StarDate

Billy Henry
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StarDate

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

Episodes

  1. 1 DAY AGO

    Uranus at Opposition

    Polar vortex has entered the American lexicon with a fury in recent years. It’s used to describe especially bitter outbreaks of winter weather. The northern hemisphere actually has two polar vortexes. The one that gives us the extreme cold is fairly low in the atmosphere. It’s formed by jet streams that encircle the pole that sometimes plunge southward. The other is much higher in the atmosphere. The higher vortexes are seen on every planet and moon in the solar system with much of an atmosphere. That includes Uranus, the third-largest planet. Scientists found evidence to confirm the vortex last year. Hints of a vortex around the north pole were seen in 2015. More recently, scientists looked at the pole with a giant radio telescope in New Mexico. They saw an especially bright area at the pole itself, with a dark ring around it. The bright region was warmer than the surrounding atmosphere. The combination provides strong evidence of a polar vortex. Air in the upper atmosphere moves toward the poles. It’s deflected by the planet’s high-speed rotation – forming a “vortex” around the north pole. Uranus is putting in its best appearance of the year. It’s lining up opposite the Sun, so it rises around sunset and is in view all night. It’s brightest for the year as well. But you still need binoculars or a telescope to see it, along the border between Taurus and Aries. We’ll have more about Uranus tomorrow. Script by Damond Benningfield

    2 min

  2. 2 DAYS AGO

    Mars Equinox

    It’s springtime – on Mars, anyway – because today is the spring equinox for the Red Planet’s northern hemisphere. Like the seasons on Earth, the seasons on Mars are the result of the planet’s tilt on its axis. In fact, the two planets are tilted at almost the same angle. So the north pole dips toward the Sun at the start of northern summer, while the south pole dips sunward at the start of northern winter. The equinoxes are half way between those points. But there are some differences between the seasons on Earth and Mars. Mars’s orbit is more stretched out than Earth’s orbit, so there’s a bigger difference in the planet’s distance from the Sun. Mars’s distance varies by about 26 million miles. That has a couple of effects. For one thing, it creates a big disparity between the seasons in the northern and southern hemispheres. Mars is farthest from the Sun during southern winter, and closest during summer. That means southern winters are colder than northern winters, while summers are warmer. And second, Mars moves fastest when it’s close to the Sun, and slowest when it’s far away. That causes a big difference in the length of the seasons. Northern spring is the longest – it lasts 194 Mars days. Northern fall is the shortest – just 142 days. Look for bright orange Mars climbing into good view in late evening, and high in the southwest at first light – a world that’s springing into a new season. Script by Damond Benningfield

    2 min

  3. 3 DAYS AGO

    Twin Cover-Ups

    The Moon will stage a pair of cover-ups over the next couple of nights. The first happens tonight, when the Moon covers up the planet Saturn. And the second happens just 24 hours later, when it covers the planet Neptune. The cover-ups are known as occultations. They occur because the Moon and planets all stay close to the ecliptic – the Sun’s path across the sky. But they all stray a few degrees to either side of the ecliptic. So most months, the alignment is off by a bit, so the Moon just misses the planets. At times, though, the geometry is just right, as it is now – at least for parts of the world. Tonight, for example, the occultation of Saturn will be visible from a bit of South America, most of Central America, and the southern half of Florida. There, Saturn will disappear at about 9:20 p.m. It’ll remain out of sight for about 45 minutes. Because Saturn forms a tiny disk in our sky, it’ll take a few seconds for the planet to disappear and reappear – it won’t instantly blink off and back on. The rest of the United States will see an especially close encounter between Saturn and the Moon. Saturn looks like a bright star, and will pass just a fraction of a degree from the Moon. Tomorrow night, it’s Neptune’s turn. The path of the occultation will cross most of the United States. But Neptune is so faint that you need a telescope to watch the giant planet vanish – another cover-up for the gibbous Moon. Script by Damond Benningfield

