StarDate
909 episodes - English - Latest episode: 2 days ago - ★★★★★ - 205 ratingsStarDate, the longest-running national radio science feature in the U.S., tells listeners what to look for in the night sky.
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Episodes
Cygnus Loop
July 07, 2024 05:00 - 2 minutes - 1.06 MBAbout 10,000 years ago, a massive star in Cygnus, the swan, blew itself to bits. For a few days or weeks, it blazed as the brightest object in the night sky other than the Moon – bright enough to see even during the day. Today, its glowing remains are still visible – a colorful bubble that’s more than a hundred light-years across and growing. The bubble is known as the Cygnus Loop. It’s a supernova remnant – the debris from a star that was about 20 times the mass of the Sun. After a short b...
Little Guys
July 06, 2024 05:00 - 2 minutes - 1.06 MBThree tiny constellations are stacked up in the eastern evening sky this month: the arrow, the dolphin, and the little horse. There’s not a single bright star among them. But under moderately dark skies, at least one of them is pretty easy to make out. The arrow is at the top of the stack. It’s the third-smallest of the 88 modern constellations. In ancient times, it represented a weapon used by Hercules, but there were different takes on his target. All of its stars are faint, but under esp...
Brown Dwarfs
July 05, 2024 05:00 - 2 minutes - 1.06 MBThe Sun and the planet Jupiter are the heaviest objects in the solar system. But there’s a huge gap in their masses – the Sun is more than a thousand times heavier. There’s a class of objects between those masses. Known as brown dwarfs, they’re much heavier than Jupiter, but no more than seven or eight percent of the Sun’s mass. A brown dwarf probably forms in the same way as a star – from the collapse of a cloud of gas and dust. The heat of that collapse makes the brown dwarf shine. But a...
Aphelion
July 04, 2024 05:00 - 2 minutes - 1.06 MBIt may sound strange to hear during the heat of the summer, but Earth is farthest from the Sun for the entire year right now. Our planet is receiving almost seven percent less energy from the Sun than it did when it was closest to the Sun, in January. The average distance to the Sun is 93 million miles. But the distance varies by about one and a half million miles in either direction – a result of the eccentricity of Earth’s orbit. It defines how lopsided the orbit is. And it varies over cy...
Unsteady Giant
July 03, 2024 05:00 - 2 minutes - 1.06 MBBetelgeuse grew dramatically fainter a couple of years ago. The supergiant star blasted out a giant blob of gas, which cooled to form a dust cloud that blocked part of the star from view. And a similar star might recently have gone through the same process. RW Cephei is at least 900 times the diameter of the Sun, making it one of the larger stars in the galaxy. It’s also hundreds of thousands of times brighter than the Sun. In late 2022, though, it dropped to a third of its usual brightness...
Moon and Jupiter
July 02, 2024 05:00 - 2 minutes - 1.06 MBThe four big moons of Jupiter probably are all about four and a half billion years old. But two of them look much younger. That’s because their surfaces are constantly repaved – one by fire, the other by ice. The fire moon is Io. It’s the most volcanically active body in the solar system, with more than 400 volcanoes on its surface. Some of them release gas or lava, while others produce big explosions. That activity covers up any impact craters – the scars of collisions with big space rocks...
Moon and Planets
July 01, 2024 05:00 - 2 minutes - 1.06 MBMars and Jupiter are siblings. They were born at the same time, from the same cloud of material that encircled the embryonic Sun. Yet there’s absolutely no family resemblance – they could hardly be more different. Both planets appear near the Moon at dawn tomorrow. Mars looks like a bright orange star to the upper right of the Moon. Jupiter is even brighter, and crouches below the Moon, low above the horizon. Mars is small – about half the diameter of Earth. It’s made of rock and metal. Ju...
Moon and Mars
June 30, 2024 05:00 - 2 minutes - 1.06 MBThe moons of Mars aren’t much more than big boulders that look a bit like potatoes. Phobos is about 17 miles long; Deimos, only about nine miles. But they’ve been the subject of a big scientific debate for decades — a debate about their origins. One possibility says they’re asteroids that were captured by Mars long ago. Both bodies look like asteroids. And some of the minerals on one of them are the same as those found in some meteorites that probably came from asteroids. The other possibi...
