StarDate
867 episodes - English - Latest episode: 7 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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Arcturus
April 15, 2024 05:00 - 2 minutes - 1 MBThe star Arcturus is a little bit heavier than our own star, the Sun. Yet that small difference has a big effect on the star’s evolution: Arcturus entered a late stage billions of years earlier than the Sun will. Arcturus is one of the brighter stars in the night sky, and shines yellow-orange. Both of those traits are a result of its stage in life, which was triggered by its mass. Mass is the key to how quickly a star consumes the hydrogen in its core. The gravity of a heavier star squeezes...
Moon and Gemini
April 14, 2024 05:00 - 2 minutes - 1 MBThe Moon creeps up on the twin stars of Gemini this evening. As night falls, Pollux and Castor are above the Moon. Pollux is on the left, and is a bit brighter than its “twin.” There’s a lot more to Gemini than just the twins — or even the other stars that are visible to the unaided eye. In fact, one of its most intriguing objects produces most of its energy in the form of X-rays and gamma rays, which are far beyond the range of the human eye. The object is known as Geminga — short for “Gem...
Vanishing Hunter
April 13, 2024 05:00 - 2 minutes - 1 MBThis time of year is pretty inviting for some evening skywatching. The evening hours are warm but not usually too hot, and spring storm activity generally hasn’t reached its peak — pleasant conditions for watching the stars. Unfortunately, one of the most beautiful star patterns is dropping from view, so there aren’t many more weeks to enjoy it. Orion the hunter is low in the west as night falls. Its three-star belt stands almost parallel to the horizon. And its two brightest stars bracket ...
Vaporized Planets
April 12, 2024 05:00 - 2 minutes - 1 MBPlanetary systems can be violent. In our own solar system, for example, the Moon probably was born from the debris left over when a planet as big as Mars rammed into Earth billions of years ago. And the giant planet Uranus probably was knocked over on its side by a similar collision about the same time. A more recent example comes from ASASSN-21qj — a star system that’s about 1800 light-years away, in the constellation Puppis. In December of 2021, astronomers noticed that a Sun-like star th...
Vaporizing Planet
April 11, 2024 05:00 - 2 minutes - 1 MBPlanets like Earth live in the “Goldilocks zone” — the region around a star where conditions are most comfortable for life. But most planets aren’t so cushy. They’re either far away and cold, or close in and hot. And some are so close that they’re being vaporized by their star. One example is WASP-69 b. It orbits a cool, faint star about 160 light-years from Earth. The system is in the constellation Aquarius, which is in the southeastern sky at dawn tomorrow. WASP-69 b is only a few million...
Seeing Giants
April 10, 2024 05:00 - 2 minutes - 1 MBIf you heat up some alphabet soup, you shouldn’t end up with all the letters clumped together — they should be fairly evenly spread throughout the pot. According to the current understanding of the universe, the same thing should apply to galaxies. They may clump together on smaller scales, forming clusters and even super-clusters. But when you look at the universe as a whole, the galaxies ought to be evenly spread. Yet astronomers have found giant galaxy structures that seem to defy that id...
Moon and Planets
April 09, 2024 05:00 - 2 minutes - 1 MBEuropa is one of the more intriguing bodies in the solar system — and one that scientists are especially eager to land a spacecraft on. The big moon of Jupiter may have a global ocean below its icy crust — an ocean that could host life. But landing on Europa won’t be easy. It’s hundreds of millions of miles away, and it’s embedded in Jupiter’s powerful radiation belts. And the surface near its equator could be mottled by fields of icy spikes that are up to five stories high. Such structures...
Future Eclipses
April 08, 2024 05:00 - 2 minutes - 1 MBIn case you haven’t heard, there’s a big event this afternoon — a total eclipse of the Sun. Totality is visible along a narrow path from Texas to Maine. The parts of the country outside that path will see a partial eclipse. If you miss it — well, let’s just say it’ll be a long wait until the next great eclipse over the United States. The next total eclipse visible anywhere will take place on August 12th, 2026. Its path will cross parts of Europe, but most of it will cross the high Arctic. ...
