StarDate

Billy Henry
  • 4.6 (262)
  • ASTRONOMY
  • UPDATED DAILY

StarDate, the longest-running national radio science feature in the U.S., tells listeners what to look for in the night sky.

Episodes

  1. 1D AGO

    Pointing the Way

    It’s hard to ask for a better signpost for finding things in the night sky than the planet Venus. Right now it’s the brilliant “evening star,” low in the west as twilight fades. And it points the way to two other wonders: the planet Uranus and the Pleiades star cluster. The Pleiades is fairly easy to find on its own. Its brightest stars form a tiny dipper shape. In fact, the Pleiades is often mistaken for the Little Dipper. But that dipper is in the north, anchored by the North Star. Despite its prominence, the Pleiades is best appreciated with a technique known as averted vision – seeing it from the corner of your eye. And Venus offers a good chance to try it. Look at Venus, then see if you can see the sparkly cluster to its right. They’re separated by the width of a couple of fingers held at arm’s length. Uranus is about one finger width below Venus. It’s the third-largest planet in the solar system. But it’s so far away that it looks tiny and faint. It’s an easy target for binoculars or a small telescope, though. It looks like a faint star. A telescope reveals something interesting about Venus – it doesn’t look quite complete. That’s because it’s in a gibbous phase. If you watch the planet for months, you’ll see it get thinner and thinner. That’s because Venus will cross between Earth and the Sun in late October. Like the new Moon, it’ll be lost in the Sun’s glare no matter how you look at it. Script by Damond Benningfield

    2 min

  2. 2D AGO

    Thick Ice

    Jupiter’s big moon Europa is one of the most likely bodies in the solar system to host life. The moon has a global ocean that holds more water than all of Earth’s oceans combined. The ocean might have sources of energy and chemical compounds that are needed to support microscopic life. But getting to that ocean won’t be easy. It’s covered by a crust of ice. And a recent study says the ice is pretty thick. The Juno spacecraft scanned part of Europa with an instrument that can probe conditions below the surface. It found that the average thickness of the ice is about 18 miles. That’s thicker than suggested by some earlier studies. Juno found many cracks in the ice. But they don’t penetrate anywhere close to the water. So there doesn’t appear to be a good way to get through the ice to study the ocean. That also could be a problem for any organisms in the ocean. Jupiter’s radiation zaps material on the surface, transforming it into possible nutrients. Without any holes or thin spots in the ice, there’s no direct way to flush the nutrients into the water. But another study found that large concentrations of nutrients could make blocks of ice denser than the surrounding ice. Over time, the heavier blocks could sink all the way through the ice – perhaps helping to sustain any life in Europa’s hidden ocean. Jupiter is high in the west at nightfall, and looks like a brilliant star. The twins of Gemini stand above it. Script by Damond Benningfield

    2 min

  3. 3D AGO

    Moon and Jupiter

    In December of 2024, a region on Jupiter’s moon Io blew its top. Several huge volcanoes were erupting at the same time – the most powerful volcanic event ever seen anywhere in the solar system. The outburst covered an area the size of West Virginia. During the hour that a spacecraft was watching, it produced enough energy to power the entire United States for days. Io is by far the most active body in the solar system. It has hundreds of cones, lava pools, and other volcanic features. They’re powered by a constant tug-of-war between Jupiter and some of its other big moons. They pull and stretch Io’s interior, heating it up. The 2024 eruptions were observed by Juno, a spacecraft that’s orbiting through the Jovian system. The region on Io had been quiet when Juno last looked at it, about two months earlier. So the eruptions must all have started at about the same time. That suggests they were powered by the same source of magma below the surface. The magma must have traveled through a network of underground plumbing, allowing it to power several eruptions at once. So Io’s interior might be like a sponge, with lots of open spaces – that are sometimes filled with molten rock. Jupiter appears just above our moon tonight. It looks like a brilliant star. Through binoculars, Io and Jupiter’s other big moons look like tiny stars quite close to the planet. We’ll talk about one of Jupiter’s icy moons tomorrow. Script by Damond Benningfield