The Shield
June 29, 2024 05:00 - 2 minutes - 1.06 MBA small, faint “shield” of stars scoots across the southern sky on early summer nights. It represents the coat of arms on the shield of John Sobieski, a 17th-century king of Poland and one of the country’s great national heroes. The shield is the constellation Scutum. Johannes Hevelius first drew it around 1687, using a few stars from a fairly empty region of the sky. He originally named it Scutum Sobiescianum — the shield of Sobieski. But in more recent times, the last part of the name has...
Solar Protection
June 28, 2024 05:00 - 2 minutes - 1.06 MBHurricanes and other big storms can cause widespread damage that can take days or weeks to clean up. So can big space weather storms. They can knock out satellites, disrupt radio transmissions, and cause power blackouts. Especially big storms have the potential to knock out power grids for weeks or months. So scientists and power operators are looking for ways to minimize the damage. Space weather is powered by storms on the Sun. Big explosions send particles and energy racing out into the ...
Nessie Nebula
June 27, 2024 05:00 - 2 minutes - 1.06 MBA dark ribbon of gas and dust may be about to light up like a sequence of camera flashes. That’s because it could begin giving birth to new stars, with each star triggering the birth of more stars. The ribbon is called the Nessie Nebula — named for its resemblance to the Loch Ness monster. It’s the longest ribbon of its type yet seen in the Milky Way — about 300 light-years long, but only three light-years across. It’s chilled to about 20 degrees above absolute zero. And for every light-yea...
Arrokoth
June 26, 2024 05:00 - 2 minutes - 1.06 MBAfter the New Horizons spacecraft flew past Pluto, in 2015, it still had some gas in the tank and some tread on the tires. Mission scientists wanted to take advantage of that by flying past another object in the outer solar system. But they didn’t know where to send it — there was no roadmap to other destinations. They solved that problem 10 years ago today. Using Hubble Space Telescope, they discovered a new body about four billion miles from the Sun. Eventually, it was named Arrokoth — a ...
Moon and Antares
June 19, 2024 05:00 - 2 minutes - 1.06 MBYou might think that astronomers would know just about everything there is to know about the brighter stars in the night sky. That’s not the case, though. In fact, some of those stars can be especially vexing. An example is Antares, the orange supergiant that marks the heart of Scorpius, the scorpion. The star huddles quite close to the Moon at nightfall, with the gap growing smaller as the night goes on. Antares is the 15th-brightest star in the night sky. And astronomers do know quite a ...
William Lassell
June 18, 2024 05:00 - 2 minutes - 1.06 MBBuilding the Albert Dock in Liverpool gave a man a powerful thirst. Workers drank up to a dozen pints of beer a day — and that was during the work day, with beer provided by the company. And while the workers drank, beer baron William Lassell got rich. Lassell used some of that wealth to study the stars. He designed and built one of the world’s largest telescopes, and used it to make many important discoveries. Lassell was born 225 years ago today. He made his first telescope by age 21. In...
Gentleman Astronomers
June 17, 2024 05:00 - 2 minutes - 1.06 MBModern astronomy is a job for professionals. Amateurs discover comets and make many other contributions. But most of the cutting-edge research is done by professional scientists using expensive telescopes and other equipment. In the not-so-distant past, though, many major discoveries were made by “gentleman astronomers” — rich men who built their own telescopes and shared a passion for the stars. That was especially true in Britain. There wasn’t much public money for telescopes, and only a...
Cat’s Eyes
June 16, 2024 05:00 - 2 minutes - 1.06 MBA pair of cat’s eyes glows just above the north-northwestern horizon as darkness falls. The glowing eyes drop from sight in a hurry. And they’ll drop even lower during the coming nights, before disappearing entirely in the evening twilight. The “eyes” are the stars Pollux and Castor. They mark the heads of the constellation Gemini. The stars are described as “twins,” but that’s mainly because they’re so close together. Pollux is actually twice as bright as Castor, which is close to its righ...