Total Eclipse
April 07, 2024 05:00 - 2 minutes - 1.02 MBIt’s almost time for the year’s big celestial event: a total eclipse of the Sun. Tomorrow afternoon, the Moon will pass directly between Earth and the Sun. That will block the Sun’s disk. The sky will grow dark, with a pink glow around the horizon. Stars and planets will pop into view. And the Sun’s faint outer atmosphere, the corona, will look like silvery ribbons around the Moon. Totality will be visible along a narrow path. In the United States, it’ll stretch from Eagle Pass, Texas, to Ho...
Eclipse Flights
April 06, 2024 05:00 - 2 minutes - 1.02 MBIn the mythology of ancient Egypt, Apep was the serpent god — the rival of Re, the sun god. He chased Re, and sometimes briefly caught him — creating a solar eclipse. NASA plans to launch an experiment named for the serpent god to study the eclipse on Monday. Instruments will fly on three different rockets. They won’t look at the Sun, though. Instead, they’ll study the effect of the eclipse on the ionosphere — a high-altitude layer of Earth’s atmosphere. The ionosphere carries an electric c...
Eclipse Animals
April 05, 2024 05:00 - 2 minutes - 1.02 MBColonial orb-weaver spiders may have some extra work to do on Monday, during a total solar eclipse. During an eclipse in 1991, scientists watched as spiders in Mexico began tearing down their webs as the sky darkened — something they do every evening. When the Sun returned, most of them rebuilt their webs, just as they do every morning. That’s just one example of how life reacts to eclipses. Like the spiders, many daytime animals start their evening rituals. And many nighttime animals wake u...
Eclipse Legends
April 04, 2024 05:00 - 2 minutes - 1.02 MBA total solar eclipse occurs when the Moon passes in front of the Sun, briefly blocking it from view. Before people understood the science, however, they created legends to explain the Sun’s disappearance. Many of those legends involved animals or mythical monsters. In China and elsewhere, it was thought the Sun was being devoured by a dragon. People in Vietnam blamed a hungry frog. In Scandinavia, it was a giant wolf set loose by the god Loki. In India, it was the severed head of a monster....
Eclipse Forecasts
April 03, 2024 05:00 - 2 minutes - 1.02 MBThe Great North American Eclipse is coming up on Monday. The Moon will briefly cover the Sun. That will turn day to night along a narrow path across Mexico, the United States, and Canada. The timing of the eclipse is known down to the second, and has been for decades. And today, astronomers can predict eclipses far into the future. But making such predictions isn’t easy. It requires a detailed knowledge of the Moon’s orbit around Earth, Earth’s orbit around the Sun, and even the shapes of Ea...
Corona
April 02, 2024 05:00 - 2 minutes - 1.02 MBOn Monday, millions of people will see something they’ve never seen before: the Sun’s corona — its hot outer atmosphere. It extends hundreds of thousands of miles from the surface of the Sun. But it’s so faint that it’s overpowered by the Sun’s brilliant disk. The only time we can see it is during a total solar eclipse. The corona is made of super-heated gas known as plasma. In fact, the corona is heated to a couple of million degrees Fahrenheit, and sometimes hotter. By comparison, the Sun’...
Solar Eclipse
April 01, 2024 05:00 - 2 minutes - 1.02 MBMany people dread Mondays and the start of the new work week. But there’s something to look forward to next Monday: the Great North American Eclipse. The Moon will completely cover the Sun, turning the sky dark. Tendrils of light will extend away from the Moon — the Sun’s hot outer atmosphere, the corona. If you can find a way to get to the eclipse path, it’s worth the effort. For this eclipse, the Moon is a little closer to Earth than average. So the period of totality, when the Sun is full...
Penumbral Eclipse
March 24, 2024 05:00 - 2 minutes - 1.06 MBAnyone standing on the Earth-facing hemisphere of the Moon tonight would see a partial solar eclipse, with Earth covering part of the Sun’s disk. From here on Earth, however, all we’ll see is a penumbral lunar eclipse. The eclipse is so faint that few will notice a difference — the full Moon will have only a slight shading. A penumbral eclipse occurs when the alignment of the Sun, Earth, and Moon isn’t perfect. The Moon catches only the outer part of Earth’s shadow, the penumbra, which isn’...
