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During its four years of life, the InSight lander recorded more than 1300 “marsquakes.” Most of them were tiny, and most were caused by space rocks slamming into Mars. But the largest quake it ever felt came from the planet’s insides, far below the surface. That’s an indication that Mars isn’t dead yet. The quake took place in May of 2022, just a few months before InSight’s mission ended. It was magnitude 4.7. By Earth standards, that’s not much – maybe strong enough to feel, but not strong enough to cause any damage. But by Mars standards, it was a whopper – five times more powerful than the second-strongest quake. And it rattled around the planet for six hours. The quake was centered about 1400 miles away from InSight, in a region with a rugged surface. At first, scientists suspected the quake was caused by a large meteorite impact. That would’ve created a crater a thousand feet across, and blown away dust on the surface for miles around. So they scoured pictures taken by eight spacecraft in orbit around Mars. But they didn’t find a thing – no crater, no blast zone. That means the quake probably originated inside the planet, at a depth of about 11 to 17 miles. It might have been triggered by movement along a fault line. So even though the Martian crust isn’t made of moving plates, as Earth’s is, there may still be a good bit of shakin’ and rattlin’ below the surface of Mars.  Script by Damond Benningfield

Olympus Mons is the Mauna Loa of Mars. Like the mountain on the island of Hawaii, it’s the largest volcano on its planet —in this case, Mars. Also like Mauna Loa, it built up as molten rock bubbled through a “hotspot” in the crust. Finally, Olympus Mons might once have stood in the middle of an ocean. Olympus Mons is almost 13 miles high, and covers an area the size of France – much bigger than Mauna Loa. That’s because it never moved away from the hotspot, so it kept on building for billions of years. Today, it’s either dormant or extinct. It stands on a wide base that’s about four miles high, with sheer cliffs all around. A recent study says the top of the base shows evidence of contact with water. Scientists have already seen the possible shoreline of a shallow ocean. The ocean vanished long ago, as Mars grew colder and lost most of its air. The study found features along the rim of the Olympus Mons base that look like they formed when lava spilled into liquid water – supporting the idea of a long-gone ocean. So Olympus Mons might once have been not only the biggest volcano on Mars, but the biggest island as well. Mars is inching into the dawn sky. It’s quite close to the Sun, though, and it rises at a shallow angle. If you’re in Hawaii or southern Florida or Texas, you might spot it quite low in the southeast before sunrise. The rest of the U.S. won’t see it for a few weeks. More about Mars tomorrow.  Script by Damond Benningfield

El Gordo – the fat one – might not be the most flattering name for a galaxy cluster. But it’s certainly accurate. El Gordo is the most massive cluster yet seen that’s so far away – more than seven billion light-years. The cluster is actually two clusters that are ramming together. They contain hundreds of individual galaxies. They total about 2300 times the mass of our own galaxy, the Milky Way. Most of that mass consists of dark matter. It produces no detectable energy, but it reveals its presence through its gravitational pull on the visible matter around it. Astronomers measure the amount of dark matter by seeing how the cluster distorts the light of background galaxies. They know the mass of the visible parts of the galaxies. They subtract that from the cluster’s gravitational mass to calculate the amount of dark matter. El Gordo is so far away that we see it as it looked when the universe was a bit less than half its current age – about six-and-a-half billion years after the Big Bang. No other cluster at that distance or beyond is that heavy. So the cluster provides an excellent laboratory for studying galaxies and dark matter in the early universe. El Gordo is in Phoenix, the firebird. The constellation is so far south that it’s not visible from most of the United States – only Hawaii and southern Texas and Florida. From those locations, the firebird is low in the southern sky at nightfall.  Script by Damond Benningfield