Moon and Spica
June 15, 2024 05:00 - 2 minutes - 1.06 MBThis might come as a bit of a surprise, but no star is perfectly round. A star’s rotation, and the gravitational tug of any companion stars, can distort the shape. So most stars are slightly flattened. The Sun, for example, is about six miles wider through the equator than through the poles. The Sun’s average diameter is about 865 thousand miles, though, so that slight flattening isn’t noticeable. But some stars are so squashed that they look like lozenges. And still others look like eggs. ...
Thuban
June 14, 2024 05:00 - 2 minutes - 1.06 MBArchaeologists know of only a few major artifacts of the pharaoh Khufu, who ruled Egypt more than 4500 years ago. The list includes some small statuettes — some of which might have been created long after his reign. But one artifact is at the opposite end of the size scale: the Great Pyramid of Giza, one of the seven wonders of the ancient world. The pyramid was built with the help of a guiding light — the star Thuban. At the time, it was the Pole Star. It marked due north in the sky, makin...
Flat Universe
June 13, 2024 05:00 - 2 minutes - 1.06 MBOur universe appears to be “flat” — like a sheet of paper stretching to infinity. If so, that would mean it’s finely balanced — a sort of “just right.” Albert Einstein’s theory of gravity, known as General Relativity, allows the universe to assume one of three basic shapes. One shape is “closed” — like a sphere. In such a universe, two lights beamed out parallel to each other eventually would circle all the way around to their starting point. Another possible shape is “open” — curved like ...
Vega
June 12, 2024 05:00 - 2 minutes - 1.06 MBWhen it comes to understanding a star, it’s all a matter of perspective. The angle at which you view the star makes a big difference in what you know about it. Consider Vega, the leading light of the constellation Lyra and one of the brighter stars in the northern sky. It’s in the northeast at nightfall, and climbs high overhead later on. For a long time, astronomers thought Vega was about three times as massive as the Sun, and no more than a hundred million years old. So when they discove...
Moon and Regulus
June 11, 2024 05:00 - 2 minutes - 1.06 MBLike a mixed litter of puppies, sibling stars don’t necessarily look alike. That can make it hard to figure out which stars are related to each other. One example is Regulus, the heart of the lion. It’s close to the left or lower left of the Moon as darkness falls. To the eye alone, Regulus looks like a single bright star. Instead, it’s a system of four stars — two pairs of stars that are separated by a third of a light-year. What we see as Regulus is the brightest of the four stars. Know...
Kapteyn’s Star
June 10, 2024 05:00 - 2 minutes - 1.06 MBOur home galaxy is a cosmic melting pot. While many of its stars were born in the Milky Way, many others came from outside. They were born in smaller galaxies that were captured by the Milky Way. Over time, the smaller galaxies were ripped apart, and their stars were scattered throughout the Milky Way. And one of the Sun’s close neighbors may be an example. Kapteyn’s Star is about 13 light-years away. Only about 20 other star systems are closer. The star is about a third the size and mass o...
Omega Centauri
June 09, 2024 05:00 - 2 minutes - 1.06 MBThe biggest globular star cluster in the Milky Way Galaxy may not be a child of the Milky Way. Instead, it may be a sort of orphan — the surviving core of a smaller galaxy that was captured by the Milky Way. Omega Centauri contains perhaps 10 million stars, all packed into a dense ball about 150 light-years across. In the cluster’s middle, the stars are packed so tightly that they’re only about a tenth of a light-year apart. Compare that to our part of the galaxy, where the nearest neighbor...
Menkent
June 08, 2024 05:00 - 2 minutes - 1.06 MBAs you look out into the night sky, you might think that you’re seeing a true sampling of the stars — in other words, a little of everything. That’s not the case, though. Most of what you see is the Milky Way’s equivalent of the one percenters — stars that are among the galaxy’s biggest and brightest. An example is in the constellation Centaurus, which wheels quite low across the south on June nights. It’s so low, in fact, that much of it stays below the horizon for those of us in the Unite...
Galactic Habitable Zone
June 07, 2024 05:00 - 2 minutes - 1.06 MBEarth lies in the middle of the Sun’s habitable zone. That’s the distance from the Sun where conditions are most comfortable for life. And astronomers are concentrating their hunt for life in other star systems in their habitable zones. There’s an idea that galaxies have habitable zones as well. The zones would have a good mix of chemical elements, not too much radiation, and a low risk of exploding stars. Stars consist mainly of hydrogen and helium. But to make planets like Earth, you nee...