    2 min

  4. 4 DAYS AGO

    Vanquished Pictures

    The bright Moon washes out the fainter stars tonight. One that shines through is Hamal, the leading light of Aries, the ram. It’s in the east at nightfall. It’s about 65 light-years away. And it’s a giant – bigger, heavier, and brighter than the Sun. The other stars of Aries are tougher to see. And some stars that once formed separate constellations around it are impossible to see. In fact, they were tough to spot even when they were first outlined. To the left of Hamal is Triangulum Minus, the little triangle. It was created by German astronomer Johannes Hevelius, in 1687. Its three stars are all quite faint. So even without the moonlight, they’re visible only under dark skies, away from city lights. Below Hamal is Musca Borealis, the northern fly. It consists of four faint stars. The constellation was created by Petrus Plancius, in 1612. His original name for it was Apes, the bees. Later, another astronomer called it Vespa, the wasp. Hevelius then took over. He kept the buzzy theme, but he went with Musca, the fly. But there was already a fly in the southern hemisphere, so astronomers clarified matters by adding “northern” to the name. In 1930, the International Astronomical Union adopted 88 official constellations, all with well-defined borders. The little triangle was incorporated into Triangulum. And the stars of the northern fly became part of Aries – buzzing around the rump of the ram. Script by Damond Benningfield

    2 min

  5. 5 DAYS AGO

    Capella

    Capella is a big mismatch. It’s a system of four stars, divided into two widely separated pairs. The members of one pair are both about two and a half times the mass of the Sun. But the members of the other pair are only about half the Sun’s mass. As a result, the two pairs face quite different futures. Capella is the brightest star of Auriga, the charioteer, and the sixth-brightest star in the entire night sky. It climbs into good view in the northeast in early evening and soars high overhead during the night. The system appears to be about 600 million years old – four billion years younger than the Sun. Yet the stars in the heavier pair are both at the end of life. They’ve burned through the original hydrogen fuel in their cores. That’s made them puff up to giant proportions. Before long, both stars will shed their outer layers. The stars are close enough together that the expelled gas should act like a brake, causing the stars to spiral close together. But as the gas disperses, the stars will be much lighter. That will loosen their grip on each other, causing them to move farther apart. So no one is quite sure what the system’s final configuration will look like. The smaller stars, on the other hand, will remain in the prime phase of life for tens of billions of years longer. But as the heavier stars trim down, the two pairs are likely to drift apart – splitting up a stellar quartet. Script by Damond Benningfield

    2 min

  6. 6 DAYS AGO

    The Big Freeze

    Scientists don’t have a crystal ball to help them foretell the future of the universe. But they can devise ideas about the future based on their understanding of the history of the universe and the laws of nature. Based on that, perhaps the leading idea about the fate of the universe is the Big Freeze: The universe will get colder and darker, and eventually disintegrate into a soup of particles. The key ingredient of the Big Freeze is dark energy. Scientists don’t yet understand its nature. But it causes the universe to expand faster as it ages. And if it keeps its foot on the accelerator, the universe faces a bleak future. Hundreds of billions of years from now, the expansion rate will outpace the speed of light. Galaxies will disappear from each other – their light won’t move fast enough to reach most of the other galaxies. The final stars will be born in a few trillion years. By then, most stars will have expired. Galaxies will consist mainly of the corpses of stars, plus some faint stars and smaller objects. Over the eons, all the stars will die, and the stellar corpses will evaporate. And after trillions upon trillions of years, even black holes will vanish. Only ghostly particles will remain. This future is far from certain. Scientists have many questions about dark energy and more. They’ll need to peer deeper into their crystal balls – the laws of nature – to tell us whether the universe will die in a Big Freeze. Script by Damond Benningfield

    2 min

  7. 6 NOV

    Keeping It Going

    A faint glow fills the entire universe – the “afterglow” of the Big Bang. The glow was created when the first atoms formed – 380,000 years after the Big Bang. But the glow isn’t smooth – it has tiny ripples and bumps. That’s because the universe itself wasn’t smooth – there were slight differences in the density of matter. Without those differences, we wouldn’t exist. The denser regions had a slightly stronger gravitational pull, so they drew in the material to make the first stars and galaxies. The first stars were born in as little as a hundred million years. They were made almost entirely of hydrogen and helium, which were created in the Big Bang. The stars probably were quite heavy, so they burned out in a hurry. They forged heavier elements in their cores, then blasted them into space when they died. Some of those elements were incorporated into later generations of stars. Those stars created more heavy elements and flung them into space as well, and so on. The heavier elements are the ingredients for planets and everything on them – including us. Galaxies began to form about four hundred million years after the Big Bang, as stars and gas clouds clumped together. More stars and galaxies are being born today, but not as many. In fact, most of the stars and galaxies that will ever be born have already taken shape. So the universe may face a cold, dark fate, and we’ll talk about that tomorrow. Script by Damond Benningfield