During the Little Ice Age, much of the northern hemisphere was plunged into a deep freeze. Winters were so cold that the Thames River in England froze over, and the Vikings had to abandon their settlements in Greenland. Summers were chilly, rainy, and gloomy – perhaps helping inspire Mary Shelley to write “Frankenstein.” That era incorporates a time when the Sun was especially quiet. Known as the Maunder Minimum, it lasted from about 1645 to 1715. Astronomers recorded few sunspots then — they sometimes went months or years without seeing a single one. With less activity, the Sun emits less energy. That suggests the Sun could be at least partially responsible for the Little Ice Age. A recent study found that not only was the Sun especially quiet during that era, but its cycle of magnetic activity was especially short. At the peak of a solar cycle, the Sun is covered with many sunspots, and it produces big explosions of gas and energy. The cycle lasts an average of about 11 years, although it can vary by a couple of years either way. The study found that the cycles during the Maunder Minimum lasted only about eight years. Researchers looked at records of auroras kept by Korean astronomers. Auroras are created by particles from the Sun, so their intensity and location can reveal the Sun’s activity level. The study found a clear eight-year cycle in the records – a short cycle during an era that was short on warmth.  Script by Damond Benningfield

Jupiter has been described as the vacuum cleaner of the solar system. The planet’s powerful gravity sucks in comets and asteroids. They’re destroyed as they slam into Jupiter’s atmosphere. That keeps those objects from possibly threatening Earth and the other inner planets. Scientists have seen several of these impacts. They’ve seen some of them directly, as bright flashes of light. For others, they’ve seen the aftermath — big, dark scars in Jupiter’s atmosphere. One of the most recent impacts came last summer. Amateur astronomers in Asia saw a bright flash of light on August 28th. One of them even recorded the flash on video. It lasted several seconds. An early analysis said the flash was similar to another one a couple of years earlier. It probably was the equivalent of a blast on Earth in 1908. Known as the Tunguska event, it occurred when an asteroid or comet exploded in the upper atmosphere. It leveled hundreds of square miles of Siberian forest. The biggest impact yet seen on Jupiter took place in 1994. Jupiter’s gravity pulled apart a large comet. It then pulled in the remains, which created about a dozen big blasts. The scars from those impacts were visible for months. Jupiter keeps company with the Moon the next couple of nights. It looks like a brilliant star. It’s to the left or upper left of the Moon tonight, and closer below the Moon tomorrow night.  Script by Damond Benningfield

The star V1355 Orionis is a hothead. It pops off all the time — giant eruptions of energy and particles. All of them are superflares — many times more powerful than any eruption ever seen from the Sun. And a few years ago, the star produced one of the most powerful superflares ever seen from any star. V1355 is a binary — two stars locked in orbit around each other. One of the stars is similar to the Sun. But the other is bigger, heavier, brighter, and much more active. That star spins quickly. The rapid rotation generates a powerful magnetic field. The lines of magnetic force tangle, then snap. When the lines reconnect, the star produces giant outbursts. In December of 2020, it produced its biggest yet seen. The superflare blasted trillions of tons of material into space. And the cloud was moving at a couple of million miles per hour or faster — fast enough to escape the star and zip into interstellar space. Such a flare would be bad news for any planets in orbit around the star. It could erode some of a planet’s atmosphere like a rock wall hit with a sandblaster. It could also zap the surface with X-rays and other high-energy radiation. So any planets in the system are likely to be lifeless — blasted by V1355 Orionis. The system is about 400 light-years away, in Orion. The constellation is in the east and southeast at nightfall.  Script by Damond Benningfield

Betelgeuse will blast itself to bits as a supernova. Many astronomers agree that that’s likely to happen within the next hundred thousand years. But estimates of the exact timing range from the full hundred thousand years to as little as a few decades. Betelgeuse marks the shoulder of Orion the hunter. The bright orange star is in the east at nightfall, to the left of Orion’s three-star belt. In late 2019, the supergiant star blew out a huge blob of gas. The gas cooled and condensed, forming a dark cloud that made the star fade to a third of its normal brightness. Betelgeuse rebounded, then grew almost 50 percent brighter than normal last year. The timing of the supernova depends on what’s happening in the star’s core, which we can’t see. It may be “fusing” helium to make carbon. But it could be fusing carbon to make heavier elements. If so, then the star’s demise could come fairly soon. A study last year suggested that Betelgeuse is late in the carbon-fusion process. After that stage, it’ll “burn” through a series of elements, ending with iron. At that point, the core will collapse, and the star’s outer layers will blast into space. The study said that, if Betelgeuse is deep into the carbon-burning process, it could explode in a few centuries — or perhaps even a few decades. For now, all we know for sure is that Betelgeuse faces a spectacular demise — sometime in the next hundred thousand years.  Script by Damond Benningfield

