A hidden star catalog on an ancient manuscript attributed to Hipparchus
Credit: Early Manuscripts Electronic Library/Lazarus Project, University of Rochester

Scholars studying Biblical texts have made an almost unimaginable find—fragments of a lost star catalog compiled by the ancient astronomer Hipparchus. Hipparchus’s work represents the earliest known project to catalog the entire night sky. The find is an example of a palimpsest—a manuscript that has been written over with other writings. The discovery was announced in the fall of 2022. 

The lost fragments were discovered by researchers examining a text taken from the library of St. Catherine’s Monastery, a Greek Orthodox monastery on the Sinai peninsula in Egypt. That text was written during the Middle Ages, a period of history that lasted form about the 400’s through the 1400’s. 

The text was written not on paper, but on a specially prepared animal skin called parchment. However, parchment and other materials could be rare in the Middle Ages. For this reason, scribes sometimes scraped the surface of the parchment, clearing the page for a new manuscript. In many cases, the scraped away writing can still be detected, forming a type of hidden manuscript called a palimpsest. 

In 2012, a biblical scholar asked his college students to study the text beneath the manuscript, hoping to find earlier Christian writings. But one student spotted an astronomical passage often attributed to the ancient Greek mathematician Eratosthenes. 

In 2017, researchers at the University of Rochester in New York analyzed the pages using multi-spectral imaging. They took 42 photos of each page at various wavelengths of light. A computer algorithm then combined the various images to search for hidden markings. The researchers discovered myths about the stars’ origins compiled by Eratosthenes, along with a poem about the constellations. 

During the COVID-19 pandemic, the house-bound scholar passed the time re-examining the images. He was surprised to find what appeared to be stellar coordinates, numbers that can be used to measure the position of a star in the night sky.  

Using radiocarbon dating, the coordinates were determined to be written in the 400’s or 500’s A.D. However, the way they were written suggested that they might have been copied from Hipparchus. Moreover, astronomers know that the stars appear to change position over time due to a wobble in Earth’s axis, an effect called precession. The coordinates were so detailed that scholars could thus determine that they were taken in 129 B.C., during Hipparchus’s life. 

The oldest surviving star catalog comes from a work called the Almagest by the astronomer Ptolemy, compiled in the 100’s A.D. Hipparchus’s earlier catalog is mentioned in ancient sources. But with no surviving evidence, it was thought to be lost forever or even never to have existed. 

The new discovery sheds an amazing light on Hipparchus’s work. Compiled nearly 2,000 years before the invention of the telescope, his catalog would have required countless hours of measurement with a sighting tube or a device called an armillary sphere. For now, only a few fragments remain, but scientists hope that they will help to identify other fragments of Hipparchus’s work in other manuscripts. 

The first image of Sagittarius A*, the supermassive black hole at the center of our galaxy.
Credit: © EHT Collaboration

Finally, the faceless monster lurking at the center of our galaxy has been photographed. Sounds like science fiction? It’s true! On Thursday, May 12, scientists with the Event Horizon Telescope (EHT) team published a photograph of Sagittarius A* (saj uh TAIR eeuhs AY star). Sagittarius A* is a supermassive (huge) black hole in the center of our galaxy, the Milky Way.

A black hole is a region of space whose gravitational force is so strong that nothing can escape from it, not even light. The event horizon is the “point of no return” for a black hole: Anything that crosses this horizon is sucked into the black hole forever. Supermassive black holes at least a million times more massive than the sun lurk at the center of many galaxies.

The EHT is a global network of ground-based telescopes that use a technique called radio interferometry to produce images of black hole event horizons. The collection of radio telescopes participating in the EHT project stretches from Hawaii to Europe and all the way south to Antarctica. Several dozen of the world’s leading observatories and universities contribute to the project. Supercomputers process the image data using special algorithms in a process called correlation.

Astronomers began using the EHT to make observations of Sagittarius A* in 2017. In 2019, the EHT released an image it had captured of the event horizon surrounding the supermassive black hole at the center of the Messier 87 galaxy (M87*). It was the first time an event horizon had been photographed.