Moon and Denebola
March 23, 2024 05:00 - 2 minutes - 1.06 MBThe star that marks the tip of the lion’s tail appears to be a loner. It doesn’t have a companion star. And so far, it doesn’t appear to have any planets, either. But it does have the raw materials for making planets. And one or more worlds could have taken shape from those building blocks. Denebola is the second-brightest star of Leo, the lion. It’s to the upper left of the almost-full Moon this evening, by about the width of your fist held at arm’s length. Denebola is 36 light-years away...
Evening Mercury
March 22, 2024 05:00 - 2 minutes - 1.06 MBOnly two planets in our solar system are moonless: Mercury and Venus, the planets closest to the Sun. But 50 years ago this month, it looked like Mercury might have to drop off the list — but only for a while. The excitement began as Mariner 10 sped toward the planet, in 1974. Mariner was the first spacecraft to visit Mercury. Before then, astronomers were limited to views through telescopes. But Mercury is so close to the Sun that it could be hard to see a moon in a tight orbit around the ...
Moon and Regulus
March 21, 2024 05:00 - 2 minutes - 1.06 MBIt’s been more than half a century since the final Apollo mission left the Moon. But scientists are still learning from it. A few years ago, they started examining samples from Apollo 17 that hadn’t been touched before — a project that’s ongoing. They’re also analyzing observations made by instruments left on the Moon. That work says that lots of little tremors rattle the landing site. Astronauts Gene Cernan and Jack Schmidt set up a quartet of special microphones to “listen” for moonquakes....
A Small Search
March 20, 2024 05:00 - 2 minutes - 1.06 MBIt may be a cliche, but it’s true: If at first you don’t succeed, try, try again. That’s certainly the case for the scientists hunting for dark matter. They’ve conducted many big experiments over the past few decades. So far, though, they haven’t found a thing. So the hunt is going smaller — looking for extremely light particles known as axions. Astronomers see the effects of dark matter all across the universe. The dark matter itself emits no energy, but its gravity pulls on the visible ma...
March Equinox
March 19, 2024 05:00 - 2 minutes - 1.06 MBSpring arrives in the northern hemisphere tonight, at the moment of the March equinox, as the Sun crosses the celestial equator. Day and night are about equal across the entire planet — hence the name “equinox,” which means “equal nights.” The Sun is passing through Pisces, the fishes. In fact, it’s appeared in Pisces at the equinox for a couple of thousand years. Before that, it was in Aries, the ram. The shift is the result of an effect known as precession of the equinoxes. Earth wobbles...
Franz Gruithuisen
March 18, 2024 05:00 - 2 minutes - 1.06 MBWhen he was just 14 years old, Franz von Paula Gruithuisen found himself in the middle of the Austro-Turkish War. He wasn’t a prisoner or a refugee. Instead, he was a field surgeon. But just a year later, he was using a small telescope to observe the Moon. Those episodes marked the beginning of a diverse career in science. It featured both important contributions and false starts. Gruithuisen was born 250 years ago tomorrow, in a castle in Bavaria. His father was a servant, so his early edu...
Missing Planets
March 17, 2024 05:00 - 2 minutes - 1.06 MBThe types of planets you have as neighbors may depend on your neighborhood. The planets discovered in our region of the Milky Way Galaxy come in just about every variety: hot Jupiters, super-Earths, mini-Neptunes, lava planets, ocean planets, and others. But that may not be the case for other parts of the galaxy. As an example, there appear to be almost no super-Earths or mini-Neptunes outside the Milky Way’s disk. The disk is about a hundred thousand light-years wide, but only a few thous...
Moon and El Nath
March 16, 2024 05:00 - 2 minutes - 1.03 MBThe Moon hangs precariously above a star with a nasty-sounding name tonight: El Nath. The name comes from an Arabic phrase that means “butting” or “goring.” It indicates the star’s position in its constellation — at the tip of one of the horns of Taurus, the bull. The star itself is impressive. It’s about five times the size and mass of the Sun. And it’s much brighter. If you consider just its visible light, El Nath is about 300 times brighter than the Sun. So it looks bright even though it...
Summer Stars
March 15, 2024 05:00 - 2 minutes - 1.03 MBIf you’re ready for a taste of summer, look no farther than the dawn sky. The constellations in view at first light are just what you’ll see as night falls in July and August. Scorpius is low in the south, with Sagittarius in the southeast. The Big Dipper hangs from its handle in the northwest. And the Summer Triangle — the stars Vega, Deneb, and Altair — stands high in the east. As Earth orbits the Sun, our viewing angle on the stars changes. As a result, each star rises about four minutes...