    2 min

  4. 4D AGO

    Venus and Uranus

    Two planets cross paths in the evening sky this week. One is brilliant, the other a little too faint to see without some help. The brilliant one is Venus, the “evening star.” In all the night sky, only the Moon outshines it, so you can’t miss it. But you can miss Uranus. It’s a giant, but it’s so far away that it’s not easy to see. Several factors control how bright a planet looks: the planet’s distance from both Earth and the Sun, its size, and how much sunlight is reflected from its surface. The clouds that blanket Venus reflect much more sunlight than the clouds of Uranus do. And while Uranus is about four times the diameter of Venus, right now it’s almost 14 times farther. That makes it look smaller in our sky. The distances are also important in another way. The farther an object is from the Sun, the feebler the Sun appears. At their average distances from the Sun, each square foot of Venus receives more than 700 times more sunlight than the same size patch of Uranus. At the same time, the farther an object is from Earth, the less of its light we receive. When you put it all together, Venus looks more than seven thousand times brighter than its giant sibling. Venus blazes into view as twilight fades. Uranus is a couple of degrees to its upper left, and it’s an easy target for binoculars. The two worlds will stand almost side by side on Thursday, just a fraction of a degree apart. Script by Damond Benningfield

    2 min

  5. 5D AGO

    Lyrid Meteors

    A modest meteor shower should be at its best the next couple of nights. You need dark skies to see it – the glow of city lights will erase it from view. And even at its peak, the shower produces no more than a dozen or so meteors per hour. But the Moon won’t get in the way, so if you have good weather and a good viewing spot, it’s worth a look. The Lyrid shower occurs at this time every year as Earth passes through a trail of comet dust – debris from Comet Thatcher. The comet last visited the inner solar system in 1861, and it won’t return for almost three centuries. But each time it approaches the Sun, it sloughs off bits of rock and dirt. They spread out along the comet’s orbital path. When Earth flies through that path, some of the grains ram into the atmosphere at a hundred thousand miles per hour. They vaporize, forming the glowing streaks of light known as meteors. The shower is named for the constellation Lyra, the harp. That’s because its meteors all appear to “rain” into the sky from near Vega, Lyra’s brightest star. They can fly across any part of the sky, though, so you don’t need to be looking at Lyra to see them. The best view comes after Lyra climbs into good view, after midnight. The Moon sets a little later, making the skies nice and dark. That will provide several good hours to watch the meteors – reminders of a comet that’s billions of miles from Earth. Script by Damond Benningfield

    2 min

  6. 6D AGO

    Moon and Companions

    The Moon passes through the bull tonight. The bull’s “eye” – the star Aldebaran – is off to the left of the Moon. The bull’s face and shoulder are even closer, represented by a pair of star clusters – the Hyades and the Pleiades. For the most part, you can’t tell the distance to an astronomical object just by its appearance. Something that looks quite bright might be close, but it might also be far away and especially bright. But you can tell something about the distances to the objects around the Moon tonight by their appearance. The Pleiades looks like a tiny dipper close below the Moon. It contains hundreds of young stars, some of which are hot and bright. But the cluster’s small size is a good indication of its distance – almost 450 light-years. The Hyades looks bigger. It forms a letter V that outlines the bull’s face. It looks a good bit more spread out than the Pleiades. But that’s largely because it’s only a third as distant. Aldebaran stands at the top left point of the V. It outshines all the other points. In part, that’s because it’s less than half as far – just 65 light-years away. So these prominent features really do tell us something about their distances. One other bright light stands directly below the Moon in early evening, and it’s the brightest of all: Venus, the “evening star.” Right now, it’s closer to us than anything else except the Moon. Script by Damond Benningfield

    2 min

  7. APR 18

    Moon and Venus

    You might want to have the butter and the Mrs. Butterworth’s handy for this one – it’s all about pancakes. Some of them are as big as a major city. There are only two problems: They’re made out of dense volcanic rock, and they’re on the planet Venus. Venus is covered with many thousands of volcanic features – lava plains, cone-shaped mountains, and structures that look like crowns and spiders. Most of the features are old, but there are hints that the planet is still volcanically active today. The list of features includes pancake domes. There are scores of them – some by themselves, but many in groups. They’re almost perfectly round and flat. They can be up to a few dozen miles across, and more than half a mile tall. And their edges are steep – almost-sheer cliffs. The domes probably formed when thick molten rock bubbled to the surface. It spread out in all directions. And it continued to spread well after the lava spigot was turned off. A study published last year said that some of the pancakes dented the surface below them – perhaps one reason they’re so flat. That dimple created a moat around one of the domes, with a raised rim around the moat – a good arrangement for catching all that butter and syrup. Venus is the brilliant “evening star.” It’s quite close to the crescent Moon this evening. The Moon will stand above the planet tomorrow night; more about that on our next program. Script by Damond Benningfield