If light can’t escape a black hole, how did EHT photograph M87* or Sagittarius A*? Technically, it didn’t: all black holes are invisible and cannot be directly photographed. But matter trapped in orbit near the event horizon is extremely energized and emits large amounts of light. The black hole lurks in the circular “shadow” within the halo of high-energy matter. Thus, the EHT can take a picture of a black hole much as we can take a picture of a doughnut hole.

Despite being closer to Earth, Sagittarius A* was still harder to image than M87*. Sagittarius A* is still 27,000 light-years from Earth. It’s also more than 1,000 times smaller and less massive than M87*. So, although the high-energy matter is orbiting both black holes at about the same speed, the matter completes an orbit around Sagittarius A* in a matter of minutes. Furthermore, Sagittarius A* is “quieter”: it emits far less energy than M87*. All these factors made it difficult for EHT to capture an image of it.

Now that EHT has imaged two black holes, astronomers can compare them. Both look remarkably similar, despite their differing sizes. Both confirm what was predicted by Einstein’s theory of relativity. But plenty of questions remain. For example, are the “blobs” in the picture actual elements, or are they artifact of the correlating process? The EHT is also considering the feasibility of creating a short video of Sagittarius A* by stringing together multiple consecutive images. And plenty more supermassive black holes are waiting for their photographic debut. A major observation campaign that concluded earlier this year featured even more telescopes. Expect more exciting results soon regarding these most extreme objects in the universe.

An image of Venus, made with data recorded by Japan’s Akatsuki spacecraft in 2016, shows swirling clouds in the planet’s atmosphere.
Credit: PLANET-C Project Team/JAXA

Venus is heating up—figuratively, that is. It has always been the hottest planet in the solar system, with surface temperatures of about 870 °F (465 °C). But new findings from the mysterious planet have been pouring in. Soon, a new generation of space probes will transform Venus from a sleepy solar system backwater to a bustling hub of scientific discovery.

Venus is the second planet from the sun. It is known as Earth’s “twin” because the two planets are so similar in size. The diameter of Venus is about 7,520 miles (12,100 kilometers). This diameter is about 400 miles (640 kilometers) smaller than that of Earth. No other planet comes nearer to Earth than does Venus. At its closest approach, it is about 23.7 million miles (38.2 million kilometers) away.

But Venus is better described as Earth’s evil twin, in respect to its withering conditions. In addition to the high temperatures, the atmospheric pressure is 90 times greater than that on Earth. Carbon dioxide makes up most of the atmosphere. The skies are strewn with clouds of sulfuric acid.

Scientists sent several probes to learn more about the planet in the 1960’s and 1970’s. But as space agencies learned of its inhospitable conditions, they concentrated their efforts elsewhere, particularly Mars. The last United States National Aeronautics and Space Administration (NASA) mission to study Venus, called Magellan, launched in 1990. Thus, scientists know relatively little about Venus, despite its close proximity to Earth and its similar size.

Despite the dearth of missions in recent years, planetary scientists continue to scan the planet with Earth-based instruments and reanalyze older data. They have returned surprising results.

Last year, a team of scientists announced that they had discovered a gas called phosphine in Venus’s atmosphere. Many living things on Earth produce phosphine; and scientists have not been able to identify any non-biological processes on Venus that might produce it. This raised the possibility that microbial life could exist in Venus’s atmosphere, where the conditions are much milder. But the discovery has been controversial. Other teams have failed to find any phosphine signature.

Last month, a team led by researchers at Queen’s University Belfast left the floating-Venusian-microbes idea high and dry. They found that Venus’s atmosphere does not contain enough water vapor to support life, irrespective of the presence of phosphine. The team determined that even the most extreme microbes on Earth require an environment with dozens of times more water than is available in Venus’s atmosphere.

Another recent study has shed light onto possible changing of Venus’s surface. Previously, Earth was the only rocky planet known to have a moving surface. A team lead by Paul Byrne, a professor at North Carolina State University, found evidence that parts of Venus’s surface might be slowly moving today. Earth’s crust slowly reshapes itself by a process called plate tectonics. Large pieces of the surface, called plates, subduct (sink) under one another, forming mountain ranges and other features. New crust forms along the ridges where the plates pull away from each other. In contrast, Byrne’s team found that pieces of Venus’s crust move like pack ice in polar oceans. Learning more about crust movement on Venus will help scientists understand how such processes develop on other planets, including Earth and exoplanets that might harbor life.