Several especially bright stars highlight the eastern sky on January evenings. The list includes Betelgeuse and Rigel in Orion, Pollux and Castor in Gemini, and the brightest star of all, Sirius, in the big dog. For millennia, these and other stars were guiding lights, helping people find their way around the world — and beyond. Celestial navigation combines observations of the positions of two or more stars or other celestial bodies, precise timing, and some calculations. A skilled navigator can use the technique to reach a destination with a high degree of accuracy — to within a few hundred yards and a couple of minutes. Centuries ago, Polynesian sailors used the technique to island-hop across the Pacific Ocean. European explores used it to find their way to the Americas and the Far East. American sailors used it as well, plying the world’s oceans in times of war and peace. And Apollo astronauts used it to help them get to the Moon. With the advent of GPS in the 1980s and ’90s, though, celestial navigation began to die off. GPS is easier to use and more accurate. The United States Naval Academy even dropped celestial navigation from its classes. But a few years ago, the academy restored its training — in part because technology can fail or be blocked. All midshipmen receive a basic introduction, while navigators get more advanced training – in finding their way with the help of the stars.  Script by Damond Benningfield

When big storms on Earth are done, they leave little trace in the atmosphere that they ever existed. On Saturn, though, big storms appear to leave traces even centuries after they faded from sight. Saturn is the second-largest planet in the solar system — a ball of gas more than nine times the diameter of Earth. Its atmosphere is generally pretty bland — a few ribbons of clouds in shades of white, yellow, and tan. Every couple of decades, though, a giant storm breaks out. It can wrap all the way around the planet, and remain visible for months or years. But a recent study found that the storms leave a long-lasting imprint. Scientists used an array of radio telescopes in New Mexico to look for ammonia in Saturnian skies. They found regions where there was little ammonia high in the sky, but a lot at lower altitudes. All of those regions seemed to match the locations of the giant storms recorded since 1876 — with the possible imprint of one from centuries earlier. The big storms might have caused ammonia high in the atmosphere to cool and condense, forming big “mushballs” of ice. The mushballs fell dozens of miles into the atmosphere. They vaporized, adding their ammonia to the lower altitudes — leaving traces of long-gone storms. Saturn looks like a bright star, and is especially easy to find right now. It’s above the Moon as darkness falls tonight, and to the lower right of the Moon tomorrow night.  Script by Damond Benningfield

If you could catch the hot gas that the star Alnilam is blowing into space, in a million years you’d have enough to make two stars as heavy as the Sun. But you wouldn’t be able to tell much difference in Alnilam itself, because it’s one of the monsters of the Milky Way. Alnilam is the “buckle” in Orion’s Belt, a compact line of three bright stars. It rolls across the south on winter nights. It’s the most impressive member of the belt. As seen from Earth, it’s the brightest of the three stars, even though it’s hundreds of light-years farther away. And while each of the others consists of more than one star, Alnilam moves through the galaxy alone. Alnilam is a supergiant. It’s more than 60 times as massive as the Sun, tens of thousands of degrees hotter, and hundreds of thousands of times brighter. Its radiation is so intense, that it blows a dense “wind” of hot gas from its surface. The wind races into space at millions of miles an hour. Although Alnilam is only a few million years old, it’s nearing the end of its life. It’s probably consumed its original hydrogen fuel. Over the next few million years, it’ll burn through a series of heavier elements forged in its core. Eventually, though, it won’t be able to sustain that process any longer. Its core will collapse, while its outer layers blast into space as a supernova — briefly outshining the combined light of most of the other stars in the galaxy.  Script by Damond Benningfield

