for the same price; for example, if a country has both a paper $1 bill and a $1 coin, the value of the metal in the coin is higher than the value of the cotton and linen in the bill, and thus the bill will be spent as currency more because of that) and the Quantity Theory of Money (the idea that the amount of money in circulation is proportional to how much goods cost).


After studying law, Copernicus traveled to the University of Padua so he could become a medical advisor to his sick uncle, Bishop Watzenrode. Despite spending two years studying medical texts and learning anatomy, Copernicus left medical school without a doctoral degree. Nevertheless, he traveled with his uncle and treated him, as well as other members of the clergy who needed medical attention.


An etching of Copernicus, circa 1530.
An etching of Copernicus, circa 1530.
Hulton Archive, Getty Images

As an official in the Catholic Church, Copernicus took a vow of celibacy. He never married and was most likely a virgin (more on that below), but children were not completely absent from his life: After his older sister Katharina died, he became the financial guardian of her five children, his nieces and nephews.


Copernicus took a vow of celibacy, but did he keep it? In the late 1530s, the astronomer was in his sixties when Anna Schilling, a woman in her late forties, began living with him. Schilling may have been related to Copernicus—some historians think he was her great uncle—and she worked as his housekeeper for two years. For unknown reasons, the bishop he worked under admonished Copernicus twice for having Schilling live with him, even telling the astronomer to fire her and writing to other church officials about the matter.


A Polish stamp of Nicolaus Copernicus.

Copernicus spent over a decade studying at universities across Poland and Italy, but he usually left before he got his degree. Why skip the diplomas? Some historians argue that at the time, it was not unusual for students to leave a university without earning a degree. Moreover, Copernicus didn't need a degree to practice medicine or law, to work as a member of the Catholic Church, or even to take graduate or higher level courses. 

But right before returning to Poland he received a doctorate in canon law from the University of Ferrara. According to Copernicus scholar Edward Rosen this wasn't exactly for scholarly purposes, but that to "show that he had not frittered his time away on wine, women, and song, he had to bring home a diploma. That cost much less in Ferrara than in the other Italian universities where he studied."


During Copernicus's lifetime, nearly everyone believed in geocentrism—the view that the Earth lies at the center of the universe. Despite that, in the 1510s Copernicus wrote Commentariolus, or "the Little Commentary," a short text that discussed heliocentrism and was circulated amongst his friends. It was soon found circulating further afield, and it's said that Pope Clement VII heard a talk about the new theory and reacted favorably. Later, Cardinal Nicholas Schönberg wrote a letter of encouragement to Copernicus, but Copernicus still hesitated in publishing the full version. Some historians propose that Copernicus was worried about ridicule from the scientific community due to not being able to work out all of the issues heliocentrism created. Others propose that with the rise of the Reformation, the Catholic Church was increasingly cracking down on dissent and Copernicus feared persecution. Either way, he didn't make his complete work public until 1543.


An antique bookseller displays a rare first edition of Nicolaus Copernicus' revolutionary book on the planet system.
An antique bookseller displays a rare first edition of Nicolaus Copernicus' revolutionary book on the planet system, at the Tokyo International antique book fair on March 12, 2008. The book, published in 1543 and entitled in Latin "De Revolutionibus Orbium Coelestium, Libri VI," carries a diagram that shows the Earth and other planets revolving around the Sun, countering the then-prevailing geocentric theory.

Copernicus finishing writing his book explaining heliocentrism, De Revolutionibus Orbium Coelestium (On the Revolutions of Celestial Orbs), in the 1530s. When he was on his deathbed in 1543, he finally decided to publish his controversial work. According to lore, the astronomer awoke from a coma to read pages from his just-printed book shortly before passing away.


Copernicus dedicated his book to the Pope, but the Catholic Church repudiated it decades after it was published, placing it on the Index of Prohibited Books—pending revision—in 1616. A few years later, the Church ended the ban after editing the text to present Copernicus's views as wholly hypothetical. In 1633, 90 years after Copernicus's death, the Church convicted astronomer Galileo Galilei of "strong suspicion of heresy" for espousing Copernicus's theory of heliocentrism. After a day in prison, Galileo spent the rest of his life under house arrest.


Take a look at the periodic table of elements, and you might notice one with the symbol Cn. Called Copernicium, this element with atomic number 112 was named to honor the astronomer in 2010. The element is highly radioactive, with the most stable isotope having a half life of around 30 seconds.