Last month, space agencies announced that not one, but three missions will be exploring Venus in the next 15 years. On June 2, NASA announced it is sending two mission to Venus. The missions were selected as part of part of NASA’s lower-cost Discovery Program. NASA expects to launch both missions between 2028 and 2030.

VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) will orbit the planet and map its surface with greater detail than ever before. It will allow scientists to better understand the planet’s features.

DAVINCI+ (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) consists of a sphere that will plunge through Venus’s thick atmosphere, studying the atmosphere’s composition. The DAVINCI+ mission planners are seeking evidence of an ocean of water that might have covered Venus’s surface eons ago.

There are other players in the new Venus boom. Last year, American company Rocket Lab announced plans to launch a small probe to Venus as early as 2023. And on June 10, just over a week after NASA’s selection DAVINCI+ and VERITAS, the European Space Agency (ESA) announced that it would also be sending a probe Venus. The EnVision orbiter will search for signs of current and former tectonic activity and the presence of a past ocean. EnVision is scheduled to arrive at Venus in 2034 or 2035.

The desire to learn more about Venus is fed by more than just curiosity about our nearest neighbor. Astronomers are looking for signs of life on exoplanets. But Venus and Earth would look quite similar from light-years away. Learning more about Venus and how it evolved to become so different from Earth will help astronomers better weed out Venus-like exoplanets in their search for ones that are more like Earth.

The dish of Arecibo Observatory’s radio telescope lies heavily damaged following the collapse of the instrument platform on Dec. 1, 2020.
Credit: © estadespr, Shutterstock

The year 2020 claimed yet another victim, with the destruction of one of the most impressive telescopes ever built—the radio telescope at Arecibo Observatory. Already damaged beyond repair, the remaining cables that held the telescope’s instrument platform snapped on December 1, sending the platform crashing through the dish below. It was a spectacular and disappointing end to a telescope that has done so much to further our understanding of the universe.

The radio telescope was the primary instrument at the observatory, located in Puerto Rico, 50 miles (80 kilometers) west of San Juan. A radio telescope collects and measures radio waves given off by objects in space. At 1,000 feet (305 meters) in diameter, the Arecibo radio telescope was the world’s most powerful when it opened in 1963. It remained the largest dish (bowl-shaped reflector) in the world until 2016, when the dish of the Five-hundred-meter Aperture Spherical radio Telescope (FAST) was completed in Guizhou Province, China.

The Arecibo dish was built into a natural basin-shaped valley. The dish focused radio waves onto receivers mounted on the large instrument platform suspended above. The waves came from such distant objects as pulsars (rapidly spinning stars whose waves arrive on Earth as regular pulses). Arecibo astronomers discovered the first binary pulsar (a pulsar in orbit around a companion star) in 1974. In the early 1990′s, astronomers at the observatory discovered planets beyond the solar system and ice at the poles of Mercury. Until the middle of 2020, astronomers were using the radio telescope for a variety of astronomical observations, including monitoring and assessing the threat level of near-Earth asteroids.

The Arecibo Observatory radio telescope as it appeared before its collapse in 2020. The instrument platform (top center) crashed through the dish on December 1.
Credit: © Than Tibbetts, Shutterstock

The impressive appearance of the massive dish surrounded by the lush, forested hills of Puerto Rico’s interior seemed particularly to capture the public imagination. The radio telescope appeared in the sci-fi motion picture Contact (1997) and the James Bond film GoldenEye (1995), for example.

The final collapse of the telescope began in August 2020, when an auxiliary cable that held the instrument platform broke. The falling cable tore several large gashes in the dish. In November, before engineers had a chance to repair the dish or replace the cable, a main support cable broke. The United States National Science Foundation (NSF) quickly determined that the telescope could no longer be saved without putting lives at risk. The NSF was considering plans to decommission the telescope—taking it permanently out of service—when the collapse occurred.