Getting Ready
June 06, 2024 05:00 - 2 minutes - 1.06 MBA possible new space telescope probably won’t launch for a couple of decades, if at all. But astronomers are already looking for targets for it to study — star systems with planets that could host life. Habitable Worlds Observatory will have several jobs. As the name suggests, one of those jobs will be to scan planets for signs of life. The telescope will screen out the light from a star, allowing it to take pictures of planets around the star. Most important, the telescope will analyze th...
Active’ Worlds
June 05, 2024 05:00 - 2 minutes - 1.06 MBMany factors are involved in making a planet habitable: the size and composition of the planet, the stability of its orbit, its distance from its star. But scientists are still trying to figure out which factors are important. An example is plate tectonics. Earth’s surface is divided into large “plates.” They glide along the rocks below the surface. They ram together, slide over each other, and recycle the crust. They allow heat to escape to the surface, and affect the chemistry of the atmo...
Martian Traveler
June 04, 2024 05:00 - 2 minutes - 1.06 MBIt’s pretty remarkable that scientists have figured out that some meteorites come from Mars. What’s even more remarkable is they may know just where on Mars one of them came from. The meteorite is cataloged as Northwest Africa 7034. It was discovered in 2011, in the Sahara Desert. The rock weighs about 11 ounces. And because of its dark appearance, it’s nicknamed “black beauty.” An American bought the meteorite and donated it to the University of New Mexico. Detailed analysis revealed that...
Martian Lakes
June 03, 2024 05:00 - 2 minutes - 1.06 MBThe landing sites of the two most recent American Mars rovers are about 2300 miles apart — roughly the distance from Los Angeles to Washington, D.C. Yet the sites are a lot alike. Both are inside impact craters that formed at least three and a half billion years ago. And both craters once held lakes — potential homes for microscopic life. Curiosity landed in Gale Crater, in 2012. The crater is almost a hundred miles across, with a central mountain that’s three and a half miles high. Curios...
Zapping Mars
June 02, 2024 05:00 - 2 minutes - 1.06 MBThe Perseverance Mars rover packs a laser gun. It’s not for defense against Martians. Instead, it’s a scientific instrument — a way to learn about Martian rocks without drilling into them. And the sound of the laser helps in that effort. Perseverance zaps a target rock dozens of times in just a few seconds. That vaporizes some of the rock. The rover’s instruments analyze the composition of the vapor. That reveals the chemistry of the rock. Scientists use that information to infer something ...
Messier 5
May 27, 2024 05:00 - 2 minutes - 1.02 MBThe Sun is about four and a half billion years old, so it’s been around awhile. Compared to some of the galaxy’s oldest stars, though, it’s a youngster. Some stars have been around since shortly after the universe was born. In the Milky Way Galaxy, many of those ancient stars reside in globular clusters — giant balls of stars that may have formed as the Milky Way itself was taking shape. An example is Messier 5. It’s in the southeast at nightfall, in the constellation Serpens. It’s a bit t...
Serpent Rising
May 26, 2024 05:00 - 2 minutes - 1.02 MBThe head of the serpent slithers into the early evening sky this month, with its tail twisting along a bit later. Serpens is the only constellation that’s split apart. The two halves are separated by Ophiuchus, the serpent bearer. The snake’s head rises first. It’s in the east and southeast at nightfall, marked by a serpentine trail of faint stars. The tail, which is below Ophiuchus, climbs into view about an hour later. The brightest of the stars of Serpens is Unukalhai — an Arabic name t...
Sunny Skies
May 25, 2024 05:00 - 2 minutes - 1.02 MBAiello del Friuli is a village in northern Italy, about 75 miles from Venice. It’s home to about 2200 residents and more than a hundred sundials — so many that it’s known as the “village of sundials.” It hosts a sundial festival every year, in late May. The village began earning the nickname in 1994. A resident created a sundial and hung it on the side of his house. It was more than just a pointer and some numbers, though — it was a work of art. So others in the village asked him to make su...