    2 min

  8. APR 17

    Morning Meeting

    There’s a frustrating meeting of planets in the early morning sky right now. It’s frustrating because the planets are quite low in the sky in the dawn twilight, so they’re hard to see. The participants in this meet-up are Mercury, Mars, and Saturn. Tomorrow, they’ll form a tight triangle. They’ll form a straight line on Monday before they begin to separate. Mercury is the brightest of the trio, followed by Saturn, then Mars. The planets aren’t actually anywhere close to each other – they just happen to line up in the same direction. Mercury is the closest, at a distance of a bit more than a hundred million miles. Mars is more than twice that far. And Saturn is farther still – almost a billion miles. Mercury is making a small loop across the dawn before dropping back into the solar glare. It’s the closest planet to the Sun, so it never moves far from the Sun in our sky. That means our chances to see it are limited. Mars and Saturn are farther from the Sun than Earth is, so they move all the way across the sky. Both are slowly working higher into the dawn. As the months pass, they’ll rise earlier and remain in view longer. For now, Mercury, Mars, and Saturn are quite low in the east as twilight paints the sky. They’re tough to see, especially from farther north. From the U.S., the best views are from places like Miami and Honolulu. The best place to watch the meet-up is the southern hemisphere. Script by Damond Benningfield

    2 min

  9. APR 16

    Alignments

    Every time that two or more planets congregate in the night sky, fear mongers crank up the volume on their predictions of doom. They say the combined gravity of the planets will cause everything from earthquakes and storms to boils and hangnails. Don’t listen to them. All of the planets are so small or so far away that their short-term effects on Earth are negligible. Jupiter, the largest and heaviest planet in the solar system, is only one-tenth of one percent as massive as the Sun. And, on average, it’s about five times farther. When combined, those numbers tell us that Jupiter’s gravitational tug on Earth is just one-25,000th as strong as the Sun’s. The pull of the other planets is even weaker. So even if you lined up all of the planets in the same direction from Earth, their combined pull would be insignificant. That’s not the case on longer terms, though. The gravity of Jupiter and Venus change the shape of Earth’s orbit and the planet’s tilt on its axis. Mars may play a role as well. That influence creates cycles of warmer and colder climate. But the cycles play out over tens of thousands of years or longer – not over days, weeks, or even centuries. Planetary alignments are common. In fact, there’s one right now. Mars, Saturn, and Mercury are close together in the dawn twilight. But they’re so low in the sky that they’re tough to see. We’ll have more about their alignment tomorrow. Script by Damond Benningfield

    2 min

  10. APR 15

    Coma Galaxies

    The Coma galaxy cluster is like a cosmic iceberg. What you see is impressive. But what you don’t see is even more impressive. The cluster is centered more than 300 million light-years away, and it spans 25 million light-years. It contains thousands of individual galaxies. Many of them are far bigger and heavier than our own galaxy, the Milky Way. But in the 1930s, German astronomer Fritz Zwicky found something odd. He measured the motions of individual galaxies within the cluster. They were zipping along much too fast to be held in check by the gravity of the visible galaxies – they should all fly away from each other. Zwicky concluded that something else was acting as a sort of gravitational “glue.” He called it dark matter – matter that couldn’t be seen, but that exerted a gravitational pull on the visible matter around it. It took decades to confirm that finding. And even today, we don’t know what dark matter really is. The leading idea says it’s some type of subatomic particle. But despite many years of searching, no such particle has been found. All we know for sure is that dark matter accounts for about 85 percent of all the matter in the universe – the vast hidden depths of the cosmic iceberg. The Coma Cluster is in Coma Berenices. The constellation is in the east at nightfall. It’s above brilliant Arcturus, the brightest star of Bootes, and to the lower left of Leo, the lion. Script by Damond Benningfield

    2 min
  • 10 Episodes

Hosts & Guests

4.6
out of 5
262 Ratings

About

StarDate, the longest-running national radio science feature in the U.S., tells listeners what to look for in the night sky.

Information

  • Creator
    Billy Henry
  • Years Active
    2017 - 2026
  • Episodes
    10
  • Rating
    Clean
  • Copyright
    © 2022 The University of Texas McDonald Observatory
  • Show Website
    StarDate

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