The future of the Arecibo Observatory appears doubtful. The U.S. Congress could direct funds to replace the telescope, but it may be more likely that the facility will be closed permanently.

In 1975, scientists engaged in the search for extraterrestrial intelligence used the dish from the Arecibo telescope to beam a powerful signal into space. This signal was designed by astronomer Frank Drake with the help of famous science popularizer Carl Sagan to give any intelligent being who discovers it information about Earth and humans. Encoded within the message was an image of the dish itself. Although it is unlikely that any alien civilizations will receive the message, it serves a lasting monument to the telescope’s legacy.

January 8, 2020

Late last year, on Dec. 18, 2019, the European Space Agency (ESA) launched the CHEOPS telescope into space, where it will study the composition of exoplanets. Exoplanets, or extrasolar planets, orbit stars other than our sun. The CHEOPS telescope was launched aboard a Russian-made Soyuz rocket from the Guiana Space Center on the northern coast of South America. CHEOPS—pronounced KAY ops—is an acronym for Characterizing Exoplanets Satellite. If the acronym sounds familiar, Cheops was also the Greek name of the ancient Egyptian king Khufu, who constructed the Great Pyramid at Giza.

A Soyuz rocket carrying the ESA’s CHEOPS telescope lifts off from the Guiana Space Center on Dec.18, 2019. Credit: ESA/S. Corvaja

CHEOPS is small for a satellite, measuring just 5 feet (1.5 meters) long. The craft turns within a polar orbit that allows it to fly between night and day. Its back, covered in solar panels, receives continuous sunshine, while the telescope and camera on the other side is always peering into dark, sunless, and limitless space.

This artist’s impression shows CHEOPS with its back to the sun and the telescope pointed into dark space. Credit: ESA/C. Carreau

The CHEOPS mission is not to discover new exoplanets, but rather to learn more about the exoplanets we already know exist. CHEOPS will study exoplanets larger than our own Earth but smaller than the planet Neptune. Scientists want to know if these intermediate sized exoplanets are more like “super-Earths”—large rocky worlds—or “mini-Neptunes”—small gas giants. By studying an exoplanet’s atmosphere, diameter, mass, and other properties, CHEOPS can determine its composition and whether or not it might be able to support life. Astronomers have discovered over 4,000 exoplanets so far, but there are likely hundreds of billions more to be found.

CHEOPS will use the transit method to study exoplanets. It will aim its camera at a star and capture periodic dips in the star’s light output. These dips occur when an exoplanet passes in front of—or transits—a star in relation to CHEOPS’s point of view.

CHEOPS is a stepping stone between the first exoplanet observatories, such as Kepler and COROT, and the powerful observatories of the near future. The United States National Aeronautics and Space Administration (NASA) James Webb Space Telescope (JWST), scheduled for launch in 2021, will be able to determine the gases present in the atmospheres of some exoplanets and even record low detail images of those gases. The European Southern Observatory’s Extremely Large Telescope (ELT) will also be able to image rocky exoplanets and characterize their atmospheres after it is completed in 2025. The ELT is a ground-based observatory being built in the Atacama Desert of northern Chile. Kepler and COROT prepared the way for CHEOPS, and the JWST and ELT will further examine the most promising CHEOPS targets as scientists continue the hunt for extraterrestrial life.

September 28, 2018

A recently rediscovered letter from Italian  astronomer  Galileo (1564-1642) shows his careful wording to try to avoid persecution during the Inquisition, an effort by the Roman Catholic Church to seek out and punish heretics—that is, people who held beliefs that differed from the accepted beliefs of the church. In the letter—found in a London library where the letter was misplaced decades ago—Galileo states his arguments against the church’s mistaken doctrine that the Sun orbits Earth.

A rediscovered letter by the famous Italian astronomer and physicist Galileo shows he tempered his comments to try to avoid persecution by the Roman Catholic Church. Credit: Uffizi Gallery, Florence, Italy (Art Resource)

The seven-page letter, written to a friend in 1613 and signed G.G. in Galileo’s own hand, helps solve a mystery that has surrounded the astronomer ever since the Roman Catholic Church condemned him for heresy in 1633. The letter shows that Galileo knew he may have dangerously provoked powerful enemies in the church and that he worked to contain the potential fallout.