“Tadpoles” swim through the Orion Nebula, a giant stellar nursery more than 1300 light-years from Earth. Like tadpoles, they’re not yet fully mature. Also like tadpoles, not all of them will survive their hostile environment. The tadpoles are known as protoplanetary disks – proplyds for short. They’re giant “cocoons” of gas and dust. Each one envelops a central star that’s still being born. And some of them may give birth to planets. The proplyds look like tadpoles because they’re being sculpted by the radiation of nearby stars. The stars are exceptionally hot and bright. They produce a lot of ultraviolet radiation. The UV acts like a blowtorch, blasting the proplyds. The side of a proplyd that faces the stars is hot and bright, so it forms the “head” of the tadpole. The “tail” is formed by gas flowing away from it. The proplyds are quite young – no more than a couple of million years old. Their central stars are still taking shape. Many of them shoot out “jets” of hot gas from their poles that are billions of miles long. A disk of cooler gas and dust may surround the infant star. If it survives the blowtorch, the disk may give birth to planets – worlds born from the remains of stellar tadpoles. The Orion Nebula is visible to the unaided eye. It looks like a wide, fuzzy star in Orion’s Sword. Orion is in the east and southeast at nightfall, with the sword to the right of its three-star belt.  Script by Damond Benningfield

One of the most remarkable sights in the night sky is M42, the Orion Nebula. It looks like a hazy patch of light in Orion’s Sword, which is to the right of his three-star belt in early evening. The nebula is one of the most-distant objects that’s visible to the eye alone – more than 1300 light-years away. It’s also one of the biggest – a couple of dozen light-years across. What’s really remarkable, though, is the nebula’s identity. It’s a nursery that’s given birth to thousands of stars, with thousands more being born today. And all of that activity has taken place over just a few million years. M42 contains huge clouds of gas and dust. Clumps of this material collapse to form stars. The most massive stars form a cluster known as the Trapezium. These stars are much bigger, brighter, and heavier than the Sun. They produce a lot of ultraviolet energy. It zaps the gas around them, making it glow. If you could travel inside M42, you’d see hundreds or thousands of stars. Some would be too bright to look at directly, while others would look like dull embers. Ribbons and curtains of gas would surround you, glowing pink, green, or blue-white. Dark lanes and blobs would run through the background – dense clouds of dust where more stars are taking shape. You’d also see some objects that look a bit like tadpoles – proplyds – the possible birthplaces of planets. We’ll have more about that tomorrow.  Script by Damond Benningfield

Proxima Centauri b is the closest planet outside our own solar system. So it’s natural to wonder whether it might support life. As with many other exoplanets, the answer is maybe. It has some big plusses, but perhaps some even bigger minuses. The planet orbits Proxima Centauri, the closest star to our own – a bit more than four light-years away. It’s so faint, though, that it’s not visible without a telescope. Proxima b is one of three possible planets orbiting the star. But it’s the only one in the “habitable zone” – the region around the star that’s thought to be comfortable for life. And the planet is about the same size and mass as Earth. Those are the plusses. The minuses have to do with the star — a red dwarf. It’s much smaller, cooler, and less massive than the Sun. And most of the time, it produces much less than one percent as much energy as the Sun does. Sometimes, though, Proxima flares up. It produces explosions of energy and particles that are a thousand times stronger than anything yet seen from the Sun. Proxima b is only about four-and-a-half million miles from the star – just five percent of the distance from Earth to the Sun. So the flares blast the planet with X-rays and charged particles. That could erode the planet’s atmosphere – if it has one – and zap any life on the surface. So the odds seem to be against finding life on this nearby neighbor – at least for now.  Script by Damond Benningfield