Brightest Black Hole
May 24, 2024 05:00 - 2 minutes - 1.06 MBBlack holes are the darkest objects in the universe — they produce no light at all. Yet they power some of the brightest objects. Known as quasars, these beacons can outshine entire galaxies of hundreds of billions of stars. In fact, the brightest one seen so far emits more light every minute than the Sun will produce in its entire 10-billion-year lifetime. A black hole’s gravity is so powerful that nothing can escape from it — not even light. But before anything disappears into the black h...
Black-Hole Sun
May 23, 2024 05:00 - 2 minutes - 1.06 MBStars like the Sun aren’t massive enough to become black holes when they die. But there’s a possible exception to that rule: if the star is born with a small black hole inside it. The idea was first proposed by Stephen Hawking. And it’s supported by a recent study. Normally, a star like the Sun just isn’t massive enough to collapse to make a black hole. But the universe might be sprinkled with black holes created in the Big Bang. Such black holes could be just about any mass — from almost ...
Man in the Moon
May 22, 2024 05:00 - 2 minutes - 1.06 MBOur brains can see things that aren’t there. They connect points and shapes to create “pictures.” So we might see a dragon in some puffs of clouds, “canals” on the surface of Mars, or a scorpion in the stars. One of the most persistent pictures is the “man in the Moon” — a face created from features on the lunar surface. Stories about the man in the Moon — or, in some cases, the woman in the Moon — go back centuries, from cultures around the planet. In China, for example, the face represen...
Balanced Moon
May 21, 2024 05:00 - 2 minutes - 1.06 MBThe Moon is in a sort of cosmic balance tonight. It’s passing through Libra, the balance scales — the only constellation of the zodiac that doesn’t represent a living thing. But the scales are associated with two living things — Virgo, which represents a goddess, and Scorpius, the scorpion. In various cultures of the Mediterranean, the stars of Libra were attached to one or both of those figures. In ancient Babylon, the stars represented a scale held by Shamash, the Sun god. He was also th...
Sun Rays
May 20, 2024 05:00 - 2 minutes - 1.06 MBOne of the icons of classic western movies is the sunset. Even in black and white, rays of sunlight radiate into the sky like jets of water erupting from a fountain. They add a bit of grandeur to any sunrise or sunset. They’re known as crepuscular rays, from the Latin word for twilight. Technically, the name applies to rays that appear during morning or evening twilight, while the Sun is below the horizon. In modern usage, though, it applies to rays of sunlight shining from behind clouds or...
Mizar and Alcor
May 18, 2024 05:00 - 2 minutes - 1.06 MBA horse and rider gallop across the north and northwest on May evenings. They’re in the handle of the Big Dipper, which is high in the sky at nightfall and low in the northwest at dawn. They’re the stars Mizar and Alcor. Mizar is the brighter of the two, with fainter Alcor just a whisker away. They’re so close together that the skywatchers of bygone centuries thought of them as a horse and rider. Mizar is a system of four stars, all of which are a little hotter and brighter than the Sun. A...
Moon and Twins
May 12, 2024 05:00 - 2 minutes - 1.03 MBThe Moon passes especially close to the star Pollux tonight — the brighter “twin” of Gemini. The star stands just to the right of the Moon at nightfall. The other twin, Castor, is farther along the same line. The Moon always passes closer to Pollux than to Castor. That’s because of the relationships of the three bodies to the ecliptic — the Sun’s path across the sky. The Moon’s orbit is tilted a bit with respect to the ecliptic. Over the course of a month, it meanders to either side of the...
Cape Canaveral
May 11, 2024 05:00 - 2 minutes - 1.03 MBIt’s hard to think of the White Sands region of New Mexico as confining. It covers thousands of square miles, and few people live there. In the late 1940s, though, the U.S. military was feeling hemmed in. It was launching rockets from White Sands. They could go high, but they couldn’t go very far without flying over towns or cities — a possible danger to residents. So Congress passed a bill establishing the Joint Long-Range Proving Ground at Cape Canaveral, on the Atlantic coast of Florida....
Krypton
May 10, 2024 05:00 - 2 minutes - 1.03 MBScience and science fiction can intertwine in some interesting ways. Consider krypton — the chemical element and the fictional planet. The element was discovered in 1898. It makes up a tiny fraction of Earth’s atmosphere — about one part in a million. It’s colorless, odorless, and tasteless. And it almost never reacts with other matter. It’s used in some fluorescent light bulbs and in lasers. In 1938, the creators of “Superman” needed a home planet for their visitor from another world. The...