Galileo Galilei is one of the most significant figures in the history of western scientific thought. In 1609, Galileo built his first telescope. Turning it to the sky, he saw clear evidence that many ideas about the heavens, established since the time of ancient Greece and Rome, were false. He was convinced of the truth of the theory, proposed by the Polish astronomer Nicolaus Copernicus in 1543, that all planets, including Earth, revolve around the sun. However, this theory contradicted official doctrine in the Roman Catholic Church.

Historians had known that in December 1613, Galileo wrote a letter to his friend Benedetto Castelli, a mathematician at the University of Pisa. In this letter, he discussed how the Copernican theory compared with official church doctrine concerning astronomy. Galileo wrote thousands of letters in his lifetime and many included important scientific discoveries, so people often made copies that were widely circulated. In 1615, one of Galileo’s enemies sent a copy of the 1613 letter to church inquisitors in Rome. The inquisitors sought out and severely punished heretics. In early 1616, Galileo was summoned to Rome to face the inquisitors and discuss whether the Copernican theory conflicted with the Roman Catholic faith.

Several copies of the 1613 letter exist today, although there are two different versions—one that was sent to Rome and another that is less provocative. Some historians suspect clergymen may have forged one version to anger the inquisitors, causing them to charge Galileo with heresy. Galileo sometimes complained to friends about such plots against him.

The rediscovered original letter shows that Galileo altered his words to make them less provocative. Many words and phrases are scratched out and rewritten with a softer tone that inquisitors would have found more agreeable. For example, Galileo referred to certain parts in the Bible as “false if one goes by the literal meaning of the words.” He crossed through the word false, and replaced it with the phrase, look different from the truth. Galileo’s ploy worked. In 1616, he was cleared of charges of heresy. But he was also ordered not to hold, teach, or defend the Copernican theory in any way.

In 1632, Galileo finished his most complete work on the structure of the heavens. It was a book called the Dialogue Concerning the Two Chief World Systems. In this work, the information presented clearly indicated the superiority of the Copernican system. Once again, Galileo was summoned to Rome. This time, he had to answer to the charge of willfully disobeying the order not to defend Copernicus’s theory. In 1633, the Inquisition found Galileo guilty of the charge. The church forced him to recant (publicly withdraw his statement) and sentenced him to life imprisonment. Because of Galileo’s advanced age and poor health, the church allowed him to serve his imprisonment under house arrest in a villa outside Florence. He died on Jan. 8, 1642.

September 12, 2018

High in the Atacama Desert of Chile, a system of stone pillars and rock piles called saywas was recently found to be an ancient Inca calendar. Once thought only to mark a local Inca trail, a team of archaeologists, astronomers, historians, and researchers recently showed how the saywas work as a complicated and connected calendar to identify and predict equinoxes, solstices, and other astronomical events. The Inca trail in the Atacama Desert is part of the Qhapaq Ñan, an extensive Inca road network that stretches from southern Colombia to central Chile.

The sun peeks over the Andes Mountains at dawn, illuminating a line of ancient Inca saywas in the Atacama Desert of northern Chile. Credit: A. Silber, ALMA/ESO/NAOJ/NRAO

Working at 13,800 feet (4,200 meters) above sea level in the desert mountains near Taltal, a small city in northern Chile, the scientific team began visiting the saywas and taking measurements in 2017. The team included local indigenous people as well as experts from the Chilean Museum of Pre-Colombian Art, the nearby Atacama Large Millimeter/submillimeter Array (ALMA) observatory, and the European Southern Observatory. The research was funded by BHP/Minera Escondida, a mining company with more material interests in the desert.

The scientific team began the study by documenting alignments between certain saywas and the sunrises on the March equinox and June solstice. They then began connecting saywa points with other important dates on the ancient Inca calendar. Operating much in the same way as Stonehenge in England, the saywas align with sunrises on certain dates, while also projecting shadows on the ground that lead to other stone points. The researchers also found that certain saywas align with constellations at night, further strengthening the researchers’ conclusion, published in 2018, that the network of stones served as a large calendar for Inca astronomers.