Moon and Pleiades
March 14, 2024 05:00 - 2 minutes - 1.03 MBTwo beautiful objects team up this evening: the Moon and the Pleiades. The little star cluster is close above the Moon. Binoculars will help you pick out some of its brighter stars through the moonlight. The Pleiades has more than a thousand stars. They were born from the same cloud of gas and dust. But that doesn’t mean the stars are all alike. They come in many varieties. The brightest of them are much more impressive than the Sun. The brightest of all is Alcyone. It’s about six times th...
Moon and Jupiter
March 13, 2024 05:00 - 2 minutes - 1.03 MBScientists are finding so many moons of the solar system’s giant planets that they can hardly keep up with them. By the end of last year, Saturn was in the lead, with 146 confirmed moons. Jupiter — the biggest planet — came in second, with 95. But some of its moons are the most amazing of all — worlds with giant volcanoes, or hidden oceans that could host microscopic life. Most of the moons of both planets are a lot less interesting. They’re basically big chunks of rock and ice. Some of them...
Colorful Stars
March 12, 2024 05:00 - 2 minutes - 1.03 MBStars come in a whole spectrum of colors, from icy blue to deep red. But our eyes can see the color in only a few stars — most of them are simply specks of white. That’s because most stars are too faint to show off their palette. The human eye can pick out the colors of only the brightest ones. Our eyes contain two types of light receptors: rods and cones. They’re in the retina, at the back of the eye. There are about a hundred million rods. They’re sensitive to low levels of light, so the...
Planetary Poetry
March 11, 2024 05:00 - 2 minutes - 1.03 MBPlanetary scientists may see many descriptions this week that are similar to this one: Return to Mimas Blow up the Death Star (moon) and Find hidden oceans. That’s from a presentation about one of Saturn’s moons by Adeene Denton and colleagues at last year’s Lunar and Planetary Science Conference in Texas. It’s become a tradition for scientists to provide a simple description of their work as haiku. The conference has even held a contest for the best one. The winner in 2022 came from Benjam...
Puppis
March 10, 2024 06:00 - 2 minutes - 1.03 MBSometimes, you can have too much of a good thing. That was the case with a constellation that was created thousands of years ago. It was so big that astronomers eventually split it apart. Argo Navis represented the Argo — the ship that carried Jason and the Argonauts through many adventures. But the constellation was unwieldy. So, in the 1750s, Nicolaus Louis de la Caille divided it into three constellations: Carina, the keel; Vela, the sail; and Puppis, the deck at the stern of the ship. P...
Close Moon
March 09, 2024 06:00 - 2 minutes - 1.03 MBThe Moon is nowhere in sight the next couple of days. That’s because it’s new — it crosses between Earth and the Sun, so it’s hidden in the Sun’s glare. But coastal residents will definitely feel its presence. That’s because the Moon is closest to Earth for the year. The combination of the lunar phase and the Moon’s distance means that we’ll have some of the highest tides of the year. The tides are caused by the gravitational pull of the Moon and Sun. The Moon is closer to us, so its influe...
Moving Dipper
March 08, 2024 06:00 - 2 minutes - 1 MBThe Big Dipper is on the move. Not just its nightly circle around the North Star. And not even its shifting position from month to month. The stars themselves are moving through the Milky Way Galaxy. And most of them are moving together. The stars of the Big Dipper are in Ursa Major, the great bear. The constellation has given its name to a widely spread group of stars that appear to move together — the Ursa Major Moving Group. It consists of a few dozen stars in all. Its core is in Ursa Maj...
Solar Soundings
March 07, 2024 06:00 - 2 minutes - 1 MBThe Sun is building toward the peak of its magnetic cycle, probably sometime this year. That’s when it produces more sunspots, flares, and giant clouds of charged particles. All of those can have an effect on our technology — knocking out satellites and power grids, disrupting radio transmissions, and more. So scientists pay close attention during these active times. In fact, they’re planning to launch half a dozen small rockets over the next month. Three of them will look at a flare, while...