Moon and Elnath
May 09, 2024 05:00 - 2 minutes - 1.03 MBThe names of the stars that are visible in the night sky can be obscure. But that’s not the case for the star known as Elnath. The name comes from Arabic, and it means “the butting one.” That makes perfect sense when you consider that it forms the tip of one of the horns of Taurus, the bull. It’s the second brightest star in the constellation. Elnath is quite impressive. It’s about five times the mass of the Sun, more than four times wider than the Sun, and about 700 times brighter. Its sur...
Saturn and Aquarius
May 08, 2024 05:00 - 2 minutes - 1 MBIt’s easy to see pictures in the night sky. Just pick out some stars and connect them to make a pattern. The skywatchers of ancient Babylon linked some stars to show a man pouring water from a jar. Today, that picture is known as Aquarius, the water bearer. The constellation is in the east-southeast before dawn. Near the left side of the constellation, you’ll find a much smaller star picture: a bowling ball scattering some pins. The ball is the planet Saturn, which looks like a bright star....
Hercules Cluster
May 07, 2024 05:00 - 2 minutes - 1 MBIn our region of the Milky Way Galaxy, the stars are a long way apart. The Sun’s nearest neighbor is more than four light-years away — 25 trillion miles. In the core of a globular cluster, though, the stars are packed hundreds of times more densely. That means the stars are only a few light-months apart, or even light-weeks — much closer than in our own neighborhood. One of the most prominent globular clusters is in Hercules, the strongman. M13 — the Hercules Cluster — is perhaps 25,000 lig...
Hercules
May 06, 2024 05:00 - 2 minutes - 1 MBThe geography of the sky owes a lot to Claudius Ptolemy. He was a Greek astronomer who lived and worked in Alexandria, the capital of Greek-controlled Egypt. Almost 1900 years ago, Ptolemy published one of the most important astronomical works in history. Known as the Almagest, it contained Ptolemy’s models of the motions of the Sun, Moon, and planets, and much more. One of its most important features was a catalog of stars and constellations. It listed 48 constellations visible from the no...
Leo Triplet
May 05, 2024 05:00 - 2 minutes - 1 MBMost of the “star pictures” in the night sky look nothing like their namesakes. But one beautiful exception lunges across the southwestern sky on May evenings: Leo, the lion. It’s high in the sky at nightfall. Leo consists of two patterns of stars that the brain puts together to make a lion. A backward question mark represents the head and mane. And a triangle of stars to the lower left forms the lion’s hindquarters and tail. Leo is best known for its bright stars — especially Regulus, its...
Moon and Mercury
May 04, 2024 05:00 - 2 minutes - 1 MBOver the centuries, no planet has been as frustrating to study as Mercury. The Sun’s closest planet never moves far from the Sun in our sky. So when astronomers pointed telescopes at Mercury, it was almost always screened by twilight and a thick layer of Earth’s atmosphere. So most of what we know about Mercury has come from spacecraft that visited the planet. You can see the difficulty yourself the next few days. Mercury is quite low in the east not long before sunrise. It’s almost at its ...
Moon and Saturn
May 02, 2024 05:00 - 2 minutes - 1 MBThe solar system is pretty settled. The planets appear to be following orbits that have remained stable for billions of years. But in the early days, things might have been a lot more chaotic. According to one model, in fact, the giant planets Jupiter and Saturn might have moved much closer to the Sun before they moved back out again. The planets probably took shape from a disk of gas and dust around the Sun. Small bits of material stuck together to make bigger bits, all the way up to plane...
Nereid
May 01, 2024 05:00 - 1 MBOne of the larger moons of the planet Neptune has been through a lot. It might have started as an asteroid, and was captured by Neptune’s gravity. Or it might have started as a moon, but was hurled into a wild orbit when Neptune grabbed its largest moon. And since then, it’s been battered by impacts with other space rocks. Nereid was discovered 75 years ago today, by Gerard Kuiper. It was only the second moon seen around the giant planet, and it’s the third-largest of Neptune’s 16 known moo...