    2 min

  8. 5 NOV

    Getting Started

    Our universe has a long and complicated history. And scientists are still trying to understand it all. The general picture says the universe was born 13.8 billion years ago, in the Big Bang. For the first tiny fraction of a second, the universe expanded at many times the speed of light – an epoch known as cosmic inflation. When inflation ended, the expansion slowed dramatically. But a lot happened over the following few minutes. During the first second, the basic forces of nature took shape: gravity, electromagnetism, and the forces that bind matter together. These forces made it possible to forge protons and neutrons. By about three minutes, the universe had expanded and cooled enough for these particles to stick together. They formed the nuclei of the first elements – mainly hydrogen and helium. The universe was still extremely hot and dense. And it was “foggy,” so we can’t see anything from that era. By about 380,000 years, though, the fog began to clear. Electrons latched on to the nuclei to form complete atoms. That process left a faint “afterglow” that we see across the entire universe. There are lots of questions about the details of this picture. And some scientists aren’t convinced about the overall outline – they have different views about the age of the universe, whether inflation ever happened, and more. There’s a little more agreement about what came next, and we’ll talk about that tomorrow. Script by Damond Benningfield

    2 min

  9. 4 NOV

    Moon and Venus

    It’s hard to imagine a less comfortable place for life than the clouds of Venus. They’re made mainly of sulfuric acid – something you wouldn’t want to dip your fingers into. Yet studies in the past few years are raising at least the possibility that microscopic life could inhabit those clouds. There’s almost no way for anything to live on the surface of the planet. The atmosphere is too hot, dense, and toxic. But the clouds are about 30 miles high, where the conditions are more like those on Earth. A few years ago, scientists reported finding phosphine in the clouds. On Earth, it’s a compound that’s almost always produced by living organisms. Other studies have found no trace of it. But earlier this year, astronomers reported finding new evidence of the compound. Another study this year reported finding ammonia. On Earth, it’s produced mainly by living organisms and industrial processes. And yet another study said that some of the key building blocks in amino acids could survive in a high concentration of sulfuric acid. None of that means that anything actually lives in the clouds. But it does mean that scientists will be taking a much closer look at Venus’s clouds in the years ahead. Venus is the brilliant “evening star.” It’s quite low in the southwest as night falls. Tonight, it’s close to the upper right of the crescent Moon. It’ll be a little farther to the lower right of the Moon tomorrow night. Script by Damond Benningfield

    2 min

  10. 3 NOV

    Stellar Pearls

    Star clusters line up in the evening sky at this time of year like pearls on a necklace. As the sky gets nice and dark, they climb straight up the northeastern sky. They stretch from the bright star Capella, which is quite low; up through the “W” of Cassiopeia; then to Cygnus, the tail of the swan, high overhead. There’s a good line of clusters because that path outlines the Milky Way – the subtle glow of the disk of our home galaxy. Most of the clusters are classified as “open.” All of the stars in such a cluster were born together, from a giant cloud of gas and dust. But as the clusters orbit the center of the Milky Way, they’re slowly pulled apart. So over time, all the stars in such a cluster go their own way. Perhaps the highlight of this path is the Double Cluster – two clusters in Perseus, just below Cassiopeia. Under dark skies, they’re visible to the unaided eye as a faint cloud of light. Individually, the clusters are known as NGC 869 and 884. They’re about 7500 light-years away. Combined, their stars and gas add up to about 20 thousand times the mass of the Sun. And they’re quite young as stars go – about 14 million years. At that tender age, the clusters haven’t had time to fall apart. And with their great mass, they’re likely to hold together longer than most clusters – perhaps several hundred million years. Tomorrow: the crescent Moon and the “evening star.” Script by Damond Benningfield

    2 min
  • 10 Episodes

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 - 2024
  • Episodes
    10
  • Rating
    Clean
  • Copyright
    © 2022 The University of Texas McDonald Observatory
  • Show Website
    StarDate

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