Six in Sync
March 06, 2024 06:00 - 2 minutes - 1 MBA nearby star has one of the largest families of planets yet seen — an even half-dozen. Only two other known exoplanet families are bigger. But this system is different from the others. All of the planets march in time — their orbits are in perfect sync. The star is known as HD 110067. It’s about a hundred light-years away, in the constellation Coma Berenices, which is in the east this evening. The star is a bit smaller and cooler than the Sun. But it’s probably several billion years older....
Coma Cluster
March 05, 2024 06:00 - 2 minutes - 1 MBDescriptions of the Coma Cluster of galaxies sound like bad car-dealership commercials. The cluster contains more than a thousand galaxies. They’re bound together by their mutual gravitational pull. The heart of the cluster is about 330 million light-years away. But the cluster may span as much as two hundred million light-years. But wait — that’s not all! There’s a lot more to the cluster than we can see. In 1933, Fritz Zwicky found that galaxies in the cluster are moving fast — too fast fo...
Coma Berenices
March 04, 2024 06:00 - 2 minutes - 1 MBA sprinkling of faint stars stands in the east a few hours after sunset right now. It’s to the upper right of brilliant Arcturus, the brightest star in that part of the sky. Those ribbons of stars are the main features of Coma Berenices. The constellation represents Queen Berenice II of Egypt. The legend says that when her husband was about to head into battle, she offered her beautiful golden hair to the gods in exchange for his safety. When he returned undamaged, she cut her hair and plac...
Star Structure
March 03, 2024 06:00 - 2 minutes - 1 MBAll stars are big balls of glowing gas, powered by nuclear fusion. But stars come in many different sizes, masses, and colors. And they’re put together in different ways. The Sun is in the middle range. It consists of three main layers — the core, the radiation zone, and the convection zone. The core is where a star generates energy. Stars in the prime phase of life “fuse” hydrogen atoms to make helium, releasing energy in the process. In the Sun, the core is surrounded by the radiation z...
Moon and Antares
March 02, 2024 06:00 - 2 minutes - 1 MBThe night sky plays tricks. Objects that appear close together in the sky can actually be far apart. As an example, look at the Moon and the star Antares before dawn tomorrow. There’s almost no separation between them. In fact, for some parts of the eastern U.S., there won’t be any separation at all — the Moon will cover the star for a while, hiding it from view. That makes it look like the Moon and Antares are close together in space. But that’s not the case. The Moon is our closest astron...
Uncertain Stars
March 01, 2024 06:00 - 2 minutes - 1 MBMany bright stars highlight the sky this evening: Sirius, the brightest of them all; Regulus, the heart of the lion; several sparklers in Orion, and more. Astronomers know a lot about these stars. But most of what they know is a bit uncertain. So when they pin numbers to a star, they give themselves some wiggle room to compensate. Consider Sirius, which is in the south at nightfall. It’s one of the Sun’s closest neighbors, at a distance of about 8.6 light-years. But that could be off by up ...
Leap Year
February 29, 2024 06:00 - 2 minutes - 1.03 MBThe remaining dates of 2024 will take a big leap. They’ll jump over a day of the week. That’s because this is leap year, and today is leap day — extending the year from 365 days to 366. Leap years are needed to keep the calendar in sync with the seasons. Without it, the equinoxes and solstices would slide across the calendar. So after many centuries, the spring equinox would happen in February, with the winter solstice backing into November. And over the ages, the shift would grow even large...
Missing Mars
November 18, 2023 06:00 - 2 minutes - 1.02 MBThree of the five planets that are easily visible to the unaided eye are in decent view now, with one more just starting to join them. Brilliant Jupiter, the largest planet in the solar system, is in the east at nightfall. Saturn, the second-largest, is in the southwest at the same time, well to the upper left of the Moon. Venus, the “morning star,” is in the southeast at dawn. And little Mercury is about to climb into the western sky during evening twilight. Only one planet is missing: Mar...
Meteor Trains
November 17, 2023 06:00 - 2 minutes - 1.02 MBFor fans of rail travel, “meteor train” may evoke images of a classic rail line of the early 20th century, or of Amtrak’s modern-day silver meteor train. For skywatchers, though, the phrase conjures different images: glowing streaks in the night sky than can last for a long time. And tonight is a good night to look for them, because the Leonid meteor shower should be at its peak. A meteor shower flares to life when Earth flies through the path of a comet. Tiny bits of rock and dirt shed by...