Mercury’s appearances in our sky are like a game of whack-a-mole. First, the planet pops into view in the morning sky, then it ducks into the Sun’s glare, then it pops up in the evening sky, and so on. It never stays in view for long – no more than a few weeks, and often only a few days. So you have to strike fast to catch it. This is one of its morning pop-up times. Mercury is quite low in the southeast as the dawn twilight gets brighter, so you need a clear horizon to see it. And although it looks like a fairly bright star, it can be hard to spot against the bright sky. Mercury pops in and out of view so often because it’s the closest planet to the Sun, while Earth is the third planet. As a result, Mercury stays close to the Sun as seen from Earth – it never climbs very high into the sky. And Mercury’s tighter orbit means that it crosses between Earth and the Sun, or behind the Sun, every few months. That carries it from morning to evening and back again in a hurry, leaving little time to catch it. Mercury is in better view tomorrow because it has some bright companions. It’s close to the upper left of the crescent Moon. Venus, the brilliant “morning star,” is high above the Moon. And Antares, the brightest star of the scorpion, is to the lower right of Venus. And although the Moon will have dropped from view on Wednesday, Mercury will remain in decent view for another week or so.  Script by Damond Benningfield

Bright lights encircle the crescent Moon during the early dawn twilight tomorrow – the star Antares and the planets Venus and Mercury. Antares appears closer to the Moon than the other two companions. From most of the United States, only a sliver of sky will separate them at first light. For skywatchers in the western part of the country, though, that sliver will disappear as the Moon occults Antares. The Moon will cross between Earth and the star, blocking it from view. Antares occultations come in groups. They’re tied to an 18.6-year cycle in which the Moon moves farthest north and south across the sky. The current group started last year, and continues into 2028. The next series won’t begin until 2041. But only some of the occultations will be visible from the U.S. The Moon’s brightest companion is the planet Venus, the “morning star.” Venus is dropping back toward the Sun in our sky, but it’ll take its time. It will remain in view until April. After that, it’ll pass behind the Sun, then hide in the Sun’s glare. It’ll return to view – as the “evening star” – in July. Mercury is the Moon’s farthest companion tonight. It’s the closest planet to the Sun, so it never moves far from the Sun in our sky. In fact, this is one of its best appearances of the year. It looks like a bright star well to the lower left of the Moon. But it will be much closer to the Moon on Tuesday morning. More about that tomorrow.  Script by Damond Benningfield

The two brightest stars of Gemini — Pollux and Castor — are in pretty good view in the east-northeast not long after the sky gets good and dark. Pollux is the brighter one, with Castor close above it. But Gemini is a big constellation, so it’s a long way over to the third-brightest star, Alhena, which marks a foot of one of the twins. It’s off to the right of the other two, by about twice the width of your fist held at arm’s length. Alhena consists of two stars. The star we see is about three times the Sun’s mass and diameter. It’s about 125 times brighter than the Sun. And it’s thousands of degrees hotter. That makes it a “class A” star.vb Astronomers classify stars with the letters O-B-A-F-G-K-M. The classes are based on the surface temperatures of the stars. O stars are the hottest and bluest, while M stars are the coolest and reddest. Class A stars are toward the top of the temperature scale. And they’re not very common. They account for perhaps one percent of all stars in the galaxy. And Alhena is at the very top of the A stars – one of the hottest – so it shines pure white. Its companion star has never been seen directly – it’s too faint and too close to see through the glare of the brighter star. But instruments reveal some details. It’s about the same mass as the Sun. It’s probably in the same class as well – class G — the spot for yellow stars like the Sun and the unseen star of Alhena.  Script by Damond Benningfield

Delta Geminorum has one claim to fame. It was just half a degree from Pluto when the little world was discovered, in 1930. Pluto has moved a third of the way around the sky since then. But Delta Gem has stayed put. It’s the seventh-brightest star in Gemini. It connects the body and legs of one of the twins. The star is also known as Wasat. The name comes from Arabic, and means “middle.” But no one knows what middle is represented. Delta Gem is a system of at least three stars. Two of them form a tight pair. But the third is far away – more than a hundred times the distance from Earth to the Sun. At that rate, the star takes about 1200 years to orbit the other two. The system’s main star is a subgiant. That means it’s burned through most of the hydrogen in its core. It’s making the transition to the next phase of life: a giant. It’s already bigger than the Sun, but it’ll get even bigger over the next few million years. It’ll shine hundreds of times brighter than it does now, making it Gemini’s brightest star. And it’ll get brighter for another reason as well. Today, it’s about 60 light-years away. A million years from now, though, it should pass within about seven light-years of Earth – making it one of the brightest stars in all the night sky. Delta Gem is low in the east-northeast at nightfall, to the right of Gemini’s current leading light, Pollux. They soar high overhead later on, and remain in view all night.  Script by Damond Benningfield