Frombork Cathedral

Although Copernicus died in 1543 and was buried somewhere under the cathedral where he worked, archeologists weren't sure of the exact location of his grave. They performed excavations in and around Frombork Cathedral, finally hitting pay dirt in 2005 by finding part of a skull and skeleton under the church's marble floor, near an altar. It took three years to complete forensic facial reconstruction and compare DNA from the astronomer's skeleton with hair from one of his books, but archeologists were able to confirm that they had found his skeleton. Members of the Polish clergy buried Copernicus for a second time at Frombork in 2010.


The Nicolaus Copernicus Monument in Warsaw, Poland.

A prominent statue of the astronomer, simply called the Nicolaus Copernicus Monument, stands near the Polish Academy of Sciences in Warsaw, Poland. There are also replicas of this monument outside Chicago's Adler Planetarium and Montreal's Planétarium Rio Tinto Alcan. Besides monuments, Copernicus also has a museum and research laboratory—Warsaw's Copernicus Science Centre—dedicated to him.

Lawrence Livermore National Laboratory, Wikimedia Commons // CC BY-SA 3.0
7 Giant Machines That Changed the World—And 1 That Might
Lawrence Livermore National Laboratory, Wikimedia Commons // CC BY-SA 3.0
Lawrence Livermore National Laboratory, Wikimedia Commons // CC BY-SA 3.0

From a 17-mile-long particle accelerator to a football-field–sized space observatory, here are seven massive machines that have made an equally huge impact on how we build, how we observe our universe, and how we lift rockets into space. We've also included a bonus machine: a technological marvel-to-be that may be just as influential once it's completed.


Large Hadron Collider
Carlo Fachini, Flickr // CC BY-ND 2.0

The Large Hadron Collider, a particle accelerator located at CERN outside of Geneva, Switzerland, is the largest machine in the world: It has a circumference of almost 17 miles and took around a decade to build. The tubes of the LHC are a vacuum; superconducting magnets guide and accelerate two high-energy particle beams, which are moving in opposite directions, to near-light-speed. When the beams collide, scientists use the data to find the answers to some of the most basic questions of physics and the laws that govern the universe we live in.

Since the LHC started up in 2008, scientists have made numerous groundbreaking discoveries, including finding the once-theoretical Higgs boson particle—a.k.a. the "God" particle—which helps give other particles mass. Scientists had been chasing the Higgs boson for five decades. The discovery illuminates the early development of the universe, including how particles gained mass after the Big Bang. Scientists are already working on the LHC's successor, which will be three times its size and seven times more powerful.


Built in 1965, NASA's crawler-transporters are two of the largest vehicles ever constructed: They weigh 2400 tons each and burn 150 gallons of diesel per mile. In contrast, the average semi truck gets roughly 6.5 miles per gallon. The vehicles' first job was to move Saturn V rockets—which took us to the moon and measured 35 stories tall when fully constructed—from the massive Vehicle Assembly Building (the largest single-room building in the world) to the launch pad at Cape Canaveral. The 4.2-mile trip was a slow one; the transporters traveled at a rate of 1 mph to ensure the massive rockets didn't topple over. Without a vehicle to move rockets from the spot they were stacked to the launch pad, we never could have gotten off the ground, much less to the moon.

After our moon missions, the crawler-transporters were adapted to service the Space Shuttle program, and moved the shuttles from 1981 to 2003. Since the retirement of the orbiters, these long-serving machines are once again being repurposed to transport NASA's new Space Launch System (SLS), which, at 38 stories tall, will be the biggest rocket ever constructed when it's ready, hopefully in a few years (the timeline is in flux due to budgetary issues).


National Ignition Facility (NIF) target chamber
Lawrence Livermore National Security, Wikimedia Commons // CC BY-SA 3.0

Three football fields could fit inside the National Ignition Facility, which holds the largest, most energetic, and most precise laser in the world (it also has the distinction of being the world's largest optical instrument). NIF—which took about a decade to build and opened in 2009—is located at the Lawrence Livermore National Laboratory in Livermore, California. Its lasers are used to create conditions not unlike those within the cores of stars and giant planets, which helps scientists to gain understanding about these areas of the universe. The NIF is also being used to pursue the goal of nuclear fusion. If we can crack the code for this reaction that powers stars, we'll achieve unlimited clean energy for our planet.


When Seattle decided it needed a giant tunnel to replace an aging highway through the middle of the city, the city contracted with Hitachi Zosen Corporation to build the biggest tunnel boring machine in the world to do the job. The scope of Bertha's work had no precedent in modern-day digging, given the dense, abrasive glacial soil and bedrock it had to chew through.