The first written accounts of the saywas were recorded during the Spanish conquest of Andean  South America in the 1500′s and 1600′s. The saywas’ remote locations in the empty desert, far from Inca cities, led the Spanish to believe that the stone piles were little more than pathway markers to help guide people through the vast, barren desert. The saywas did in fact aid in navigation, but the larger purpose of the stone markers remained unknown for centuries. In recent years, however, knowledge of the Inca has greatly expanded, and the study of ancient Quechua and Aymara (Inca languages) dictionaries led to the examination of the relationship between the saywas and the Inca astronomical system.

The ancient Inca capital of Cusco (in modern-day Peru) was surrounded by columns used to measure time, create calendars, and predict equinoxes and solstices as well as the planting and harvesting seasons. The remote saywas, however, were tucked away in the Atacama Desert. Perhaps that was merely the best view of the heavens, allowing Inca astronomers to get the most accurate measurements while Cusco was obscured by clouds and mist. Modern astronomers use the high desert for the same purpose. The sprawling ALMA observatory is only a (figurative) stone’s throw away.

August 9, 2018

Astronomers at the Carnegie Institution for Science in Washington, D.C., recently discovered a new batch of moons orbiting Jupiter, the largest planet in our solar system. The new group of 12 moons—which bring’s Jupiter’s moon total to an astounding 79—includes an oddball, however: one is going “the wrong way.”

Ganymede is the largest of Jupiter’s moons. Astronomers recently found 12 new and much smaller moons orbiting Jupiter, bringing the planet’s solar system-leading total to 79. Credit: NASA

Led by astronomer Scott Sheppard, the Carnegie team had been looking for “Planet Nine,” a hypothetical major planet in the Kuiper belt, a band of objects in the outer regions of our solar system. In March 2017, Jupiter moved into the astronomers’ search area. The telescope the team was using was uniquely suited for finding small or faraway objects: it could block out light from larger nearby heavenly bodies. Sheppard took time away from Planet Nine to poke around Jupiter, and his curiosity was rewarded with the discovery of 12 new moons. The first two bodies orbit close to Jupiter, and were quickly confirmed as moons. The other 10 skew farther out from the mighty planet and were not announced as moons until July 17, 2018.

Callisto, another large moon of Jupiter, has a diameter of almost 3,000 miles (4,800 kilometers), many times the size of Jupter’s newly discovered moons. Credit: NASA

The new moons are small, some less than a mile (several hundred meters) in diameter. Their orbital characteristics tell scientists a lot about them. Nine of the 10 newest moons orbit in retrograde, meaning in the opposite direction of the rotation of Jupiter. This leads the astronomers to think they formed from objects captured by Jupiter’s hefty gravitational pull. Most moons form with their parent planet and have prograde orbits, meaning they orbit in the same direction as the host planet. But captured objects often have retrograde orbits. Sheppard’s team thinks these nine moons are parts of captured objects broken up by collisions over millions or billions of years.

The tenth of the newest moons, however—which Sheppard calls Valetudo, a great-granddaughter of the Roman mythological god Jupiter—travels in a prograde orbit. It dives through the orbits of the other nine moons, putting it on an eventual collision course. When moon finally meets moon, the impact will either destroy the bodies or make them even smaller.

September 22, 2017

Today, at 4:02 p.m. Eastern Time, the autumnal equinox marks the beginning of autumn in the Northern Hemisphere. In the Southern Hemisphere, where the seasons are reversed, the event is called the vernal equinox and marks the start of spring. The word vernal means of spring. An equinox is either of the two moments each year (the other is in March, again changing the seasons) when the sun is directly above Earth’s equator. On the days of the equinoxes, all places on Earth receive approximately 12 hours of sunlight. Today, the sun rose at 6:43 a.m. Eastern Time and will set at 6:52 p.m.—a total of 12 hours and 9 minutes of daylight. The term equinox comes from a Latin word meaning equal night. The equinoxes occur at different times of day each year on March 19, 20, or 21 and on September 22 or 23.