The night sky is getting brighter. The main culprit is light pollution – the glow of streetlamps, billboards, and many other artificial light sources. But there’s another source of brightness that’s far outside Earth’s atmosphere: satellites. The number of satellites is, well, skyrocketing. As many satellites have been placed in Earth orbit in the past five years as in the first six decades of the Space Age. And the pace is picking up. Companies are launching thousands of spacecraft every year. Most of them bring Internet access to underserved parts of the world. That’s becoming a problem for astronomers. The satellites can form bright streaks in their images of the universe, or block their targets from view. It’s also becoming a problem for casual skywatchers. The satellites reflect a lot of sunlight, casting a “haze” across the night. And when satellites collide or break apart, they produce thousands of bits of debris, all of which add to the glow. A recent study reported that the congested space around Earth has already brightened the night sky by about 10 percent. And if the projected launch rate comes true, it could make the sky even brighter. Even under dark skies, away from city lights, that could reduce the number of visible stars by almost a third. And it could make it harder to see meteor showers, faint auroras, and the soft glow of the Milky Way – hiding them behind a high curtain of light.  Script by Damond Benningfield

The Quadrantid meteor shower should be at its best tonight. Unfortunately, “best” doesn’t mean great. That’s because the last-quarter Moon gets in the way. It’s in view during the expected peak hours, so its glare will wipe out all but the brightest meteors. The shower is named for an extinct constellation – the wall quadrant - an instrument that astronomers used for centuries to track the positions of stars. That region of the sky is in Boötes the herdsman, near the handle of the Big Dipper. The Quadrantids appear to come from a trail of dust left by an asteroid or dead comet. As it orbits the Sun, it sheds bits of rock and dirt. Today, the parent body’s orbit doesn’t cross Earth’s orbit. But it must have in the distant past. That left a trail of debris for Earth to pass through. As we cross the trail, some of the debris hits the atmosphere at about 90,000 miles per hour. The particles vaporize, forming the streaks of light known as meteors or shooting stars. The Quadrantids include quite a few “fireballs” – especially bright meteors that can explode. They’re formed by larger bits of debris – the size of pebbles. They can be bright enough to see through the Moon’s glare. And a few fireballs are usually seen for a few nights after the shower’s peak. Look for the meteors in the wee hours of the morning. You might see up to a few dozen of them – blazing bits of rock and dust high in the sky.  Script by Damond Benningfield

It might be winter here in the northern hemisphere, but the Sun is biggest and closest to us for the entire year today. Earth is at a point in its orbit called perihelion. The Sun is about 91.4 million miles away – about one and a half million miles closer than average. Earth’s orbit isn’t a perfect circle. Instead, it’s an ellipse – a shape that looks like a slightly flattened circle. So over the course of a year, the Earth-Sun distance varies by about three percent. The oceans and atmosphere distribute heat around the planet, so the changing distance doesn’t cause a change in global temperatures. The date of perihelion isn’t fixed. Instead, it shifts forward by an average of about one day every 58 years. That’s because Earth “wobbles” on its axis like a gyroscope that’s running down. About 800 years ago, Earth was closest to the Sun on the winter solstice, in December. And about 4300 years from now, it’ll be closest on the spring equinox, in March. The changing distance to the Sun doesn’t create the seasons. Instead, the seasons are caused by Earth’s tilt on its axis. But the distance to the Sun does have an impact on the seasons. Earth moves fastest in its orbit when it’s closest to the Sun, and slowest when it’s farthest away. That means the seasons are different lengths. In the northern hemisphere, winter is the shortest season – about five days shorter than summer, when Earth is farthest from the Sun.  Script by Damond Benningfield