In 2013, Bertha—named after Bertha Knight Landes, Seattle's first female mayor—was tasked with building a tunnel that would be big enough to carry four lanes of traffic (a two-lane, double-decker road). Bertha needed to carve through 1.7 miles of rock, and just 1000 feet in, the 57-foot, 6559-ton machine ran into a steel pipe casing that damaged it. Many predicted that Bertha was doomed, but after a massive, on-the-spot repair operation by Hitachi Zosen that took a year-and-a-half, the borer was up and running again.

In April 2017, Bertha completed its work, and engineers started the process of dismantling it; its parts will be used in future tunnel boring machines. Bertha set an example for what is possible in future urban tunnel work—but it's unlikely that tunnel boring machines will get much bigger than Bertha because of the sheer weight of the machine and the amount of soil it can move at once. Bertha's tunnel is scheduled to open in 2019.


international space station

The international space station is a highly efficient machine, equipped with instrumentation and life support equipment, that has kept humans alive in the inhospitable environment of low-Earth orbit since November 2, 2000. It's the biggest satellite orbiting the Earth made by humans. The major components were sent into space over a two-year period, but construction has slowly continued over the last decade, with astronauts adding the Columbus science laboratory and Japanese science module. The first module, Zarya, was just 41.2 feet by 13.5 feet; now, the ISS is 356 feet by 240 feet, which is slightly larger than a football field. The station currently has about 32,333 cubic feet of pressurized volume the crew can move about in. That's about the same area as a Boeing 747 (though much of the ISS's space is taken up by equipment). The U.S.'s solar panels are as large as eight basketball courts.

From the space station, scientists have made such important discoveries as what extended zero-G does to the human body, where cosmic rays come from, and how protein crystals can be used to treat cancer. Though NASA expects the most modern modules of the ISS to be usable well into the 2030s, by 2025 the agency may begin "transitioning" much of its ISS operations—and costs—to the private sector [PDF] with an eye on expanding the commercial potential of space.


The Laser Inferometer Gravitational-Wave Observatory (LIGO) is actually made up of four different facilities—two laboratories and two detectors located 2000 miles apart, in Hanford, Washington, and Livingston, Louisiana. The detectors, which took about five years to build and were inaugurated in 1999, are identical L-shaped vacuum chambers that are about 2.5 miles long and operate in unison. The mission of these machines is to detect ripples in the fabric of spacetime known as gravitational waves. Predicted in 1915 by Einstein's theory of general relativity, gravitational waves were entirely theoretical until September 2015, when LIGO detected them for the first time. Not only did this provide further confirmation of general relativity, it opened up entirely new areas of research such as gravitational wave astronomy. The reason the two detectors are so far from each other is to reduce the possibility of false positives; both facilities must detect a potential gravitational wave before it is investigated.


Antonov An-225 in Paramaribo
Andrew J. Muller, Wikimedia Commons // CC BY-SA 4.0

The Russians originally had a rival to the U.S. Space Shuttle program: a reusable winged spacecraft of their own called the Buran—and in the 1980s, they developed the AN-225 Mriya in order to transport it. With a wingspan the size of the Statue of Liberty, a 640-ton weight, six engines, and the ability to lift into the air nearly a half-million pounds, it's the longest and heaviest plane ever built. Mriya first flew in 1988, and since the Buran was mothballed in 1990 after just one flight (due to the breakup of the Soviet Union rather than the plane's capabilities), the AN-225 has only been used sparingly.

The monster plane has inspired new ideas. In 2017, Airspace Industry Corporation of China signed an agreement with Antonov, the AN-225's manufacturer, to built a fleet of aircraft based on the AN-225's design that would carry commercial satellites on their backs and launch them into space. Currently, virtually all satellites are launched from rockets. Meanwhile, Stratolaunch, a company overseen by Microsoft co-founder Paul Allen, is building a plane that will be wider (but not longer) than Mriya. The giant plane will carry a launch vehicle headed for low-Earth orbit.


This forward-thinking project, funded by Amazon and Blue Origin founder Jeff Bezos, focuses on reminding people about their long-term impact on the world. Instead of a traditional clock measuring hours, minutes, and seconds, the Clock of the Long Now measures times in years and centuries. The clock, which will be built inside a mountain on a plot of land in western Texas owned by Bezos, will tick once per year, with a century hand that advances just once every 100 years. The cuckoo on the clock will emerge just once per millennium. Construction began on the clock in early 2018. When this massive clock is completed—timeline unknown—it will be 500 feet high. What will be the impact of this one? Only the people of the 120th century will be able to answer that question.


More from mental floss studios