The equinoxes are the two moments of the year when the sun is directly above the equator. As Earth moves in its orbit around the sun, the position of the sun changes in relation to the equator, as shown by the dotted lines in this diagram. The sun appears north of the equator between the March equinox and the September equinox. It is south of the equator between the September equinox and the next March equinox. Credit: WORLD BOOK diagram

The time interval from the March equinox to the September equinox is longer than that between the September equinox and the next March equinox. This time difference results from the Earth’s elliptical (oval-shaped) orbit around the sun. Our planet moves faster in its orbit when it is closer to the sun. The distance between the Earth and the sun is shortest in January. Therefore, the Earth completes the semicircle from the September equinox to the March equinox faster than it does the opposite semicircle.

Astronomers also use the term equinox for either of two imaginary points where the sun’s apparent path among the stars crosses the celestial equator. The celestial equator is an imaginary line through the sky directly over the equator.

After the autumnal equinox, the weather cools and nights become longer than days, and days continue to shorten until the winter solstice. The weather then warms and daylight begins its recovery toward the summer solstice in June. The winter solstice is technically the shortest day of the year, and the day of the summer solstice enjoys the most sunlight.

August 22, 2017

Yesterday, on August 21, huge crowds gathered across the United States to watch the solar eclipse within the path of totality, the 70-mile (113-kilometer) wide swath of land from Oregon to South Carolina where the moon completely covered the sun. In Newport, Oregon, throngs of sky watchers greeted the eclipse as it made first landfall at 10:15 a.m. local time. Many thousands of eclipse chasers filled the totality town of Carbondale, Illinois (where the eclipse was longest). Local merchants greeted the tourists with special jewelry, cookies, doughnuts, and other eclipse-themed goods. Across the country, roads toward the path of totality were jammed with traffic and hotels were booked solid—sometimes a year or more in advance of the big event.

This photograph, taken from Northern Cascades National Park in Washington, shows the moon passing before the sun during the solar eclipse of Aug. 21, 2017. Credit: Bill Ingalls, NASA

A total solar eclipse can have a powerful psychological effect on people. Many people, especially in large urban areas, don’t often have reason to look toward the sky in the middle of the day. But, as the moon begins to move over the sun, people could not help but notice the odd darkening of the sky unlike anything they had ever seen. Many people reported feeling a profound sense of awe and a spiritual connection with other people. Others reported a tremendous feeling of unease as the sunlight dimmed and gradually faded completely. But, unlike the experience in ancient times, there were no reports of panic among the masses of eclipse watchers. Astronomers have long been able to precisely predict the time and place of such celestial events. Yesterday, people cheered and applauded the eclipse as they might ooh and aah at a fireworks show, and eclipse glasses (with lenses dark enough to safely view the sun) were passed from hand to hand.

The moon totally blocks the sun during the solar eclipse of Aug. 21, 2017, above Madras, Oregon. Only the sun’s corona is visible around the moon. Credit: Aubrey Gemignani, NASA

At peak totality, the bright disk of the sun was replaced by a dark spot, surrounded by a blazing ring–the sun’s outer atmosphere (called the corona) that is easily visible only during an eclipse. In some regions, people felt a noticeable temperature drop as day briefly turned to night. Stars and planets became visible in the midday sky. Crickets began chirping, thinking night had begun a bit early, and birds roosted and went silent. Some eclipse chasers were surprised and annoyed by mosquitoes, which were fooled into thinking dusk had arrived and went hunting a few hours early.

People gaze skyward wearing eclipse glasses during the solar eclipse of Aug. 21, 2017, on the Oregon State University campus in Corvallis, Oregon. Credit: Mark Floyd, Oregon State University (licensed under CC BY-SA 2.0)

The great solar eclipse of 2017 left the United States just north of Charlotte, South Carolina, at 4:10 p.m. local time. Peak totality ended at 2:49 p.m. at that location. Anyone who missed the eclipse this year will not have to wait long for another chance. The next total solar eclipse visible from a large portion of the United States will occur on April 8, 2024. And Carbondale, Illinois, will once more have a chance to shine. It is the only city that will be in the path of totality in both 2017 and 2024. It’s not too early to start planning!