Leonid Meteors
November 16, 2023 06:00 - 2 minutes - 1.02 MBA meteor shower with a Jekyll-and-Hyde personality should be at its best over the next few nights. This is one of its “Jekyll” years, though, so it’ll be meek. At best, you might see 10 or so meteors per hour. The Leonid meteors are spawned by Comet Tempel/Tuttle 55. It was discovered in 1866, and it returns to the inner solar system once every 33 years or so. As it orbits the Sun, it sheds comet dust — small bits of rock and dirt. Earth flies through trails of this material every November....
Surviving the Heat
November 14, 2023 06:00 - 2 minutes - 1.02 MBVenus will reign as the “morning star” for the rest of the year. It’s the shiniest planet in the solar system. Because of its global cloud cover, it reflects more than three-quarters of the sunlight that strikes it. That’s compared to about 30 percent for Earth and just 12 percent for the Moon. Scientists have found a brighter planet about 230 light-years away, in the constellation Sculptor. LTT 9779b reflects as much as 80 percent of the light from its parent star. That makes it the most r...
Epsilon Eridani
November 13, 2023 06:00 - 2 minutes - 1.02 MBIt’s been a quarter of a century since astronomers discovered a planet orbiting the star Epsilon Eridani, a close neighbor. Since then, various teams have spent hundreds if not thousands of hours observing the system. Yet there’s still not complete agreement on the planet’s details. There wasn’t even agreement that the planet even existed until the past few years. Epsilon Eridani is 10 and a half light-years away; only eight systems of true stars are closer. The star itself is a bit smaller...
Dragonfish Nebula
November 12, 2023 06:00 - 2 minutes - 1.02 MBIt might sound impossible to hide a cluster of hundreds of the biggest and brightest stars in the galaxy — but it’s not. In fact, what could be the most impressive stellar nursery in the Milky Way wasn’t discovered until 2010. It’s hidden behind clouds of dust, which absorb the stars’ visible light. Astronomers found it by looking at infrared light, which shines through the dust. The Dragonfish Nebula is about 30,000 light-years away. It’s in Crux, the southern cross, which is too far south...
Helix Nebula
November 11, 2023 06:00 - 2 minutes - 1.02 MBFew sights in the universe are more impressive than a dying star. The star expels its outer layers of gas, leaving only its small, hot core. Radiation from the core energizes that gas, causing it to glow in a rainbow of colors. It can look like a cat’s eye, a butterfly, an hourglass, or many other shapes. Such an object is known as a planetary nebula. One of the closest and brightest is the Helix Nebula. It’s about 650 light-years away, in Aquarius. It looks like a set of concentric rings....
Moon and Spica
November 10, 2023 06:00 - 2 minutes - 1.02 MBA pair of bright, heavy stars perches just above the Moon at dawn tomorrow. They’re so close together, though, that they’re almost impossible to see as anything more than a single pinpoint of light. Spica is the brightest star of Virgo. It’s 250 light-years away. And both of its stars are much bigger and more massive than the Sun. The heavier of the two probably will end its life as a supernova — a titanic explosion that will blast the star to bits. The two stars are only a few million mil...
Sparking a Passion
November 09, 2023 06:00 - 2 minutes - 1.02 MBHarvey Nininger was on his way home 100 years ago tonight when he saw something that changed his life: a “fireball” — a brilliant space rock burning up in the atmosphere. Nininger taught biology at McPherson College, a small liberal-arts school in Kansas. On his walk home from work, he’d stopped to visit with a colleague when the fireball flashed overhead. It created a lot of questions for Nininger. But he found few answers — no one was studying meteors or meteorites — space rocks that fell...
More Moon and Venus
November 08, 2023 06:00 - 2 minutes - 1.02 MBVenus may be the most inhospitable planet in the solar system — at least at the surface. Temperatures are about 865 degrees Fahrenheit, the pressure is more than 90 times the pressure on Earth, and the atmosphere is made mostly of carbon dioxide — not a pleasant place to visit. But the story might be different in Venus’s clouds, which blanket the entire planet. The upper layers of clouds are made of sulfuric acid — not a pleasant place, either. A little deeper in the clouds, though, conditi...